April 14, 2026 • 57 mins
In this episode of Stuff to Blow Your Mind, Robert and Joe discuss the royal histories and curious biologies of such resplendent fish as the common gold fish and koi.
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Speaker 1 (00:03):
Welcome to Stuff to Blow Your Mind production of iHeartRadio.
Speaker 2 (00:13):
Hey, welcome to Stuff to Blow Your Mind.
Speaker 3 (00:14):
My name is Robert Lamb, and I'm Joe McCormick.
Speaker 2 (00:17):
And in today's episode and the episode to follow, we're
going to be getting into the topic of golden fishes,
specifically varieties of carp that have been historically selectively bred
to produce brightly colored fish golden fish even, but colors
that are not limited just to gold or yellows, oranges
(00:40):
and so forth, as well as some less bright colors
as well. But basically this process by which humans have
turned wildfish into almost swimming jewels to delight the eye
and perhaps inspire the imagination. However, I do have to
(01:02):
stress that for a lot of us, we might not
find the goldfish all that awe inspiring. I don't know
about you, Joe, but I certainly was exposed to the
goldfish pretty early on, like a lot of kids. I've
seen goldfish my whole life. I had a goldfish at
some point. I've seen them carried around, doomed to a
(01:26):
lonesome death and tiny plastic bags by children who perhaps
won them at a fair or just bought them at
a store without a lot of forethought. So I don't know,
like I have, I have mixed feelings about the goldfish
and maybe less respect for their beauty because of these
experiences with them.
Speaker 3 (01:48):
For a few years, when I was in elementary school,
my family had a relatively small freshwater aquarium that I
really liked. I would just, you know, I would watch
it like team. I would just sit there and look
at it. I don't think we ever had any goldfish
that I recall. We got a variety of fishes from
(02:08):
a little little fish store in town. I still remember
where that place was. It no longer exists. But the
thing that I was really interested in was there was
a tiny type of frog, like aquatic frog that had
little little legs that would swim around in the tank.
I never thought since I grew up to look up
what that was, but yeah, some kind of little, little,
(02:32):
little bitty frog that would swim around, and I thought
that was really cool. But yeah, I guess it never
struck me as strange that we didn't bother to put
any goldfish in our aquarium, but we didn't. I do
think I had some friends who had goldfish. One friend
of mine had a goldfish actually now that I remember
in a like your classic setup sort of the coin
(02:54):
shaped tank on the table. That is, it's not even
a tank really, it's like a you know, a jar
that would put marbles in. But a fish was living
in there. I'm sure the fish was not not too
happy to be in such such a small space.
Speaker 1 (03:06):
Yeah.
Speaker 2 (03:07):
I was to chatting with my wife about this, and
I knew that when she was a kid, they often
had you know, aquariums and pets around and and uh.
And I asked ask her, well, dude, y'all had a goldfish, right,
and she was like, no, no, we never had a goldfish.
Like there was this this prevailing understanding that goldfish were
not happy and so they never they never got one.
(03:29):
But but for me, it's like I just grew up
thinking like this was sort of the default mundane fish,
which is crazy considering you know, we'll get into it
even a bit in this episode. I think that the
history of the goldfish, uh, and there were times when
it was definitely not a common fish. If you were
a commoner, it was illegal to have one.
Speaker 3 (03:48):
Uh.
Speaker 2 (03:48):
These were the fish of royalty. These were uh, these
were again little gems, but they become they became so
mundane and so every day for a lot of us
that we just didn't even see them as interesting fish.
You were more in you didn't have the goldfish, but
you were interested in the frog. We had the goldfish.
I was more interested in the little sucker cleaner organisms
(04:08):
that would feed on the sides of the tank, and
the goldfish I kind of just took for granted. I
didn't even really question, like, why is it golden like this?
What's what's the purpose of its coloration? And you know,
and honestly never even gave it a lot of a
lot of respect as an organism. But as we'll get into,
(04:29):
there are a lot of fascinating things about the goldfish,
things that that play into their history of domestication and
artificial selection, but also just their their their natural gifts
as an organism.
Speaker 3 (04:42):
Yeah, so it's interesting how that the goldfish, in being
both historically and visually in some ways remarkable but also
culturally extremely commonplace, is kind of a it encapsulates something
about the broader family of fish, is that it belongs
to the carp family, which is both in some ways
(05:05):
very remarkable. They're interesting and unique things about the carp family,
but it's also very commonplace. It is, I believe the
most are one of the most diverse and numerous of
all vertebrate taxa.
Speaker 2 (05:20):
Yeah. Yeah, And in fact, if we had just called
this episode stuff to blow your mind carp, I don't know,
some of you might be morbidly interested with some of
you might be like, no, thank you, I don't need
to know about carp. What's more every day than a
carp You're wrong.
Speaker 3 (05:34):
There's some weird, cool carp stuff.
Speaker 2 (05:36):
We're here. Absolutely is the other side of the golden
fish coin. Of course, the koi, and this is another
fish that will you will find a lot of places.
And in fact, my wife's family had at least one
koi fish. They had like a small koi pond growing up,
and I imagine a number of you out there listening
(05:58):
do as well. I've never never can up to koi,
but h and I also encountered them for the first time.
I think later on in life encountered or noticed them.
It's possible they were pointed out to me as a
child and I was like, yeah, whatever, I'm thinking about
Ninja's or something instead. But but much later on, you know,
I got to to visit some really remarkable koi ponds,
and some you know, generally and there they're in garden environments,
(06:21):
so there's a lot going on to sort of captivate you.
I got to see some really impressive coi pons in
both China and Japan, and and for that reason, I
think I have perhaps an unfair tendency to see the
koi as something special and sort of like a true gem,
some sort of a wild, magical creature, whereas I again
(06:44):
I'm I'm probably unfairly dismissive of the goldfish, but there's
I do find a lot of serenity in the koi.
Like the koi, I guess they feel more wild, even
if when they are inherently captive in some sort of
a pond environment, because there's often there's often a way
with you know, some sort of a decorative pond where
(07:05):
you at least create the illusion of wildness. Whereas the aquarium,
even a very nice aquarium, one that is very well
capped and the animals are happy, there is still that
boxing in of the environment that can feel more like
a complete domination of the thing.
Speaker 3 (07:21):
Yeah, yeah, I know what you mean.
Speaker 2 (07:23):
But as we'll discuss, like there is there is a
fair amount of domination in play when it comes to
the goldfish, less domination maybe with the koi, and a
lot of that is going to have to do with
how old these selected breeds are.
Speaker 3 (07:37):
So earlier, you said something alluding to the fact that
the gold the goldness of or the orangeness of a
goldfish or a koyfish, is in some way a trait
that is not entirely natural to the species from which
these are derived, that this is a selectively bred or
encouraged trait.
Speaker 2 (07:57):
Yeah. So in general, as we'll discuss, like, are these
are fish that have been that have been selectively bred
in a way to enhance, to encourage and enhance certain features,
especially coloration, And so on one hand, you can look
at a goldfish in particular and you can say, well,
that we did that, We made that happen. That is
(08:20):
not something that belongs in nature. This is maybe something
more akin to alchemy and the turning of lead into gold.
And and you know, I think it is fair to
say that when it comes to selective breeding, it can
feel a bit like alchemy at times, like when you
compare say a pug and a Great Dane, and you
remind yourself these this is the same species. These are
(08:41):
both domestic dogs. They can technically mate with each other.
These are the same the same thing, but they don't
feel like the same thing at all. Or you can
compare broccoli and cabbage and they don't feel at all
like the same species.
Speaker 3 (08:57):
You know, we sort dog breeds by temperament, but we
do withchrciferous vegetables.
Speaker 2 (09:03):
But get I think one interesting thing to go ahead
and get out of the way, is just that the
idea that Okay, yes, these are examples where we have
bred the creature to enhance a certain color, for example,
but that doesn't mean that gold doesn't have a place
in the natural world. For varying reasons, you do encounter
creatures that feature gold or something like gold in general
(09:27):
in these episodes when we talk about something being gold,
and we also might just be talking about them being
orangeur yellow, or what have you. And that could be
due in general across various animal species to pigmentation but
also to like physical characteristics that are creating this impression
of color.
Speaker 3 (09:47):
Okay, they're in the gold zone.
Speaker 2 (09:50):
Yeah yeah, yeah, for some reason, they're in the gold
zone when human eyes look upon them. And of course
we love it when that happens, and there's a but
there are a number of like real, you know, serious
reasons for this colorization in different organisms. For instance, we
see sexual dimorphism in play, you know, where the coloration
(10:12):
on the male is important for for mate selection and breeding.
Like with the golden pheasant. If you've ever had a
chance to see a golden pheasant, say it a zoo
or some sort of avery. Uh. They these are impressive birds.
The male sport brilliant looking gold, orange and yellow colors.
There's some black in there as well, extremely eye catching,
(10:35):
and that is by you know, design, They are trying
to catch the eye of their perspective mate some other
There are plenty of other examples out there. There's a
golden tortoise beetle. This is a species of beetle capable
of changing its color colorization, with some individuals taking on
a shiny metallic gold appearance via structural color change. And indeed,
(11:00):
if you look up in images and descriptions of these,
they can look rather unreal. They can. I've seen them
described often is sometimes looking like drops of gold, like
very metallic looking. But it's going to vary depending on
species or the individual in the species, and well, I
(11:20):
don't think we have all the answers on exactly like
why they do it. It seems like the main ideas
have to do with the fact that the change may
help males attract mates, and it might also aid in
predation deterrence, kind of getting into the sort of prevailing
logic that brightly colored organisms are often trying to, especially
(11:41):
smaller organisms like insects, are trying to send a message
to say, hey, I'm here and I'm loud, that it
might be a bad idea to eat me. You might
not like it, and if you don't like it, I
want you to remember that you didn't like but yeah,
Like another example, you can think to the world of
pot and dart frogs, where you have multiple brightly colored
(12:04):
you know, very obvious to the eyes species, and there
is a golden poison dart frog as well, and as
with other poison dart frogs, this is a warning to
potential predators, you know, and you know saying hey, you
probably shouldn't shouldn't eat me, you might not like what
you eat. And then we also have to remember we've
talked about this before. Is that so often when we're
(12:26):
considering the coloration of an animal, we're taking it outside
of the context of their natural habitat. And so there
are various examples of organisms that are to some degree golden,
where if you place them in their natural habitat in
the places where they're trying to be hidden, they are
actually hidden. For example, there's the Asian golden cat, which
(12:47):
to be clear, isn't like super brightly colored gold, but
still gold enough for humans to call them such. And
then you have things like the leopard as well, where
you know, outside of the context of their environment, this
may look like a very loud old design. Like if
you and I were to wear like leopard print shirts
for our recording here, which I do think is a
(13:07):
great idea, especially if we match, you know, it would
be sending an outlandish signal like we're definitely trying to
stick out. But the leopard is has that coloration as
part of its camouflage, So within context of its environment, that's.
Speaker 3 (13:23):
Stealthy, right, because the leopard is not against a gray
mate background. Yeah, so in its environment the colors it
has make sense.
Speaker 2 (13:42):
Now coming back more specifically, took the goldfish and to
the koi, as I believe we've stated already. These are
both karp. The goldfish species is Caressius aratus, and koi
is a domesticated form of either of the the amor
carp that's Cyprnous roberfuscus or the common carp, which is
(14:08):
Soprinus carpio. And in either case we're talking we're talking
about carp, but we're talking about two different carp species
that have been altered through domestication. However, while the koi
retains the same species as its wild counterpart, the goldfish
is granted its own species and has arguably, and this
(14:29):
is the point, this is a point of some disagreement
among experts undergo gone speciation, probably from the Crucian carp,
though I don't think this is completely settled either.
Speaker 3 (14:41):
Some of the studies that I've been looking at and
that I'm going to talk about later in this episode
talk about the goldfish and the Crusian carp as different species,
so they are generally regarded as such, but yeah, they're
thought of as at least close relatives, if not or
at least close relatives or sharing a very recent common ancestor.
Speaker 2 (15:04):
Yeah, yeah, it can. It can honestly get a little
confusing researching it, at least for me. But I guess
one of the things with taxonomy is you have to
realize that at some point somebody just sort of calls it,
and then there can still be a fair amount of disagreement,
change and correction on that particular call later on. So
(15:24):
there have been there have been some changes, for example,
regarding how we look at the goldfish over the course
of it of its history and taxonomy. And again, as
we'll discuss, the cultivation of the goldfish goes back to
over a thousand years ago. On the cooi is a
much more recent creation. So both are examples of human
(15:44):
breeders artificially selecting for desired features, especially color in carp species,
to produce fish that are maximally pleasing to the human eye. Now,
one question I think a lot of people might have
at this point is where does the gold come from?
Has to be there somewhere in the wild organism, uh,
you know, it's not created out of nothing. There has
(16:07):
to be some sort of trait that is then seen, admired,
and then encouraged through selective selective breeding. Right, And so
to really get into that, we have to sort of
talk about the history of this kind of selective breeding,
and in fact, the history of aquaculture the basically the
fish based alternative to agriculture, and this is this alone
(16:33):
is a pretty fascinating topic looking at just for how
long human beings have realized that they could master to
some degree an aquatic environment or various aquatic organisms and
and and use them in the same way that that
within agriculture we've used various plant species.
Speaker 3 (16:51):
Right now, I would assume that we were that humans
have been catching and eating wildfish much longer than they
have been farming fish, just in the same way that
hunter gatherers. You know, we're gathering and eating wild plants
long before they were actually like planting crops and growing
them themselves.
Speaker 2 (17:11):
Right, right, And unluckily we do have a lot of
historical writings about it. I was reading there's a twenty
twenty five Forbes article by Scott Traver's titled the Incredible
Tale of How the Common carp evolved into the thousand
dollars COI. And in this the author mentions, for example,
that the Romans certainly practiced cultivation of the Eurasian carp,
(17:36):
plenty of the elder rights of other fish being raised
on Roman estates. So on one level, it certainly goes
back as far as the Romans, but it goes much
further back than that. In general, the domestication of different species,
different fish species, it originates multiple times, different examples of aquaculture,
(17:57):
emerging between at least three thousand, five hundred and two thousand,
five hundred BCE, originating at least twice in China and
North Africa. However, I've also seen arguments that the Chinese
carp cultivation may go back as far as six thousand BCE.
This according to Nakajima at All in twenty nineteen's Common
(18:20):
Carp Aquaculture and Neolithic China dates back eight thousand years.
This was published in Nature, Ecology and Evolution. So Chinese
aquaculture certainly goes back a long time, no matter how
you you know what findings you're presenting here integrated with
rice farming and the earliest surviving Chinese text on the subject,
Treatise on Fish Breeding, was written by Fan Lie around
(18:43):
four seventy five BCE. This is also known as the
Fish Breeding Classic. There's a on top of this, there's
just a lot of There are also later texts that
deal with this and in general, there's a lot of
rich lore associated with different carp species in China, And
in the next episode I might pull out one or
(19:04):
two of these tales if they feel particularly insightful for
our topic here, but a lot of them hinge on
the idea that a carp is sustaining, it's a source
of nourishment, and so it can end up taking on
this this air of you know, of auspicious symbolism, and
it can even become a vehicle of divine ascension. So
(19:25):
there are tales of fishermen ascending into heaven on winged
talking carp that they've caught.
Speaker 3 (19:32):
Wait a minute, does this connect to that that myth
we've talked about before of like the carp leaping over
the say, leaping over the waterfall or leaping over the
rainbow something like, oh.
Speaker 2 (19:42):
You know, yeah, yeah, I think you're I think you're right.
I guess one of the things about it. On one hand,
there's like the cart specific aspect of this, but then
I guess we also have to acknowledge across all human experience.
There's something about the gamble of fishing, and maybe it's
little different than the gamble of the hunt, right there's
(20:03):
a certain amount of you know, certainly skill and knowing
your environment and knowing the species you're after, but there's
also kind of a roll of the dice, right, so
there's a sense of the divine when you actually do
hook that really nice fish that is going to sustain
you and allow you to live the next uh, you know,
through the next meal time.
Speaker 3 (20:22):
Yeah. Yeah, I wonder to what extent hunters and fishers
would agree with this point of view, But I guess
I've always thought of a major difference being that, certainly
in the archaic context, I've thought of hunting as a
more athletic activity, one that you know, is related to
the humans speed and strength in some way, though obviously
(20:44):
you know, strategy and coordination or a big part of
it too, and of course your tools. But that fishing
is a more pure game of chess with the environment
that it it's because you're not having to like chase
down the fish by running faster or you know, or
throw something harder to hit it. That it is all
(21:04):
Maybe not all, because now I'm thinking about spearfishing and
stuff too, So I guess I'm really I'm going back
on what I was saying originally but maybe my naive
point of view originally was that fishing is the slightly
less less of the jock art of sourcing protein from
the environment. It's more of the nerdy sort of chess
with the environment, trying to understand what this water source is,
(21:27):
what lives at, what part of it, and how to
attract it and things like that.
Speaker 2 (21:31):
I think there is often something in fishing where we
are casting something into an unseen world or world that
we see much less off. And again that's not going
to apply to every instance of fishing. Certainly there's spearfishing
and you know, fishing that is done underwater while one
is diving.
Speaker 3 (21:51):
And so forth.
Speaker 2 (21:51):
But yeah, I suspect that there's something to this. Again,
we'd love to hear from many fisher people out there
who would like to chime in.
Speaker 3 (22:00):
Yeah.
Speaker 2 (22:01):
Well, eventually, one of course, sees the spread of these
different aquaculture traditions and aquaculture species out of Europe and
into other areas, out of China, out of North Africa.
You know, I don't want to get too bogged down
with discussions of hoo did it first or indeed exactly
how far back these practices go, but we can at
(22:21):
least state that for a very long time humans have
known how to manipulate certain fish populations for their own benefit,
most mostly for food. I mean, that's the key reason,
far ahead of any ideas we might develop about encouraging
different colors. We knew that fish were a reliable source
of protein, and if we you know, we certainly can
(22:43):
figure out how to catch them in the wild. But
then what if you can control the wild itself, well,
then that gives you an even bigger advantage when it
comes to hooking one. So multiple different carp species were
prized by the Chinese, and among these you encounter different
color colorizations. But with both the common carp as well
as the Prussian carp and the Crucian carp, you encounter
(23:07):
a certain degree in the variation of exact color. A
dull gold is often described in the wild, but depending
on the genetics, even wild specimens can take on a
more pronounced color palette, you know, with brighter colors. So
I think one really key factor here concerning these various
carved species, and this is something that really surprised me.
(23:29):
This is also something that's very much in play with
the common goldfish that you might encounter the pet store
is that they have chromatophores. These are in fact, they
have different types of chromatophors that control dark and light colorization.
And to be clear, you know, we're not talking about
that level of color chains that you see with something
(23:50):
like a cuddlefish where it is like actively psychedelic, but
they can produce lighter or darker shades based on a
number of factors including diet, water temperature, and exposure to light.
I believe this is actually something that experienced and knowledgeable
goldfish keepers know is that you want to make sure
that your fish gets plenty of light because this helps
(24:13):
keep your fish bright and golden. And in general, this
adaptation is thought to provide camouflage in their natural environment.
So you know, there's like a mirroring or shimmering quality
of fish scales that can aid in both communication with
other fish and throw off would be predators. That's something
that you encounter with this fish in general, that's not
(24:36):
specific to carp or goldfish. And then this can also
get into like countershading and so forth, just something that
can visually throw off a potential predator. So the presentation
of a golden fish in general is a combination of
selectively breeding to encourage inherently brighter or more human desired colors,
(24:58):
while also providing optimal artificial conditions to encourage the most
desired color performance via those chromatophores. So you know, it's
more than one thing going on. There so many different
ways to manipulate your fish into looking pretty.
Speaker 3 (25:24):
Well. Would you like to talk about goldfish doing something
potentially a little more ghastly?
Speaker 2 (25:29):
Oh? Yes, I think we do need to make people
fear the goldfish a little bit. Give let's put a
little more respect on them.
Speaker 3 (25:36):
There's nothing to fear in reality, it's certainly given the
size difference between a human and a goldfish. But so
I wanted to think about the fact that, Rob, would
you agree people are generally not afraid of goldfish bites?
Speaker 2 (25:51):
This is not a concern, right, I've never this is
the first time I've even entertained the possibility, right, Like,
It's the kind of thing generally you're concerned about the
fish as well being, not the people that are interacting
with it.
Speaker 3 (26:04):
And I'm not trying to convince anybody otherwise. It is
totally reasonable to not be afraid of goldfish bites, because
if you look at the mouth of a goldfish, it
looks very harmless. You will see no teeth at all,
just a kind of smooth, flexible ring of soft looking flesh,
often opening and closing slowly as if blowing kisses. You know,
(26:26):
it's a very sweet, inoffensive, harmless little mouth. And actually,
by the way, that opening and closing of the mouth
repeatedly is part of a life sustaining activity that lots
of fish use called buckle pumping, in which the fish
repeatedly sucks in mouthfuls of water so that the water
can be passed over the gills for oxygen, but also
(26:49):
so that little bits of food that get pulled in
can be captured and swallowed. So the outer jaw of
a goldfish is indeed adapted for sucking, not for chewing,
and not for biting, and carp like goldfish are generally
said to have toothless jaws, okay, and yet a curious
(27:09):
piece of evidence occasionally makes one wonder about the about
the toothless mouth of the goldfish. People who keep goldfish
occasionally report finding on the floor of the aquarium tank
little white calcified as stones objects that really really look
(27:30):
like tiny teeth and rob i have some pictures in
the outline for you to look at here. What is it?
What do you think you're looking at?
Speaker 2 (27:38):
Well, I'm certainly primed to see these as teeth now,
But if I were to be skeptical and trying to
come up with another explanation, I would think, well, maybe
this is either something else that the animal is producing,
be it some sort of like flaky scales or something
that it is excruding, or this something else in the
(28:01):
aquarium environment.
Speaker 3 (28:02):
You know, right, Well, if you got pebbles at the
bottom of the varium tank, you know, they might just
blend in. A goldfish might spit out some of these
and you'd never even notice.
Speaker 2 (28:10):
Yeah, or somebody's messing with you. Someone is you have
a pranks during in your midst and they're dropping tiny
teeth every day just to throw you.
Speaker 3 (28:17):
Off, right, Who keeps putting teeth in my tank? Yeah?
So the question is are they teeth? And if so,
how can a toothless fish be losing teeth? The answer is, yes,
they are teeth, and yes they come from the goldfish.
The goldfish does have teeth, but not in its mouth.
Speaker 2 (28:39):
All Right, I'm okay, I'm unsettled. Let's find out more so.
Speaker 3 (28:43):
Fish in the carp family generally have these smooth outer
jaws that are used for sucking in water and bits
of material, not for chewing, But the carp can chew
with what's referred to as for ingeal teeth. This has
come up on the show before. It's been a while,
(29:03):
but the way it works is further back in the
goldfish's throat, maybe about as far back as the gills
or a little bit further. The goldfish or the carp
generally is equipped with blunt, molar like teeth mounted on
the pharyngeal bones, which the fish uses to chew up
(29:24):
whatever plant matter, little invertebrates, other tough foods. It chews
them by sucking them into the mouth, taking them back
into the throat, and then grinding the food the bits
of food with these teeth against a hard plate on
the roof of the throat cavity. These pharyngeal teeth are
(29:45):
sort of like in many ways, they're not like this,
but in some ways are like a shark's teeth, specifically
in throughout the fish's life, at various points they fall
out and are replaced by new teeth that grow in
so keepers of various carp species like goldfish occasionally find
(30:06):
these lost teeth scattered on the floor of the tank.
Speaker 2 (30:10):
All right, so there, and to a certain extent, they're
little xenomorphs, and we were generally not even giving them
credit for this.
Speaker 3 (30:16):
A little bit now there there is a distinction to
be made here because we've talked about pharyngeal jaws before
that there are some in nature that are much more
like the xenomorph in the movie. For example, the jaws
of the Moray eel, which there really is in the
Moray eel, is like a second mouth inside the mouth,
the second set of jaws that you know, reaches out
(30:38):
and snatches with the jaws that come out from the throat.
The goldfish or the carp are not like that. What
you're talking about here is not a second set of jaws.
It is again teeth mounted on bones in the throat
that can chew, but they don't like reach out and snatch.
Speaker 2 (30:53):
Does that make a throat that choose which which I
think also sounds pretty monstrous.
Speaker 3 (30:57):
The throat that choose right sore. Still no reason to
be afraid of goldfish bites. If a goldfish nibbles on
you with the outer jaws. It's nothing. It feels like
a little tickle or kind of a barely perceptible little
bit of suction. It's cute, frankly, But if you were
small enough and managed to get sucked into a goldfish's
mouth and down the throat, then you would absolutely be
(31:21):
in for a world of hurt.
Speaker 2 (31:22):
Oh wow. Yeah, And in general, if you become that
small you have a lot of problems on your hand.
But certainly make sure it doesn't happen while you're peering
over the top of the goldfish bowl.
Speaker 3 (31:33):
Actually, I mean it's a never ending mental exercise that
if you were small enough, nearly every cute animal becomes monstrous. Yeah,
your cat would eat you. Your cat would eat you
in a second.
Speaker 2 (31:45):
Absolutely. Let's see a little more about the goldfish here.
I want to give a little more historical background here.
And I was reading a little bit about this in
The Evolutionary Origin and Domestication History of Goldfish by chin
at All, published in PNAS in twenty twenty, and this
(32:05):
gets into a lot of genetic data, but they also
provide just a nice overview of the known history of goldfish,
and they cite the Chrustian carp origins of the goldfish,
and point out that the appearance of red scales on
normally gray or silver carp was first discovered or phillleast
first recorded during the Chinese Gin dynasty two sixty five
(32:27):
through four to twenty CE, and then during the Tang
dynasty six eighteen through nine oh seven CE, goldfish with
preferred phenotypes were selected for ornamental ponds and water gardens,
and then during the Song dynasty nine to sixty through
twelve seventy nine CE, the gold or yellow variety of
goldfish became the symbol of the imperial family. And this
(32:49):
is the time during which the goldfish was considered a
royal fish and it was not for commoners to raise them.
They were forbidden to raise them. Again, very different from today,
where everybody can pretty much get a goldfish. There's nobody's
going to ask for your royal bloodline before you purchase
one in a bag up at a local fair for
(33:10):
you know, like a quarter. But but yeah, there was
a time when they were there. There was a lot
of elitism in owning a goldfish. But any rate, everybody
loves the idea of a golden fish. The seventeenth century
saw the introduction of the goldfish into Europe and into
Japan and then eventually to America around eighteen fifty. Now,
(33:32):
in any way you cut it, we're talking about a
good millennium of folks messing with goldfish, a thousand years
of domestication. And the authors point out that since the
fish produces, any given fish can produce thousands of eggs,
and dozens of these fish can be raised in the
same pond, So that means that a millennium of goldfish
(33:53):
domestication has produced quote strong artificial selection. Charles Darwin even
fixated on them for this reason, as did English biologist
William Bateson and Chinese genetic researcher Shisan ci Chen, who
worked a lot on the topic of goldfish genetics. So
(34:14):
the other interesting thing here is when we're talking about
a thousand years of domestication messing with the goldfish, you
may be far more aware of this. If you're aware
of this, if you are a goldfish person, or if
you spend a lot of times a lot of time
going to aquariums and local aquarium stores. But it's impacted
far more than just their color. It's changed their body shape,
(34:35):
their finn configuration, their eyestyle and color. And this is
why goldfish have served as a great genetic model system
for studying fish physiology and evolution, and it has also
resulted in so many different varieties of goldfish. They fall
into some very you know, just broad categories include like
(34:58):
long bodied goldfish, double tailed, or fancy goldfish, egg shaped,
dorsal finned, dorsal finless, just to name a few, without
even getting into the variety of colors where you know,
you may have reds, yellows, blacks, oranges, gray's whites, browns,
and blues. As with domesticated dog species, you would be
(35:20):
hard you know, you'd be hard pressed to necessarily identify
these as the same species. Looking at some of these
different goldfish varieties, Yeah, I mean, like one is kind
of like a like a like a more like egg shaped,
like golden fish. Another one is you know, longer and
(35:40):
like blue and black. I mean, they just don't look
like they should be the same species.
Speaker 3 (35:44):
What's the one I've seen that has the bulbous eyes
that are pointing up?
Speaker 2 (35:49):
Do you know what I'm talking I forget what they're
called offhand, but yeah, like there's like that is one
type of goldfish you'll see with like the enormous bulging
eyes where they look like some sort of a shock
cartoon character. But it is the you know, it's technically
the same species as this other sort of slimmer goldfish,
the kind of goldfish that might look more like the
logo for a business, that sort of thing, you know,
(36:11):
where it's it's less, I don't know, less goofy looking
in some way.
Speaker 3 (36:25):
Well, Rob, if you're ready, I wanted to talk about
a particular specific deep dive on goldfish biology that I
did that has to do with their tolerance for anoxic conditions.
Are you ready for if we do that? Yeah?
Speaker 2 (36:40):
Absolutely, this is this is really fascinating, and I think
is this is one of the early things that I
stumbled upon where I was like, oh, yeah, goldfish, they
do deserve a closer look.
Speaker 3 (36:51):
So, the goldfish is a very hardy fish. It can
survive across a large range of temperatures. It can eat
many different kinds of food, It can tolerate murky and
turbid waters. Turbid meaning like cloudy water with a lot
of sediments suspended in it. It can just do well
in a lot of different circumstances. And that has made
(37:13):
it a fish that's fairly easy to spread, of course
around the world, also can make it an invasive fish
sometimes because it's so easily adaptable and can do well
in all kinds of waters and in a fairly unique way.
One of the ways that it's hardy is that can
it can even tolerate anoxic conditions, meaning it is specially
(37:35):
evolved to survive being deprived of oxygen. I was reading
about this in a column written for the Journal of
Experimental Biology by biologist de Jean Michelle Weber, formerly of
the University of Ottawa, called Revealing How Goldfish Defy Anoxia.
This column was from the year twenty sixteen, and this
(37:56):
was not new research at the time it was published.
It was a review column about previous discoveries about respiration
and fish. So all vertebrate animals ultimately at some point
need oxygen to survive. Many vertebrates will die within minutes
if they can't get it, and this need for oxygen
(38:17):
is also true of animals that live underwater. These underwater
animals use organs like gills to extract dissolved oxygen from
the water so they can breathe. And I do want
to note something because I used to have this misconception.
This misconception, fish and other aquatic animals do not, as
(38:37):
I assumed when I was a kid, break apart the
water molecules and harvest the oxygen from the H two
O itself. The water molecules stay intact. Instead. The reality
is that liquid water usually contains some quantity of pure
oxygen gas or O two dissolved within it. So healthy
(39:00):
water for fish usually has somewhere between six and eight
parts per million of dissolved two. But of course the
amount of dissolved oxygen in water can fluctuate a lot,
and when for any number of reasons, the oxygen levels
in the water get too low, aquatic vertebrates can't breathe,
(39:20):
and this is often the explanation when you see dead
zones in the water. If you come across a place
in the water with huge masses of fish and other
creatures floating belly up in the same area, often what
happened is they were suffocated by oxygen poor water. But
despite the fact that vertebrates all ultimately need oxygen to live,
(39:43):
there are a few special water dwelling vertebrates which research
shows can survive days or in a few cases if
conditions are right, even weeks or months without oxygen, and
those longer time scales. Usually what that depends on is
very cold conditions, you know, that are slowing down the
(40:05):
metabolism greatly and putting these animals into a state of torpor.
But still some animals can survive days, weeks, or even
months without oxygen. So this small club of anoxyotolerant animals includes,
according to Weber, two species of turtle and several fish
in the carp family, and one of those carp species
(40:27):
is the goldfish Carassius aratus. Weber discusses how it had
been known for many decades that some species of carp
could survive for extended periods in water that was deprived
of oxygen. Goldfish and their wild relatives, the Crucian carp,
can often survive actually four months over wintertime in the
(40:50):
low oxygen waters that are trapped beneath a frozen pond,
and amazingly, by the nineteen seventies, researchers had found that
these carp could still produce a high output of CO
two even when living in water that had very little
oxygen in it. In other words, you might say, in
(41:10):
a metabolic sense. They were breathing out when there was
almost nothing to breathe in, So how would that be possible?
Weber points to a fascinating discovery specifically in goldfish in
the year nineteen eighty, published by two researchers named Eric
Showbridge and Peter Hochochka. They found that the goldfish quote
(41:34):
tolerates a prolonged, normally lethal lack of oxygen by using
large glycogen stores to generate ethanol as a byproduct of
energy metabolism. So, ethanol is alcohol. It's the normal, regular
kind of alcohol, the kind you're probably most familiar with,
the kind that's in beer, wine and whiskey. So what
(41:56):
does producing alcohol in the body have to do with
b being able to survive without oxygen? I'll explain so again,
all vertebrate animals normally rely on oxygen for the chemical
reactions that drive metabolism, which allow our cells to keep living.
So the simplified version of this reaction is oxygen combines
(42:19):
with the carbohydrate glucose, which we ultimately get from food,
providing energy for cells in the form of the compounded
adenozine triphosphate or ATP, and then this reaction so it
produces the ATP that the cells need, and it releases
the byproduct of carbon dioxide and water. Our bodies purge
(42:40):
excess carbon dioxide by exhaling, and this is the normal
process that we use when oxygen is plentiful. When our
cells are deprived of oxygen, they fall back on a
secondary process called anaerobic respiration respiration without oxygen. Under this process,
our cells still break down glucose and turn it into
(43:03):
cellular energy, but they do so with much less efficiency,
so there's less energy output and they spit out a
product called lactic acid. Anaerobic respiration only works as a
temporary stop gap in times of need, most often during
extreme physical exertion. Now, under normal circumstances, a bit of
(43:27):
lactic acid build up in the body is okay if
you can get the oxygen you need, because over time
the liver can convert the lactic acid back into glucose.
But if you're not able to get enough rest and oxygen,
the unrelieved buildup of lactic acid leads to a condition
again known as lactic acidosis, in which the body's overall
(43:50):
pH becomes too low, and this can cause all kinds
of systemic problems and eventually, if bad enough, it can
cause death. So anaerobic respiration can only be a temporary
band aid to meet short term energy needs. But goldfish
and close relatives like the Krucian carp have an amazing
(44:12):
adaptation for making anaerobic respiration more tolerable in the long term.
And that adaptation is their bodies have evolved a process
for making the waste product of oxygen free respiration ethanol
instead of lactic acid. So these fish are fermenting alcohol
(44:32):
in their muscles. Oh wow. Yeah, So the alcohol produced
by anaerobic respiration and carp is purged from the fish
into the surrounding water through the gills. But that doesn't
mean there's no build up. And according to what I
was reading, goldfish that spin to winter season frozen under
ice that they're going to be swimming or floating at
(44:54):
least in very low oxygen waters, and they might have
a rather high blood alcohol concentration, so they survive the
winter but spend most of the time in a sense drunk.
Speaker 2 (45:05):
Okay, all right.
Speaker 3 (45:07):
Weber describes how researchers discovered that in these goldfish, tissues
all over the body, including crucial organs like the brain
and the heart rely on forms of anaerobic respiration. When necessary,
the brain and the heart use what's called a classic glycolysis,
and they do produce these negative byproducts. But like excess
(45:29):
lactic acid or lactate from the brain and heart and
other tissues is transported to the muscles, where they thought
it was for further transformed into alcohol and CO two.
And then so the body transports the excess alcohol to
the gills where it gets essentially breathed out into the water.
(45:50):
You might think, which is funny, because this is a
new variation on like beer breath. Is literally the way
that the body is purging. The byproduct of its respiration
is spitting alcohol out into the water. And Weber wrights
a funny observation tied in with unrelated psychology research in
(46:10):
the nineteen sixties and seventies. I'm just going to read
from Weber here quote. Interestingly, psychologists studying the effects of
alcohol on behavior had been using the goldfish as a
model vertebrate for years before this discovery. They had noticed
that it equilibrates ethanol and bourbon particularly quickly between the
(46:33):
external medium medium and the central nervous system, so it like,
you know, it distributes it throughout the tissues pretty quickly.
Resuming the quote, this characteristic had conveniently eliminated the need
for invasive measurements of alcohol levels directly within the brain
of the tested animals. So does that make sense? Like,
(46:53):
because the goldfish equilibrate here is the term they use.
It's like they could by controlling the amount of alcohol
in the medium, they could pretty finely tune the amount
of alcohol in the goldfish.
Speaker 2 (47:05):
Yes, okay, see what you're saying.
Speaker 3 (47:08):
Yeah. Also funny that when you test the effects of
a human drug like alcohol and a wild animal, you
just kind of assume that the wild animal is like
a pristine laboratory in itself, Like, there's no reason to
believe a goldfish would be an experienced drinker. But in
a way it sort of is. It's not a drinker,
(47:28):
but a native participant in alcohol culture, a brewery unto itself.
Speaker 2 (47:34):
Wow, that is impressive. And again you just you would
normally expect this of the common, even boring goldfish that
it is, you know, an evolve career drinker there in
its little tank.
Speaker 3 (47:48):
So Weber describes an account of the original research by
Showbridge and Hochashka where they were testing goldfish in oxygen
deprived water tanks, and at one point, after the fish
had been in the tanks, I think it says for
twelve hours, Showbridge lean leaned over the tank and sniffed
the water and said, there is booze in here, which
(48:12):
makes me wonder has anybody ever tried to operate a
distillery based on the workhorse organism of goldfish instead of yeast,
Like that would not be efficient at all. Yeast are
much more efficient at producing alcohol. But it would be
a good gimmick, wouldn't it.
Speaker 2 (48:26):
You know? Yeah, yeah, I don't don't know how that
would affect the taste. Maybe this is just my mind
playing with the idea of fish swimming and future drinking alcohol.
Speaker 3 (48:38):
But I don't know, well, I don't know enough about
the distilling process actually, Like, so is the alcohol distilled
from to what extent our flavors from the original fermentation
medium brought through the distilling process, or is that something
that needs to be added back in in some way?
I don't actually.
Speaker 2 (48:56):
Don't know, but but you know, just the memories serves
there are certain either types or brands of beer that
have some sort of a fish product tied up in
the process.
Speaker 3 (49:07):
Right, really, Oh, I didn't know that.
Speaker 2 (49:09):
I believe that's right. If I'm really wrong on that,
we'll take this out. But if I'm remembering correctly, there's
at least some types of beer that are made with
some sort of a fish product.
Speaker 3 (49:22):
Oh, okay, but I assume that would be like a
flavoring of some kind, not that the alcohol in the beer.
Guy is probably still coming from yeast. Right, Okay, we
just looked it up. There is a fish product used
in beers, but I was correct that it is not
the fish or not the source of alcohol in any
beer that we know of. It's not the alcohol. It's
like an additive used for something about the color or.
Speaker 2 (49:43):
Clarity, yeah, clarifying the beer.
Speaker 3 (49:47):
So anyway, I wanted to note one more development about
the history of research on the ethanol production in goldfish.
There was a study in twenty seventeen that probed deeper
into the details of oxyatolerance in goldfish and crusion carp.
It was called extreme noxyatolerance incrusion carp and goldfish through
(50:08):
neofunctionalization of duplicated genes, creating a new ethanol producing pyrivate
decarboxalase pathway. This was by Figurnis at all published in
the Nature portfolio journal Scientific Reports, and the author is
begin by flagging the same things that we just talked
(50:28):
about that fish in the genus Carassius, such as the
crusion carp in the goldfish, can survive prolonged periods without
oxygen by using a metabolic pathway that results in the
end product of not lactic acid but alcohol, which is
easy to purge through the gills. And the question is
chemically and genetically how do they do that? I'm going
(50:50):
to read from the results portion of the abstract here
quote here we show that this has been made possible
by the evolution of a pyrivate decarboxalase analogous to that
in Brewers yeast and the first described invertebrates, in addition
to a specialized alcohol dehydrogenase. Whole genome duplication events have
(51:12):
provided additional gene copies of the pyrivate dehydrogenase multi enzyme
complex that have evolved into a pyrivate decarboxylase, while other
copies retained the essential function of the parent enzymes. We
reveal the key molecular substitution in duplicated pyrivate dehydrogenase genes
that underpins one of the most extreme hypoxic survival strategies
(51:36):
among vertebrates, and that is highly deleterious to humans. So
the gist of the finding is that these carp are
able to produce ethanol as the output of their cellular
respiration or metabolism because their muscles have these special metabolic
proteins that are activated in the absence of oxide. And
(52:00):
this adaptation, they speculate, may have come sometime around eight
million years ago, and they don't know that for sure,
but they think it happened possibly around that time when
an ancestor of the goldfish and the Crucian carp underwent
a type of evolutionary accident called a whole genome duplication event. Essentially,
(52:21):
that's when an organism's genetic information makes an entire copy
of itself and then is passed on, so the genome doubles,
the genetic information doubles, and this allowed the formation of
parallel pathways for metabolism to evolve, and one of the
two pathways created similar enzymes to those that brewers yeast
(52:45):
used to convert carbohydrates into ethanol, and so I was
reading some media about this and one of the authors
of this study, Michael Brenbrink, who's an evolutionary physiologist at
the University of Liverpool, was quoted in a press release
that accompanied the paper saying quote, during their time in
oxygen free water in ice covered ponds, which can last
(53:07):
for several months in their Northern European habitat, blood alcohol
concentrations in krusion carp can reach more than fifty milligrams
per one hundred milliliters, which is above the drink drive
limit in these countries. However, this is still a much
better situation than filling up with lactic acid, which is
the metabolic end product for other vertebrates including humans, when
(53:30):
devoid of oxygen. So the fish, it's you know, it's
not biologically good for the fish to get drunk, but
it's better than it's better than the alternative, better than
the lactic acid.
Speaker 2 (53:42):
And to be clear, I think in no European country
that I'm aware of is a fish legally allowed to
drive an automobile.
Speaker 3 (53:50):
So I don't know, I haven't surveyed the law.
Speaker 2 (53:52):
Drunk or not know they are not allowed to drive automobiles.
Speaker 3 (53:58):
We should, we should invite the legal department into this
discussion you can see if they can advise. But anyway,
I thought that was really interesting, especially in that you
get a sort of convergent evolution in a way like
that these fish are arriving at some of the same
enzymatic processes that actually a fungus uses that Brewers used
(54:20):
to uses to make to you know, process sugars and
make ethanol. That the fish arrived essentially at the same
enzymatic pathway or a very similar one.
Speaker 2 (54:30):
Yeah, it's quite a superpower. And and again, you know,
the toughness of these organisms is key as well to
their domestication. Like human domestication is quite a process, and
it certainly it is certainly beneficial to the organism involved
(54:51):
if it is tough enough to survive that domestication. You know,
the creatures that have been domesticated tend to be pretty
pretty robust, at least in the beginning, until they've turned
completely into pugs or what have you. Pugs are tough
in their own way. I don't want to be too
hard on tugs. Yeah, they've survived. Just look at them.
They've been through a lot that they're still here.
Speaker 3 (55:12):
Okay, does that wrap things up for part one.
Speaker 2 (55:15):
Yes, but we'll be back in part two. We're going
to get more into the Koi fish properly. We may
come back with some additional information about the goldfish that
we didn't have time for here. But yeah, we'll be
back in part two. And in the meantime, go ahead
and write in. We'd love to hear from you. By
the time this comes out, we will have already recorded
part two. But if nothing else, this is something we
(55:38):
can get into in further episodes of Listener Mail. It's right,
all right. Well, just a reminder to everyone out there
that Stuff to Blow Your Mind is primarily a science
and culture podcast with core episodes on Tuesdays and Thursdays.
Those are the main fish tanks. We have a smaller
fish tank on Wednesday for short form episodes, and then
we have a we have a different sort of fish
(55:58):
tank on Fridays. That's where Weird House Cinema lives. That's
our time to just set aside most serious concerns, just
talk about a weird movie.
Speaker 3 (56:05):
That's the day we look in the fish tank with
that that fish that mister Burns created.
Speaker 2 (56:10):
Yeah it's the three Eyes.
Speaker 3 (56:11):
Yes, all right, huge, Thanks as always to our excellent
audio producer JJ Posway. If you would like to get
in touch with us with feedback on this episode or
any other one, if you would like to suggest a
topic for us to cover in the future, or if
you would just like to say hi, get in touch,
you know, talk to us about whatever. You can email
us at contact at Stuff to Blow your Mind dot com.
Speaker 1 (56:41):
Stuff to Blow Your Mind is production of iHeartRadio. For
more podcasts from my Heart Radio, visit the iHeartRadio app,
Apple Podcasts, or wherever you listen to your favorite shows.
Speaker 2 (57:00):
Sist with Ratatatator
Welcome to Stuff to Blow Your Mind production of iHeartRadio.
Speaker 2 (00:13):
Hey, welcome to Stuff to Blow Your Mind.
Speaker 3 (00:14):
My name is Robert Lamb, and I'm Joe McCormick.
Speaker 2 (00:17):
And in today's episode and the episode to follow, we're
going to be getting into the topic of golden fishes,
specifically varieties of carp that have been historically selectively bred
to produce brightly colored fish golden fish even, but colors
that are not limited just to gold or yellows, oranges
(00:40):
and so forth, as well as some less bright colors
as well. But basically this process by which humans have
turned wildfish into almost swimming jewels to delight the eye
and perhaps inspire the imagination. However, I do have to
(01:02):
stress that for a lot of us, we might not
find the goldfish all that awe inspiring. I don't know
about you, Joe, but I certainly was exposed to the
goldfish pretty early on, like a lot of kids. I've
seen goldfish my whole life. I had a goldfish at
some point. I've seen them carried around, doomed to a
(01:26):
lonesome death and tiny plastic bags by children who perhaps
won them at a fair or just bought them at
a store without a lot of forethought. So I don't know,
like I have, I have mixed feelings about the goldfish
and maybe less respect for their beauty because of these
experiences with them.
Speaker 3 (01:48):
For a few years, when I was in elementary school,
my family had a relatively small freshwater aquarium that I
really liked. I would just, you know, I would watch
it like team. I would just sit there and look
at it. I don't think we ever had any goldfish
that I recall. We got a variety of fishes from
(02:08):
a little little fish store in town. I still remember
where that place was. It no longer exists. But the
thing that I was really interested in was there was
a tiny type of frog, like aquatic frog that had
little little legs that would swim around in the tank.
I never thought since I grew up to look up
what that was, but yeah, some kind of little, little,
(02:32):
little bitty frog that would swim around, and I thought
that was really cool. But yeah, I guess it never
struck me as strange that we didn't bother to put
any goldfish in our aquarium, but we didn't. I do
think I had some friends who had goldfish. One friend
of mine had a goldfish actually now that I remember
in a like your classic setup sort of the coin
(02:54):
shaped tank on the table. That is, it's not even
a tank really, it's like a you know, a jar
that would put marbles in. But a fish was living
in there. I'm sure the fish was not not too
happy to be in such such a small space.
Speaker 1 (03:06):
Yeah.
Speaker 2 (03:07):
I was to chatting with my wife about this, and
I knew that when she was a kid, they often
had you know, aquariums and pets around and and uh.
And I asked ask her, well, dude, y'all had a goldfish, right,
and she was like, no, no, we never had a goldfish.
Like there was this this prevailing understanding that goldfish were
not happy and so they never they never got one.
(03:29):
But but for me, it's like I just grew up
thinking like this was sort of the default mundane fish,
which is crazy considering you know, we'll get into it
even a bit in this episode. I think that the
history of the goldfish, uh, and there were times when
it was definitely not a common fish. If you were
a commoner, it was illegal to have one.
Speaker 3 (03:48):
Uh.
Speaker 2 (03:48):
These were the fish of royalty. These were uh, these
were again little gems, but they become they became so
mundane and so every day for a lot of us
that we just didn't even see them as interesting fish.
You were more in you didn't have the goldfish, but
you were interested in the frog. We had the goldfish.
I was more interested in the little sucker cleaner organisms
(04:08):
that would feed on the sides of the tank, and
the goldfish I kind of just took for granted. I
didn't even really question, like, why is it golden like this?
What's what's the purpose of its coloration? And you know,
and honestly never even gave it a lot of a
lot of respect as an organism. But as we'll get into,
(04:29):
there are a lot of fascinating things about the goldfish,
things that that play into their history of domestication and
artificial selection, but also just their their their natural gifts
as an organism.
Speaker 3 (04:42):
Yeah, so it's interesting how that the goldfish, in being
both historically and visually in some ways remarkable but also
culturally extremely commonplace, is kind of a it encapsulates something
about the broader family of fish, is that it belongs
to the carp family, which is both in some ways
(05:05):
very remarkable. They're interesting and unique things about the carp family,
but it's also very commonplace. It is, I believe the
most are one of the most diverse and numerous of
all vertebrate taxa.
Speaker 2 (05:20):
Yeah. Yeah, And in fact, if we had just called
this episode stuff to blow your mind carp, I don't know,
some of you might be morbidly interested with some of
you might be like, no, thank you, I don't need
to know about carp. What's more every day than a
carp You're wrong.
Speaker 3 (05:34):
There's some weird, cool carp stuff.
Speaker 2 (05:36):
We're here. Absolutely is the other side of the golden
fish coin. Of course, the koi, and this is another
fish that will you will find a lot of places.
And in fact, my wife's family had at least one
koi fish. They had like a small koi pond growing up,
and I imagine a number of you out there listening
(05:58):
do as well. I've never never can up to koi,
but h and I also encountered them for the first time.
I think later on in life encountered or noticed them.
It's possible they were pointed out to me as a
child and I was like, yeah, whatever, I'm thinking about
Ninja's or something instead. But but much later on, you know,
I got to to visit some really remarkable koi ponds,
and some you know, generally and there they're in garden environments,
(06:21):
so there's a lot going on to sort of captivate you.
I got to see some really impressive coi pons in
both China and Japan, and and for that reason, I
think I have perhaps an unfair tendency to see the
koi as something special and sort of like a true gem,
some sort of a wild, magical creature, whereas I again
(06:44):
I'm I'm probably unfairly dismissive of the goldfish, but there's
I do find a lot of serenity in the koi.
Like the koi, I guess they feel more wild, even
if when they are inherently captive in some sort of
a pond environment, because there's often there's often a way
with you know, some sort of a decorative pond where
(07:05):
you at least create the illusion of wildness. Whereas the aquarium,
even a very nice aquarium, one that is very well
capped and the animals are happy, there is still that
boxing in of the environment that can feel more like
a complete domination of the thing.
Speaker 3 (07:21):
Yeah, yeah, I know what you mean.
Speaker 2 (07:23):
But as we'll discuss, like there is there is a
fair amount of domination in play when it comes to
the goldfish, less domination maybe with the koi, and a
lot of that is going to have to do with
how old these selected breeds are.
Speaker 3 (07:37):
So earlier, you said something alluding to the fact that
the gold the goldness of or the orangeness of a
goldfish or a koyfish, is in some way a trait
that is not entirely natural to the species from which
these are derived, that this is a selectively bred or
encouraged trait.
Speaker 2 (07:57):
Yeah. So in general, as we'll discuss, like, are these
are fish that have been that have been selectively bred
in a way to enhance, to encourage and enhance certain features,
especially coloration, And so on one hand, you can look
at a goldfish in particular and you can say, well,
that we did that, We made that happen. That is
(08:20):
not something that belongs in nature. This is maybe something
more akin to alchemy and the turning of lead into gold.
And and you know, I think it is fair to
say that when it comes to selective breeding, it can
feel a bit like alchemy at times, like when you
compare say a pug and a Great Dane, and you
remind yourself these this is the same species. These are
(08:41):
both domestic dogs. They can technically mate with each other.
These are the same the same thing, but they don't
feel like the same thing at all. Or you can
compare broccoli and cabbage and they don't feel at all
like the same species.
Speaker 3 (08:57):
You know, we sort dog breeds by temperament, but we
do withchrciferous vegetables.
Speaker 2 (09:03):
But get I think one interesting thing to go ahead
and get out of the way, is just that the
idea that Okay, yes, these are examples where we have
bred the creature to enhance a certain color, for example,
but that doesn't mean that gold doesn't have a place
in the natural world. For varying reasons, you do encounter
creatures that feature gold or something like gold in general
(09:27):
in these episodes when we talk about something being gold,
and we also might just be talking about them being
orangeur yellow, or what have you. And that could be
due in general across various animal species to pigmentation but
also to like physical characteristics that are creating this impression
of color.
Speaker 3 (09:47):
Okay, they're in the gold zone.
Speaker 2 (09:50):
Yeah yeah, yeah, for some reason, they're in the gold
zone when human eyes look upon them. And of course
we love it when that happens, and there's a but
there are a number of like real, you know, serious
reasons for this colorization in different organisms. For instance, we
see sexual dimorphism in play, you know, where the coloration
(10:12):
on the male is important for for mate selection and breeding.
Like with the golden pheasant. If you've ever had a
chance to see a golden pheasant, say it a zoo
or some sort of avery. Uh. They these are impressive birds.
The male sport brilliant looking gold, orange and yellow colors.
There's some black in there as well, extremely eye catching,
(10:35):
and that is by you know, design, They are trying
to catch the eye of their perspective mate some other
There are plenty of other examples out there. There's a
golden tortoise beetle. This is a species of beetle capable
of changing its color colorization, with some individuals taking on
a shiny metallic gold appearance via structural color change. And indeed,
(11:00):
if you look up in images and descriptions of these,
they can look rather unreal. They can. I've seen them
described often is sometimes looking like drops of gold, like
very metallic looking. But it's going to vary depending on
species or the individual in the species, and well, I
(11:20):
don't think we have all the answers on exactly like
why they do it. It seems like the main ideas
have to do with the fact that the change may
help males attract mates, and it might also aid in
predation deterrence, kind of getting into the sort of prevailing
logic that brightly colored organisms are often trying to, especially
(11:41):
smaller organisms like insects, are trying to send a message
to say, hey, I'm here and I'm loud, that it
might be a bad idea to eat me. You might
not like it, and if you don't like it, I
want you to remember that you didn't like but yeah,
Like another example, you can think to the world of
pot and dart frogs, where you have multiple brightly colored
(12:04):
you know, very obvious to the eyes species, and there
is a golden poison dart frog as well, and as
with other poison dart frogs, this is a warning to
potential predators, you know, and you know saying hey, you
probably shouldn't shouldn't eat me, you might not like what
you eat. And then we also have to remember we've
talked about this before. Is that so often when we're
(12:26):
considering the coloration of an animal, we're taking it outside
of the context of their natural habitat. And so there
are various examples of organisms that are to some degree golden,
where if you place them in their natural habitat in
the places where they're trying to be hidden, they are
actually hidden. For example, there's the Asian golden cat, which
(12:47):
to be clear, isn't like super brightly colored gold, but
still gold enough for humans to call them such. And
then you have things like the leopard as well, where
you know, outside of the context of their environment, this
may look like a very loud old design. Like if
you and I were to wear like leopard print shirts
for our recording here, which I do think is a
(13:07):
great idea, especially if we match, you know, it would
be sending an outlandish signal like we're definitely trying to
stick out. But the leopard is has that coloration as
part of its camouflage, So within context of its environment, that's.
Speaker 3 (13:23):
Stealthy, right, because the leopard is not against a gray
mate background. Yeah, so in its environment the colors it
has make sense.
Speaker 2 (13:42):
Now coming back more specifically, took the goldfish and to
the koi, as I believe we've stated already. These are
both karp. The goldfish species is Caressius aratus, and koi
is a domesticated form of either of the the amor
carp that's Cyprnous roberfuscus or the common carp, which is
(14:08):
Soprinus carpio. And in either case we're talking we're talking
about carp, but we're talking about two different carp species
that have been altered through domestication. However, while the koi
retains the same species as its wild counterpart, the goldfish
is granted its own species and has arguably, and this
(14:29):
is the point, this is a point of some disagreement
among experts undergo gone speciation, probably from the Crucian carp,
though I don't think this is completely settled either.
Speaker 3 (14:41):
Some of the studies that I've been looking at and
that I'm going to talk about later in this episode
talk about the goldfish and the Crusian carp as different species,
so they are generally regarded as such, but yeah, they're
thought of as at least close relatives, if not or
at least close relatives or sharing a very recent common ancestor.
Speaker 2 (15:04):
Yeah, yeah, it can. It can honestly get a little
confusing researching it, at least for me. But I guess
one of the things with taxonomy is you have to
realize that at some point somebody just sort of calls it,
and then there can still be a fair amount of disagreement,
change and correction on that particular call later on. So
(15:24):
there have been there have been some changes, for example,
regarding how we look at the goldfish over the course
of it of its history and taxonomy. And again, as
we'll discuss, the cultivation of the goldfish goes back to
over a thousand years ago. On the cooi is a
much more recent creation. So both are examples of human
(15:44):
breeders artificially selecting for desired features, especially color in carp species,
to produce fish that are maximally pleasing to the human eye. Now,
one question I think a lot of people might have
at this point is where does the gold come from?
Has to be there somewhere in the wild organism, uh,
you know, it's not created out of nothing. There has
(16:07):
to be some sort of trait that is then seen, admired,
and then encouraged through selective selective breeding. Right, And so
to really get into that, we have to sort of
talk about the history of this kind of selective breeding,
and in fact, the history of aquaculture the basically the
fish based alternative to agriculture, and this is this alone
(16:33):
is a pretty fascinating topic looking at just for how
long human beings have realized that they could master to
some degree an aquatic environment or various aquatic organisms and
and and use them in the same way that that
within agriculture we've used various plant species.
Speaker 3 (16:51):
Right now, I would assume that we were that humans
have been catching and eating wildfish much longer than they
have been farming fish, just in the same way that
hunter gatherers. You know, we're gathering and eating wild plants
long before they were actually like planting crops and growing
them themselves.
Speaker 2 (17:11):
Right, right, And unluckily we do have a lot of
historical writings about it. I was reading there's a twenty
twenty five Forbes article by Scott Traver's titled the Incredible
Tale of How the Common carp evolved into the thousand
dollars COI. And in this the author mentions, for example,
that the Romans certainly practiced cultivation of the Eurasian carp,
(17:36):
plenty of the elder rights of other fish being raised
on Roman estates. So on one level, it certainly goes
back as far as the Romans, but it goes much
further back than that. In general, the domestication of different species,
different fish species, it originates multiple times, different examples of aquaculture,
(17:57):
emerging between at least three thousand, five hundred and two thousand,
five hundred BCE, originating at least twice in China and
North Africa. However, I've also seen arguments that the Chinese
carp cultivation may go back as far as six thousand BCE.
This according to Nakajima at All in twenty nineteen's Common
(18:20):
Carp Aquaculture and Neolithic China dates back eight thousand years.
This was published in Nature, Ecology and Evolution. So Chinese
aquaculture certainly goes back a long time, no matter how
you you know what findings you're presenting here integrated with
rice farming and the earliest surviving Chinese text on the subject,
Treatise on Fish Breeding, was written by Fan Lie around
(18:43):
four seventy five BCE. This is also known as the
Fish Breeding Classic. There's a on top of this, there's
just a lot of There are also later texts that
deal with this and in general, there's a lot of
rich lore associated with different carp species in China, And
in the next episode I might pull out one or
(19:04):
two of these tales if they feel particularly insightful for
our topic here, but a lot of them hinge on
the idea that a carp is sustaining, it's a source
of nourishment, and so it can end up taking on
this this air of you know, of auspicious symbolism, and
it can even become a vehicle of divine ascension. So
(19:25):
there are tales of fishermen ascending into heaven on winged
talking carp that they've caught.
Speaker 3 (19:32):
Wait a minute, does this connect to that that myth
we've talked about before of like the carp leaping over
the say, leaping over the waterfall or leaping over the
rainbow something like, oh.
Speaker 2 (19:42):
You know, yeah, yeah, I think you're I think you're right.
I guess one of the things about it. On one hand,
there's like the cart specific aspect of this, but then
I guess we also have to acknowledge across all human experience.
There's something about the gamble of fishing, and maybe it's
little different than the gamble of the hunt, right there's
(20:03):
a certain amount of you know, certainly skill and knowing
your environment and knowing the species you're after, but there's
also kind of a roll of the dice, right, so
there's a sense of the divine when you actually do
hook that really nice fish that is going to sustain
you and allow you to live the next uh, you know,
through the next meal time.
Speaker 3 (20:22):
Yeah. Yeah, I wonder to what extent hunters and fishers
would agree with this point of view, But I guess
I've always thought of a major difference being that, certainly
in the archaic context, I've thought of hunting as a
more athletic activity, one that you know, is related to
the humans speed and strength in some way, though obviously
(20:44):
you know, strategy and coordination or a big part of
it too, and of course your tools. But that fishing
is a more pure game of chess with the environment
that it it's because you're not having to like chase
down the fish by running faster or you know, or
throw something harder to hit it. That it is all
(21:04):
Maybe not all, because now I'm thinking about spearfishing and
stuff too, So I guess I'm really I'm going back
on what I was saying originally but maybe my naive
point of view originally was that fishing is the slightly
less less of the jock art of sourcing protein from
the environment. It's more of the nerdy sort of chess
with the environment, trying to understand what this water source is,
(21:27):
what lives at, what part of it, and how to
attract it and things like that.
Speaker 2 (21:31):
I think there is often something in fishing where we
are casting something into an unseen world or world that
we see much less off. And again that's not going
to apply to every instance of fishing. Certainly there's spearfishing
and you know, fishing that is done underwater while one
is diving.
Speaker 3 (21:51):
And so forth.
Speaker 2 (21:51):
But yeah, I suspect that there's something to this. Again,
we'd love to hear from many fisher people out there
who would like to chime in.
Speaker 3 (22:00):
Yeah.
Speaker 2 (22:01):
Well, eventually, one of course, sees the spread of these
different aquaculture traditions and aquaculture species out of Europe and
into other areas, out of China, out of North Africa.
You know, I don't want to get too bogged down
with discussions of hoo did it first or indeed exactly
how far back these practices go, but we can at
(22:21):
least state that for a very long time humans have
known how to manipulate certain fish populations for their own benefit,
most mostly for food. I mean, that's the key reason,
far ahead of any ideas we might develop about encouraging
different colors. We knew that fish were a reliable source
of protein, and if we you know, we certainly can
(22:43):
figure out how to catch them in the wild. But
then what if you can control the wild itself, well,
then that gives you an even bigger advantage when it
comes to hooking one. So multiple different carp species were
prized by the Chinese, and among these you encounter different
color colorizations. But with both the common carp as well
as the Prussian carp and the Crucian carp, you encounter
(23:07):
a certain degree in the variation of exact color. A
dull gold is often described in the wild, but depending
on the genetics, even wild specimens can take on a
more pronounced color palette, you know, with brighter colors. So
I think one really key factor here concerning these various
carved species, and this is something that really surprised me.
(23:29):
This is also something that's very much in play with
the common goldfish that you might encounter the pet store
is that they have chromatophores. These are in fact, they
have different types of chromatophors that control dark and light colorization.
And to be clear, you know, we're not talking about
that level of color chains that you see with something
(23:50):
like a cuddlefish where it is like actively psychedelic, but
they can produce lighter or darker shades based on a
number of factors including diet, water temperature, and exposure to light.
I believe this is actually something that experienced and knowledgeable
goldfish keepers know is that you want to make sure
that your fish gets plenty of light because this helps
(24:13):
keep your fish bright and golden. And in general, this
adaptation is thought to provide camouflage in their natural environment.
So you know, there's like a mirroring or shimmering quality
of fish scales that can aid in both communication with
other fish and throw off would be predators. That's something
that you encounter with this fish in general, that's not
(24:36):
specific to carp or goldfish. And then this can also
get into like countershading and so forth, just something that
can visually throw off a potential predator. So the presentation
of a golden fish in general is a combination of
selectively breeding to encourage inherently brighter or more human desired colors,
(24:58):
while also providing optimal artificial conditions to encourage the most
desired color performance via those chromatophores. So you know, it's
more than one thing going on. There so many different
ways to manipulate your fish into looking pretty.
Speaker 3 (25:24):
Well. Would you like to talk about goldfish doing something
potentially a little more ghastly?
Speaker 2 (25:29):
Oh? Yes, I think we do need to make people
fear the goldfish a little bit. Give let's put a
little more respect on them.
Speaker 3 (25:36):
There's nothing to fear in reality, it's certainly given the
size difference between a human and a goldfish. But so
I wanted to think about the fact that, Rob, would
you agree people are generally not afraid of goldfish bites?
Speaker 2 (25:51):
This is not a concern, right, I've never this is
the first time I've even entertained the possibility, right, Like,
It's the kind of thing generally you're concerned about the
fish as well being, not the people that are interacting
with it.
Speaker 3 (26:04):
And I'm not trying to convince anybody otherwise. It is
totally reasonable to not be afraid of goldfish bites, because
if you look at the mouth of a goldfish, it
looks very harmless. You will see no teeth at all,
just a kind of smooth, flexible ring of soft looking flesh,
often opening and closing slowly as if blowing kisses. You know,
(26:26):
it's a very sweet, inoffensive, harmless little mouth. And actually,
by the way, that opening and closing of the mouth
repeatedly is part of a life sustaining activity that lots
of fish use called buckle pumping, in which the fish
repeatedly sucks in mouthfuls of water so that the water
can be passed over the gills for oxygen, but also
(26:49):
so that little bits of food that get pulled in
can be captured and swallowed. So the outer jaw of
a goldfish is indeed adapted for sucking, not for chewing,
and not for biting, and carp like goldfish are generally
said to have toothless jaws, okay, and yet a curious
(27:09):
piece of evidence occasionally makes one wonder about the about
the toothless mouth of the goldfish. People who keep goldfish
occasionally report finding on the floor of the aquarium tank
little white calcified as stones objects that really really look
(27:30):
like tiny teeth and rob i have some pictures in
the outline for you to look at here. What is it?
What do you think you're looking at?
Speaker 2 (27:38):
Well, I'm certainly primed to see these as teeth now,
But if I were to be skeptical and trying to
come up with another explanation, I would think, well, maybe
this is either something else that the animal is producing,
be it some sort of like flaky scales or something
that it is excruding, or this something else in the
(28:01):
aquarium environment.
Speaker 3 (28:02):
You know, right, Well, if you got pebbles at the
bottom of the varium tank, you know, they might just
blend in. A goldfish might spit out some of these
and you'd never even notice.
Speaker 2 (28:10):
Yeah, or somebody's messing with you. Someone is you have
a pranks during in your midst and they're dropping tiny
teeth every day just to throw you.
Speaker 3 (28:17):
Off, right, Who keeps putting teeth in my tank? Yeah?
So the question is are they teeth? And if so,
how can a toothless fish be losing teeth? The answer is, yes,
they are teeth, and yes they come from the goldfish.
The goldfish does have teeth, but not in its mouth.
Speaker 2 (28:39):
All Right, I'm okay, I'm unsettled. Let's find out more so.
Speaker 3 (28:43):
Fish in the carp family generally have these smooth outer
jaws that are used for sucking in water and bits
of material, not for chewing, But the carp can chew
with what's referred to as for ingeal teeth. This has
come up on the show before. It's been a while,
(29:03):
but the way it works is further back in the
goldfish's throat, maybe about as far back as the gills
or a little bit further. The goldfish or the carp
generally is equipped with blunt, molar like teeth mounted on
the pharyngeal bones, which the fish uses to chew up
(29:24):
whatever plant matter, little invertebrates, other tough foods. It chews
them by sucking them into the mouth, taking them back
into the throat, and then grinding the food the bits
of food with these teeth against a hard plate on
the roof of the throat cavity. These pharyngeal teeth are
(29:45):
sort of like in many ways, they're not like this,
but in some ways are like a shark's teeth, specifically
in throughout the fish's life, at various points they fall
out and are replaced by new teeth that grow in
so keepers of various carp species like goldfish occasionally find
(30:06):
these lost teeth scattered on the floor of the tank.
Speaker 2 (30:10):
All right, so there, and to a certain extent, they're
little xenomorphs, and we were generally not even giving them
credit for this.
Speaker 3 (30:16):
A little bit now there there is a distinction to
be made here because we've talked about pharyngeal jaws before
that there are some in nature that are much more
like the xenomorph in the movie. For example, the jaws
of the Moray eel, which there really is in the
Moray eel, is like a second mouth inside the mouth,
the second set of jaws that you know, reaches out
(30:38):
and snatches with the jaws that come out from the throat.
The goldfish or the carp are not like that. What
you're talking about here is not a second set of jaws.
It is again teeth mounted on bones in the throat
that can chew, but they don't like reach out and snatch.
Speaker 2 (30:53):
Does that make a throat that choose which which I
think also sounds pretty monstrous.
Speaker 3 (30:57):
The throat that choose right sore. Still no reason to
be afraid of goldfish bites. If a goldfish nibbles on
you with the outer jaws. It's nothing. It feels like
a little tickle or kind of a barely perceptible little
bit of suction. It's cute, frankly, But if you were
small enough and managed to get sucked into a goldfish's
mouth and down the throat, then you would absolutely be
(31:21):
in for a world of hurt.
Speaker 2 (31:22):
Oh wow. Yeah, And in general, if you become that
small you have a lot of problems on your hand.
But certainly make sure it doesn't happen while you're peering
over the top of the goldfish bowl.
Speaker 3 (31:33):
Actually, I mean it's a never ending mental exercise that
if you were small enough, nearly every cute animal becomes monstrous. Yeah,
your cat would eat you. Your cat would eat you
in a second.
Speaker 2 (31:45):
Absolutely. Let's see a little more about the goldfish here.
I want to give a little more historical background here.
And I was reading a little bit about this in
The Evolutionary Origin and Domestication History of Goldfish by chin
at All, published in PNAS in twenty twenty, and this
(32:05):
gets into a lot of genetic data, but they also
provide just a nice overview of the known history of goldfish,
and they cite the Chrustian carp origins of the goldfish,
and point out that the appearance of red scales on
normally gray or silver carp was first discovered or phillleast
first recorded during the Chinese Gin dynasty two sixty five
(32:27):
through four to twenty CE, and then during the Tang
dynasty six eighteen through nine oh seven CE, goldfish with
preferred phenotypes were selected for ornamental ponds and water gardens,
and then during the Song dynasty nine to sixty through
twelve seventy nine CE, the gold or yellow variety of
goldfish became the symbol of the imperial family. And this
(32:49):
is the time during which the goldfish was considered a
royal fish and it was not for commoners to raise them.
They were forbidden to raise them. Again, very different from today,
where everybody can pretty much get a goldfish. There's nobody's
going to ask for your royal bloodline before you purchase
one in a bag up at a local fair for
(33:10):
you know, like a quarter. But but yeah, there was
a time when they were there. There was a lot
of elitism in owning a goldfish. But any rate, everybody
loves the idea of a golden fish. The seventeenth century
saw the introduction of the goldfish into Europe and into
Japan and then eventually to America around eighteen fifty. Now,
(33:32):
in any way you cut it, we're talking about a
good millennium of folks messing with goldfish, a thousand years
of domestication. And the authors point out that since the
fish produces, any given fish can produce thousands of eggs,
and dozens of these fish can be raised in the
same pond, So that means that a millennium of goldfish
(33:53):
domestication has produced quote strong artificial selection. Charles Darwin even
fixated on them for this reason, as did English biologist
William Bateson and Chinese genetic researcher Shisan ci Chen, who
worked a lot on the topic of goldfish genetics. So
(34:14):
the other interesting thing here is when we're talking about
a thousand years of domestication messing with the goldfish, you
may be far more aware of this. If you're aware
of this, if you are a goldfish person, or if
you spend a lot of times a lot of time
going to aquariums and local aquarium stores. But it's impacted
far more than just their color. It's changed their body shape,
(34:35):
their finn configuration, their eyestyle and color. And this is
why goldfish have served as a great genetic model system
for studying fish physiology and evolution, and it has also
resulted in so many different varieties of goldfish. They fall
into some very you know, just broad categories include like
(34:58):
long bodied goldfish, double tailed, or fancy goldfish, egg shaped,
dorsal finned, dorsal finless, just to name a few, without
even getting into the variety of colors where you know,
you may have reds, yellows, blacks, oranges, gray's whites, browns,
and blues. As with domesticated dog species, you would be
(35:20):
hard you know, you'd be hard pressed to necessarily identify
these as the same species. Looking at some of these
different goldfish varieties, Yeah, I mean, like one is kind
of like a like a like a more like egg shaped,
like golden fish. Another one is you know, longer and
(35:40):
like blue and black. I mean, they just don't look
like they should be the same species.
Speaker 3 (35:44):
What's the one I've seen that has the bulbous eyes
that are pointing up?
Speaker 2 (35:49):
Do you know what I'm talking I forget what they're
called offhand, but yeah, like there's like that is one
type of goldfish you'll see with like the enormous bulging
eyes where they look like some sort of a shock
cartoon character. But it is the you know, it's technically
the same species as this other sort of slimmer goldfish,
the kind of goldfish that might look more like the
logo for a business, that sort of thing, you know,
(36:11):
where it's it's less, I don't know, less goofy looking
in some way.
Speaker 3 (36:25):
Well, Rob, if you're ready, I wanted to talk about
a particular specific deep dive on goldfish biology that I
did that has to do with their tolerance for anoxic conditions.
Are you ready for if we do that? Yeah?
Speaker 2 (36:40):
Absolutely, this is this is really fascinating, and I think
is this is one of the early things that I
stumbled upon where I was like, oh, yeah, goldfish, they
do deserve a closer look.
Speaker 3 (36:51):
So, the goldfish is a very hardy fish. It can
survive across a large range of temperatures. It can eat
many different kinds of food, It can tolerate murky and
turbid waters. Turbid meaning like cloudy water with a lot
of sediments suspended in it. It can just do well
in a lot of different circumstances. And that has made
(37:13):
it a fish that's fairly easy to spread, of course
around the world, also can make it an invasive fish
sometimes because it's so easily adaptable and can do well
in all kinds of waters and in a fairly unique way.
One of the ways that it's hardy is that can
it can even tolerate anoxic conditions, meaning it is specially
(37:35):
evolved to survive being deprived of oxygen. I was reading
about this in a column written for the Journal of
Experimental Biology by biologist de Jean Michelle Weber, formerly of
the University of Ottawa, called Revealing How Goldfish Defy Anoxia.
This column was from the year twenty sixteen, and this
(37:56):
was not new research at the time it was published.
It was a review column about previous discoveries about respiration
and fish. So all vertebrate animals ultimately at some point
need oxygen to survive. Many vertebrates will die within minutes
if they can't get it, and this need for oxygen
(38:17):
is also true of animals that live underwater. These underwater
animals use organs like gills to extract dissolved oxygen from
the water so they can breathe. And I do want
to note something because I used to have this misconception.
This misconception, fish and other aquatic animals do not, as
(38:37):
I assumed when I was a kid, break apart the
water molecules and harvest the oxygen from the H two
O itself. The water molecules stay intact. Instead. The reality
is that liquid water usually contains some quantity of pure
oxygen gas or O two dissolved within it. So healthy
(39:00):
water for fish usually has somewhere between six and eight
parts per million of dissolved two. But of course the
amount of dissolved oxygen in water can fluctuate a lot,
and when for any number of reasons, the oxygen levels
in the water get too low, aquatic vertebrates can't breathe,
(39:20):
and this is often the explanation when you see dead
zones in the water. If you come across a place
in the water with huge masses of fish and other
creatures floating belly up in the same area, often what
happened is they were suffocated by oxygen poor water. But
despite the fact that vertebrates all ultimately need oxygen to live,
(39:43):
there are a few special water dwelling vertebrates which research
shows can survive days or in a few cases if
conditions are right, even weeks or months without oxygen, and
those longer time scales. Usually what that depends on is
very cold conditions, you know, that are slowing down the
(40:05):
metabolism greatly and putting these animals into a state of torpor.
But still some animals can survive days, weeks, or even
months without oxygen. So this small club of anoxyotolerant animals includes,
according to Weber, two species of turtle and several fish
in the carp family, and one of those carp species
(40:27):
is the goldfish Carassius aratus. Weber discusses how it had
been known for many decades that some species of carp
could survive for extended periods in water that was deprived
of oxygen. Goldfish and their wild relatives, the Crucian carp,
can often survive actually four months over wintertime in the
(40:50):
low oxygen waters that are trapped beneath a frozen pond,
and amazingly, by the nineteen seventies, researchers had found that
these carp could still produce a high output of CO
two even when living in water that had very little
oxygen in it. In other words, you might say, in
(41:10):
a metabolic sense. They were breathing out when there was
almost nothing to breathe in, So how would that be possible?
Weber points to a fascinating discovery specifically in goldfish in
the year nineteen eighty, published by two researchers named Eric
Showbridge and Peter Hochochka. They found that the goldfish quote
(41:34):
tolerates a prolonged, normally lethal lack of oxygen by using
large glycogen stores to generate ethanol as a byproduct of
energy metabolism. So, ethanol is alcohol. It's the normal, regular
kind of alcohol, the kind you're probably most familiar with,
the kind that's in beer, wine and whiskey. So what
(41:56):
does producing alcohol in the body have to do with
b being able to survive without oxygen? I'll explain so again,
all vertebrate animals normally rely on oxygen for the chemical
reactions that drive metabolism, which allow our cells to keep living.
So the simplified version of this reaction is oxygen combines
(42:19):
with the carbohydrate glucose, which we ultimately get from food,
providing energy for cells in the form of the compounded
adenozine triphosphate or ATP, and then this reaction so it
produces the ATP that the cells need, and it releases
the byproduct of carbon dioxide and water. Our bodies purge
(42:40):
excess carbon dioxide by exhaling, and this is the normal
process that we use when oxygen is plentiful. When our
cells are deprived of oxygen, they fall back on a
secondary process called anaerobic respiration respiration without oxygen. Under this process,
our cells still break down glucose and turn it into
(43:03):
cellular energy, but they do so with much less efficiency,
so there's less energy output and they spit out a
product called lactic acid. Anaerobic respiration only works as a
temporary stop gap in times of need, most often during
extreme physical exertion. Now, under normal circumstances, a bit of
(43:27):
lactic acid build up in the body is okay if
you can get the oxygen you need, because over time
the liver can convert the lactic acid back into glucose.
But if you're not able to get enough rest and oxygen,
the unrelieved buildup of lactic acid leads to a condition
again known as lactic acidosis, in which the body's overall
(43:50):
pH becomes too low, and this can cause all kinds
of systemic problems and eventually, if bad enough, it can
cause death. So anaerobic respiration can only be a temporary
band aid to meet short term energy needs. But goldfish
and close relatives like the Krucian carp have an amazing
(44:12):
adaptation for making anaerobic respiration more tolerable in the long term.
And that adaptation is their bodies have evolved a process
for making the waste product of oxygen free respiration ethanol
instead of lactic acid. So these fish are fermenting alcohol
(44:32):
in their muscles. Oh wow. Yeah, So the alcohol produced
by anaerobic respiration and carp is purged from the fish
into the surrounding water through the gills. But that doesn't
mean there's no build up. And according to what I
was reading, goldfish that spin to winter season frozen under
ice that they're going to be swimming or floating at
(44:54):
least in very low oxygen waters, and they might have
a rather high blood alcohol concentration, so they survive the
winter but spend most of the time in a sense drunk.
Speaker 2 (45:05):
Okay, all right.
Speaker 3 (45:07):
Weber describes how researchers discovered that in these goldfish, tissues
all over the body, including crucial organs like the brain
and the heart rely on forms of anaerobic respiration. When necessary,
the brain and the heart use what's called a classic glycolysis,
and they do produce these negative byproducts. But like excess
(45:29):
lactic acid or lactate from the brain and heart and
other tissues is transported to the muscles, where they thought
it was for further transformed into alcohol and CO two.
And then so the body transports the excess alcohol to
the gills where it gets essentially breathed out into the water.
(45:50):
You might think, which is funny, because this is a
new variation on like beer breath. Is literally the way
that the body is purging. The byproduct of its respiration
is spitting alcohol out into the water. And Weber wrights
a funny observation tied in with unrelated psychology research in
(46:10):
the nineteen sixties and seventies. I'm just going to read
from Weber here quote. Interestingly, psychologists studying the effects of
alcohol on behavior had been using the goldfish as a
model vertebrate for years before this discovery. They had noticed
that it equilibrates ethanol and bourbon particularly quickly between the
(46:33):
external medium medium and the central nervous system, so it like,
you know, it distributes it throughout the tissues pretty quickly.
Resuming the quote, this characteristic had conveniently eliminated the need
for invasive measurements of alcohol levels directly within the brain
of the tested animals. So does that make sense? Like,
(46:53):
because the goldfish equilibrate here is the term they use.
It's like they could by controlling the amount of alcohol
in the medium, they could pretty finely tune the amount
of alcohol in the goldfish.
Speaker 2 (47:05):
Yes, okay, see what you're saying.
Speaker 3 (47:08):
Yeah. Also funny that when you test the effects of
a human drug like alcohol and a wild animal, you
just kind of assume that the wild animal is like
a pristine laboratory in itself, Like, there's no reason to
believe a goldfish would be an experienced drinker. But in
a way it sort of is. It's not a drinker,
(47:28):
but a native participant in alcohol culture, a brewery unto itself.
Speaker 2 (47:34):
Wow, that is impressive. And again you just you would
normally expect this of the common, even boring goldfish that
it is, you know, an evolve career drinker there in
its little tank.
Speaker 3 (47:48):
So Weber describes an account of the original research by
Showbridge and Hochashka where they were testing goldfish in oxygen
deprived water tanks, and at one point, after the fish
had been in the tanks, I think it says for
twelve hours, Showbridge lean leaned over the tank and sniffed
the water and said, there is booze in here, which
(48:12):
makes me wonder has anybody ever tried to operate a
distillery based on the workhorse organism of goldfish instead of yeast,
Like that would not be efficient at all. Yeast are
much more efficient at producing alcohol. But it would be
a good gimmick, wouldn't it.
Speaker 2 (48:26):
You know? Yeah, yeah, I don't don't know how that
would affect the taste. Maybe this is just my mind
playing with the idea of fish swimming and future drinking alcohol.
Speaker 3 (48:38):
But I don't know, well, I don't know enough about
the distilling process actually, Like, so is the alcohol distilled
from to what extent our flavors from the original fermentation
medium brought through the distilling process, or is that something
that needs to be added back in in some way?
I don't actually.
Speaker 2 (48:56):
Don't know, but but you know, just the memories serves
there are certain either types or brands of beer that
have some sort of a fish product tied up in
the process.
Speaker 3 (49:07):
Right, really, Oh, I didn't know that.
Speaker 2 (49:09):
I believe that's right. If I'm really wrong on that,
we'll take this out. But if I'm remembering correctly, there's
at least some types of beer that are made with
some sort of a fish product.
Speaker 3 (49:22):
Oh, okay, but I assume that would be like a
flavoring of some kind, not that the alcohol in the beer.
Guy is probably still coming from yeast. Right, Okay, we
just looked it up. There is a fish product used
in beers, but I was correct that it is not
the fish or not the source of alcohol in any
beer that we know of. It's not the alcohol. It's
like an additive used for something about the color or.
Speaker 2 (49:43):
Clarity, yeah, clarifying the beer.
Speaker 3 (49:47):
So anyway, I wanted to note one more development about
the history of research on the ethanol production in goldfish.
There was a study in twenty seventeen that probed deeper
into the details of oxyatolerance in goldfish and crusion carp.
It was called extreme noxyatolerance incrusion carp and goldfish through
(50:08):
neofunctionalization of duplicated genes, creating a new ethanol producing pyrivate
decarboxalase pathway. This was by Figurnis at all published in
the Nature portfolio journal Scientific Reports, and the author is
begin by flagging the same things that we just talked
(50:28):
about that fish in the genus Carassius, such as the
crusion carp in the goldfish, can survive prolonged periods without
oxygen by using a metabolic pathway that results in the
end product of not lactic acid but alcohol, which is
easy to purge through the gills. And the question is
chemically and genetically how do they do that? I'm going
(50:50):
to read from the results portion of the abstract here
quote here we show that this has been made possible
by the evolution of a pyrivate decarboxalase analogous to that
in Brewers yeast and the first described invertebrates, in addition
to a specialized alcohol dehydrogenase. Whole genome duplication events have
(51:12):
provided additional gene copies of the pyrivate dehydrogenase multi enzyme
complex that have evolved into a pyrivate decarboxylase, while other
copies retained the essential function of the parent enzymes. We
reveal the key molecular substitution in duplicated pyrivate dehydrogenase genes
that underpins one of the most extreme hypoxic survival strategies
(51:36):
among vertebrates, and that is highly deleterious to humans. So
the gist of the finding is that these carp are
able to produce ethanol as the output of their cellular
respiration or metabolism because their muscles have these special metabolic
proteins that are activated in the absence of oxide. And
(52:00):
this adaptation, they speculate, may have come sometime around eight
million years ago, and they don't know that for sure,
but they think it happened possibly around that time when
an ancestor of the goldfish and the Crucian carp underwent
a type of evolutionary accident called a whole genome duplication event. Essentially,
(52:21):
that's when an organism's genetic information makes an entire copy
of itself and then is passed on, so the genome doubles,
the genetic information doubles, and this allowed the formation of
parallel pathways for metabolism to evolve, and one of the
two pathways created similar enzymes to those that brewers yeast
(52:45):
used to convert carbohydrates into ethanol, and so I was
reading some media about this and one of the authors
of this study, Michael Brenbrink, who's an evolutionary physiologist at
the University of Liverpool, was quoted in a press release
that accompanied the paper saying quote, during their time in
oxygen free water in ice covered ponds, which can last
(53:07):
for several months in their Northern European habitat, blood alcohol
concentrations in krusion carp can reach more than fifty milligrams
per one hundred milliliters, which is above the drink drive
limit in these countries. However, this is still a much
better situation than filling up with lactic acid, which is
the metabolic end product for other vertebrates including humans, when
(53:30):
devoid of oxygen. So the fish, it's you know, it's
not biologically good for the fish to get drunk, but
it's better than it's better than the alternative, better than
the lactic acid.
Speaker 2 (53:42):
And to be clear, I think in no European country
that I'm aware of is a fish legally allowed to
drive an automobile.
Speaker 3 (53:50):
So I don't know, I haven't surveyed the law.
Speaker 2 (53:52):
Drunk or not know they are not allowed to drive automobiles.
Speaker 3 (53:58):
We should, we should invite the legal department into this
discussion you can see if they can advise. But anyway,
I thought that was really interesting, especially in that you
get a sort of convergent evolution in a way like
that these fish are arriving at some of the same
enzymatic processes that actually a fungus uses that Brewers used
(54:20):
to uses to make to you know, process sugars and
make ethanol. That the fish arrived essentially at the same
enzymatic pathway or a very similar one.
Speaker 2 (54:30):
Yeah, it's quite a superpower. And and again, you know,
the toughness of these organisms is key as well to
their domestication. Like human domestication is quite a process, and
it certainly it is certainly beneficial to the organism involved
(54:51):
if it is tough enough to survive that domestication. You know,
the creatures that have been domesticated tend to be pretty
pretty robust, at least in the beginning, until they've turned
completely into pugs or what have you. Pugs are tough
in their own way. I don't want to be too
hard on tugs. Yeah, they've survived. Just look at them.
They've been through a lot that they're still here.
Speaker 3 (55:12):
Okay, does that wrap things up for part one.
Speaker 2 (55:15):
Yes, but we'll be back in part two. We're going
to get more into the Koi fish properly. We may
come back with some additional information about the goldfish that
we didn't have time for here. But yeah, we'll be
back in part two. And in the meantime, go ahead
and write in. We'd love to hear from you. By
the time this comes out, we will have already recorded
part two. But if nothing else, this is something we
(55:38):
can get into in further episodes of Listener Mail. It's right,
all right. Well, just a reminder to everyone out there
that Stuff to Blow Your Mind is primarily a science
and culture podcast with core episodes on Tuesdays and Thursdays.
Those are the main fish tanks. We have a smaller
fish tank on Wednesday for short form episodes, and then
we have a we have a different sort of fish
(55:58):
tank on Fridays. That's where Weird House Cinema lives. That's
our time to just set aside most serious concerns, just
talk about a weird movie.
Speaker 3 (56:05):
That's the day we look in the fish tank with
that that fish that mister Burns created.
Speaker 2 (56:10):
Yeah it's the three Eyes.
Speaker 3 (56:11):
Yes, all right, huge, Thanks as always to our excellent
audio producer JJ Posway. If you would like to get
in touch with us with feedback on this episode or
any other one, if you would like to suggest a
topic for us to cover in the future, or if
you would just like to say hi, get in touch,
you know, talk to us about whatever. You can email
us at contact at Stuff to Blow your Mind dot com.
Speaker 1 (56:41):
Stuff to Blow Your Mind is production of iHeartRadio. For
more podcasts from my Heart Radio, visit the iHeartRadio app,
Apple Podcasts, or wherever you listen to your favorite shows.
Speaker 2 (57:00):
Sist with Ratatatator
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