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May 21, 2024 57 mins

In this episode of Stuff to Blow Your Mind, Robert and Joe discuss the weird and wonderful parrotfish: changers of sex, poopers of sand and – if the myths and legends are true – great friends and a parent of fishes. 

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Speaker 1 (00:03):
Welcome to Stuff to Blow Your Mind production of iHeartRadio.

Speaker 2 (00:12):
Hey you welcome to Stuff to Blow your Mind.

Speaker 3 (00:14):
My name is Robert Lamb and I am Joe McCormick.
And today on the podcast, we're going to be beginning
a look at parrotfish or parrot fishes. This is one
of those topics that literally just started with me looking
at a picture. I was staring at a picture of
a bizarre, goofy, goofy appearing animal and thinking I want

(00:37):
to know more about this critter, and then discovering that, indeed,
this organism is a peculiar and fascinating story, and there
is so much more to it than you might guess
just by looking at it at its strange beak or
toothy mouth.

Speaker 2 (00:51):
Yeah, parrotfish are pretty fascinating. I've snorkeled among the parrotfish
many times and can a test that they are. They're
curiously fish, They're pleasure to watch, They're often very colorful.
So I'm going to throw in more of my observations
as we proceed. But I think, on the other hand,
in coral reef environments, where I've done most of my snorkeling,

(01:14):
and where a lot of snorkeling takes place. They can
actually be easy to take for granted because they're generally
around in significant numbers that these environments. Often these are
protected reefs that I've been to, they're not particularly shy,
They're easily found in shallow water, so you know, oftentimes
you're dealing with like reef environments that are either very

(01:36):
accessible just from the shore or just a very short
boat ride sort of a situation. So in a way,
it's easy to take them for granted because they're there,
you see them, and then you end up focusing a
lot more of your attention looking for some of the
harder to find organisms that are going to live in
these reef environments. So it's actually a great opportunity to

(01:57):
stop and focus on this remarkable fish that I honestly
had never really thought about devoting a whole episode or
series of episodes too. But there's more than enough to
talk about.

Speaker 3 (02:06):
I've never snorkeled and seen them in person, so I'm
envious of this experience and maybe I will someday. I
look forward to that. But I've seen video and in
some cases that there's almost a feeling of like bees
buzzing around a shrub that's covered in flowers. You know,
it's just kind of the general gentle grazing activity of

(02:27):
some animals surrounding a plant like structure, but in this
case it's the big skeleton of stony corals.

Speaker 2 (02:34):
Yeah, the grazing observation is key, and it's something that
has long been observed for these creatures, as we'll discuss.
You know, going back into ancient times, even when we
didn't have snorkelers as we think of them today, you
still had individuals fishing in shallow environments, sometimes fishing for
the parrotfish in question, and observing that, hey, these creatures

(02:56):
appear to be grazing, unlike most of the fish we
are observing.

Speaker 3 (03:01):
So parrotfish are not one species, but a larger group
of fish, containing about ninety something individual species. I've seen
different estimates on the numbers. I think it's older ones
that say maybe like eighty species, others say closer to
one hundred, but I think ninety something is about right.
They range broadly in terms of size and appearance. In fact,

(03:23):
they range broadly in terms of appearance even within a species,
as we'll get to maybe in this part or maybe later,
but some adult parrotfish are less than a foot in length,
and some of the largest are almost four feet or
about one point two meters in length, so they can
range from medium small to quite large. These fish are
sometimes taxonomized as a family called Scarid and in other

(03:48):
cases regarded as a subfamily of Labyridy, which are commonly
known as the rasses. I think you can see some
morphological similarities with the fish called rasses, kind of the
way they swim. These they're pectoral fins and stuff like that.
But a characteristic com into many parrotfishes is that they
tend to live around coral reefs, especially in the tropics.

Speaker 2 (04:11):
I also want to throw in there that there are
occasionally fish that are just sort of commonly called a
parrotfish or informally called a parrotfish, that are not parrotfish,
mainly the blood red parrot chick lid, which apparently is
a popular aquarium species. This is not actually related to
proper parrotfish that we're going to be talking about here today.

(04:32):
And I've also seen some some fossil evidence that is
sometimes categorized as a parrotfish in a way that I'm
not sure actually lines up with what we're talking about here.
But if you've seen a picture of a parrotfish, proper parrotfish, indeed,
go ahead and look one up if you're in a
position to do so. I think it's hard to miss

(04:53):
what we're talking about. These are very recognizable fish, though
again they do very greatly in coloration.

Speaker 3 (04:59):
Size, that's right, Yeah, So if you look up pictures
of them, you'll see that they're often kind of elongated
in body. They have different shapes. Some are more kind
of that elongated oval shape and others are blunter in
the front with like blunt heads. They're, in fact, are
parrotfish called like the blunt head pair of parrotfish or
the steep head parrotfish. The coloration you'll see on them

(05:22):
depends on some facts about them and not just their species.
But sometimes they have quite bright patterns of almost neon color,
surprising colors to see in nature, very you know, tropical
kind of color signals. There's one picture I kept seeing
where the fish had a color pattern that reminded me
of the jazz design from paper cups in the nineties.

(05:44):
But if you also threw some hot pink in there,
so there's a lot to take in when you look
at a parrot fish. But before you notice any of that,
but you know, the head shape, the body shape, the
coloration patterns, what you will probably notice first about any
given parrotfish is the mouth. I mean, look at these chompers,
rob I've included just several pictures. I know you've seen

(06:06):
them in person, so your experience of the teeth the
beak is probably more direct and visceral and profound even
than mine. But I was just looking at these pictures
for quite a while the other day, and my god,
these beaks, these mouths, it's it's incredible.

Speaker 2 (06:23):
Yeah. Yeah, their mouths are quite fascinating in some of
the photos. Yeah, they can actually look a little intimidating, though,
I would say, based on the species that I've primarily
been exposed to in Hawaii and the Caribbean, they tend
to look more silly than threatening. But they're definitely very

(06:44):
cool looking, not taking anything away from that.

Speaker 3 (06:46):
Yeah, So I guess it varies from species to species.
So parrotfish have these rows of fused teeth on the
outside of their jaws, which, in some cases, as the
name implies, look very very similar to the beak of
a parrot. It can look like a bird's beak, but
in other cases these fused rows of teeth look like

(07:07):
jagged monster jaws, sort of like a horseshoe shaped ceramic
saw blade. But in other cases still they are like
a big goofy cartoon overbite, like Alfred y Newman's mouth
got hit with the radiation from the amazing colossal Man.

Speaker 2 (07:24):
Now I want to throw in one more note here
about species classifications coloration. It is worth noting that with
parrotfish that classifications and naming have long proof challenging because
they tend to show different colorizations depending on an individual's
age and sex. So, for examples pointed out by the
Waikiki Aquarium, the spectacled parrotfish is reddish brown when it's

(07:49):
a juvenile, then it develops a pale tail spot when
it becomes a reproductive female, and then develops bright blue
green coloration with pink markings when it becomes male. So
you can imagine a lot of the early confusion at
figuring out, well, what is a different species of parrotfish?
And you will have multiple species of parrotfish in a
given region, and then what is just parrotfish are the

(08:12):
same species that's just in a different phase of its life.

Speaker 3 (08:15):
Cycle, that's right. In fact, I was even reading, like
some blog posts by marine biologists who had worked with
these animals firsthand, talking about just how difficult it was
sometimes to identify these fish because of all the variation
even within species. But to come back to the main attraction,
the teeth, the beaks. The crazy thing is, as much

(08:38):
as these look like biting teeth in some cases, in
reality they are scraping teeth. Because parrotfish are primarily herbivores
for the most part, they do not eat by swimming
around biting semi circular chunks out of other fish, as
you might imagine just looking at their mouths. They mostly

(08:58):
eat by grazing along the hard surfaces of coral reefs,
scraping away algae and soft bits of coral and other
bits of organic matter along with some hard bits of
the coral skeletons with their teeth. So that's what the
teeth are for. These are for grazing. These are the

(09:19):
life of a herbivore, not the life of a predator.

Speaker 2 (09:22):
Now, of course, as this we'll be discussing here, Coral,
of course is hard matter, and one of the crazy
things about snorkeling with parrotfish is that you don't just
get to watch them, you get to listen to them.
So as they feast on the algae that's growing on
the coral, they're scraping the coral and it's producing a
sound in the snorkeler's ear that I would compare to

(09:43):
kind of a static paper crunching or even the snap
crackle crunch of rice crispies and milk. It's one of
those things when when you first explore. When I first
experienced it, I wasn't exactly sure what I was listening to,
because it's kind of like, is there something in my
ear and it's just just the sound of the ocean
and so forth. But no, it it becomes clear, and

(10:04):
it's often pointed out to one that yeah, this is
the sound of these the parrotfish feeding, and yeah, it's
it's pretty remarkable. So you listen to them, you watch them,
and they just become part of the background sound escape
to your snortling.

Speaker 3 (10:19):
It's a funny other comparison to bees almost, you know,
the way the buzzing of a bee just kind of
like blends in becomes the ambient sound of a landscape.
The tooth and beak scraping on coral sound produced by
these animals is maybe comparable to the buzzing of bees.

Speaker 2 (10:36):
Yeah, and it's also consistent, like that's the other thing.
They're constantly grazing, and therefore it is a constant soundtrack.
It's not like say the occasional sound of a woodpecker
in a forest, Like it's just NonStop. So it's just
in the background, and you could easily if you didn't
know what you were listening to, you might not realize
that this is the sound of organisms feeding.

Speaker 3 (10:55):
Now, I think there were probably other people out there
like me, Rob. I don't know if you've fall into
this category of people whose minds are easily captured and
revolted by just imagining kind of tooth trauma. Like I
very easily can like get a shiver across my whole
body when I imagine, say, trying to bite down on
a rock. And that is what you have to constantly

(11:19):
imagine when you're thinking about these animals. It's not technically
a rock, though I guess in some cases they do
scrape rocks as well, but most often it's going to
be like a rock. It will be the skeletons of
stony corals. But can you just imagine that, as painful
as it might be, imagine having to live by like seeing,
you know, a moss covered rock and thinking, I'm going

(11:40):
to use my front teeth to scrape that bad boy clean,
and I'm going to bite off some chunks of the
rock as I'm getting the moss off of it. Delicious.

Speaker 2 (11:49):
Yeah, yeah, it can be a bit squeamish. It can
make one a bit squamish sometimes imagining these other dental
scenarios in the natural world.

Speaker 3 (11:58):
So I want to talk a bit more late or
about how parrotfish eat and get their nutrition, and a
bit more about their teeth. But before we do that, Rob,
I think you've found some interesting stuff about writings on
parrotfish from the ancient world.

Speaker 2 (12:10):
Yeah. I did. And this was a whole avenue that
I had not been down. I had no idea this
was a thing. So again, given that species of parrotfish
are found around the world, and that they can frequently
be found in shallow water, and that they have traditionally
been caught for culinary purposes for food, it should come

(12:33):
as no surprise that these fish were known to people
of the ancient world. You know, even in times when
folks didn't have access to the underwater world in any
way comparable to what we have today, they still knew
what these fish were, and in some cases they had
some rather insightful ideas about what they were doing. In

(12:54):
other cases, there are some very long standing misconceptions about
what parrotfish do. So in this we're going to actually
bring up the work of our dear old friend Roman
historian Plenty of the Elder, who is one of several
sources of antiquity that discusses the parrot fish, you know,
and of course there's a lot of shared content and

(13:15):
so forth going on. The fish would have been known
as the scaris. This is of course, now where we
get the name of the genus for parrotfish, and we
might assume that in particular we're dealing with discussions of
the Mediterranean parrotfish, though based on what I was reading,
also you had like the red sea parrotfish that was
also known to various cultures of antiquity. So Plenty of

(13:39):
the Elder in the Natural History seventy nine CE rites
at the present day the first place, and this is
he's speaking from a culinary perspective here. First place at
the Roman table is given to the scas the only
fish that is said to ruminate and to feed on grass,
and not on other fish commonly found in the Carpathian Sea,

(14:03):
and never of its own accord passes lectum a promontory
of trois now. Nineteenth century naturalist George Cuvier and his
annotations to Plenty points out again that the first place
here is in reference to the Roman dinner table, where
this fish was celebrated for several attributed characteristics that I'll

(14:25):
get to in a minute, and was also typically quote
salted with the intestines in it. M m okay, and
some Roman authors actually absolutely insisted that you do not
eat this fish without the intestines included. It's just too
delicious this way.

Speaker 3 (14:40):
Oh boy. So like, are you saying they would eat
the intestines directly or it's like you got to leave
the intestines in there to give the meat some flavor.

Speaker 2 (14:49):
You've got to leave them in Yeah, okay. And I
know they were often in many cultures salted and then traded,
So I'm offhand, I'm not entirely sure if this is
a deaf in case of we're talking about salted parrotfish
with the intestines still in, or some other form of
preparing them. But at any right, they really liked it.
There are also Roman references to eating parrotfish livers as.

Speaker 3 (15:13):
A delicacy, so all the value here is just for
their flesh as food. This is a first place distinction
that would probably not be so flattering to the fish itself.

Speaker 2 (15:24):
Right right, And the Romans weren't alone in appreciating eating parrotfishes.
We'll get to some other far flowing examples. Plenty of
humans have eaten parrotfish and still eat parrotfish. The Greeks
love them. There's some I think twenty species of Mediterranean parrotfish. Again,
there's the red sea parrotfish, considered a delicacy in antiquity.

(15:46):
And in both of these cases I believe they were
often dried and then widely traded. I've read that, in fact,
they were easily dried. I'm not sure about the particulars
of that, but but I I'll take the word on
it that, Okay, this is a fish that is easier
to dry and prepare and then trade across distances. You
don't have to eat it fresh by the seaside. Anyway,

(16:11):
it was celebrated at the Roman table, not just because
you ate it salted and with the guts in it,
but also for several reasons, according to Cuvier. And I
think a lot of these seem to get down to
the fact that I'm assuming the Romans liked a great
story at the table. You know, it's not just about
what the fish smells like, taste like, looks like on

(16:31):
the plate, but also what is the story of it,
what ideas are wrapped up in this particular organism. So
hear that first of all, it was thought to be
the only ruminating fish.

Speaker 3 (16:42):
So wait, does that mean ruminating as in like chewing
the cud like a cow or a sheep.

Speaker 2 (16:49):
Yes, though basically I think what this comes down. First
of all, they're not truly chewing the cut. They're not
truly ruminating, you know, they're not chewing something that is
previously been chewed and swallowed. They are grazing like a cow.
And I think it has to do with observations of
these animals grazing, and it's like, oh, look, they're like

(17:11):
a cow. They're ruminating. But still the idea that they're
ruminating the idea that they're chewing their cut continues to
be mentioned all through antiquity on all the way up
through like medieval besty areas, though some voices such as
Saint Ambrose in the fourth century said that did point
out the chud. The cud chewing thing is not accurate,

(17:32):
that's not what they're doing. So but still a lot
of misinformation about these fish persisted for a very long
time now. As Aristotle also observed in History of Animals,
the parrettfish were thought to be vegetarians, and indeed, I
guess you could say they're essentially herbivores. Many sources will

(17:52):
classify them as such, but also note that they're maybe
more more correct to say that they're algavores. But still, well,
ancient people observe that these fish are not eating in
the same way that other fish are.

Speaker 3 (18:05):
Wow, this is something I feel like I should know
the answer to, but I actually don't. What is it called?
If you mostly eat you know, algae or plant things
that are like plants, plants, or types of bacteria microorganisms,
but sometimes you eat animals, but the animals are not
like you know, large moving animals, they're you know, basically

(18:27):
small invertebrate animals like corals.

Speaker 2 (18:29):
Yeah, I guess you would be some sort of a
coral war or something to that effect, right, But on
a number of the different fish databases that I was
looking at, yeah, sometimes they'll say herbivore, sometimes they'll say
herbivore algivore, and then sometimes there's kind of an omnivore
note as well. I guess there's always a margin of error,
as we've discussed here, like even things like a cow,

(18:50):
which we think of is kind of a pure herbivore.
There are examples, as we've discussed on the show in
the past, where they have been observed to if meat
is available, they might eat set meat.

Speaker 3 (19:00):
But it is true that in the cases where parrotfish
are eating animals, they're not generally like chasing after other
fish and eating them or something. I don't know if
that might happen in some particular case, but that's not
generally what parrotfish do. They're mostly going to be eating algae,
and then if they're eating animals, they're like marine invertebrate animals.

Speaker 2 (19:21):
Yeah. So I mean we can, I think basically say
that ancient people were correct in this judgment. Now, and
I guess maybe it made the story at the dinner
table a little more interesting. They're like, this is the
cow of the sea, that sort of thing. Now, the
third attribute that Kuvia mentions is quote because it had
the faculty of producing a sound. Now, perhaps I'm not

(19:44):
completely understanding Kuvier's point here, but I guess this is
referring to that constant chewing sound, that constant grazing sound
that one hears if your head is below water with
the fish. And again, this is not something that I
would think actually impacts one's enjoyment of dinner. But again,
I guess they liked a good story.

Speaker 3 (20:05):
You know, sometimes people they say they want their steak
rare by saying I want it still mooing. It's a
kind of a gruesome way to ask for it, But
people do say that. Can you say that, like, I
want my parrotfish steak rare, I want it still scraping.

Speaker 2 (20:18):
I guess. So the fourth attribute that he mentions is
quote for its salacious propensities numbers being taken by means
of a female attached to a string. This, I guess
alluding to a supposed method of catching them. And I
suppose the Romans just like randy food, though I'm not
sure it was actually considered an afrodisiac, because I didn't

(20:38):
see it listed in another source I was looking at
that had to do with various foods of the Romans
did believe were aphrodisiacs.

Speaker 3 (20:45):
Uh huh okay.

Speaker 2 (20:46):
And then, fifthly for its quote remarkable sagacity and affording
assistance to another when taken in the net.

Speaker 3 (20:55):
Huh Now what would that mean?

Speaker 2 (20:57):
So this is referring to something that is that that
pops up in various old sources as well, and again
continues to persist for centuries. May be particularly referring to
a passage in Ovid. Ovid has the following passage quote,

(21:17):
The scaris is caught by a stratagem beneath the waves,
and at length dreads the bait. Fraught with treachery, it
dares not strike the osres. This refers to a reed
basket with an effort of its head, but turning away
as it loosens the twigs with frequent blows of its tail,
it makes its passage and escapes safely into the deep. Moreover,

(21:40):
if perchance any kind scars swimming behind sees it struggling
with the osures he takes hold of its tail in
his mouth and it is thus turned away and so
it makes its escape.

Speaker 3 (21:54):
So, okay, we have.

Speaker 2 (21:55):
This idea that these fish, these parrotfish are are essentially
I don't think you social would be the term, but
they are. They help each other out. They're capable of
some form of altruism where if they see another one
of their kind stuck in one of these wicker basket traps,
they will try and help them out.

Speaker 3 (22:17):
Huh.

Speaker 2 (22:18):
And so this idea ends up sticking around for against
centuries and centuries. The idea that the scarce or parrotfish
is not only a cud chewing herbivore of the sea,
but also a friendly fish that looks out for it's fellows.

Speaker 3 (22:32):
Well, that's fascinating, But I wonder what would this belief
about their friendly behavior be based on. So the idea
is they help each other avoid traps or save each
other from traps. Is there any modern research on this?

Speaker 2 (22:44):
So the main source I found on this, and this
is where I got turned onto the idea, was the
blog of Fishtories. It's like histories and fish combined. That's
fis ht o r I s dot net. It is
a blog maintained by Via hendricks On, information scientist and
historian of science. She discusses this whole weird scenario with

(23:07):
imagery of the parrotfish, because indeed there's there's there's imagery associated.
I included this illustration for here for you here Joe
from a munch latter later source. But uh, but but
she does point out that, based on what we can tell,
the fish are actually anything but friendly to each other
in these scenarios. Wicker baskets like this are still used

(23:30):
in some places to catch fish, she points out. But
she writes that the parrotfish have actually been observed too
violently attacked their fellow parrotfish that become caught in the
reeds of the fishing basket. So I don't I don't
know that there's really much evidence to back this up.
I also get to an example here in a bit

(23:52):
involving traditional Hawaiian techniques for catching parrotfish that also uses
a basket. Like the idea of being essentially that the
parrotfisher roaming around the corals feeding and they kind of
have these paths that they follow. They also tend to
sort of group together, and you may have like what

(24:12):
seems to be a leader of the pack, and if
you set up these baskets at the right time, you
can catch them, and you can end up catching a
bunch of them even and you can then release the
ones you don't want, make use of the ones you
want to harvest. So I don't know. On one level,
it seems like, Okay, you're ending up with an artificial
environment scenario here, where you're dealing essentially with captive fish

(24:36):
doing things in a captive environment and a high stakes
environment for them that they might not do otherwise. And
that may mean attacking each other that I guess could
also mean some sort of observational behavior, especially without the
aid of any kind of like snorkeling mask and so forth,
it might look like ones helping the others out. I'm

(24:57):
not sure, But still the idea becomes entrent, and the
image of the parrotfish helping each other escape from fishing
baskets ends up becoming a symbol of friendship. Oh yeah,
So this is something that she discusses at length in
another paper. This is something that published in Emblems of
the Natural World from twenty fifteen Ichthyology and Emblematics in

(25:22):
Conrad Gesner's Historia Piscium and Joham Kamarius's Kamarus the Youngers
Simbola at Emblemata. She points out that Plenty was one
of the key sources for this misconception, but plenty of
others sources in the ancient world echoed at Plutarch chimes
in on it, and so some sources identified this as

(25:45):
a sign of intelligence in the parrotfish, while other fishes
were often held up as examples of a lack of
intelligence in fish, such as then Conrad Guestner's sixteenth century
work Historia Animalium, the mackerel was held up as a
stupid fish.

Speaker 3 (26:02):
How do you get that distinction as a fish? I
don't know.

Speaker 2 (26:04):
I mean, maybe they just it's probably a little bit unfair,
right in some cases the macvil looks to and you're
basing everything on the human perspective and human expectations of
what an animal's intelligence is, you know, whereas ultimately you
can I think you can approach these scenarios by saying, well,
the yeah, the parrotfish is in a way a genius.
It's as smart as it needs to be to do
the things that it does.

Speaker 3 (26:25):
Well. Actually, you know what I wonder if some of
this I have no idea if it applies in this case,
but I wonder if some general ideas about smartfish versus
dumbfish come just from the experience of fishing for different
types of fish, because I know, you know, and people
who are into fishing right in and let us know

(26:46):
if this matches your experience. In my experience, people who
like to fish will like say that a fish that
is harder to catch is a smart fish, and one
that's easier to catches like a dumbfish. And I don't
know if intelligence actually has anything to do with how
easy they are to catch or not. You know, might
just have to do with like ingrained behavioral patterns, someone

(27:08):
responding distress or something.

Speaker 2 (27:10):
Yeah, yeah, And it's kind of curious because it sounds
like if you have the right traps for it, catching
parrotfish is generally not considered super challenging. So but you know,
we have this other narrative that emerges again that they're
helping each other and that they can sort of help
each other escape from these traps and so forth. Now

(27:41):
I mentioned Hawaiian traditions because again, you have parrotfish all
over and you do have them in the Hawaiian Islands,
and in Hawaii, the parrotfish was historically known in the
Hawaiian language as uhu. The fish are prominent there and
they were eaten by Hawaiians Traditionally. There's a saying in Hawaiian,

(28:02):
according to the online Hawaiian dictionary Ulucal, that translates to
my craving makes my mouth water for the parrotfish passing
before my eyes. The Hawaii Coral Reef Network points out
that not only were they a delicacy, but their liver
was especially favored. So again, you know, you know, other
side of the world you still have people eating parrotfish

(28:24):
and also realizing that the liver is apparently really good.
Interesting now, the fish itself, to the Hawaiians, had connotations
of physical beauty, as in one's love interest, but also
in terms of a desirable bachelor. There was also apparently
a tradition that held that a fisherman could observe the
behavior of a parrotfish and it would serve as a
kind of portent as to what was going on back home.

(28:46):
So like, you know, certain things the parrotfish was doing.
It's like, okay, everything's cool. Back of the house. Other
things the parrotfish might be doing. It's like you need
to go back and check on your wife, that sort
of thing. Now, the parrotfish who also factors into one
of the stories of a legendary figure in Hawaiian mythology.
And I could not find a like a solid pronunciation

(29:09):
guide for this name, So I hope I'm saying it
somewhere close to correctly. In my apologies if I'm not
punia kaya. This is a in these stories, he's a
He's a dashing young man who one day leaves his parents'
house because he feels this call of the ocean. He
wants to go fishing, and so he catches this young,
supernatural fish the first ooh, and it makes it his pet,

(29:34):
and then he releases it where it becomes the parent
of all fish. And so afterwards he's able to go
call upon the fish to deliver fellow fish to the fisherman.

Speaker 3 (29:44):
Hmmm.

Speaker 2 (29:44):
Yeah, I was reading more about this in Native Use
of Fish in Hawaii by Margaret Titcomb, and the author
makes a connection to the manner in which parrotfish move
along in a school, often single file, seemingly led by
a leader. So that, yeah, this special trap was devised
by the early Hawaiians for use during a particular season.

(30:05):
The trap allowed them to allow the fish to file
into the trap led by the leader, but then they're
unable to escape, and they keep the trap in use
during the May June July season, collect enough fish for
personal use, and then release the rest, though another source
I've looked at seems to indicate that excess fish might
have been harvested to feed pigs and dogs, So I

(30:25):
don't know. There may be some variety in the practice,
or there might be a misconception on one side or
the other, but at any rate, this is how they
caught them, and I guess by virtue of that leader
fish leads into this idea that there's kind of like
a fish that is a friend of the people that
will help you catch more.

Speaker 3 (30:45):
Fish, Like it's the leader of the school is deliberately
leading them into the trap for you.

Speaker 2 (30:51):
Yeah, though not so much that it's like a trader fish,
but more than like it is this fish that a
like a legendary figure made a deal that's sort of yeah.
So yeah, this was a new one to me as well.
I don't think i'd heard this in my previous trips
to Way, so and there may be some more interesting
parafish mythologies out there that I'll have to turn up

(31:13):
for the next episode.

Speaker 3 (31:15):
That's really interesting. I like it. As I promised earlier,
I wanted to come back and talk a bit more
about how parrotfish eat and a little bit about the
equipment they used to do it and what happens after
they do it, after they eat. So one source I
was looking at here is a chapter in the Biology

(31:36):
of parrot Fishes by CRC Press twenty eighteen. And this
chapter was by Peter C. Wainwright and Samantha A. Price.
It's called Innovation and Diversity of the Feeding Mechanism in
parrot Fishes. And I'll probably come back to this in
subsequent episodes as well. But about the authors, Peter C.
Wainwright is a biologist at UC Davis and Samantha A.
Price is a biologist at Clemson. And so the author

(31:59):
is here say that how parrotfishes eat. To the various
species of parrotfish, how they eat is quote one of
the fundamental ecological processes in coral reef ecosystems. So when
you think about parrotfish, you shouldn't just think of them
as something you occasionally see in a coral reef, but

(32:20):
rather they are an integral part of how coral reef
ecosystems work, and kind of the whole ecosystem doesn't really
work without them. Now, as we mentioned earlier, the feeding
process of parrotfish involves a lot of scraping and biting
into hard stony materials. Parrotfishes swim around coral reefs using

(32:42):
their teeth to scrape edible stuff off the outside of coral,
and they break off some coral and bring it along
with them in the process. Now, what is that edible
stuff on the outside of the coral. The authors say
that it includes primarily algae. Algae is a big part,
but also detritis, and in a marine context this usually

(33:04):
means dead organic material, so parts of dead organisms, fecal matter,
all that yummy stuff. Sometimes it will include bacteria, little
colonies of bacteria. And then they just say, quote a
wide range of encrusting invertebrates, so all kinds of little
invertebrate animals that could be found on a coral reef.

(33:25):
This might include coral polyps themselves, and it might also
include things like sponges. Now, a couple of sources I
was looking at sort of classified several different types of
parrotfish feeding strategies, and the main variation here seemed to
be how deep the parrotfish would cut into the stony
parts of the coral. So you might have some that

(33:47):
are referred to more as browsers or grazers that tend
to typically just take the soft parts off the surface
of the coral. You've got scrapers which scrape the coral
a little harder and get some of what underneath. And
then you've got what are called excavators, which are really
just taking chunks out of the hard stuff. So the
parrotfishes swim along on the reef, scraping the stuff off

(34:10):
with their outer teeth or excavating bits of it and
inevitably leaving scars on the rock or the coral skeletons
as they go. And then all of this mixture of
both hard and soft parts goes into the mouth, where
it is subjected to a second obstacle, which is the
trial of the inner jaws. Because parrotfishes don't only have

(34:33):
these fascinating outer teeth, they have a second set of
teeth at the back of their mouth. Known as the
phyryngeal jaw. Now you might have read about phyngeal jaws
with respect to other animals that have them. A number
of fish and creatures that live in the sea have them,
and a well known example is the more eel.

Speaker 2 (34:54):
That's right, Yeah, And of course, you know, those of
you who've watched any amount of science fiction, you might
also note that very angel jaws from in the world
of fictional monsters, we do have, of course, the alien xenomorph,
at least the main morph of the creature that we
see in those films where we see this inner jaw

(35:14):
that functions as both a feeding mechanism and a puncturing weapon,
while elsewhere in the alien universe we see other morphs,
such as the deacon and the neo morph that boast
extendable inner jaws rather than a secondary set of jaws.
But yeah, the generally you often see some like comparative
biology write ups, and I think I've done right up

(35:35):
to this in this nature in the past where when
you're you're comparing xenomorph physiology to the natural world. The
more a eel is like a prime stopping point of comparison.

Speaker 3 (35:47):
Now, the exact design of the phyngeal jaw in the
xenomorph is a little bit extra like. I'm not aware
of any examples in the in the natural world where
like the inner jaw comes out of the mouth and
stabs like a spear, like bites through the torso of
a prey animal. The inner jaws in the cases I'm
aware of, tend to stay mostly within the outer jaws,

(36:09):
but they do do something fascinating and perhaps to some horrifying.
So in the case of the more a eel, which
is a predator, the fyringial jaw helps the eel capture
and swallow large live prey animals without allowing them to escape.
So the eel first bites the prey with its regular
outer jaws. These are the jaws you'd see, you know,

(36:31):
with the teeth. They have backward curving teeth, and those
the orientation of the teeth. The backward curving nature of
them helps them keep the prey in place without allowing
it to back out and escape. And then while the
eel is holding the prey in place with these outer jaws,
the inner jaws reach up from out of the eel's

(36:52):
throat to bite the animal and pull it further inside
the mouth and down into the esophagus. So it's a
two step capture and conveyance mechanism. Now, just to stick
with the morey eel in a sidebar for a second.
I got interested in this. The evolutionary reasoning for this
is an interesting question. Apparently, most predatory fish rely in

(37:15):
large part on suction to capture and swallow their prey.
So these other fish use their muscles to rapidly expand
the mouth through the throat cavity. And so when it
expands like this, it creates a negative pressure and it
sucks in water from outside the mouth, including the prey
in that water. And this suction mechanism can either be

(37:39):
the action that pulls the prey into the mouth in
the first place, or can also be that after a
predatory fish bites the prey with its jaws, the suction
mechanism then pulls the prey farther into the mouth and
down into the esophagus.

Speaker 2 (37:53):
Yeah, scorpionfish is a great example of this, and you
can find some great video footage of this where it's
an ambush press down there, hidden on the floor of
the sea, and then as its prey comes by, it
just kind of goes wolf and just rapidly sucks it
into its mouth and it's just gone like that, and
the scorpion fish is of course you'll note get very

(38:14):
robust looking, kind of frog ish looking, and that is
key here too, right.

Speaker 3 (38:20):
So I was reading a two thousand and seven National
Science Foundation press release about research on moray eels published
in Nature that year, and the studies lead author, a
UC Davis scientist named Rita Meta, says that her study
found because of the way more eel bodies are shaped,
they're not able to generate much suction in the mouth cavity,

(38:44):
so instead they have this secondary set of jaws in
the throat. More eels are predators that often live in
coral reefs and they hide in little holes, gaps and
niches in the reef, and so a possible reason given
for this evolutionary difference why they have the fryngial jaws
instead of the suction mechanism is that by having pharyngeal jaws,

(39:07):
they can attack and swallow relatively large prey in tight,
confined little spaces where there would not be enough room
for them to expand the mouth or throat cavity to
create suction.

Speaker 2 (39:19):
Fascinating. It makes perfect sense.

Speaker 3 (39:22):
So that's an interesting idea. But I also think it's
an interesting parallel. You've got more eels and parrotfishes, which
are both coral reef dwellers and both have fryngial jaws,
but they use these inner jaws for totally different purposes. Again,
in the eel, it's to pull the prey down the
throat once it's in the mouth. Parrot fishes are again

(39:43):
not generally going to be chasing large live prey. They're
mostly herbivores, and they eat by scraping or gouging the
coral and getting stuff off the outside or in the
layers underneath the surface. This material that they scrape off
of rocks and coral, which mostly inclin ludes, algae and
other microbial organisms, but also dead organic matter and coral

(40:05):
skeleton bits, is pulled down into the pharyngeal teeth, where,
to quote Wainwright and Price, it is quote mixed with
mucus and ground to a fine slurry before being passed
to the intestines. And Rob I was just looking up
some photos of parrotfish pharyngeal teeth, and oh boy, what

(40:25):
what are we looking at?

Speaker 2 (40:27):
Here.

Speaker 3 (40:28):
These are some organs, like they're clearly specialized for grinding
down this mixture of hard and soft substances into a mucous,
lubricated slurry. But some of these pieces of parrotfish anatomy
look like a car transmission gear made out of bone.
Others look like a bone pine cone. It's it's interesting.

Speaker 2 (40:50):
Yeah, yeah, yeah, it does kind of look like interlocking
gear teeth. Yeah, it's crazy.

Speaker 3 (40:56):
So the digestive system extracts nutrients from this lurry, and
then the parrotfish excretes what is left over, which is
a big part of which is sand. Because they're grinding
down this coral, they bite off and scrape off pieces
of coral, grind up that coral with the nightmare throat teeth,
and then they poop sand. So I've read it described

(41:19):
that if you swim around with these buddies, you will
see them just like letting out kind of poofs of
sand or blasting clouds of sand into the water column.

Speaker 2 (41:29):
Yeah. Absolutely, yeah, Like they're just they're kind of constantly
doing it. I mean, it makes sense. They're grazing. They're
kind of like goats, and they're kind of pooping like goats.
Except it's coming out in this kind of like puff
of sand, and I know you included some photos here
where it's like more than a puff. It looks like
they're crop dusting. It's quite impressive.

Speaker 3 (41:50):
In fact, parrotfish poop so much sand. They are by
themselves a significant source of the bioeroosion of coral and
a significant source of fine grained white sand in certain environments,
as in, when you are walking along a beautiful white
sand beach on some tropical island, there is a very

(42:13):
good chance a large proportion of the sand under your
feet is parrotfish poop.

Speaker 2 (42:19):
That's right. There beach creation machines, and some of the
estimates for individual sand creation are quite stunning.

Speaker 3 (42:26):
Unbelievable to me actually, Like I had no idea about
this going in. So you might be thinking, yeah, how
much sand can can these fish really poop? Again, it
depends where you are. There are obviously other sand creation
mechanisms in the sea, so this is not the only one.
But in some places parrotfish are responsible for a lot
of the sand that's there. One example I came across

(42:47):
is a paper in the journal Geology from twenty fifteen
by pariet Al called linking reef ecology to island building.
Parrotfish identified as major producers for island building sediment in them.
And so again this is by Perry at All and
so the Maldives Archipelago. This is an island chain that

(43:07):
contains approximately twelve hundred individual reef islands, which are islands
that are made entirely out of sediment that is produced
from underwater coral reefs. So the primary reason these islands
exist is that there are coral reef ecosystems on an
underwater platform. Of course, the reefs themselves are mostly made

(43:28):
up of the calcium carbonate skeletons of stony coral polyps,
and over time these coral reefs decompose into sediments like
sand and gravel. Perry at all right quote, All coral
reef islands are inherently dependent on their surrounding reef habitats,
not only because they provide the foundations for island development,

(43:49):
but also because they are the primary production sites for
the sediments necessary to sustain island building growth and maintenance.
So without sediments from the coral reefs dec composing into
sand and gravel, you may not have an island here.
But the authors of this study say, before their research,
how exactly that sediment is produced from the coral reef

(44:11):
is poorly quantified, so they investigated they're looking at where
does the sediment come from, and they used the example
of Karu, which is an interior reef island in the Maldives.
They found that the area around this island produces about
six hundred and eighty five thousand kilograms of sediment per year,

(44:31):
about seventy five percent of which comes from a place
they called the outer reef flat. So if you look
at the island from above, you'll see the part that
rises above water and is forested and has plants and
all that, the beach surrounding it, and then there's sort
of an inner lagoon and then an inner reef ring
and an outer reef ring. So most of the sediment

(44:53):
is coming from that outer ring of coral reef environments
in the water. About seventy five percent of the sediment
comes from the outer reef flat. Now, within that outer reef,
which creates about seventy five percent of the island's yearly
supply of new sand, the authors discovered that more than
eighty five percent of the sand is produced by parrotfish.

(45:16):
And if you're curious what the second place was, the
runner up producer of reef sand in a distant second
place at about eight point eight percent. In the outer
reef is a type of macroalgy called halimata, which makes
like calcified body parts and then those get shed and
eventually decompose a breakdown into sand. But almost all of
it is coming from what the parrotfish excrete. So parrotfish

(45:40):
are continually defecating this island into existence, and they remain
critical for maintaining its existence the author's right quote. The
generation of sediments suitable for maintaining this reef island is
thus critically dependent on a narrow zone of high productivity reef,
but most especially on the maintenance of healthy parrotfish populations

(46:02):
that can convert reef framework to sand grade sediment, And
so the parrotfish are crucial for the health of island
environments like this. But this is not just true of
these tiny coral reef islands that are generated from coral
reef sediments, even on many other coasts and larger islands
where the island itself might be you know, have other

(46:23):
geological explanations like it's not just sand rising out of
the water. It might be a volcanic island, or the
coast of a continent or something. In places where there
are coral reefs, beaches in many cases are still largely
parrotfish lavatory constructions. A figure sighted in several reputable looking sources,
though I couldn't find the exact origin of it, is

(46:45):
that around seventy percent of the sand on the white
Sandy beaches of Hawaii is parrotfish excretion. It's hard to imagine,
like you're walking on a beach or even on a
whole island and to imagine it having a biological fish
digestive system origin of this kind.

Speaker 2 (47:05):
I know, it's it's just it's crazy. It's one of
those mind blowing facts though that again, it gets pointed
out a lot when you are, you know, going to
these places and snorkeling, it becomes easy to sort of
take for granted and you have to sort of remind yourself.
Then when you're walking on the beach, it's like, no,
for real, all the sand and it's still kind of
you know, beggars the imagination.

Speaker 3 (47:27):
Yeah. Now, another thing that's interesting is that, of course
we know now that parrot fishes are very important for
creating the sand that in some cases makes it possible
to have an island, and like these reef island environments

(47:49):
or helps replenish the beaches. But you might think, on
the other hand, well, the parrot fishes are the enemy
of the coral reefs though, because they're preying on, you know,
the coral, they're like scraping the coral. In fact, it
is thought that parrotfishes help protect coral reefs because as
they're going along taking bites out of the barrel coral reefs,

(48:11):
they might be leaving scars in them, biting pieces off,
taking chunks out. But by grazing in this way, they
prevent the reefs from becoming overgrown by things like algae
and other encrusting invertebrates like sponges and stuff. So they
may eat some coral as they munch along, but overall

(48:31):
they keep the coral reefs healthy.

Speaker 2 (48:34):
That's right. This is a very important fact concerning like
necessary conservation for parrotfish because and it goes beyond that too,
Like I was reading that by constantly eating algae off
the coral, again, they're they're constantly in doing this cleaning
the coral, creating new surfaces on the coral, and this
is where baby corals can attach and grow, so that

(48:58):
that's in play. And on top of this, yeah, they're
keeping like seaweed, which remember is a microalgae. They're keeping
seaweed growth in check. And this is apparently one of
the prime results of parrotfish overfishing in parts of the
Caribbean and the Pacific seaweed overgrowth. And I was even
reading this is from Kramer at All in twenty seventeen's

(49:20):
prehistorical and historical declines in Caribbean coral reef accretion rates
driven by loss of parrotfish. The authors here say that
we see this connection proven out in sediment fossils. There's
a strong observable connection between declines and coral accretion rates
and parrotfish abundance. So and it's more evidence that we

(49:40):
need to conserve our parrotfish in order to help prevent
coral reef environments from becoming quote, algael dominated habitats. And yeah,
so this is worth keeping in mind. If you're traveling
somewhere and parrotfish is on the menu, it's advisable to
eat something else. And indeed, there are a number of
efforts and protections in places around the world to help

(50:03):
protect these populations like the parrotfish are a vital part
of those coral environments which are already threatened in a
number of ways. This is one that we can we
can we can do a lot to help coral reefs,
but not eating parrotfish is perhaps even more accessible than
some of the things we need to do to protect them.

Speaker 3 (50:23):
Now, there's one more brief thing I wanted to get
into before we wrap up part one here, and that
is about the material makeup of parrotfish teeth. I was
reading about this in a press release for the Lawrence
Berkeley National Laboratory. This was published in twenty seventeen. It's
called X Rays Reveal the Biting Truth about Parrotfish Teeth

(50:44):
by Glenn Roberts Jr. And so this is talking about
research conducted at the Berkeley Lab which used X rays
to examine parrotfish teeth and better understand what makes them
so resilient in the face of essentially scraping, biting, and
chewing on rocks all day. You know, on these coral
skeletons are not soft. You know, they're hard Calcium carbonate

(51:06):
and they're just these teeth are relentlessly munching. So the
particular parrotfish species in question was the steep head parrotfish
also known as the blunt head parrotfish scientific name Chlorurus
micro rhinos. And in this analysis, the researchers found that
the resilience of parrotfish teeth was due to this woven

(51:29):
microstructure of minerals in the enameloid of the teeth. And
the article compares it in fact in structure to chain mail,
which I thought was interesting. So this microstructure creates a
tooth the material that is incredibly hard at the biting surface.
The article points out that the hardness of the biting

(51:51):
surface is about five hundred and thirty tons of pressure
per square inch and they compare this to the weight
of eighty eight African elephants on a single square inch
of space. Now, that microstructure of the teeth fits into
a larger structure, the sort of morphology of the jaw,
which is that these parrotfish have like fifteen rows of

(52:13):
teeth totaling about one thousand teeth, all fused together, biologically
glued or cemented together into this single beak like structure,
and the stiffness of the underlying mineral crystals increases as
it goes toward the tip the biting surface, and the
article quotes one of the researchers involved named PUPA. Gilbert,

(52:35):
who is a professor in the physics department at the
University of Wisconsin Madison, who says, quote, parrotfish teeth are
the coolest biominerals of all. They are the stiffest, among
the hardest, and the most resistant to fracture and to
abrasion ever measured. And so given the incredible material qualities
of these parrotfish teeth and beaks, researchers are looking into

(52:58):
ways that the oven crystals of parrotfish teeth might be
used as an inspiration for human engineering, a design pattern
that could be reproduced in synthetic materials to create a tougher,
more resilient product.

Speaker 2 (53:10):
Now, just a couple of notes about these teeth for one.
On one hand, to come back to the alien xenomorph.
You know, it is interesting that they're sometimes described, at
least for some of the morphs, as possessing metal teeth.
And here we have the parrotfish, whose teeth are sometimes
described as being stronger than many metals men metals, so
it's kind of interesting comparison there. Also, you know, inevitably

(53:33):
there is the question in the same way that we
can't look at a creature that is biting coral and
you know, think about our own teeth biting coral, we
also can't help but look at a creature with interesting
teeth and wonder what happens if I get bitten by
one of these? So I mean, to be clear, you know,
humans are not on the menu for the parrotfish. There

(53:55):
are accounts of parrotfish rarely biting humans, though it does
seem very rare, and the incidents I was looking at,
most of them seem to be related to incidents with
fishermen who were actively harvesting them or you know, engaging
with a trap or something. But they have bitten humans before,
so it can happen. But I mean that can be

(54:18):
said of a lot of creatures, like you know, a
horse can bite you.

Speaker 3 (54:22):
Oh Lord, why did I google this? But I did?

Speaker 2 (54:24):
Oh? Did you just google the art? You may have
googled one that comes up a lot.

Speaker 3 (54:28):
Came across a news article that claims to be a
photo of a wound from somebody who was bitten by
a parrotfish and it looks it's grotesque. Listeners be warned.

Speaker 2 (54:42):
Yeah, there's a particular story that comes up in search
involving a fisherman that is that was bitten in a
delicate area by one of these parrotfish. So yeah, I
you know, weighed carefully if you decide to pursue these
stories for yourself. But yeah, it can't happen. It has happened,
But uh, these are generally not considered you know, risky fish,

(55:04):
and people snorkele around them almost constantly without issue.

Speaker 3 (55:09):
They're not looking to bite you. They're just trying to
go about their business. They're scraping, they're buzzing't.

Speaker 2 (55:14):
Like bees, they have so much coral to scrape, like
biting you takes time away from vital coral scraping time.
All right, Well, we're gonna go and close up this
episode now, but we actually have even more exciting content
to cover about the parrotfish we didn't. We briefly mentioned
their their their their sex changing ability, so we're going

(55:37):
to get into that for sure. There's also some other
stuff that will and I think in ways get us
even closer to that xenomorph area. Again.

Speaker 3 (55:45):
So yeah, we're gonna have some cocoonings, some all kinds
of good stuff to get into next time.

Speaker 2 (55:50):
Yeah yeah, so tune in for that. In the meantime,
I'd love to hear from anyone else out there who
has personal experience being around parrotfish. You know, we're not
encouraging anyone to actively seek out and eat parrotfish, but
you know, it has been a tradition of cuisines. So
if you would like to write in and share your
culinary experience with parrotfish, if you have tasted a parrotfish liver, yes,

(56:14):
we would like to know what that is like that.
We just would like to know. We'd like to know
what the Romans were into when they were consuming their
parrot fish meals. So right in, it's all fair game
as always, you know, if you have when you do
write into us, you can always flag something is and
say hey, don't use my name on this, I want
it to be anonymous. Or you can say, hey, this

(56:35):
is information for you, but don't actually read this. That's
fair as well. Just write in. We would love to
hear from you. Just a reminder that stuff to blow
your mind is primarily a science and culture podcast with
core episodes on Tuesdays and Thursdays, listener mail on Mondays,
short form episode on Wednesdays, and on Fridays. We set
aside most serious concerns to just talk about a weird
film on Weird House Cinema.

Speaker 3 (56:55):
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, to suggest
a topic for the future, or just to say hello,
you can email us at contact at stuff to Blow
your Mind dot com.

Speaker 1 (57:17):
Stuff to Blow Your Mind is production of iHeartRadio. For
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