October 1, 2025 • 32 mins
I answer your questions: animals who switch sexes, the world's smallest sharks, and marmots, as in, what's their deal?!
If you have a question you'd like me to answer, you can write to me at creaturefeaturepod@gmail.com
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Episode Transcript
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Speaker 1 (00:07):
Welcome to Creature Future production of iHeartRadio. I'm your host
of Many Parasites, Katie Golden. I studied psychology and evolutionary biology,
and today on the.
Speaker 2 (00:16):
Show, it's a listener Questions episode.
Speaker 1 (00:19):
I answer your questions that you send to me at
Creature Feature product gmail dot com. Do you have any
questions about evolutionary biology, your pets, animal behavior. I will
do my best to answer them. I love these questions.
They often make me do a little bit of homework,
do some research, phone up on my evolutionary biology and
(00:42):
so I love them and I really appreciate you guys
writing in. Let's get right into the first listener question. Hi, Katie,
I absolutely love learning and I love animals, so when
I found your podcast, I was a static. I'm constantly
annoying my friends and family with the fascinating facts I've
learned while to your podcast. I am still working my
way through your podcast, so I'm not sure if you've
(01:03):
covered this topic yet, but I am so fascinating with
animals that have evolved to change their sex. I know
there are fish, clownfish, and Asian sheep's head rass that
can do it, and also a lizard in Madagascar. I
think that lays fertilized eggs limiting the need to mate
with a male. It's just so amazing how nature can
just evolve like that in order to survive. Are there
(01:25):
other animals besides those two fish and that lizard that
have evolved in this way? No, I'd love to hear
more from a biologists perspective on this topic. Also, if
this is an episode already ready, which is it?
Speaker 2 (01:38):
Which one is it?
Speaker 1 (01:39):
I want to hear all the things. Thank you again
for such a great podcast and can't wait to hear more.
This is Chelsea from Coal Valley, Illinois. Hi, Chelsea, thank
you so much for your question. I will definitely get
into some details and facts and examples of animals who
change their sex, But first I can tell you about
the some of the episodeodes where I have covered some
(02:02):
of this. There's plenty of stuff to go over those,
so I have plenty more to talk about right now
and then also on later episodes. But a couple examples
of episodes where I cover sex swap shenanigans. There's one
that was published January twentieth. In twenty twenty one, it
was an episode called Paul Blart Jurassic Park cop where
(02:25):
we talked about whiptail lizards and clownfish. And on June nineteenth,
twenty twenty four, I did an episode called Happy Pride
that was on all sorts of animal sex diversity, both
in terms of like biological sex and also sexuality. There's
probably more episodes where I talk about these things, but
those are the two that I can remember. Anyways, I
(02:49):
am as fascinated as you are by animals and the
ways in which sex is not really a binary, or
at LEAs it's not a strict set in stone binary
in a lot of cases in animals. First, let me
explain before I go onto the new examples. Let me
(03:09):
explain the ones that you brought up, Chelsea. The clownfish
and Asian sheep's head rass. These are two species of
fish which are sequential hermaphrodites, which means they change sex
during their life cycle. So clownfish famously can change their
sex depending on their environment as well as a hierarchical
(03:35):
social system. So they start out as males, and a
dominant male will listend to the rank of breeding female,
and this is sort of like the queen of a
group of all males. Her second in command. The second
most dominant is a breeding male, and so these are
the two. These are the only two that generally breed
(03:58):
in these groups. It's these two and then a bunch
of other males, and they live together, protect each other.
Often they live among the sea and enemies because they
are able to be resistant to the ceain enemy toxins
while benefiting from the protection and the cea An enemies
benefit from the little scraps of food that the clownfish
(04:20):
lead behind. So they're living there. But then they also
live in a social group where you have a queen
dominant female, then the second in command, which is a male.
Those two breed, and then the rest of the males
just kind of orbit around them benefit from the territory,
but they are not breeding. If the breeding female dies
(04:43):
is lost moves on, the second in command male actually
turns into a female, and then he becomes a she
and becomes the breeding female, the new sort of like
queen of this little colony, and then just the non
breeding males then becomes her consort, the next second in command,
(05:07):
who will eventually then take over her spot and become
female when she dies or if she's killed. So this
is how it works, right, It's a really interesting system.
These fish will change sex throughout their lifetime based on
the social hierarchy, which is there's really in one of
(05:29):
these little colonies, there's only one female who's breeding and
then her second in command. It's not really a harem
situation where she's breeding with all the males. That's not
really happening. She's breeding with her one second in command male,
and then the rest of the males are just in
a way waiting their turn. And they also benefit from
the protective nature of having a colony. So you know,
(05:54):
it's a really interesting system. So the Asian, she said
wrass are similarly really interesting. So they start out as
normal looking tropical fish. The young ones are sort of
orangish orangish with a white stripe. Older ones turn more
(06:15):
of an olive tan color, they still have the little
racing stripe. Now, unlike the clownfish, which all start out
as males, the sheep head rass all start out as females.
When they get old enough, which is about ten to
fifteen years old and big enough, they actually turn in
(06:37):
two males at that point and they undergo a really
dramatic change in body size and shape, so they look
very very different from their juvenile female forms. They lose
any of the youthful coloration. They turn a sort of
(06:57):
tan brown color or a reddish color.
Speaker 2 (07:00):
Uh.
Speaker 1 (07:01):
And most notably, their heads kind of balloon out and
get bulbous and puffy and big, so they have this
huge growth on the forehead, an extruded, puffy lower jaw,
and they grow from a little over a foot at
their mature female size to up to two feet as
(07:23):
a male. So the change from female into a male
is permanent and they'll live the rest of their lives
as a big headed dude. And this is a really
interesting case where it doesn't really seem the environment might
play a role, but in general it's just once they
get big enough, they are able to turn from a
(07:46):
female into a male, and.
Speaker 2 (07:49):
This is just their life cycle.
Speaker 1 (07:51):
So clownfish and cheap drasts are far from the only
fish who can change their sex. There are many many
species of both sequential hermaphrodites. These are the clownfish and
the rass are the two examples of that, but there
are also a lot of species of fish who can
change back and forth where it's not a permanent change. So,
(08:14):
coral gobies are a genius of small colorful fish that
live in nooks and crannies of coral reefs. They're very pretty,
very cute, but they don't want to waste encounters with
other coral gobies. So if they happen to both be
the same sex, usually one of them will rapidly change
sex in order to mate with the other. And in
(08:35):
a lot of species they form long term pair bonds.
So for them, when their partner dies, if their partner
dies before them, they'll go find another goby and if
they are the same sex with this other gobi, they
will change their sex to mate with them, to match
with them, and they can switch back and forth if
(08:55):
they need to. So really really interesting again, like this
is something where they have you know, it is easier
for them to be able to change their sex than
to make sure that they're finding a male or a
female if they happen to be the opposite sex. Incredible.
(09:16):
So another one that you mentioned are the New Mexico
whiptail lizards. So they are I think this is the
lizard that you're mentioning, Chelsea. Now, these are a type
of lizard, a species that are found in New Mexico
and Arizona, and they don't change their sex, but they
(09:40):
are all females, so they do not need males to reproduce,
and they're a hybridization basically of these very closely related
species of lizards. And so what happens is that these
females actually have three chromosomes triploid rather than having two
(10:03):
chromosomes like humans and a lot of animals have, and
so they are able to reshuffle these three chromosomes and
produce a reshuffled clone in an act of parthenogenesis. So
that's reproduction without sex. So usually asexual reproduction can cause
(10:29):
issues when you don't have a.
Speaker 2 (10:31):
Lot of genetic diversity.
Speaker 1 (10:33):
So you'll have a lot of species of animals, particularly
insects and invertebrates, where they will have an asexual reproduction
phase and then a sexual reproduction phase so that they're
able to multiply a lot without needing to go through sex.
But then they will every so often have some sex
(10:57):
so that they can introduce some genetic Diversityids do this
where some generations are asexual and then another there's every
so often there will be a generation of them that
are sexually reproducing, and then that helps them increase the
genetic diversity of their population. A lot of like coral species.
(11:21):
What they do is they will go through asexual reproduction
phase budding, creating.
Speaker 2 (11:27):
Clones, and then those clones.
Speaker 1 (11:30):
Will then go through a sexual reproduction phase, so that
you're basically going back and forth between asexually reproducing and
then sexually reproducing. So the benefit of asexual reproduction is
you can do it really quickly. You don't need to
find a partner, which is great when you're coral and
you can't.
Speaker 2 (11:48):
Move, and.
Speaker 1 (11:52):
You can do like a lot of it at once.
But then the benefit of sexual reproduction is the introducing
more diverse genome and that is useful because if you
have a disease or change in the climate or a
new predator, having a larger, richer genetic library increases the
(12:15):
chance that some of your offspring is going to have
some genetic quality or mutation or capability of a future
mutation that will allow them to survive. So the whiptailed
lizards kind of bypass that by having that set of
three chromosomes that they can kind of shuffle and create
new combinations that allow them to asexually reproduce. Interestingly, they
(12:40):
don't need to have sex because they don't need to
be fertilized, and they don't do that, but they do
pseudocopulation where essentially one female lizard will hump another female lizard,
and it's actually useful in addition to probably being a
nice social activity for them, it induces ovulation and it's
(13:03):
a really interesting thing where it's like there's no real
practical purpose to it other than encouraging ovulation and probably
being a way for them to socially connect. So yeah,
really really interesting reptiles there. Another example of an interesting
reptile is the bearded dragon, which this is another case
(13:29):
of non set in stone sex. So this actually happens
when they are still in the egg. So, like many reptiles,
the temperature of incubation will determine the sex of the embryo,
but unlike some other reptile species, they also have a
(13:54):
chromosomal determinant of sex upon fertilization. So what this is
that they will sometimes have like say, one sex upon fertilization,
but then that can be overridden by the temperature of incubation.
(14:17):
And this typically happens when you have a male chromosomally
and then a high incubation temperature, which actually will turn
it into a fully functional physiological female with male chromosomes.
So yeah, this is this is a case in which
(14:39):
like the male embryo transitions physiologically into a female in
the embryo as the embryo inside the egg before it hatches,
so it's able to get pregnant, breed act like a female,
but it has the genetics of a male. In human
(15:00):
we have cases like this. It's not due to the
temperature in utero, but there are definitely cases of people
who are intersex or have androgen and sensitivity syndrome, where
you have you may have genes that say one thing
right like say x Y like your male, but then
(15:24):
you have your physiologically appear female. So you know, this
does happen in humans. It's just not like as it
doesn't happen as a rule, whereas in bearded dragons it
happens every time the eggs are incubated at a higher temperature.
(15:44):
So you know, if anyone tells you that sex is
really a very simple binary, they have not listened to
this podcast or really gotten into the juicy bits of
evolutionary biology where things get a lot more fun. So
(16:05):
I hope that helps satisfy some of your curiosity. But
I'm definitely we'll talk more on the show about these
kinds of things because there are so many, many, many,
many examples of interesting sex sort of like either sex
changes or different kinds of systems than what we think,
(16:29):
like what is the traditional view of what is normal
and natural in terms of having a male and a
female and they have sex and they have an offspring.
A lot of different ways to do it in nature.
So thank you for that question. Onto the next listener question.
This one's short and sweet, but I like it. What
are the smallest sharks and.
Speaker 2 (16:49):
What do they hunt? This is from Ada.
Speaker 1 (16:52):
So the smallest known sharks are the dwarf lantern sharks,
which are tiny guys who can fit in the palm
of your hand. They grow to be about only up
to eight inches long, which is around twenty centimeters. They
are found in the waters off of Colombia and Venezuela.
(17:15):
They live at depths of over nine hundred feet which
is over two hundred and eighty meters, so they're relatively
rare to spot because they're in the twilight zone, which
is this depth of the ocean. Where there's a little
bit of light but not much. They are a brownish
(17:38):
dark gray color and they have big old eyes. So
they also have a series of black markings along their
sides and on their bellies. Actually also on their bellies.
They have photophores, which are light producing cells, so they
can actually light up in the dark twilight zone depths
where they live. So the light producing cells accomplish a
(18:01):
couple of things. They can attract prey, which I don't
know if we have a lot of specifics on what
they eat exactly, but it is going to be things
like invertebrates or smaller vertebrates like smaller fish. But really interestingly,
(18:23):
this light also acts as camouflage, which sounds counterintuitive, right
you're lighting yourself up. That seems like it'd making more noticeable,
But like I said, the photophores are along their belly,
and so if you're a predator, you're only going to
see those lights looking up and upwards. When you're in
(18:43):
the toilet zone, light is actually filtering down. So if
you look down and you're in the twilet zone, it's
all darkness, but if you look up, you're seeing light
filtering in from the sun or the moon, and if
you have something that has a dark underside and it's
not illuminated, you're going to see like a shadow above
(19:06):
you and see like, oh, that looks like a nice snack.
But with these lantern sharks, because their bellies are slightly luminous,
it actually blends in with the light filtering down from above,
so predator looks up and can't necessarily tell the difference
between the lit up belly of this lantern shark and
the rest of the diffuse light coming in from above.
(19:29):
You actually see this not always with light producing coloration,
but with say white bellies for animals, where they'll have
a darker top and then white bellies a la an orca,
and that helps camouflage them. For orcas, it's not as
(19:49):
much for detection, maybe as being able to ambush prey.
But yeah, so for the lantern sharks though, they are
literally lighting up with bioluminescence these photophores. So interestingly, there
is a similarly sized shark, maybe a little bigger, like
by a fraction.
Speaker 2 (20:08):
Of an inch. It's maybe on average.
Speaker 1 (20:10):
Bigger, but it's a completely different species of shark in
a completely different region in the waters near Japan. The
philippines in Australia actually at a similar depth in the
twilight zone as this other the lantern shark, but they're
very morphologically that is, like physically similar to the lantern shark,
(20:34):
despite being a completely different, unrelated species in a different
area of the world. This is called the small eye
pygmy shark and it's also tiny brown and they also
have photophores, light producing cells on their bellies, and it's
thought they use the same strategy as the lantern shark,
(20:56):
so the lights help them camouflage but also tracked small prey.
We do know a little more about what kind of
prey these guys eat, which is small squid, shrimp, krill,
and smaller fish like lantern fish. Now lanternfish, don't get
that confused with lantern sharks. The lantern sharks that we
(21:19):
just talked about too big for these guys live in
a different area. But lantern fish, which are these tiny
little guys, our prey for the small eye pygmy shark.
So my guess would be that it's slightly smaller look
alike the lantern fish or lantern shark that we talked
(21:39):
about earlier probably eats very similar things, probably shrimp, krill,
other invertebrates, and then smaller fish.
Speaker 2 (21:48):
So there you go.
Speaker 1 (21:50):
They do hunt, but they also gotta be sneaky because
they are small and snack sized, and they use that
really cool trick of lighting their tummies so that when
you're looking up above, they blend in with the light filtering.
Speaker 2 (22:06):
Down in the twilight zone.
Speaker 1 (22:07):
Whereas if you're looking above and down below at them,
you don't see the lights on their bellies. You just
see that dark brown color that blends in with the
murkiness of the depths.
Speaker 2 (22:19):
So really really cool. Thank you for your question.
Speaker 1 (22:24):
Onto the next listener question. I got sent a video
of a marmot and the email goes, I saw this
cute marmot video on Reddit today and don't think I've
heard you talk about them that much. I'd love some
more episodes about rodents. I love rats, but also Keppy barras.
I would love to hear any episodes about Marmott's, Beaver's,
(22:44):
Kepby Burrows, etc. While not a rodent, I love higher
axes now because of you, hope you enjoy the video
from Chloe. The video is of a marmot stealing a
cracker from a man slowly approaching the camera, stopping every
time the man looks at him, and then every time
the man looks away, comes right up steals the cracker
(23:06):
right out of his hands, which is a very very
marmot behavior. So thank you for this video and for
question Chloe. I'll talk a little bit about marmots right now.
Definitely will have occasion to talk about more rodents in
the future on the podcast. So marmots are very very cool.
(23:28):
I've personally run into them hiking in the Sierra Nevadas.
There's the yellow bellied marmot in Canada and western US.
Speaker 2 (23:37):
They're quite big.
Speaker 1 (23:38):
They're like, I would say, like a very fat cat size,
like they're larger than your average cat, and they're very cute.
They are indeed large rodents. In fact, they're technically a
type of ground squirrel. They don't look very squirrely, they
(23:59):
don't generally have the fluffy long tails like squirrels. There
are many different species of these though, so there are
fifteen species found in Europe, Asia and North America, so
they get around. If you're not sure what a marmot is,
think of a groundhog. The ground hog is actually a
(24:21):
species of marmot. So if you've seen a groundhog, you'll
have a general idea of what a marmot looks like.
Of course, different species have slightly different colorations, slightly different shapes.
A lot of them are a bit bigger than a groundhog.
You might hear about marmots in the news every so often,
(24:42):
well pretty rarely, when someone contracts the bubonic plague from
them by hunting and consuming their meat, particularly if it's
raw or undercooked. So this doesn't really happen in North America.
This is usually something that happens in Northeast Asia. So
technically you could get the plague from an infected marmot
(25:05):
if fleas travel from the marmot to humans, but that's
really rare these days. I was unable to find an
example of that happening in recent history. I think probably
it's just very uncommon to be living in close quarters
with marmots to the point where a flea is gonna
(25:27):
bite an infected marmot, get off the marmot and get
on you and bite you. The last time there was
a plague caused by marmots was the Manchurian Plague of
nineteen ten in Northeast Asia, during which people caught the
pneumonic plague from marmot fleas killed a lot of people,
(25:50):
killed like at least sixty thousand people, so.
Speaker 2 (25:53):
It was very serious.
Speaker 1 (25:55):
But yeah, it's really not very common, not something to
worry about. I have not seen any cases of plague
being transmitted from marmot's to humans in America.
Speaker 2 (26:09):
In North America.
Speaker 1 (26:11):
It could happen, but it's I haven't seen any documentation
of it, because they are technically a carrier of the
the bacteria that can cause the plague. Yeah, it's just
really rare that someone would be in close proximity with
a marmot and a flea would jump from that marmot,
(26:35):
which would happen to be infected, which is also very rare,
and then happen to by the person. It just it
doesn't really happen personally. I wouldn't cuddle with a marmot,
but yeah, they're probably not going to want.
Speaker 2 (26:50):
To cuddle with with you either.
Speaker 1 (26:52):
A wild marment is not going to have interest stealing
your food. Yes, and you're you're not going to get
sick by a marmot just running up and stealing your food,
but you should still do your best to secure your
food when you're hiking. But yeah, the more recent cases
of plague have been from people hunting and consuming their meat,
(27:14):
particularly raw and undercooked meat, but even that is extremely
extremely rare. So Prairie dogs, which are another very rare
source of the plague, are highly related to marmots. Marmots
differ from perry prairie dogs because they're a lot larger.
(27:37):
They don't have as large and strictly struct structured communes
as prairie dogs do. Prairie dogs basically live in like
quite large prairie dog cities, whereas marmots kind of live
in smaller population marmot towns. Marmots, depending on the species,
are still quite highly social with each other. They will
(27:59):
groom each other, allow their young to play together. There's
usually like a breeding pair that lives with a bunch
of different other breeding pairs, and they all have their
babies and stuff. Different species may be more or less social,
but they're usually pretty friendly with each other. They're not
going to be necessarily friendly with you. They can be
(28:20):
quite aggressive and territorial if you're not in the cool
marmot club. The marmots that I encountered while backpacking were
really bold. They were very unafraid of hikers. They actually
stole my brother's hiking pole. My brother got it back
after a extremely funny chase. Probably what they were after
(28:46):
is the salty sweat on the handle of the hiking pole.
So we have salt in our sweat, and if you're backpacking,
if you're hiking, you're going to sweat a lot, and
so that's salty sweat gets on your hiking equipment, from
your palms, transferred onto the handles of your hiking poles,
or on your backpack, or on your clothes. And marmots
(29:11):
love salt. It's an important mineral in their diet. They're
attracted to the smell of it and they want to
eat it, and so it's actually if you look up
marmots stealing hiking poles or chewing on hiking poles, it's
very common. And they especially love the ones the poles
that like have the cork because that absorbs a nice
(29:34):
amount of sweat. And so if you're hiking in a
marmot area, it is as important to secure anything that
has your sweat on it as it is to secure
your food, because the marmots will steal it and sometimes
chew the handle of your hiking pole right off, chew
(29:54):
up your clothes or your backpack because they love salt.
Speaker 2 (29:58):
They'll also go.
Speaker 1 (29:59):
After your fo which again you should The video of
the Mormon eating the crackers very cute, but you shouldn't
be encouraging them to eat human food. Not great for them.
Also turns them into bold little thieves. They were a
menace for us when we were backpacking. They were very
(30:20):
very unafraid of us, really trying to steal our things
right in front of us. They've learned that we're not
about to do anything to them. So yeah, they've become
pretty incorrigible, very cute, very cute guys though, So thank
you guys so much for your questions. I will reveal
(30:44):
the answer to last week's mystery animal sound next week
on the full length episode. I do want to say, like,
I got a lot of people who guessed correctly, so
I'm really proud of you guys for that. And so yeah,
if you want to hear that sound, if you listen
to the last two weeks episode at the end we
(31:06):
do the animal sound gissing game. And yeah, if you
have your own question and you would like.
Speaker 2 (31:13):
Me to answer it.
Speaker 1 (31:14):
You can write to me at Creature featurepod at gmail
dot com any question about evolutionary biology, animal behavior, even
pet questions. I'll be happy to read them and answer them.
And yeah, thanks to the Space Cossacks for their super
awesome song Exolumina. Creature features a production of iHeartRadio. For
(31:36):
more podcasts like the one you just heard, visit the
iHeartRadio app, Apple podcast, or Hey guess what wherever.
Speaker 2 (31:42):
You listen to your favorite shows.
Speaker 1 (31:44):
I'm not your mother. I can't tell you what to do.
I do suggest you not let a marmot eat your
hiking pole. It's not good for them, and then you
don't have a hiking pole, which man, I love hiking poles.
They're great for your knees. That's my advice. See you
next Wednesday.
Welcome to Creature Future production of iHeartRadio. I'm your host
of Many Parasites, Katie Golden. I studied psychology and evolutionary biology,
and today on the.
Speaker 2 (00:16):
Show, it's a listener Questions episode.
Speaker 1 (00:19):
I answer your questions that you send to me at
Creature Feature product gmail dot com. Do you have any
questions about evolutionary biology, your pets, animal behavior. I will
do my best to answer them. I love these questions.
They often make me do a little bit of homework,
do some research, phone up on my evolutionary biology and
(00:42):
so I love them and I really appreciate you guys
writing in. Let's get right into the first listener question. Hi, Katie,
I absolutely love learning and I love animals, so when
I found your podcast, I was a static. I'm constantly
annoying my friends and family with the fascinating facts I've
learned while to your podcast. I am still working my
way through your podcast, so I'm not sure if you've
(01:03):
covered this topic yet, but I am so fascinating with
animals that have evolved to change their sex. I know
there are fish, clownfish, and Asian sheep's head rass that
can do it, and also a lizard in Madagascar. I
think that lays fertilized eggs limiting the need to mate
with a male. It's just so amazing how nature can
just evolve like that in order to survive. Are there
(01:25):
other animals besides those two fish and that lizard that
have evolved in this way? No, I'd love to hear
more from a biologists perspective on this topic. Also, if
this is an episode already ready, which is it?
Speaker 2 (01:38):
Which one is it?
Speaker 1 (01:39):
I want to hear all the things. Thank you again
for such a great podcast and can't wait to hear more.
This is Chelsea from Coal Valley, Illinois. Hi, Chelsea, thank
you so much for your question. I will definitely get
into some details and facts and examples of animals who
change their sex, But first I can tell you about
the some of the episodeodes where I have covered some
(02:02):
of this. There's plenty of stuff to go over those,
so I have plenty more to talk about right now
and then also on later episodes. But a couple examples
of episodes where I cover sex swap shenanigans. There's one
that was published January twentieth. In twenty twenty one, it
was an episode called Paul Blart Jurassic Park cop where
(02:25):
we talked about whiptail lizards and clownfish. And on June nineteenth,
twenty twenty four, I did an episode called Happy Pride
that was on all sorts of animal sex diversity, both
in terms of like biological sex and also sexuality. There's
probably more episodes where I talk about these things, but
those are the two that I can remember. Anyways, I
(02:49):
am as fascinated as you are by animals and the
ways in which sex is not really a binary, or
at LEAs it's not a strict set in stone binary
in a lot of cases in animals. First, let me
explain before I go onto the new examples. Let me
(03:09):
explain the ones that you brought up, Chelsea. The clownfish
and Asian sheep's head rass. These are two species of
fish which are sequential hermaphrodites, which means they change sex
during their life cycle. So clownfish famously can change their
sex depending on their environment as well as a hierarchical
(03:35):
social system. So they start out as males, and a
dominant male will listend to the rank of breeding female,
and this is sort of like the queen of a
group of all males. Her second in command. The second
most dominant is a breeding male, and so these are
the two. These are the only two that generally breed
(03:58):
in these groups. It's these two and then a bunch
of other males, and they live together, protect each other.
Often they live among the sea and enemies because they
are able to be resistant to the ceain enemy toxins
while benefiting from the protection and the cea An enemies
benefit from the little scraps of food that the clownfish
(04:20):
lead behind. So they're living there. But then they also
live in a social group where you have a queen
dominant female, then the second in command, which is a male.
Those two breed, and then the rest of the males
just kind of orbit around them benefit from the territory,
but they are not breeding. If the breeding female dies
(04:43):
is lost moves on, the second in command male actually
turns into a female, and then he becomes a she
and becomes the breeding female, the new sort of like
queen of this little colony, and then just the non
breeding males then becomes her consort, the next second in command,
(05:07):
who will eventually then take over her spot and become
female when she dies or if she's killed. So this
is how it works, right, It's a really interesting system.
These fish will change sex throughout their lifetime based on
the social hierarchy, which is there's really in one of
(05:29):
these little colonies, there's only one female who's breeding and
then her second in command. It's not really a harem
situation where she's breeding with all the males. That's not
really happening. She's breeding with her one second in command male,
and then the rest of the males are just in
a way waiting their turn. And they also benefit from
the protective nature of having a colony. So you know,
(05:54):
it's a really interesting system. So the Asian, she said
wrass are similarly really interesting. So they start out as
normal looking tropical fish. The young ones are sort of
orangish orangish with a white stripe. Older ones turn more
(06:15):
of an olive tan color, they still have the little
racing stripe. Now, unlike the clownfish, which all start out
as males, the sheep head rass all start out as females.
When they get old enough, which is about ten to
fifteen years old and big enough, they actually turn in
(06:37):
two males at that point and they undergo a really
dramatic change in body size and shape, so they look
very very different from their juvenile female forms. They lose
any of the youthful coloration. They turn a sort of
(06:57):
tan brown color or a reddish color.
Speaker 2 (07:00):
Uh.
Speaker 1 (07:01):
And most notably, their heads kind of balloon out and
get bulbous and puffy and big, so they have this
huge growth on the forehead, an extruded, puffy lower jaw,
and they grow from a little over a foot at
their mature female size to up to two feet as
(07:23):
a male. So the change from female into a male
is permanent and they'll live the rest of their lives
as a big headed dude. And this is a really
interesting case where it doesn't really seem the environment might
play a role, but in general it's just once they
get big enough, they are able to turn from a
(07:46):
female into a male, and.
Speaker 2 (07:49):
This is just their life cycle.
Speaker 1 (07:51):
So clownfish and cheap drasts are far from the only
fish who can change their sex. There are many many
species of both sequential hermaphrodites. These are the clownfish and
the rass are the two examples of that, but there
are also a lot of species of fish who can
change back and forth where it's not a permanent change. So,
(08:14):
coral gobies are a genius of small colorful fish that
live in nooks and crannies of coral reefs. They're very pretty,
very cute, but they don't want to waste encounters with
other coral gobies. So if they happen to both be
the same sex, usually one of them will rapidly change
sex in order to mate with the other. And in
(08:35):
a lot of species they form long term pair bonds.
So for them, when their partner dies, if their partner
dies before them, they'll go find another goby and if
they are the same sex with this other gobi, they
will change their sex to mate with them, to match
with them, and they can switch back and forth if
(08:55):
they need to. So really really interesting again, like this
is something where they have you know, it is easier
for them to be able to change their sex than
to make sure that they're finding a male or a
female if they happen to be the opposite sex. Incredible.
(09:16):
So another one that you mentioned are the New Mexico
whiptail lizards. So they are I think this is the
lizard that you're mentioning, Chelsea. Now, these are a type
of lizard, a species that are found in New Mexico
and Arizona, and they don't change their sex, but they
(09:40):
are all females, so they do not need males to reproduce,
and they're a hybridization basically of these very closely related
species of lizards. And so what happens is that these
females actually have three chromosomes triploid rather than having two
(10:03):
chromosomes like humans and a lot of animals have, and
so they are able to reshuffle these three chromosomes and
produce a reshuffled clone in an act of parthenogenesis. So
that's reproduction without sex. So usually asexual reproduction can cause
(10:29):
issues when you don't have a.
Speaker 2 (10:31):
Lot of genetic diversity.
Speaker 1 (10:33):
So you'll have a lot of species of animals, particularly
insects and invertebrates, where they will have an asexual reproduction
phase and then a sexual reproduction phase so that they're
able to multiply a lot without needing to go through sex.
But then they will every so often have some sex
(10:57):
so that they can introduce some genetic Diversityids do this
where some generations are asexual and then another there's every
so often there will be a generation of them that
are sexually reproducing, and then that helps them increase the
genetic diversity of their population. A lot of like coral species.
(11:21):
What they do is they will go through asexual reproduction
phase budding, creating.
Speaker 2 (11:27):
Clones, and then those clones.
Speaker 1 (11:30):
Will then go through a sexual reproduction phase, so that
you're basically going back and forth between asexually reproducing and
then sexually reproducing. So the benefit of asexual reproduction is
you can do it really quickly. You don't need to
find a partner, which is great when you're coral and
you can't.
Speaker 2 (11:48):
Move, and.
Speaker 1 (11:52):
You can do like a lot of it at once.
But then the benefit of sexual reproduction is the introducing
more diverse genome and that is useful because if you
have a disease or change in the climate or a
new predator, having a larger, richer genetic library increases the
(12:15):
chance that some of your offspring is going to have
some genetic quality or mutation or capability of a future
mutation that will allow them to survive. So the whiptailed
lizards kind of bypass that by having that set of
three chromosomes that they can kind of shuffle and create
new combinations that allow them to asexually reproduce. Interestingly, they
(12:40):
don't need to have sex because they don't need to
be fertilized, and they don't do that, but they do
pseudocopulation where essentially one female lizard will hump another female lizard,
and it's actually useful in addition to probably being a
nice social activity for them, it induces ovulation and it's
(13:03):
a really interesting thing where it's like there's no real
practical purpose to it other than encouraging ovulation and probably
being a way for them to socially connect. So yeah,
really really interesting reptiles there. Another example of an interesting
reptile is the bearded dragon, which this is another case
(13:29):
of non set in stone sex. So this actually happens
when they are still in the egg. So, like many reptiles,
the temperature of incubation will determine the sex of the embryo,
but unlike some other reptile species, they also have a
(13:54):
chromosomal determinant of sex upon fertilization. So what this is
that they will sometimes have like say, one sex upon fertilization,
but then that can be overridden by the temperature of incubation.
(14:17):
And this typically happens when you have a male chromosomally
and then a high incubation temperature, which actually will turn
it into a fully functional physiological female with male chromosomes.
So yeah, this is this is a case in which
(14:39):
like the male embryo transitions physiologically into a female in
the embryo as the embryo inside the egg before it hatches,
so it's able to get pregnant, breed act like a female,
but it has the genetics of a male. In human
(15:00):
we have cases like this. It's not due to the
temperature in utero, but there are definitely cases of people
who are intersex or have androgen and sensitivity syndrome, where
you have you may have genes that say one thing
right like say x Y like your male, but then
(15:24):
you have your physiologically appear female. So you know, this
does happen in humans. It's just not like as it
doesn't happen as a rule, whereas in bearded dragons it
happens every time the eggs are incubated at a higher temperature.
(15:44):
So you know, if anyone tells you that sex is
really a very simple binary, they have not listened to
this podcast or really gotten into the juicy bits of
evolutionary biology where things get a lot more fun. So
(16:05):
I hope that helps satisfy some of your curiosity. But
I'm definitely we'll talk more on the show about these
kinds of things because there are so many, many, many,
many examples of interesting sex sort of like either sex
changes or different kinds of systems than what we think,
(16:29):
like what is the traditional view of what is normal
and natural in terms of having a male and a
female and they have sex and they have an offspring.
A lot of different ways to do it in nature.
So thank you for that question. Onto the next listener question.
This one's short and sweet, but I like it. What
are the smallest sharks and.
Speaker 2 (16:49):
What do they hunt? This is from Ada.
Speaker 1 (16:52):
So the smallest known sharks are the dwarf lantern sharks,
which are tiny guys who can fit in the palm
of your hand. They grow to be about only up
to eight inches long, which is around twenty centimeters. They
are found in the waters off of Colombia and Venezuela.
(17:15):
They live at depths of over nine hundred feet which
is over two hundred and eighty meters, so they're relatively
rare to spot because they're in the twilight zone, which
is this depth of the ocean. Where there's a little
bit of light but not much. They are a brownish
(17:38):
dark gray color and they have big old eyes. So
they also have a series of black markings along their
sides and on their bellies. Actually also on their bellies.
They have photophores, which are light producing cells, so they
can actually light up in the dark twilight zone depths
where they live. So the light producing cells accomplish a
(18:01):
couple of things. They can attract prey, which I don't
know if we have a lot of specifics on what
they eat exactly, but it is going to be things
like invertebrates or smaller vertebrates like smaller fish. But really interestingly,
(18:23):
this light also acts as camouflage, which sounds counterintuitive, right
you're lighting yourself up. That seems like it'd making more noticeable,
But like I said, the photophores are along their belly,
and so if you're a predator, you're only going to
see those lights looking up and upwards. When you're in
(18:43):
the toilet zone, light is actually filtering down. So if
you look down and you're in the twilet zone, it's
all darkness, but if you look up, you're seeing light
filtering in from the sun or the moon, and if
you have something that has a dark underside and it's
not illuminated, you're going to see like a shadow above
(19:06):
you and see like, oh, that looks like a nice snack.
But with these lantern sharks, because their bellies are slightly luminous,
it actually blends in with the light filtering down from above,
so predator looks up and can't necessarily tell the difference
between the lit up belly of this lantern shark and
the rest of the diffuse light coming in from above.
(19:29):
You actually see this not always with light producing coloration,
but with say white bellies for animals, where they'll have
a darker top and then white bellies a la an orca,
and that helps camouflage them. For orcas, it's not as
(19:49):
much for detection, maybe as being able to ambush prey.
But yeah, so for the lantern sharks though, they are
literally lighting up with bioluminescence these photophores. So interestingly, there
is a similarly sized shark, maybe a little bigger, like
by a fraction.
Speaker 2 (20:08):
Of an inch. It's maybe on average.
Speaker 1 (20:10):
Bigger, but it's a completely different species of shark in
a completely different region in the waters near Japan. The
philippines in Australia actually at a similar depth in the
twilight zone as this other the lantern shark, but they're
very morphologically that is, like physically similar to the lantern shark,
(20:34):
despite being a completely different, unrelated species in a different
area of the world. This is called the small eye
pygmy shark and it's also tiny brown and they also
have photophores, light producing cells on their bellies, and it's
thought they use the same strategy as the lantern shark,
(20:56):
so the lights help them camouflage but also tracked small prey.
We do know a little more about what kind of
prey these guys eat, which is small squid, shrimp, krill,
and smaller fish like lantern fish. Now lanternfish, don't get
that confused with lantern sharks. The lantern sharks that we
(21:19):
just talked about too big for these guys live in
a different area. But lantern fish, which are these tiny
little guys, our prey for the small eye pygmy shark.
So my guess would be that it's slightly smaller look
alike the lantern fish or lantern shark that we talked
(21:39):
about earlier probably eats very similar things, probably shrimp, krill,
other invertebrates, and then smaller fish.
Speaker 2 (21:48):
So there you go.
Speaker 1 (21:50):
They do hunt, but they also gotta be sneaky because
they are small and snack sized, and they use that
really cool trick of lighting their tummies so that when
you're looking up above, they blend in with the light filtering.
Speaker 2 (22:06):
Down in the twilight zone.
Speaker 1 (22:07):
Whereas if you're looking above and down below at them,
you don't see the lights on their bellies. You just
see that dark brown color that blends in with the
murkiness of the depths.
Speaker 2 (22:19):
So really really cool. Thank you for your question.
Speaker 1 (22:24):
Onto the next listener question. I got sent a video
of a marmot and the email goes, I saw this
cute marmot video on Reddit today and don't think I've
heard you talk about them that much. I'd love some
more episodes about rodents. I love rats, but also Keppy barras.
I would love to hear any episodes about Marmott's, Beaver's,
(22:44):
Kepby Burrows, etc. While not a rodent, I love higher
axes now because of you, hope you enjoy the video
from Chloe. The video is of a marmot stealing a
cracker from a man slowly approaching the camera, stopping every
time the man looks at him, and then every time
the man looks away, comes right up steals the cracker
(23:06):
right out of his hands, which is a very very
marmot behavior. So thank you for this video and for
question Chloe. I'll talk a little bit about marmots right now.
Definitely will have occasion to talk about more rodents in
the future on the podcast. So marmots are very very cool.
(23:28):
I've personally run into them hiking in the Sierra Nevadas.
There's the yellow bellied marmot in Canada and western US.
Speaker 2 (23:37):
They're quite big.
Speaker 1 (23:38):
They're like, I would say, like a very fat cat size,
like they're larger than your average cat, and they're very cute.
They are indeed large rodents. In fact, they're technically a
type of ground squirrel. They don't look very squirrely, they
(23:59):
don't generally have the fluffy long tails like squirrels. There
are many different species of these though, so there are
fifteen species found in Europe, Asia and North America, so
they get around. If you're not sure what a marmot is,
think of a groundhog. The ground hog is actually a
(24:21):
species of marmot. So if you've seen a groundhog, you'll
have a general idea of what a marmot looks like.
Of course, different species have slightly different colorations, slightly different shapes.
A lot of them are a bit bigger than a groundhog.
You might hear about marmots in the news every so often,
(24:42):
well pretty rarely, when someone contracts the bubonic plague from
them by hunting and consuming their meat, particularly if it's
raw or undercooked. So this doesn't really happen in North America.
This is usually something that happens in Northeast Asia. So
technically you could get the plague from an infected marmot
(25:05):
if fleas travel from the marmot to humans, but that's
really rare these days. I was unable to find an
example of that happening in recent history. I think probably
it's just very uncommon to be living in close quarters
with marmots to the point where a flea is gonna
(25:27):
bite an infected marmot, get off the marmot and get
on you and bite you. The last time there was
a plague caused by marmots was the Manchurian Plague of
nineteen ten in Northeast Asia, during which people caught the
pneumonic plague from marmot fleas killed a lot of people,
(25:50):
killed like at least sixty thousand people, so.
Speaker 2 (25:53):
It was very serious.
Speaker 1 (25:55):
But yeah, it's really not very common, not something to
worry about. I have not seen any cases of plague
being transmitted from marmot's to humans in America.
Speaker 2 (26:09):
In North America.
Speaker 1 (26:11):
It could happen, but it's I haven't seen any documentation
of it, because they are technically a carrier of the
the bacteria that can cause the plague. Yeah, it's just
really rare that someone would be in close proximity with
a marmot and a flea would jump from that marmot,
(26:35):
which would happen to be infected, which is also very rare,
and then happen to by the person. It just it
doesn't really happen personally. I wouldn't cuddle with a marmot,
but yeah, they're probably not going to want.
Speaker 2 (26:50):
To cuddle with with you either.
Speaker 1 (26:52):
A wild marment is not going to have interest stealing
your food. Yes, and you're you're not going to get
sick by a marmot just running up and stealing your food,
but you should still do your best to secure your
food when you're hiking. But yeah, the more recent cases
of plague have been from people hunting and consuming their meat,
(27:14):
particularly raw and undercooked meat, but even that is extremely
extremely rare. So Prairie dogs, which are another very rare
source of the plague, are highly related to marmots. Marmots
differ from perry prairie dogs because they're a lot larger.
(27:37):
They don't have as large and strictly struct structured communes
as prairie dogs do. Prairie dogs basically live in like
quite large prairie dog cities, whereas marmots kind of live
in smaller population marmot towns. Marmots, depending on the species,
are still quite highly social with each other. They will
(27:59):
groom each other, allow their young to play together. There's
usually like a breeding pair that lives with a bunch
of different other breeding pairs, and they all have their
babies and stuff. Different species may be more or less social,
but they're usually pretty friendly with each other. They're not
going to be necessarily friendly with you. They can be
(28:20):
quite aggressive and territorial if you're not in the cool
marmot club. The marmots that I encountered while backpacking were
really bold. They were very unafraid of hikers. They actually
stole my brother's hiking pole. My brother got it back
after a extremely funny chase. Probably what they were after
(28:46):
is the salty sweat on the handle of the hiking pole.
So we have salt in our sweat, and if you're backpacking,
if you're hiking, you're going to sweat a lot, and
so that's salty sweat gets on your hiking equipment, from
your palms, transferred onto the handles of your hiking poles,
or on your backpack, or on your clothes. And marmots
(29:11):
love salt. It's an important mineral in their diet. They're
attracted to the smell of it and they want to
eat it, and so it's actually if you look up
marmots stealing hiking poles or chewing on hiking poles, it's
very common. And they especially love the ones the poles
that like have the cork because that absorbs a nice
(29:34):
amount of sweat. And so if you're hiking in a
marmot area, it is as important to secure anything that
has your sweat on it as it is to secure
your food, because the marmots will steal it and sometimes
chew the handle of your hiking pole right off, chew
(29:54):
up your clothes or your backpack because they love salt.
Speaker 2 (29:58):
They'll also go.
Speaker 1 (29:59):
After your fo which again you should The video of
the Mormon eating the crackers very cute, but you shouldn't
be encouraging them to eat human food. Not great for them.
Also turns them into bold little thieves. They were a
menace for us when we were backpacking. They were very
(30:20):
very unafraid of us, really trying to steal our things
right in front of us. They've learned that we're not
about to do anything to them. So yeah, they've become
pretty incorrigible, very cute, very cute guys though, So thank
you guys so much for your questions. I will reveal
(30:44):
the answer to last week's mystery animal sound next week
on the full length episode. I do want to say, like,
I got a lot of people who guessed correctly, so
I'm really proud of you guys for that. And so yeah,
if you want to hear that sound, if you listen
to the last two weeks episode at the end we
(31:06):
do the animal sound gissing game. And yeah, if you
have your own question and you would like.
Speaker 2 (31:13):
Me to answer it.
Speaker 1 (31:14):
You can write to me at Creature featurepod at gmail
dot com any question about evolutionary biology, animal behavior, even
pet questions. I'll be happy to read them and answer them.
And yeah, thanks to the Space Cossacks for their super
awesome song Exolumina. Creature features a production of iHeartRadio. For
(31:36):
more podcasts like the one you just heard, visit the
iHeartRadio app, Apple podcast, or Hey guess what wherever.
Speaker 2 (31:42):
You listen to your favorite shows.
Speaker 1 (31:44):
I'm not your mother. I can't tell you what to do.
I do suggest you not let a marmot eat your
hiking pole. It's not good for them, and then you
don't have a hiking pole, which man, I love hiking poles.
They're great for your knees. That's my advice. See you
next Wednesday.
Creature Feature News
Host
Katie Goldin
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