Listener Q's: Sex Swapping, Smallest Shark, Marmots!

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 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 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?

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 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 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 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 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 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

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 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, 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 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, 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 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 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 tan brown color or a reddish color.

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 female into a male, and.

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 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

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. 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 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 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 issues when you don't have a.

But then they will every so often have some sex 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. What they do is they will go through asexual reproduction phase budding, creating.

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 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 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 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

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. 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 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

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 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.

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

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, 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.

bit of light but not much. They are a brownish 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

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, 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 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 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. 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 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.

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, 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 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 about earlier probably eats very similar things, probably shrimp, krill, other invertebrates, and then smaller fish.

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 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.

I've personally run into them hiking in the Sierra Nevadas. There's the yellow bellied marmot in Canada and western US.

think of a groundhog. The ground hog is actually a 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, 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 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 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, killed like at least sixty thousand people, so.

source of the plague, are highly related to marmots. Marmots differ from perry prairie dogs because they're a lot larger. 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

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 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 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 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

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 up your clothes or your backpack because they love salt.

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 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

do the animal sound gissing game. And yeah, if you have your own question and you would like.