Marine Iguana - Tumblr Posts

Footnote: Recognize this? Feel like reading some more? Well, here is my new blog! Due to some technical issues with the old one, I will be rblging the original MMM and CFF posts on this account, as well as continuing both series!

Creacher Feature Friday 4: Ligers, Tigons, and Mules, oh my! A Cursory Look at Sterile Hybrids

I’m supposing it’s safe to assume most of the human population knows what a mule is, pretty visible concept. Take a horse and a donkey, let ‘em have a tumble in the hay, and out comes something that’s a bit of both species, but still something pretty different, they can’t themselves reproduce. If you understand that much, then you’re already walking in with a little bit of baseline knowledge of a phenomenon known as hybrid incompatibility.

Now, animals can be incompatible to each other as hybrids in a whole list of ways because of the broadness of the term. It doesn’t exactly mean that two different species cannot produce offspring together, but it encompasses any case where two different species mate and produce an offspring that suffers from a reduced fitness as compared to its parents- Fitness in this context of course meaning the ability of an animal to thrive and reproduce in its environment, so that can include anything from a pure genetical problem to just the mixing of traits not being as well suited to a habitat as the parent’s more specialized adaptations. Very often, though, a downgrade will take the form of the offspring just outright having a reduced or eliminated fertility. Like the mule, like the liger, many hybrids simply dead-end their lines just by virtue of being unable to continue mating and reproducing. That’s what applies to the critters what I want to get into today. Without further ado, here’s a whacky little list I got of some worthy mentions I find MUCH cooler than mules.

*Side Note: the actual mechanics for how hybrid sterility happens is something that comes down to DNA and is to put it lightly, freaking complicated, and ultimately (like most boxes we try to apply to nature) is more of a messy spectrum than a strict is/is not binary. There are actual freak cases of mules that have managed to be the exception to the rule, believe it or not. But as a general it applies to broadly call them, and the following examples of sterile hybrids. Just a thing to keep in mind!

• Ligers and Tigons

Whether through word or mouth, actual articles, or some old animal planet shows, ligers are probably one of the most well-known “exotic” hybrids because of the attention they started getting in zoos that managed to breed them. And yeah, they’re pretty cool. For obvious reasons they only exist in captivity, and they’re the direct result of a male lion mating with a female tiger. Tigons, on the vise versa other hand, are a hybrid between a male tiger and a female lion. You wouldn’t think that would make such a huge difference, but it really does. For one, there’s some noticeable differences in the offspring’s mane (in males) and the pattern of their coat. Personally I find Tigons much more gorgeous than their counterpart on this front.

Second, ligers are absolute units. Not just compared to tigons, but compared to big cats in general. They very typically grow much larger than either of their parents, reaching lengths of about 10-12 feet and easily being able to clock in at weights of over 900 pounds on average. You wanna talk about “chonkers”?

Yeah. Yeah.

It’s not particularly a great thing either and it makes them especially controversial to create. Basically, they don’t inherit key growth-limiting genes from a lioness that a pure cub would, but they are carrying a now completely unrestrained growth-encouraging gene from the male lion parent. It essentially causes all ligers to be born with a form of gigantism, which can predispose them to a bunch of health complications. Tigons still have their own issues as well, which is a predictable enough fact considering this is more or less parallel to some of those “because we can” designer dog mutts.

Something tigons and ligers do share is that all males of either case are born completely sterile. Females, however, have been on some occasions able to produce second generation hybrids, which is a whole can of worms on itself once you start getting into Titagons, Tiligers, Litigons, Liligers… real things by the way. This is a problematic lasagna with many strange layers, indeed. Personally, I’d just steer clear of any institution that intentionally interbreeds big cats in ways like this, and leave it at that.

• Hybrid Iguanas

Hey look, an example that was actually found happening in the wild! There’s a rarity alright. So, there are a handful of iguana species native to the Galápagos Islands. Three of them are terrestrial, and one is the impressively unique marine iguana- the only modern seafaring lizard species, in fact. I’ll give them their own Friday feature one day but anyway. Typically, the land and sea iguanas don’t have much of an overlap in breeding season or territory, but there was a curious incident we discovered on the South Plaza island back in 80s-90s.

Marine Amblyrhynchus cristatus (top left), the land-dwelling Conolophus subcristatus (top right), and a hybrid offspring of the two species (bottom)

At the time, see, the Galapagos were going through a pretty intense round of warm tropical cycles that caused a substantial loss of seabed kelp surrounding the islands. Since this is what makes up almost the entirely of the marine iguana’s diet, it led to an epidemic of scarce pickings among their species. Many of them starved off, but others, including the more aggressive, explorative, in-season males, started encroaching inland out of desperation for food. And this, along with the south island’s generally small size, is the main posed explanation for the dozens of hybrid land-sea iguanas that have been spotted on the strip over the years. Genetic testing has shown them to be the result of male marine lizards and female land iguanas, specifically, and though our knowledge could still change in the future, these hybrids are also assumed to be sterile first gens, which would explain why we don’t see many of them at once when we do.

• Commercial Bananas

Come on, you know I Just had to throw a plant in with the lot. They’d feel left out otherwise after I dedicated two of the last 3 write ups to fungus. There’s a number of crops that could have gotten this mention, but nanners is a funny word, so here’s the spill. We royally fucked up banana genetics a long time ago in their domestication. Every, single, banana you have ever grabbed out of the produce section of your local grocery is an asexual clone unfit for wild survival. They’re hybrids, too. Specifically, nearly all domestic varieties can trace a lineage back to a crossing between Musa acuminata and Musa balbisiana, originally two wild natives to South Asia. One of which just had some unappetizing flesh and the other was too chock flipping full of seeds for human preferences, real big seeds. It’s not really even recognizable as a “banana” to us now. See what I mean.

Well, the good news was that the offspring of the two, by some random miracle, produces fruit that was just culinarily superior in every single way to either of the parents’. It was effectively seedless, tastier, more vibrant, more nutrient packed, more “banana” if you will. The bad news was that these seedlings were completely sterile. Oops…unless👀?

The game changing good news 2.0 was that farmers realized they could still be easily propagated into genetically identical new plants off of cuttings from the original hybrids. And that’s how we got to the current state of commercial bananas. Personal confession, I still can’t freaking stand the smell, taste, or texture of them either way. Never have, never will, but maybe some of you can feel an appreciation for this happy little accident of agriculture that I cant.

I had some more examples to add onto the list that came up in my research, like Zebra-donkey/horse mixes, but I think I’m pretty comfortable with the length of this for the week. Perhaps I’ll give it a second part in the future. Until then, peace~