A family of fishes that can be found in the form of many deep adapted species, including the deepest swimming fish ever convincingly documented by science, at least as of now. The deep dwelling varieties of snailfish often look like fat, slimy, pale pink tadpoles with translucent skin. In the words of one article, we talked about guts wrapped in cellophane. In my observation, kind of often like a wad of see-through chewing gum with a tail. But when the angles were just right, of course, as you pointed out, Rob, they can also be surprisingly cute with kind of placid, unassuming eye spots, making them look like like a creature of the hundred acre wood. Yes, yes. But one whose skin is dissolving. But despite looking either like a half dissolved Emil from Robocop or like a cute little piglet fish. It turns out snailfishes are the top predators of many deep ocean trench environments. So they eat amphipod scavengers and other little animal forms you find down there. They're kind of the kings and queens of the underworld. Oh, and also there is good reason for suspecting they're some of the worst smelling fish on earth. We discuss in that episode why is likely the case.

Yeah, with science. This is not just a they look smelly discussion. There's actual science to back this up. After

talking about snailfishes, we also looked at anglerfish, a beautiful monster of a marine predator. Actually, an anglerfish is not just one species, also a very diverse group that has a lot of different varieties. But it has its own deep adapted varieties as well. And there are so many things that make anglerfish interesting, not just how gorgeously cartoon grotesque they look, or at least in some of their forms, you know, with the jail bar teeth and the doom cute prey lure. There are also really interesting questions about their relationship with the bacteria they farm to create their glowing lure. How do they acquire these bacteria, etc. And also we talked about their truly amazing mating and reproduction practices with the tiny male grafting its body onto that of the much larger female to become a kind of carry-along sperm dispenser, which itself requires interesting adaptations. For example, in the anglerfish immune system, how does the anglerfish avoid rejecting the grafted male's tissue? And could knowledge of this sort be used to improve outcomes for organ transplants and other related issues in human medicine? Anyway, that's all the previous episodes. Today we're back to round out the discussion of dark ocean predators with our fourth and final part.

That's right. Now, before we jump into full discussion on our selections here, I do have a quick example I want to point out, it's an extreme example of something we discussed previously. The advantage in the deep waters, in the dark ocean, of having an oversized stomach that allows you to consume all you can eat when a rare meal presents itself. And this brings us to the black swallower. This is the rare fish that can swallow a fish bigger than itself via a distensible stomach. You might be tempted to imagine like a fish with like a beer belly. That is not severe enough for what can occur here. Joe, I included an illustration and a photo here, and I encourage everyone out there when it's safe to do so, look up some images of the black swallower fish, and it's pretty amazing. So essentially, it has a stomach that balloons up enough to contain a fish twice its own length and 10 times its own

mass. It looks like a sardine with like a small mattress folded up on its stomach.

If this were not actually real, it would seem grotesque enough that it had to be, you know, something out of the human imagination. It's just it looks bizarre. Just this stomach stuffed with an oversized fish, a fish larger than itself. And there are various discussions in the literature of like, how does it actually eat the fish? How does it like walk its jaws up the body of the fish that it has consumed?

It is true. It's hard to understand how what you're looking at is real, especially in, you shared a couple of images, Rob. One is like an illustration, but the other is like a photo of, I think, I guess one of these ate something a little too big for its own good. And it's like a much larger fish inside the smaller fish's belly. I don't understand how it got that in there.

But you are right. It is possible for these fish to eat something that's too big. And here's the crazy detail on all that. Apparently, most of the specimens of black swallower that scientists have studied, they've made their way to the surface because the fish in question apparently ate another fish too big for it to digest before decomposition set in on their meal. So, in other words, their two large meals rotted in their giant gut before their stomach could break it down, resulting in all those decomposition gases turning the fish into a surface-bound rock balloon, which just takes them out of their deepwater habitat right up to the surface, killing them. Yeah,

you don't want that. Yeah.

So I just had to bring this one up because the deep ocean, as we discussed, it is a place sometimes of extremes. And here is an extreme example via deep water evolution of an oversized stomach to allow these individuals to eat all they can when a meal presents itself.