What's inside the 'world's ugliest animal,' the blobfish

• The blobfish was crowned the world's ugliest animal in 2013 – a title it still defends today.
• But drop this fellow 9,200 feet below sea level, and the water holds up all that flab like a push-up bra, making the fish a little more handsome.
• Between the skin and the muscles is a lot of fluid. And that's the secret to the fish's distinct appearance – and its survival.
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Following is a transcript of the video.

Narrator: This creature was crowned the world's ugliest animal in 2013, a title it still defends today. On land, he's got a body like Jell-O and a big old frown. But drop this fellow 9,200 feet below sea level, and the water holds up all that flab like a push-up bra, making the fish a little more handsome. Same old fish, but with a little more support. So, what is all that water pressure holding together?

David Stein: Between the skin, that flabby skin, and the muscles is a lot of fluid.

Narrator: This is David Stein, a deep-sea-fish biologist who was lucky enough to dissect 19 blobfishes in the 1970s. Blobfish look blobby because they are full of water. Under their skin, blobfish have a thick layer of gelatinous flesh that floats outside their muscles.

Stein: If you pick up a blobfish by the tail, then it kind of flows to the head.

Narrator: This water-filled, Jell-O-like layer allows the blobfish to stay somewhat buoyant, which is important because blobfishes don't have a swim bladder.

Stein: And fishes that have swim bladders are able to adjust their buoyancy. They can secrete gas into the swim bladder or remove it. A fish that lives on the bottom doesn't need to be able to maintain its buoyancy.

Narrator: So, the Jell-O layer isn't a perfect substitute, but the blobfish doesn't need to be a strong swimmer. The predator has a highly specialized hunting strategy that's perfect for the rocky barrens of the deep sea.

Stein: It just sits there and waits for dinner to come by.

Narrator: If all you do is sit, you don't need much under your skin. Just watery tissue, some yellow pockets of fat, and a smidgen of muscle. In case you hadn't guessed, blobfishes aren't exactly yoked. They have very little red muscle, the kind that allows you, a human, to run a mile or a tuna fish to migrate across oceans. Instead, blobfish have a lot of white muscle, which allows them to swim in short bursts and lunge at prey that on occasion ramble by.

This is a baby blobfish. It's a cleared and stained specimen, meaning all its tissue has been dissolved to show only the bones and cartilage. Those thin red lines you see, they're the blobfish's bones dyed red. If you're having trouble seeing the bones, you're not the only one. Blobfish have poorly ossified skeletons, meaning they're thinner and more fragile than the bones of most shallow-water fish. This is another handy deep-sea adaptation, as it takes a lot of precious energy to build strong bones.

But the blobfish saves its energy to develop what might be the most important bone in its body: its jaws, which also happened to be the reason it looks so gloomy. The fish needs enormous jaws so it can snap up any prey that passes by and swallow it whole, maybe even smacking its blubbery lips as it eats. And that brings us to its stomach. If you're the kind of creature that eats anything that swims by, some surprising things can wind up in your stomach. Stein found a wide range of foods and not-foods in the blobfish he dissected. Fish, sea pens, brittle stars, hermit crabs, an anemone, a plastic bag, and also lots of rocks.

Stein: Their stomach contents kind of bear out the fact that they're probably not too bright.

Narrator: He also found octopus beaks, the cephalopods' hard, indigestible jaws. This means that one of the world's flabbiest fishes has been able to eat one of the sea's most cunning predators. If you're surprised, just think about the blobfish's thick skin. What would it be harder to grab in a fight: a sack of bones or a sack of Jell-O? Stein suspects it might be the latter.

Stein: If the skin is loose, perhaps the suckers can't really get a good grip on it.

Narrator: Stein found sucker marks across the blobfish's body, a hint that the fish might've been in some deep-sea fights. So while all of this Jell-O might look a little unconventional, well, it seems to have served its purpose. The blobfish is perfectly suited to life in the deep sea, where beauty standards are probably quite different. After all…

Stein: Ugly is kind of in the eye of the beholder.

EDITOR'S NOTE: This video was originally published in December 2020.