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There are creatures in the sea hiding their true natures, defying our attempts to easily classify them, deceiving us into believing that they are crabs… When, in fact, they are not.

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Host: Sarah Suta (she/her)
In the depths of the ocean, many creatures are not what they seem.

Our last trip into the sea brought us face to face with the vampire squid, which is not actually a squid at all, but something, else. A branch of the cephalopod family tree so ancient that it is neither octopus, nor a squid.

But it is not the only pretender down here. There are other creatures hiding their true natures, defying our attempts to easily classify them, deceiving us into believing that they are crabs. When, in fact, they are not.

They never were. [♪♪ INTRO ♪♪] As Nautilus Live’s remotely operated vehicle descends into the depths in search of strange and bizarre beasts, it sometimes encounters them even before it reaches the sea floor. Like this swarm of so-called “tuna crabs,” floating in the water column. They propel themselves backwards with their lobster-like tails to rocket through the sea, and stop by stretching their many-jointed legs outward, like a living parachute.

And while we may call them crabs, they are not true crabs, but merely another type of crustacean that has taken on a somewhat crab-like form, and not the most convincing one, even. They appear suspended part-way through the process known as carcinization, the convergent evolution of the crab body plan from forms more lobster- and shrimp-like. And the common name of the group they belong to is the ‘squat lobsters,’ giving the lie to their ‘tuna crab’ ruse, as they do more closely resemble lobsters with shortened tails than actual crabs.

But there are certainly better-disguised imposters waiting in the deep, creatures that seem to have lost their tail altogether. These false crabs rest on the seafloor, propped up on long, spider-like legs, their round, red bodies covered in sharp spines. And they can be large, with some species having a leg-span of up to one-and-a-half meters, much bigger than the 12- to 13-centimeter-long tuna crabs.

These are the so-called king crabs. The ones spotted here by Nautilus Live represent just a few of the many species in that family that exist in oceans around the world. Their range covers most of the globe, though they’re generally not found in the tropics, often preferring colder, deeper waters.

The ones you see here were found off the west coast of North America, in the frigid waters of the Pacific Ocean. If you look closely, you may spot one of the things that gives away that these king crabs are not members of the taxonomic order Brachyura, a.k.a. true crabs, at all. Count their legs.

They have three pairs of walking legs, one set of claws, and a set of small, hidden back legs tucked away. True crabs tend to have four pairs of walking legs, in addition to their claws. Such a small difference and yet we humans give it biological meaning, marking one group of crabs ‘true’ and another ‘false.’ If you’re a fan of what we do on this channel, we’ve teamed up with Emily Graslie to create a limited edition art print of some of our beasts.

You can get one now over at We also still have Bizarre Beasts calendars available for sale at Thanks for coming along with us on this journey into the sea.

We’ll be back on the first Friday of next month with another episode of Bizarre Beasts. [♪♪ OUTRO ♪♪]