Hi everybody, welcome to another excellent episode of Weird Biology! I definitely had some trouble picking an animal for this week. “Bunjy,” you say, wringing your hands dolefully, “It’s been a while since you did an invertebrate, maybe do one of those” Well, you couldn’t be more right!
So without further ado, I’d like to introduce you to a good, soft boy.
“Oh,” you say dejectedly, still wringing your hands, “Worm?”
Okay first off, how dare you, worms are great. Second, they aren’t even worms, despite the name. Velvet Worms are actually panarthropods, most closely related to arthropods and tardigrades. (Though they look more like a velveteen slap bracelet.) Velvet Worms consist of about 200 known species in their very own adorable phylum, Onychophora.
The panarthropods first wriggled into existence all the way back during the Cambrian Period, 540 or so million years ago. (Plus or minus a few million years.) They have changed very little since then, making the transition onto land but keeping the adorable alien-teddy-bear look.
Velvet Worms are found across the tropics and southern hemisphere, and reach lengths of up to 8 inches depending on species. They come in many colors, though Red Flavor is probably the most well-known. They are velvety squooshy soft to the touch, and have between 13 and 43 pairs of adorable tiny feets (again, depending on species). Also, they don’t have a skeleton and operate entirely by hydraulics.
Unlike vertebrates like you, the Velvet Worm moves by rapidly inflating and deflating parts of their squishy squashy bodies with internal fluid. Just imagine that they’re made entirely of water balloons that can wiggle awkwardly in any direction. Given their soft wobbly balloony body and adorable face, it may surprise you to learn that Velvet Worms are actually voracious predators. They are efficient and successful killers, mainly eating insects and other small creatures.
They hunt by sneaking up on possible prey and papping it gently with their retractable antenna to see if it is good for eating. Which is, uh, not the stealthiest option. I mean, can you imagine if every time you wanted a snack you had to walk up to it like “LET ME JUST RUB MY HANDS ALL OVER YOU TO SEE IF YOU’RE EDIBLE, HOLD STILL PLEASE”. It seems to work okay for the Velvet Worm, though. But anyway once it has the prey lined up in its sights, the Velvet Worm unleashes its secret weapon.
The Velvet Worm turns its whole face into a high-powered hose that jets a double stream of sticky slime up to a foot away! It’s the super-soaker of nightmares. And once the target is slimed, it ain’t goin nowhere. The slime rapidly hardens into a solid mess, literally gluing the victim in place. It’s the most righteously awesome special attack of any invertebrate short of the Bombardier Beetle.
After the Velvet Worm has immobilized its prey, it unleashes its even more secret weapon. Hidden in that soft gooshy adorable face are a pair of razor-sharp nightmare jaws and a powerful dissolving enzyme. The Velvet Worm uses them both on its victim, making quick work of prey. Some species of Velvet Worms will even hunt cooperatively, using their x2 Combined Slime Cannon to bring down large prey they wouldn’t be able to handle separately. These hunting parties are led by a female warlord (wormlord?) who will eat her fill before the other Velvet Worms are allowed to feast.
(Cold, merciless and completely adorable.)
This group hunting behavior shows that Velvet Worms have surprisingly complex behaviors. But it’s still got nothing on their reproductive strategy, which has been best described as “yikes”. After a brief courtship, the male Velvet Worm just kind of plops a packet of sperm onto the female’s back and leaves. Which, not very romantic, but okay. But then the female then proceeds to dissolve some of her skin and absorb the sperm into her bloodstream. Holy crap. Several months later, the female gives birth to a new crop of wriggly babies. It’s a functional strategy, but probably leads to an interesting domestic life. (“Don’t sass back at me mister, I dissolved my skin for you!”)
Though Velvet Worms in all their splendid weirdness are still commonly found across the world, we don’t actually know how they’re doing ecologically because they aren’t studied very often. We do know that Velvet Worms are threatened by habitat destruction and human expansion, and scientists suspect that individual species range from near threatened to critically endangered. This is not allowed.
Conservation programs need to be enacted for these good soft boys, and soon. We hope that Velvet Worms and their many many soft gentle feet stick around for a long time to come.