Velvet Worms

by Kim Woolcock

When I started writing It’s Tough to be Tiny, I didn’t know what a velvet worm was. I stumbled across a reference to them while researching small creatures with superpowers, and the name immediately hooked me. Velvet worms?? Would they be fuzzy and cute? And why had I never heard of them?
It turns out they are not fuzzy but they are very cute. And they are deadly hunters. I am a sucker for creatures that are cute but deadly, and as soon as I started reading about them, I knew velvet worms needed a place in the book.
 

The velvet worm Euperipatoides flexes its slime glands.
Image by: Andras Kezzei/Flikr

Velvet worms have soft, squishy bodies, and a kind of nubbly appearance (the nubbins are tiny whiskers that help them feel their way through tight spaces). To me, they look like living sock puppets. Their unique way of hunting is what makes them famous, though. They shoot their prey with sticky goo that comes out of two nozzles (slime papillae) on their face. The goo nozzles wiggle back and forth, like a garden hose that no one’s holding onto. The prey gets covered in a layer of sticky goo that rapidly hardens into a stiff cage of glassy threads. The velvet worm can then bite the prey to inject innard-melting enzymes, and drink the prey milkshake at its leisure.

A velvet worm attacking its prey
By: Stacey Thomas

Scientists have been fascinated for almost a hundred years by how the slime transforms from a sprayable goo to a glassy thread (the process is reversible, too—the dried slime melts in water, and can re-harden!). Even cooler, the prey actually helps in its own capture. Its struggles help to dry out and stiffen the threads, similar to how kneading transforms bread from a sticky lump into a stretchy dough.

A velvet worm devouring its prey
By: Stacey Thomas

So how had I never heard of them? They are not exactly the most cosmopolitan creatures. There are only about 200 known species of velvet worms (phylum Onychophora), mostly in the litter layer in tropical and southern hemisphere forests. They hunt at night, and even the scientists who study them say they are kind of hard to find.
Adding to their mystery, velvet worms have recently been found to be related to Hallucigenia sparsa, a puzzling fossil from the Cambrian explosion about 500 million years ago. A tubelike creature with spines on one side and tentacles on the other, it was called Hallucigenia because it was so bizarre looking that scientists couldn’t tell which way was up or which end was its head, never mind what other animals it might be related to.
 

Hallucigenia sparsa fossil
Taken by: Michael Brett-Surman

A recent study used state-of-the-art electron microscopes to examine the claws of Hallucigenia and modern velvet worms, and found that they both have claws with layers like an onion, indicating they are related. I love knowing that Hallucigenia, once so bizarre no one had ANY idea what it was related to, has such adorable descendants.
If you’d like to learn more about the amazing world of minibeasts, check out my book It’s Tough to be Tiny: The Secret Life of Small Creatures, illustrated by Stacey Thomas (Flying Eye Books, 2022). It’s all about the superpowers of small creatures, from springtails to cone snails, and how they stay safe, hunt for their lunch, or buddy up with bigger creatures for the benefit of both. It’s full of glitter and gross, because nature is both.
 

Resources:

A Baer, S Schmidt, G Mayer, and MJ Harrington. (2019) Fibers on the fly: Multiscale mechanisms of fiber formation in the capture slime of velvet worms. Integrative and Comparative Biology 59(6): 1–10. https://doi.org/10.1093/icb/icz048

Baker CM, Buckman-Young RS, Costa CS, and Giribet G. (2021) Phylogenomic analysis of velvet worms (Onychophora) uncovers an evolutionary radiation in the neotropics. Molecular Biology and Evolution 38(12): 5391–5404. https://doi.org/10.1093/molbev/msab251

Garwood RJ, Edgecombe GD, Charbonnier S, Chabard D, Sotty D, and Giribet G. (2016) Carboniferous Onychophora from Montceau-les-Mines, France, and onychophoran terrestrialization. Invertebrate Biology 135(3):179–190. doi: 10.1111/ivb.12130.

Smith, M, Ortega-Hernández, J. (2014) Hallucigenia’s onychophoran-like claws and the case for Tactopoda. Nature 514, 363–366. https://doi.org/10.1038/nature13576

https://theconversation.com/the-worlds-weirdest-creature-finds-descendants-in-cuddly-velvet-worms-30438

https://www.nytimes.com/2015/07/07/science/hallucigenia-cambrian-explosions-strange-looking-poster-child.html

https://www.wired.com/2014/03/the-creature-feature-10-fun-facts-about-velvet-worms/