Icky, Sticky Velvet Worms

The first time I ever saw, let alone heard of velvet worms was in my invertebrate zoology lab last semester. To explain how perplexing that encounter was, you need to understand how this class worked: when I attended lab every Tuesday around noon, I usually had to complete between ten and twelve workstations regarding that week’s invertebrate animal phylum. Each station either consisted of one or several microscopes, about three to twenty shells or jars of preserved organisms, sometimes newspaper articles, live animal(s) and/or dissected animal(s), plus a worksheet with the assignment printed on it.

Due to the bulk of notes I had to take and animals/animal parts I had to draw and label, each station could take anywhere between 10 and 20 minutes or more. This meant that by the time I reached my final station each week, I was hungry, cramping in the hand, cold because that lab was always freakishly chilly, probably calculating how much time I had left before my bus arrived, and definitely not operating at 100% brain capacity.

On November 2, 2021, this was the state in which I knelt on the chair at my last station of the day, peered into the microscope, and immediately wondered if I was hallucinating. Staring back at me from the slide was the caterpillar from the black lagoon. This dude, to be precise:

Velvet worms, as you may have guessed from the antennae and limbs, are not actually worms. Nor are they caterpillars. Nor are they, in fact, arthropods. But, seeing as their phylum Onychophora is part of the Panarthropoda clade with Tardigrada and Arthropoda, I’m going to say that they’re close enough to get featured on this blog. Plus, they’re really wacky and I really want to talk about them, so here goes nothing:

First of all, velvet worms have retractable claws. Seriously! Velvet worms have anywhere between 14 and 43 stubby little legs, and each leg hides a little claw that can be retracted when walking around. These claws are the reason behind the velvet worms’ phylum name, Onychophora, which means “claw-bearers.”

If you’re like me and you’ve never seen one of these funky fellas before, you might live in the Northern Hemisphere. Velvet worms live in South America, Australia, and parts of Africa and Southern Hemisphere islands, but even in their native range they can be tricky to find. Like a lot of arthropods, velvet worms breathe through holes in their cuticle (outer body covering) called spiracles. Unlike most arthropods, however, velvet worms have no way of closing their spiracles, so they must live in warm, damp areas like leaf litter to avoid drying out. If you’re out looking for velvet worms yourself, you’ve got decent odds at finding them under rocks, logs or leaves in the woods.

Notice that white bulge under the velvet worm’s antennae? That’s one of its oral papillae, which the velvet worm uses to spit a glue-like substance at its insect prey. Once the insect is thoroughly covered in spit and rendered immobile, the velvet worm feeds like a spider: it bites open the insect’s exoskeleton and spits digestive fluids inside, then slurps up the resulting bug-soup. Yum. Gross.

Another interesting factoid about velvet worms is that most are ovoviviparous, meaning their eggs hatch inside their bodies, while others lay eggs or birth fully developed young like mammals. One species even reproduces by parthenogenesis, in which females basically give birth to clones of themselves. In terms of their similarities to the Arthropoda phylum, velvet worms must shed their cuticle to grow and can communicate with one another using pheromones, chemical secretions released from the velvet worm’s crural gland.

Although they may spit glue at you and possibly nip you if you bother them, velvet worms aren’t poisonous and pose no threat to humans. Nothing much seems to be threatening them at the moment, either; although negatively impacted by habitat loss and being captured as pets, velvet worms are not endangered and actually have stable population numbers around the globe.

Like a lot of other Americans I know, I am kind of afraid of Australia on account of the wide array of dangerous creatures lurking there. Now, however, the velvet worms have provided me with an incentive to visit. Then again, I can also find them in Chile, New Zealand, and plenty of other hopefully-less-dangerous places… Kudos to you, Australia, but I don’t think I’m ready to join you in surviving killer snakes, spiders, and buff kangaroos just yet. If any of y’all come across a velvet worm, though, send me a pic!