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  • Dan Moskovitz

My Favourite Spineless Creature: The Peripatus

Lovingly Crafted by Dan Moskovitz (he/him)

In the undergrowth, there is a predator. Silently waiting, it eventually senses its prey. A soft step on one leg. A second on another. More on the third, fourth, and fifth legs. Then, suddenly, it shoots two jets of white sticky fluid which traps the unfortunate beetle. The fluid keeps the beetle immobilized while the peripatus injects its catch with saliva, which digests its soft tissue. The peripatus then sucks it all out, as if drinking through a straw.

I love peripatuses (ngāokeoke). They’re small nocturnal caterpillar-like creatures with stubby little legs and antennae, usually sporting a spotted dark velvet skin. I had never heard of them until last summer when I was frantically applying for an internship somewhere, anywhere. I stumbled upon one all about peripatus in VUW’s own school of biology. While applying, I looked them up and quickly got obsessed. It didn’t take long to realize how I wanted the internship more than anything. I was lucky enough to get it, and since then my love for these creatures, also called velvet worms, has only grown. 

A peripatus. Image credit: Perran Coppard.

Ngāokeoke inhabit forested areas, usually inside a bit of rotting wood. They head out at night to hunt and require humid, damp, and warm conditions. As peripatuses’ pores are perennially open, they have no mechanisms to stop themselves from drying out—hence why they spend most of their time nestled in a nice damp rotting log. They are native but not endemic to New Zealand, and are usually between 2 to 8 centimeters long, though ones in the Caribbean can get up to a whopping 22cm. 

While called velvet worms, peripatus aren’t worms, and you should feel silly for thinking so. They may look like caterpillars, but they aren’t those either. Rather, ngāokeoke is something far odder. Neither worm nor insect, but something in between. 

To be between a worm and an insect is a whole order of uniqueness. Peripatus are in their own separate phylum, Onychophora. Which leads to the creature with already too many names also being called Onychophorans. But more importantly, a phylum is about the highest level of biological categorisation there is. Peripatus constitutes one, insects are in another, and the true worms are split up between four other phyla, but that’s a different kettle of chordates.

For comparison purposes, humans sit in phylum Chordata. Our flatmates in phylum Chordata include all other mammals, birds, reptiles, amphibians, fish, tunicates, and lancelets. Tunicates, for reference, are immobile marine filter feeders. That’s our flatmate. 

To put it another way, a peripatus is as similar to a worm or an insect as you are to a starfish.

Being between worms and insects on the evolutionary ladder also means peripatuses are extraordinarily old. 500 million years old, in fact. Dinosaurs didn’t even arrive on the scene until 230 million years ago. Even more remarkable is how peripatus haven’t changed much over the years; they look pretty much the same now as they did back then. 

But let’s go back to their projectile slime I described in the hook. This is one of the most distinctive things about peripatuses. So much so that the Wikipedia page for Onychophorans has the subheading “slime” alongside the more scientifically titled headings, resulting in a hilarious discordance: 

Screenshot from Oncyohpora Wikipedia page.

As ambush predators, ngāokeoke shoots said slime to catch their prey. Range varies, but has been reported to usually be around a centimeter—a big shot for a small invertebrate. The closest analogue to said slime is spider silk. Which is why I like to describe velvet worms as spiders with guns.

Can you imagine the fame a creature like this would have if it wasn’t tiny? Imagine a lion prowling the savannah who will shoot you from range, immobilize you, inject you with spit, and then watch and wait while you are digested alive from the inside out. That’s what we’re talking about on the small scale. 

The uniqueness of peripatuses doesn’t end there. You may recall from high school biology how one of mammals’ distinctive traits is our ability to give birth to live young. Well, we’re not special. Velvet worms were doing it for millions of years before us. In fact, the females of some species have two uteri (uteruses). Meaning they can be raising different baby onychophorans at different stages of development. This is one area of extraordinary diversity throughout the Onychophorans; some lay eggs. Some have eggs which hatch inside the mother’s body before she gives birth to the young. One (non-NZ) species even reproduce through parthenogenesis, an interesting and complicated method of reproduction where young grow from unfertilized eggs and males are not required. 

One area of my research is: ‘where on earth are Wellington’s peripatuses?’. We know they’re hanging out in rotting logs in both Zealandia and Ōtari-Wilton’s bush, but beyond that, dunno. Do they prefer native bush or introduced flora? Also no idea. Because like most invertebrates, they’re criminally understudied. Vertebrates tend to get six times the overall financial investment of invertebrates. Personally, I find that really sad; velvet worms are just one example of the incredible biodiversity lurking in our undergrowth. 

Who knows what other amazing things are beneath your notice.


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