Invertebrates are by far the most interesting animals I blog about. All those movies where insects take over the world and stuff totally make sense. See, every time I find a cool fact about an invertebrate, I then look it up online and see what else I can find out about it. And every time there’s about five more amazing fact about that particular creature. And today’s animal is no exception.
Velvet worms are funny looking insects in the phylum Onychophora. They are called worms, and kind of look like that, but they have legs. So it makes them look like caterpillars, except these guys wont turn into anything beautiful like a butterfly. And these worms don’t need to; they’re already cool enough. Here’s a picture:
Velvet worms maintain their shape due to the pressure from the fluid inside their bodies. Which means these little guys don’t have a rigid skeleton, either internal or external. Their fluid filled bodies create enough rigidity to allow muscles to act, letting the worm move. This it does by contracting and stretching the body, I assume in a manner similar to inchworms. Which is by far the cutest way of moving. I don’t know why I find it so cute, but I do.
Despite the fact that they are worm-like, and worms aren’t usually associated with high society, velvet worms have a surprisingly complex social structure. They live in groups of around fifteen individuals, all closely related. Within the groups there is a dominance hierarchy; the alpha female feeds first, followed by other females and then the males. The hierarchy is determined by aggressive behaviour, mainly by biting and crawling on top of one another. Which is definitely a reasonable way to establish dominance. Groups are also extremely aggressive to intruders. So to summarize, velvet worm society is a lot like high school, with worms forming cliques and clawing and biting each other to get to the top of the social ladder.
Velvet worms have a very interesting way of hunting. They crawl around at night, possibly using air currents to locate prey. Once they find their victim, the worm moves closer to the animal and brushes it gently with its antennae to establish if it is a suitable meal or not. The worm’s soft and slow way of moving helps it avoid detection from its prey. Once the target has been identified, the worm squirts a slime at the prey, which glues the hapless victim in place. The worm can shoot slime up to four centimetres. If the first squirt doesn’t completely immobilize the prey, additional shots may be thrown at the animal’s legs or fangs. The worm then bites the prey, further immobilizing it. It then feeds, in appropriate dominance order, and reingests any dried slime, so as to not waste any nutrients. I think a pretty awful horror movie could be made about giant velvet worms. Ten foot long worms that shoot glue? Pretty awesome, right?
We’re not done yet though! Velvet worms also have some crazy ways of reproducing. Most velvet worms reproduce sexually, and two particular species (in the genus Peripatopsis) have a strange way of doing this. A male worm places two spermatophores on the female’s back, where her own cells then collect and decompose the skin beneath the sperm. This lets the sperm enter the body where they then make their way to the ovaries and fertilize her eggs. Sounds like a pretty kinky way to have sex to me. Another interesting thing: some species of velvet worms produce live young, something not usually seen in the worm world.
Anyway, there’s lots more I could say about velvet worms, but I like to try and keep these posts relatively short. I’ve highlighted the most interesting things anyway. I wonder if it’d be fun to have a pet velvet worm… You could make it shoot slime at your enemies. Yup, pretty fun.
Cover image By Tony Wills – Own work CC BY-SA 3.0