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Sunday, February 19, 2012

Creature Feature: Velvet Worms.

Velvet worms have come up on this blog before. They are one of those obscure animals that biologists fawn over, but everyone else is nigh-oblivious to. Velvet worms are slowly growing in popularity in the pet trade, so you may well be seeing them soon, but for now, this will be an introductory post into their wonderful, weird world.

 

Velvet worms are small (10 cm max) invertebrates in the phylum Onychophora (lit. "claw-bearers"). (For those of you unfamiliar with scientific classification, velvet worms having their own phylum means that they're as big a group as arthropods. The phylum most of you are familiar with is probably Chordata - i.e. everything with a spinal cord.) They live in most tropical regions of the world, including (but not limited to) South America, Australia, and parts of Africa. (Yes, these guys are so weird and ubiquitous that even Australia could not make them any weirder.) They are nocturnal hunters that eat other, smaller invertebrates. They are a very big group of invertebrates themselves, so this will be one of my less complete entries.

Velvet worms do indeed look like something out of the Burgess Shale. Those little conical legs and antennae look an awful lot like yesterday's creature, which was as nightmare fuel-ish as Hallucigenia. The body structure of velvet worms has gone virtually unchanged for over 500 million years. Climate change aside, I would call that success.

On the biological side of things, it was once thought that velvet worms were a transition stage between annelid worms and modern day arthropods. Now, in part thanks to genetic testing (most likely), we know that they are actually somewhere between tardigrades (water bears) and insects. This still makes them invaluable to evolutionary science.



Along with being interesting as living fossils, velvet worms have one more creep factor: one of their favorite defenses is to shoot a string of glue into a predator's face. The same gluey string is used to ensnare prey as in the clip above. It even has nice little nozzles to use as miniature glue guns. Velvet worm used String Shot!

Oddly enough, velvet worms are social animals. They live in groups of 15 or more. Velvet worms found together are often closely related - especially the males, since the females are more aggressive (and even feed first!). The mating behavior varies with the species, but in short, the males put their spermatophores on their heads and look for a female that finds their headgear attractive. Their little invertebrate brains are complex enough for elaborate courtship and social interactions. Evolution has treated them very well.



This is just a small sampling of the weirdness that is velvet worms. Now I'm starting to want them as pets, too. Breathe, breathe...my menagerie is large enough. Expect a sequel entry regardless.

2 comments:

  1. What a fascinating creature! How about velvet worm week? I find the fact that they've been around so long and never developed eyes, mind boggling. Are there many creatures like that?

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  2. They should totally get their own week! I was wondering what to do for my next one...I'll put it up on a poll.

    You mean creatures that can live without eyes, or living fossils in general?

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