I had no idea such things existed, but behold the remipede:
Yes, it's a crustacean, although it doesn't look like any I've seen before. You're not likely to run into them casually; they're found deep in Central American caves, with one species found in the Canary Islands and another in Western Australia. Besides being weird-looking critters, they're also the only known venomous crustacean. Take a look at that clawed face!
There are no known instances of humans being bitten by one of these things — they aren't exactly living underfoot. They have big sacs inside those front claws that contain a cocktail of proteases, chitinases, and a neurotoxin.
They poison their prey with an injection of a poisonous mixture that simultaneously paralyzes or kills them, and reduces their guts to a slurry that can be sucked out.
This toxin is represented by two distinct contigs that have the conserved cysteine pattern characteristic of β/δ agatoxins with virtually identical spacing [C-x(6)-C-x(6)-C-C-x(4)-C-x-C-x(6)-C-x-C] (Figure 5). β/δ agatoxins are a recently described type of spider venom neurotoxin (Billen et al. 2010), which causes pre-synaptic voltage-gated sodium channels to open at resting membrane potentials in insects. The resulting neurotransmitter release generates a stream of action potentials in motorneurons, resulting in irreversible spastic paralysis of the victim.
von Reumont BM, Blanke A, Richter S, Alvarez F, Bleidorn C, Jenner RA. (2013) The first venomous crustacean revealed by transcriptomics and functional morphology: remipede venom glands express a unique toxin cocktail dominated by enzymes and a neurotoxin. Mol Biol Evol. 2013 Oct 16. [Epub ahead of print]
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I've read the bit here, and the articles, and there seems to be no description as to how big the critter is. From the video I'm guessing about 3 to 5 cm but I find it remarkable, especially because I've noticed this trend in other scientific sources, that they leave out the simplest and most obvious characteristic, relative size.
Yes, I know that relative size is not a measure of scientific importance and not disclosing it up front is a way of preventing the report being discounted early on, but it is something most people want to know.
Even if you didn't want to disclose it up front it would be nice if there was something to scale off of.
Nobody has been bitten? That is what post-docs are for. You know it has to be done. In the interest of science.
You could just leave an undergraduate in the room, alone, with the critter and let nature take its course. You would want cameras, lot of cameras, from multiple angles. If you could wire the person for vital signs...
@ Art: Size: about the size of your pinky. Here's a link: