Hell, even if you have kinda-limbs we’ll consider letting you in. We’re looking at you, the more than 100 species of velvet worms, with your adorably stubby legs, face cannons that fire immobilizing slime, and nasty jaws that bore right through arthropod armor. You’re so ancient and unique and bizarre, so far removed from something like the average earthworm, that you get your very own phylum. But welcome to the club all the same.
The velvet worm may be velvety and squishy and tiny—between 0.5 and 6 inches long—but this critter is a ruthless hunter, not to mention quite the survivor. Velvet worms have been stalking Earth almost as long as land animals have existed. “They evolved during the Cambrian, approximately 540 million years ago, from a marine group called the lobopodians,” said biologist Ivo de Sena Oliveira of Germany’s University of Leipzig. “And despite their fragile aspect, velvet worms were able to overcome several geological, climatic, and vegetation changes until today.”
Perhaps that’s not surprising when you consider the weapons the velvet worm has at its disposal. On either side of its head are cannons—actually modified limbs—connected to a reservoir of slime made of proteins. In mere milliseconds, the worm can fire this goo at prey as far as 8 inches away, just like Spider-Man, only without the insufferable movie adaptations. The more its victim struggles to free itself from the slime, the more ensnared it becomes, like people watching Spider-Man movies.
Once their target is immobilized, “the velvet worms just walk slowly to the prey, make a small hole in its exoskeleton using the jaws, inject digestive saliva into its body,” and suck out the pre-digested tissues. And lest the slime go to waste, the worm eats that up as well. (Watch one hunt in the killer National Geographic video below.)
But how does the velvet worm find its prey in the first place? These are, according to Oliveira, absolute “sensorial machines.” Not only do they have eyes that likely provide them with monochromatic vision (a bit like seeing the world as an ’80s-era computer monitor, though probably not puke-green), but they also utilize their antennae to sniff out chemicals and changes in air currents. But most importantly, their entire body is covered with tiny bumps known as dermal papillae, which give the worm its velvety texture.
Dermal Insemination, Hydrostatic Skeletons, and Other 10-Dollar Words to Get You to Keep Reading This Article
To watch a velvet worm amble around is quite hypnotic, as its many stubby legs ripple up and down its body. Like all manner of other invertebrates, the velvet worm has a hydrostatic skeleton that supports its body not with bone, but with pressurized fluid. (You may have noticed that when you kill a spider it’ll flip over and curl up its legs. That’s not for cartoonish effect—the critter is in fact losing its internal pressure). But what the worm can do with this system is unique.
Now, when it comes to getting busy, the velvet worms have gotten downright creative with it during their half billion years of evolution—and why wouldn’t you, really. Males put off pheromones, a bit like wearing cologne, to attract the ladies. In most species, according to Oliveira, when the two come together they’ll mate by pairing their genital openings, with the male transferring a bundle of sperm called a spermatophore directly into the female’s body.
Other species take rather more bizarre approaches. Some Australian varieties, for instance, have “developed specialized head organs, with which the male can hold the spermatophore and put it into the female’s genital opening,” said Oliveira. And “males of some Chilean velvet worms lay spermatophores all over the female’s body, and the females are able to absorb them through the skin.” This is known as dermal insemination.
“I would rather associate such aggregations with environmental conditions,” he said, “as these animals naturally tend to concentrate in areas with optimal temperature and humidity conditions.” Velvet worms are quite susceptible to drying out, and must compete for space in rotting logs, which “are the only microhabitats that retain humidity and provide shelter for them and many other invertebrates during the dry season.”
So yeah, fine, perhaps we need to rethink social organization’s place in the velvet worm’s list of amazing qualities. But it still gets to stay in the worm club. Maybe we can make it secretary, or even treasurer, if that’ll help.
source: wired.com BY MATT SIMON