This is a bit of a shame, when they are such unusual animals with amazing capabilities. Series B, Biological Sciences Vol. Richard Silcox Guest Writer. All Posts. While we can try to convince you that these are not in fact plush toy centipedes, velvet worms certainly look like them. Even with the knowledge that this is not the case, velvet worms are still remarkable creatures, and unusual in almost every way.
Eoperipatus sumatranus. Underside shot of Eoperipatus sumatranus. Related Stories. The ugly-cute little monsters from the dark abyss. She hunts for aliens under the Baikal ice. Velvet worms are ambush predators, hunting other small invertebrates by night. To subdue their prey, they squirt a sticky, quick-hardening slime from a pair of glands on their heads.
After the prey is ensnared, the velvet worm bites into it, injecting digestive saliva that helps liquefy the insides for easier snacking. The slime is energetically costly to make, so velvet worms will often eat any excess slime they have produced to shore up their reserves. Check out a sliming in action here. At least one species is highly social with a strict dominance hierarchy.
The group hunts together, and after a kill the dominant female always feeds first, followed by the other females, then the males, and finally the young. The social hierarchy is established and maintained through aggression: higher-ranking individuals will chase, bite, kick, and crawl over subordinates.
Velvet worms are survivors. They belong to a clade that has been around for over million years. Fossilized marine versions of velvet worms from the Cambrian period have been found in the Burgess Shale in Canada million years old and the Chengjiang formation in China million years old. Velvet worms are now considered to be close relatives of arthropods and tardigrades. They're of interest to paleontologists because they might help provide an idea of what the ancestors of arthropods were like.
They have a number of bizarre reproductive strategies. All the velvet worms reproduce sexually, except for Epiperipatus imthurni they reproduce by parthenogenesis and no males have ever been observed.
The other velvet worm species have evolved several creative ways to deliver the male's sperm to the female's egg. Some species deposit their spermatophores directly into the female's genital opening, though the means by which they do this varies.
The velvet worm bites off parts of the prey then sucks them up after they have been softened by digestive saliva extruded from the velvet worm's mouth. Any undigested portions are excreted by the anus at the rear end of the body. Segmental excretory organs the nephridia also remove metabolic wastes. The slime is also squirted in self-defence. An enemy with a face full of slime gives the velvet worm time to escape.
Velvet worms are quite secretive and display 'photonegative' behaviour, meaning they hide away from light. Velvet worms breathe through little holes called 'trachea' that are scattered over the body. These pores are permanently open, so water from the body can easily be lost. The porous nature of their cuticle means that velvet worms can easily dry out, so they are restricted to areas of high humidity, such as in logs, under stones, in the soil, or among leaf litter.
Reproduction takes place in an extremely curious manner. The male deposits packets of sperm spermatophores on the body of the female, for example on her back or sides. Some species deposit their spermatophores directly into the genital opening of the female. This method has been observed in a few Australian species. In those species that deposit sperm on the skin of a female, the skin tissue collapses where the sperm are deposited and the sperm migrate into the female's body, where they penetrate the ovaries to fertilise the eggs.
Many species have a pair of sperm receptacles close to the ovaries, and these can be used to store sperm for many months to fertilise eggs as needed. This is a useful adaptation when encounters between males and females may occur only rarely. The males of most species have glands on the underside of the legs that secrete a pheromone to attract females.
Embryonic development is unusually diverse in onychophorans. Some species lay large yolk-filled eggs, while others retain yolky eggs within the female until they are ready to hatch. Some other species though none of the Australian species have small eggs without a yolky food source, and the developing young obtain nourishment from their mother's body in a manner similar to placental mammals.
The rainy season is the one time of year this Vietnamese species exits the soil, he said. Unlike arthropods a huge group of animals that includes ants and spiders , velvet worms lack hard exoskeletons. Instead their bodies are fluid-filled, covered in a thin skin and kept rigid by pressurized liquid. This hydrostatic pressure allows them to walk, albeit very slowly, on fluid-filled, stubby legs that lack joints.
Slimed Their slowness works to their advantage. To hunt, they sneak up on other insects or invertebrates. And that's when the sliming begins — velvet worms like the newfound species hunt by spraying a "net of glue" onto their prey from two appendages on their backs, Oliveira said. This nasty material consists of a mix of proteins that impedes movement. Oftentimes the velvet worms will eat any excess "glue," which is energetically costly to make.
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