Peripatus

Peripatus (velvet worms; phylum Onychophora) A genus of onychophorans that are 1.4–15 cm long, with a dry, soft, flexible, very permeable skin that is moulted, overlying a single layer of epidermis, a thin dermis, and three layers of muscle fibres. Its complete lack of hard parts allows Peripatus to squeeze into very confined spaces. The coelom is greatly reduced and the body cavity is a haemocoel. Each of the 14–44 segments of the trunk bears a pair of nephridia and a pair of legs, each leg having an eversible vesicle opening close to the nephridiopore and probably used to take up water. The loss of water from the body cannot be controlled and dry ground presents an insuperable barrier. Locomotion is slow and occurs by the extension of the segments in a peristaltic wave, each extension raising the legs from the surface and thrusting them forward. A pair of antennae, anterior to the mouth, tap the ground as the animal moves. There is an oral papilla on either side of the mouth at the end of which opens a gland secreting an adhesive substance used in obtaining food and in defence. The adhesive can be discharged as a stream, for up to about 50 cm, and hardens on contact with air, entrapping the prey or intruder in a tangle of sticky fibres. Most species are predatory on smaller invertebrates. All are nocturnal. Peripatus occurs in moist places in the tropics and the temperate regions of the southern hemisphere.