Velvet Worm

• It hunts by firing two jets of a glue that solidifies in the air from papillae on either side of its head, pinning the prey in a viscous net before approaching it.
• The onychophorans are an extremely ancient group, with fossil relatives from the Cambrian, and occupy an intermediate position between the annelids and the arthropods that makes them key to understanding the origin of insects and arachnids.
• It is viviparous and the young are born fully formed, with all their legs.
• Velvet worms form a phylum of their own, neither arthropods nor annelids, and they are among the oldest terrestrial animals: their form has barely changed since the Cambrian, and they are relatives of the Burgess Shale animals.
• It hunts by spitting glue. It has two oral papillae on the sides of its head from which it fires two jets of an adhesive secretion, in an oscillating sweeping motion that lays a net over the prey and immobilises it.
• The jet fires at high speed and travels up to several centimetres, and the oscillation is not produced by muscle: it is a passive effect of the papilla's elasticity, a mechanism that has been studied in fluid physics.
• It then injects digestive saliva and sucks up the liquefied contents, and it also eats its own glue so as not to waste the protein.
• It walks on between 13 and 43 pairs of soft, conical, unjointed legs, moved by hydrostatic pressure.
• Many species are viviparous, and some have a functional placenta, something extraordinary in an invertebrate.
• It is the type species of the genus Peripatus, described by Guilding in 1826 on Saint Vincent, and with it the study of the phylum was founded.

Skeleton type

Invertebrate - no rigid skeleton (onychophoran)

Habitat & environment

Damp leaf litter, rotting logs and forest floor of the Caribbean tropics

Sources consulted: Concha et al. (2015), Nature Communications, sobre el mecanismo de proyección; Guilding (1826); Mayer y Oliveira, revisiones de Onychophora