Peripatus is an invertebrate, said to be a living fossil because the living members appear similar to fossil species as much as old, and because the group is transitional between the Arthropoda (including crustaceans and insects) and the Annelida (segmented worms including earthworms). The group has traditionally been placed in its own phylum, the Onychophora, but may belong with the Arthropoda, making the myriapods and insects their closest relatives; an alternative view is that they are closest to the Tardigrada and Pentastomida.
Peripatus was first described and named by Lansdown Guilding, a clergyman living in St Vincent who studied the natural history of the island. Further early studies were made by Arthur Dendy in Victoria, Australia.
Peripatus resembles a caterpillar, with its many pairs of legs, while its structure has similarities to both arthropods, but it also has many similarities to annelids, as well as some special features all of its own.
Peripatus shows no external segmentation; the legs are not jointed like arthropod legs, although they possess arthropod-like claws. The outer covering of the body is a cuticle covered in unique microscopic projections known as papillae. These papillae give Peripatus its velvety texture. The body is composed of segments like those of annelids, with segmentally arranged nephridia. The eyes are similar to those of annelids.
Physiology and ecology
Peripatus feeds by trapping its prey (mostly small insects) in a white, sticky fluid it ejects from two antennae near its head. The fluid hardens on contact with the air immobilizing the prey. Peripatus then chews a hole in its prey's exoskeleton with its mandibles (which move independently of each other), injects digestive enzymes, and begins sucking out its prey's pre-digested innards.
There are about 70 species, in two families: the Peripatidae (including the genus Peripatus), which are viviparous with a placenta or a yolked egg which develops inside the body; and the Peripatopsidae which are oviparous or at least lack a placenta.
The species include:
- Peripatus antiguensis Bouvier, 1899
- Peripatus bavaysi Bouvier, 1899
- Peripatus bouvieri Fuhrmann, 1913
- Peripatus brolemanni Bouvier, 1899
- Peripatus dominicae Pollard, 1894
- Peripatus evelinae (Marcus, 1937)
- Peripatus heloisae Carvalho, 1941
- Peripatus jamaicensis
- Peripatus juanensis Bouvier, 1900
- Peripatus juliformis Guilding, 1826
- Peripatus manni Brues, 1913
- Peripatus ruber Fuhrmann, 1913
- Peripatus sedgwicki Bouvier, 1899
- Peripatus swainsonae Cockerell, 1893
- Ghiselin, Michael T. (1984). "Living Fossils". In Eldredge, N. et al. Peripatus as a Living Fossil. Springer-Verlag. pp. 214–217. Retrieved 2013-05-21.
- Smith, Brian J., (1981) Arthur (1865–1925), Australian Dictionary of Biography, Volume 8, MUP.
- Onychophora Online: velvet worms, peripatus, living fossils, by Julian Monge Najera
- New record of Peripatus (Macroperipatus)in Minas Gerais State (Brazil)