Peripatus

Peripatus
Scientific classification
Kingdom: Animalia
Phylum: Onychophora
Class: Udeonychophora
Order: Euonychophora
Family: Peripatidae
Genus: Peripatus
Guilding, 1826
Species

see text

Peripatus is a genus of Onychophora (velvet worms).

Evolutionary position

Peripatus is an invertebrate, said to be a living fossil because the living members appear similar to fossil species as much as 570 million years old, and because the group is transitional between the Arthropoda (including crustaceans and insects) and primitive Ecdysozoa such as tardigrades, priapulids and nematodes.[1] Peripatus was first described and named by Lansdown Guilding, a clergyman living in the vulcanic island St Vincent (in the Caraibbean) who studied the natural history of the island. Further early studies were made by Arthur Dendy in Victoria, Australia.[2]

Distribution

Peripatus is native to many habitats around the world, being found in Africa, Asia, Australia and New Zealand, Costa Rica and Brazil,[3][4] but none are known in Europe or Antarctica.

Anatomy

Tentacled head of the "living fossil" Peripatus ater

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.[1]

Physiology and ecology

Peripatus is a nocturnal carnivore. It respires through tracheae, as arthropods do. In Peripatus the tracheae, of which there are some 2000, consist of short, simple, unbranched tubes, that completely lack the elaborate closing mechanisms of typical arthropods and thereby render it prone to dehydration. Antennae are present on the head. Excretion is through nephridia, which are found in each of the legs.

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.

Species

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.[1]

The species include:

References

  1. 1 2 3 Ghiselin, Michael T. (1984). Eldredge, N.; et al., eds. "Living Fossils" (PDF). Peripatus as a Living Fossil. Springer-Verlag. pp. 214–217. Retrieved 2013-05-21.
  2. ↑ Smith, Brian J., (1981) Arthur (1865–1925), Australian Dictionary of Biography, Volume 8, MUP.
  3. ↑ Onychophora Online: velvet worms, peripatus, living fossils, by Julian Monge Najera
  4. ↑ New record of Peripatus (Macroperipatus)in Minas Gerais State (Brazil)
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