Epiperipatus cratensis

Epiperipatus cratensis
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Onychophora
Family:	Peripatidae
Genus:	Epiperipatus
Species:	E. cratensis
Binomial name
Epiperipatus cratensis Brito et al. 2010

Epiperipatus cratensis is a species of velvet worm in the family Peripatidae. This species is found in northeastern Brazil. This velvet worm is notable as a small species of Epiperipatus (reaching only 32 mm in length) with many legs (as many as 34 pairs in females and 33 pairs in males).

Discovery, distribution, and habitat

This species was first described in 2010 by a team of biologists led by the zoologist Samuel V. Brito. They based the original description of this species on a male holotype and three paratypes (two males and one female). These specimens were collected during the rainy season in 2007 from the banks of a river in a tropical humid forest in the Chapada do Araripe mountains of northeastern Brazil. These specimens were found by searching in small holes in the ground and under stones, leaf litter, or fallen tree trunks.

The type specimens were found in the municipality of Crato in the southern part of the state of Ceará in Brazil. The species name refers to this type locality. These specimens are deposited in invertebrate collection of the Universidade Regional do Cariri in Crato in Brazil.

This species was the first velvet worm described from the mountainous forests of northeastern Brazil. These forests represents islands of the Atlantic Forest biome isolated within the arid and hot Caatinga domain. These fragmented humid enclaves are vestiges from the interglacial periods of the Pleistocene epoch, when the Atlantic Forest advanced into the Caatinga before retreating to its original distribution.

Phylogeny

A phylogenetic analysis based on molecular data and morphology places Epiperipatus cratensis in a clade with three closely related species of Epiperipatus: E. titanicus, E. lucerna, and E. hyperbolicus. Within this clade, these three species appear in a sister group, emerging as the closest relatives of E. cratensis among all the described species of Epiperipatus in this analysis. Like E. cratensis, these three species are all found in the humid highland forests of northeastern Brazil.

Description

The male holotype measures 27 mm in length and 4.7 mm in width; the female paratype measures 32 mm in length and 5.2 mm in width. These velvet worms range from purple to white. The antennae feature only 31 to 36 complete rings, fewer than those observed in other Brazilian species of Epiperipatus. The dorsal surface of each segment features 12 transverse folds (plicae) separated by deep furrows. The basal piece of the primary papillae features five to seven scale ranks. The apical piece has a spherical shape with an asymmetric distribution of scales: two or three ranks in the back, but as many as four elsewhere.

Males of this species have 30 to 33 pairs of legs; females have 33 or 34 pairs. In males of this species, two or three pairs of the pregenital legs feature crural papillae (tubercles), with one or two papillae per leg. The soles of the feet feature four spinous pads, except for the last pair of legs, which feature only two spinous pads. The feet have three papillae, two anterior and one posterior.

This species exhibits traits considered diagnostic for the genus Epiperipatus. These traits include the number of pregenital legs with crural papillae in males and the number of scale ranks at the base of the primary papillae. Furthermore, like other species in this genus, this species features nephridial tubercles and four complete spinous pads on the fourth and fifth leg pairs, with each tubercle located between the third and fourth spinous pads on the soles of the feet.

This species shares a more extensive set of traits with its close relatives, E. titaniccus, E. lucerna, and E. hyperbolicus. For example, all four species feature bright diamond patterns on the dorsal surface of the body. Furthermore, all four species feature one accessory tooth in addition to the main tooth on the inner jaw. Moreover, males of all four species feature anal glands with inconspicuous openings.

The species E. cratensis can be distinguished from these close relatives, however, by the apical piece of the primary papillae. In E. cratensis, this piece is spherical with an asymmetric distribution of scales. In E. titanicus, this piece is conical and symmetric. In E. lucerna, this piece is asymmetric but is also conical. In E. hyperbolicus, this piece is spherical and asymmetric but is also more robust than in E. cratensis. Furthermore, E. hyperbolicus features fewer legs (23 to 25 pairs), E. lucerna can feature fewer (27 to 31 pairs), and E. titanicus features more (36 to 39 pairs) than those recorded in E. cratensis (30 to 34 pairs).