Ligiarctus Renaud-Mornant 1982

Genus Ligiarctus Renaud-Mornant, 1982 (emended by Gomes-Júnior et al. 2018)

Type species

Ligiarctus eastwardi Renaud-Mornant, 1982.

Amended diagnosis

A genus of Florarctinae with narrow head. Wide implementation of the primary clavae occupying the lateral edge of the head. Large, rigid and backwards bending primary clavae (shared with Higginsarctus gen. nov.) supported by strong internal cuticular structures at their bases. Frontal and caudal ala (without procuticular support) present in females. Frontal ala absent in males. Claws of external digits with internal distal notch.

Material examined

Holotype of Ligiarctus eastwardi Renaud-Mornant, 1982

USA • ♂, adult; Atlantic Ocean: North Carolina; 34°07.3′ N, 75°57.7′ W; depth 400 m; 1974; B.C. Coull and R.P. Higgins; R/V Eastward; fine sand; MNHN AH551.

Other material

USA • 1 ♀; Atlantic Ocean, North Carolina; 34°07.4′ N, 75°57.0′ W; depth 439 m; 16 Nov. 1983; R.P. Higgins leg. (RH 1834); R/V Cape Hatteras; NHMD-293914.

Remarks

Following the exclusion of Ligiarctus alatus (= Higginsarctus alatus gen. et comb. nov.) from Ligiarctus, the genus diagnosis is amended to include only characters exhibited by Ligiarctus eastwardi.

The original description of Ligiarctus eastwardi by Renaud-Mornant (1982) included only males. In the present study, we were able to obtain information on female characters of Ligiarctus eastwardi for the first time, from the single female collected at the type locality in 1983. The specimen is clearly an adult female with evident seminal receptacles and typical female gonopore consisting of a rosette of six cells. The female is 161 µm long from the anterior margin of the head to the posterior margin of the body. The body is ovoid, being broadest (81 µm) at the level between the second and third pair of legs. The primary clava is 53 µm long and slightly curved. Secondary clavae are not recognizable. A small frontal ala is evident, extending between the internal cirri. The caudal ala is disc-shaped without any procuticular support.

Comparing the female specimen to the holotypic male, strong secondary sexual dimorphism is indicated by body size, clava length and by the presence of a frontal ala in females. The male is much smaller (109 µm) than the female (161 µm), and the primary clavae proportionally much longer (52 µm).