Paguriscus, Lemaitre & Felder & Poupin, 2017

Lemaitre, Rafael, Felder, Darryl L. & Poupin, Joseph, 2017, Discovery of a new micro-pagurid fauna (Crustacea: Decapoda: Paguridae) in the Lesser Antilles, Caribbean Sea, Zoosystema 39 (2), pp. 151-195 : 175

Genus Paguriscus n. gen.

TYPE SPECIES. — Paguriscus robustus n. gen., n. sp., by present designation. Gender: masculine.

ETYMOLOGY. — The generic name is derived from the genus name Pagurus , and using the masculine Greek suffix - iscus which denotes something diminutive, in reference to the minute size of specimens in the single species of this new genus.

DIAGNOSIS. — Eight pairs of biserial phyllobranch gills, no pleurobranchs on somites X, XI, XII (thoracomeres 5-7, above pereopods 2-4). Rostrum triangular. Ocular acicles simple. Crista dentata with accessory tooth. Chelipeds presumably unequal [left missing in holotype and single specimen known]. Sternite of somite XI (thoracomere 6, pereopod 3) with semi-circular anterior lobe. Pereopod 4 with single row of scales on propodal rasp, dactyl lacking preungual process. Pereopod 5 semi-chelate. Male with coxae of pereopods 5 slightly asymmetrical, trapezoidal in shape, extending posteriorly to form themselves paired sexual tubes; with unpaired, left pleopods 3-5. Telson nearly symmetrical, with weak or obsolete lateral indentations; terminal margins of posterior lobes oblique, with shallow median cleft.

DISTRIBUTION. — Known only from the type species collected in Guadeloupe, Lesser Antilles, Caribbean Sea, at a depth of 19 m.

REMARKS

Despite the incompleteness of the single male specimen of the new species herein described for this new genus, there is sufficient justification for a new genus based on the unusual low gill number (eight) and formula (lacking pleurobranchs), and by the morphology of the coxae and sexual tubes of pereopods 5 in this male. In pagurids, the number of gills is known to vary from 8 to 13 pairs, with the majority having 11. Previous to the discovery of this new genus, only one pagurid species Decaphyllus barunajaya McLaughlin, 1997 , was known to have eight pairs of gills. However, in Paguriscus n. gen., there are two arthrobranchs on the third maxilliped, and all pleurobranchs have been lost, whereas in D. barunajaya there are no arthrobranchs on the third maxilliped, and pleurobranchs are present on pereopods 3 and 4.

The posteriorly projecting, and slightly asymmetrical coxae of pereopods 5 in the male of Paguriscus n. gen. ( Fig. 16G ), is an unusual condition among genera of Paguridae with sexual tubes. In other pagurids with male sexual tubes, these are present as clearly separate structures from the coxae, whereas in Paguriscus n. gen. each coxa consists of a single, calcified tube-like piece. In Paguriscus n. gen., the coxae are somewhat similar to the solid, one-piece coxal extensions of males in some coenobitids (see Tudge & Lemaitre 2006), although the similarity can be attributed to evolutionary convergence.

Figures

FIG. 16. — Paguriscus robustus n. gen., n. sp., holotype ♂ 1.3 mm, Guadeloupe, sta GS 20, MNHN-IU-2013-4395: A, shield and cephalic appendages, dorsal view; B, right pereopod 3, lateral view; C, dactyl of same, mesial view; D, sternite XI of third pereopods, ventral view; E, propodus and dactyl of right pereopod 4, lateral view; F, telson, dorsal view; G, coxae of pereopods 5, sternite XIII, and anterior part of pleon, ventral view. Scale bars: 0.5 mm.