Paguriscus robustus, 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 : 175-178

Paguriscus robustus n. sp.

( Figs 16 , 17 ; Table 1)

TYPE MATERIAL. — Holotype. ♂ 1.3 mm, Guadeloupe, sta GS 20, Port-Louis , outside Grotte aux barracudas, 16°27.34’N, 61°32.07’W, 19 m, 16.V.2012, MNHN-IU-2013-4395.

ETYMOLOGY. — The specific name is from the Latin robustus , and refers to the robust coxae of pereopods 5 that in the male of this species form the sexual tubes.

DISTRIBUTION. — Known so far only from Guadeloupe, Lesser Antilles, Caribbean Sea. Depth: 19 m.

HABITAT. — Found living in a gastropod shell.

DESCRIPTION OF HOLOTYPE

Shield ( Fig. 16A )

Glabrous, at most with scattered short setae, slightly longer than broad; anterior margin between rostrum and lateral projections weakly concave; anterolateral margins sloping; posterior margin roundly truncate. Rostrum bluntly subtriangular, reaching distally to about same level of lateral projections. Lateral projections subtriangular, terminating in small sharp spine.

Ocular peduncles

About 0.6 length of shield; dorsal surface with row of sparse short setae; corneas weakly dilated. Ocular acicles subtriangular, dorsal surface flat; terminating in strong distal spine.

Antennular peduncles

Exceeding distal margins of cornea when fully extended by about 0.5-0.7 length of ultimate segment. Ultimate segment naked except for 2 long dorsodistal bristles. Penultimate and basal segments naked; basal segment with blunt ventromesial angle, and small spine on lateral face.

Antennal peduncles

Exceeding distal margins of corneas when fully extended by nearly entire length of fifth segment. Fifth and fourth segments unarmed except for scattered short setae. Third segment with strong spine on ventrodistal angle. Second segment with dorsolateral distal angle produced into short simple or bifid spine-like process slightly overreaching distal margin of third segment; dorsomesial distal angle with small spine. First segment with or without minute, curved spine on lateroventral angle. Antennal acicle long, exceeding distal margin of cornea by about 0.3 length of acicle, broadly curving outward and terminating in strong spine, mesial margin with few short setae. Flagella missing in holotype.

Mouthparts

Mandible, maxillule, and maxilla not dissected. First maxilliped with slender endopod not exceeding distal endite. Second maxilliped without distinguishing characters. Third maxilliped ischium with crista dentata consisting of about 18 subequal, mostly sharp teeth, and one accessory tooth.

Right cheliped ( Fig. 17 A-D)

Moderately elongated, mostly glabrous except for scattered short setae. Chela with dorsal and ventral surfaces smooth, lacking spines; fingers each terminating in small, sharp corneous claw slightly overlapping when closed. Dactyl 0.5 length of palm, cutting edge with two large calcareous teeth, and row of fused small teeth forming uneven edge distally; ventromesial face ( Fig. 17D ) concave on distal half, somewhat spoon-like distally. Fixed finger similar to dactyl except for cutting edge having larger calcareous teeth more distally, and well defined dorsolateral margin consisting of faint ridge of minute teeth continued on palm and fading in strength proximally on palm; ventromesial surface concave on proximal half. Palm approximately as long as carpus, dorsally convex; dorsolateral and dorsomesial margins defined by faint and moderately sharp ridge; ventral surface convex, glabrous. Carpus about 1.3 times as long as merus; dorsal surface weakly convex, dorsodistal margin with three small spines (one dorsal, one medial, one lateral), dorsomesial margin with irregular row of sharp spines; lateral face rounded, mesial face flat, nearly vertical; ventral surface convex. Merus subtriangular, distal margin with fringe of short setae; ventrodistal margins each with one (mesial) and two (lateral) sharp spines. Ischium glabrous. Coxa with row of setae on ventromesial distal angle.

Left cheliped

Missing in holotype.

Ambulatory legs ( Fig. 16B, C )

Right pereopod 3 ( Fig. 16B, C ) exceeding right cheliped by about 0.3 length of dactyl, with only scattered short setae or tufts of setae. Dactyl nearly straight, 1.1 times as long as propodus, with ventromesial row of 10 long spinules. Propodus nearly straight, 1.8 times as long as carpus, with long corneous spinule on ventrodistal angle. Carpus unarmed, dorsodistal angle blunt. Merus and ischium unarmed, somewhat laterally compressed. Anterior lobe of sternite XI (of pereopods 3; Fig. 16D ) subsemicircular, with fringe of short setae on distal margin. All other ambulatory legs missing in holotype.

Fourth pereopods ( Fig. 16E )

Semichelate. Dactyl more or less straight, terminating in short, inwardly directed corneous claw, lacking preungual process; propodal rasp with single row of rounded corneous scales. Carpus unarmed except for few short setae dorsally. Merus unarmed except for with dorsodistal tuft of long setae.

Fifth pereopods

Chelate. Propodal rasp extending on dorsal surface for almost entire length of propodus, and on lateral surface for about one-third length of propodus.

Uropods and telson ( Fig. 16F )

Uropods markedly asymmetrical, left largest.Telson nearly symmetrical, longer than broad, with weak lateral indentations. Anterior lobes longer than posterior lobes. Posterior lobes nearly symmetrical, outline of margins together forming semi-circle, with chitinous lateral margins, separated by narrow, shallow median cleft; terminal margins oblique, armed with row of minute blunt spines and few short setae.

Sexual tubes ( Fig. 16G ) and pleopods

Males with coxae of pereopods 5 extended posteriorly as paired, subequal, stout and calcified sexual tubes trapezoid in shape, tube openings each with lip-like edge fringed by setae; with unpaired left pleopods 3-5. Females unknown.

Genetic data

See Table 1.

Colour

Unknown.

REMARKS

The single male specimen of this new species was collected as part of the epifauna on rocky bottom. The specimen is missing pereopods 1-3 except for the right cheliped and right pereopod 3. It is distinctive in the following characters: 1) coxae of pereopods 5 in the male extended posteriorly forming a pair of symmetrical trapezoidal sexual tubes; 2) right chela smooth, glabrous, lacking spines or setae, the mesial margin of the palm, and the dorsolateral margins of the fixed finger and anterior half of palm each weakly but distinctly delimited by a low, minutely denticulate ridge; 3) posterior lobes of telson have rounded lateral margins, the outlines of which together form a semi-circle, and the terminal margins are oblique and minutely armed; 4) ultimate antennular segment with pair of long dorsodistal bristles; and 5) antennal acicles long, exceeding corneas by one-third length of acicle. Other diagnostic characters include the rounded rostrum, ocular acicles terminating in single spine, and the propodal rasp of pereopod 4 with only one row of ovate scales.

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.

FIG. 17. — Paguriscus robustus n. gen., n. sp., holotype ♂ 1.3 mm, Guadeloupe,sta GS 20, MNHN-IU-2013-4395: A-C, right cheliped, dorsal view (A); lateral (B); mesial view (C); D, dactyl and fixed finger of right cheliped, mesial view. Scale bars: 0.5 mm.