Acanthaxius clevai, Ngoc-Ho, Nguyen, 2006

Ngoc-Ho, Nguyen, 2006, Three species of Acanthaxius Sakai & de Saint Laurent, 1989, including two new to science, from the Solomon Islands and New Caledonia (Crustacea, Thalassinidea, Axiidae), Zootaxa 1240, pp. 57-68 : 59-62

Acanthaxius clevai n. sp.

( Figs 1 , 2 , 3A–C)

Type material

Holotype: Solomon Islands, Vella Gulf, Alis, Salomon 2, St. 2260, 399– 427 m, Ph. Bouchet, A. Warren & S. Samadi coll., Nov. 2004: male, cl. 23 mm, tl. 62 mm ( MNHN Th 1491).

Paratypes: same data as holotype: 2 males, cl. 22 mm, tl. 59 mm (figured), cl. 28.5 mm, tl. 72.5 mm, 1 ovigerous female, cl. 21 mm, tl. 57.5 mm ( MNHN Th 1492).

Diagnosis

Rostrum about 2.5 times as long as broad at base, reaching half length of last article of antennular peduncle; lateral border with two spines and large basal suborbital spine. Gastric region with carinae weakly defined, bearing large spines; median carina with spine and spinule anterior to tubercle, two or three tubercles posterior to it, lateral carina with anterior spine, submedian carina with four spines. Postcervical carapace glabrous, postcervical carina absent. Abdominal pleura 2–5 ventrally rounded. Telson slightly longer than wide, with two pairs of dorsal spines; lateral borders bearing three teeth and one spinule, two mobile posterolateral spines and median spine on convex posterior border.

Antenna with lower distal spine on article 1 and 3. Maxilliped 3 with lower distal spine on coxa, basis unarmed, two lower spines on ischium, three lower spines on merus, small lower distal spine on carpus.

Pereopods 1 unequal in males, subequal in females, densely setose; propodus and dactylus with three or four and two upper spines respectively. Uropod exopod and endopod ovoid, exopod with six or seven spinules on lateral external border, three or four spines on lateral external carina; endopod with three spines on lateral external border, four large spines on median carina.

Description

Carapace ( Figs 1 , 2 A) with pointed rostrum reaching far beyond eyes to half length of last article of antennular peduncle; lateral border with two spines and large suborbital spine. Carinae weakly defined bearing large spines; median carina starting beyond rostral base with spine and spinule anterior to tubercle, two or three tubercles posterior to it; lateral carina with anterior spine; submedian carina with four spines, several round tubercles between carinae. Cervical groove well defined, postcervical carapace glabrous, postcervical carina absent. Abdominal pleuron 1 ventrally narrowed, pleuron 2 broad, pleura 3–5 ventrally rounded, pleura 6 with tiny denticle on anterior border. Telson ( Fig. 2 D) slightly longer than broad with lateral border having three teeth and one spinule, two mobile posterolateral spines and median spine on convex posterior border; two pairs of spines and faint longitudinal median groove on dorsal surface.

Antenna peduncle ( Fig. 2 E) with lower spine on article 1 and 3, acicle acute, arcuate, slightly overreaching middle of peduncular article 4. Maxilliped 3 ( Fig. 2 F) with lower distal spine on coxa, basis unarmed, two lower spines on ischium, three lower spines on merus larger distally, small lower distal spine on carpus. Other mouth appendages similar to those figured for Acanthaxius pilocheira (see Sakai, 1987: 298, fig. 2) except for the maxilla with no posterior seta on the scaphognathite.

Pereopods 1 asymmetrical, strongly setose. Large pereopod 1 ( Fig. 2 B) stout compared to body ( Fig. 1 ), ischium with two lower spines; merus with two upper distal spines, four lower spines, three or four spines on anterolateral surface; carpus with two or three upper spines, two lower spines; lateral surface with three or four spines near distal border and five or six others together with several tubercles posteriorly; propodus with three upper spines, row of six or seven submarginal spines on lower lateral surface, lateral surface of palm with several spines, acute denticles or round tubercles; fixed finger subequal in length to propodal palm, with slightly curved tip, cutting edge bearing rounded teeth with two larger ones, one proximal the other near distal third; dactylus as long as fixed finger, with more curved tip, two upper spines; cutting edge with round teeth and a larger one near proximal third.

Small pereopod 1 ( Fig. 2 C) similar to large pereopod 1 except for propodus with row of six to nine submarginal spines on lower lateral surface; lateral surface of palm with five or six spines and few tubercles; fixed finger about 1.5 lengths of propodal palm, with slightly curved tip, cutting edge bearing small acute teeth; dactylus as long as fixed finger, with more curved tip, two upper spines, cutting edge, as in fixed finger, with small acute teeth.

Pereopod 2, pereopod 3 ( Fig. 1 ) similar to those of A. gadaletae n. sp. (Fig. 3H, I) merus with three lower spines or spinules; pereopod 3 propodus bearing rows of corneous setae and a large one on lower distal border. Pereopod 4 ( Fig. 1 ) similar to pereopod 3 except for having single lower distal spinule on merus. Pereopod 5 with long and slender dactylus.

Gill formula as given by Sakai & de Saint Laurent for the genus (1989).

Pleopod 1 absent in male, present in female (Fig. 3B) as a single slender ramus, faintly biarticulated. Male pleopod 2 (Fig. 3A) with appendix masculina and appendix interna

Male pleopod 3–5 and female pleopod 2–5 (Fig. 3C) with appendix interna.

Uropod ( Fig. 2 D) exopod with six or seven spines on lateral border, mobile spine at angle of suture, eight to ten spinules along suture, three or four spinules on external carina; endopod with three spines on lateral border, four spines on median carina including distal marginal spine.

The ovigerous female MNHN Th 1492 bears eggs of 0.30–0.35 mm in diameter.

Etymology

The species is dedicated to Régis Cléva for his contribution to this work and several others on Crustacea in the Muséum National d’Histoire Naturelle.

Distribution

Only known from the type locality

Remarks

By its long and slender rostrum bearing two lateral spines and a suborbital spine, its carapace with median, submedian and lateral carina, the postcervical region glabrous, the ventrally rounded abdominal pleura 2–6, this species shows similarities to Acanthaxius pilocheira (see Sakai, 1987: 296, figs 1–2) from Kumano­nada, Japan. It differs by having fewer spines on the chelipeds, especially on the upper border of the propodus and dactylus, the telson longer than broad with more spines on lateral borders.

A. clevai n. sp. is more similar to A. gadaletae n. sp. described below and the two are compared under the latter species.

Figures

FIGURE 1. Acanthaxius clevai n. sp., holotype, male (MNHN Th 1491). Lateral view. Scale line: 5 mm.

FIGURE 2. Acanthaxius clevai n. sp. A, D, holotype, male (MNHN Th 1491).; B, C, E, F, male paratype (MNHN Th 1492) .. A, anterior part of carapace; B, large pereopod 1; C, small pereopod 1; D, telson and uropods; E, antenna; F, maxilliped 3. Scale line: 2 mm.