Acanthaxius gadaletae, 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 : 62-66

Acanthaxius gadaletae n. sp.

(Fig. 3D–I)

Type material

Holotype: Solomon Islands, Alis, Salomon 1, St. 1831, 135– 325 m, Ph. Bouchet, B.

Dayrat, A. Warren, B. Richer de Forges coll., 5 Oct. 2001: male, cl. 13 mm, tl. 35 mm ( MNHN Th 1493) (figured).

Paratypes: Solomon Islands, SW Santa Isabel, Alis, Salomon 2, St 2191, 300 m, Ph. Bouchet, A. Warren & S. Samadi coll., Nov. 2004: 1 female, cl. 13 mm, tl. 35 mm ( MNHN Th 1494) (figured); Salomon 1, St. 1761, 191– 290 m, Ph. Bouchet, B. Dayrat/A.Warren, B. Richer de Forges coll., 27 Sept 2001: 1 male, cl. 12 mm, tl. 32 mm; 2 females, cl. 12 mm & 13 mm, tl. 32 mm & 34.5 mm ( MNHN Th 1495).

Other material

New Caledonia: Jumeau West Bank, Alis, SMIB 8, St. 177, 320– 370 m, 29 Jan. 1993: 1 male, cl. 10 mm, tl. 27 mm ( MNHN Th 1496); Loyauté Islands, Lifou, Santal Bay, SE Récif Shelter, St. 1648, 150– 200 m, Atelier Lifou coll., 7–19 Nov 2000: 1 female with broken rostrum, cl. 14.5 mm (without rostrum), tl. 41.5 mm ( MNHN Th 1497).

Diagnosis

Rostrum long and slender, reaching to distal border of last article of antennular peduncle lateral border with two spines and large basal suborbital spine. Gastric region with moderately defined carinae bearing small spines; median carina with two or three spinules anterior to tubercle and one spinule posterior to it; lateral carina with anterior spine; two submedian carinae, external with four spines, internal with anterior spine and sometimes with denticles posterior to it. Postcervical region glabrous, postcervical carina absent. Abdominal pleura 3–5 slightly angled posteroventrally, each with minute anterior spinule. 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 and basis, two lower spines on ischium, three lower spines on merus, small lower distal spine on carpus.

Pereopods 1 subequal, densely setose; propodus and dactylus each with three or four upper spines. Uropod exopod and endopod ovoid, exopod with six or seven spinules on lateral external border, four or five spines on lateral carina; endopod with three spines on lateral external border, four large spines on median carina.

Description

Carapace (Fig. 3G) with pointed rostrum about 2.8 times as long as broad at base, reaching far beyond eyes to distal border of last article of antennular peduncle; lateral border with two spines and large suborbital spine. Carinae of gastric region moderately defined with small spines; median carina starting beyond rostral base with two or three spinules anterior to tubercle, one spinule posterior to it, lateral carina with anterior spine, two submedian carinae, external with four spines, internal with anterior spinule and unarmed posterior to it or slightly denticulated. Cervical groove well defined, postcervical region glabrous, postcervical carina absent. Abdominal pleuron 1 ventrally narrowed, pleuron 2 broad, pleura 3–5 slightly angled posteroventrally as in A. kirmilleri Kensley (see Kensley, 1996: fig. 1C) with minute spinule on anterior border. Telson (Fig.3F) 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. 3G), as in A. clevai n. sp. ( Fig. 2 E) with lower spine on article 1 and 3, acicle acute, arcuate, slightly overreaching middle of peduncular article 4. Maxilliped 3 similar to that of A. clevai n. sp. ( Fig.2 F) with lower distal spine on coxa, two lower spines on ischium, three lower spines on merus larger distally, small lower distal spine on carpus, but differing by a large lower distal spine present on basis. Other mouth appendages similar to those figured for Acanthaxius pilocheira (see Sakai, 1987: 298, fig. 2) except for the maxilla bearing no posterior seta on the scaphognathite.

Pereopods 1 subequal, strongly setose. Both large and small pereopod 1 (Fig. 3E, 3D) ischium with two lower spines; merus with two upper distal spines, four or five lower spines, three or four spines on anterolateral surface; carpus with three or four upper spines, two lower spines; lateral surface with three or four spines near distal border and four or five spinules posteriorly; propodus with four upper spines, row of six to nine submarginal spines on lower lateral surface, lateral surface of palm with several spines, acute denticles or round tubercles; fixed finger longer than propodal palm in both pereopods 1, with slightly curved tip, cutting edge bearing rounded teeth of various sizes in large pereopod 1, small pointed teeth in small pereopod 1. Dactylus as long as fixed finger, approx. 1.1 times longer than palm in large pereopod 1, 1.2–1.3 times longer than palm in small pereopod 1, with more curved tip, four upper spines; cutting edge, as in fixed finger, with round teeth in large pereopod 1, small pointed teeth in small pereopod 1.

Pereopod 2 (Fig. 3H) merus with three lower spines or spinules; pereopod 3 (Fig. 3I) propodus bearing rows of corneous setae and a large one on lower distal border.

Pleopods as described and figured for A. clevai n. sp. (Fig. 3A–C).

Uropod (Fig. 3F) exopod with six or seven spines on lateral border, mobile spine at angle of suture, eight to ten spinules along suture, four or five spinules on external carina; endopod with three spines on lateral border, four spines on median carina including distal marginal spine.

Etymology

The species is dedicated to Gabrielle Gadaleta for her contribution to several works on Crustacea in the Muséum National d’Histoire Naturelle.

Distribution

Solomon Islands, New Caledonia.

Acanthaxius clevai A, holotype, male (MNHN Th 1491), pleopod 2.; B, C, female paratype (MNHN Th 1492) pleopod 1 and 2 respectively. Acanthaxius gadaletae n. sp., D–G, holotype, male (MNHN Th 1493).; H, I, female paratype (MNHN Th 1494). A, male pleopod 2; B, C, female pleopod 1 and 2; D, small pereopod 1; E, large pereopod 1; F, telson and uropod; G, anterior part of carapace; H, I, pereopod 2 and 3. Scale line: 1 mm.

Remarks

The internal submedian carina of the gastric region of this species varies, being short and unarmed in the holotype (Fig. 3G) and the female paratype MNHN Th 1494, slightly denticulated in other specimens examined but bears two or three spinules in the female from Loyauté Islands (MNHN Th 1497). The number of spines on the pereopod 1 varies especially in specimens from New Caledonia compared with the types. The male of tl. 27 mm (MNHN Th 1496) has fewer upper spines on the pereopod 1 propodus and dactylus, two and two respectively. The large female of tl. 41.5 mm bears more spines (usually one or two additional) on certain articles of the pereopods 1. This specimen has a broken rostrum, the abdominal pleura more rounded ventrally than in the types with no anterior spinule. Another difference concerns the presence of a posterior seta on the maxilla scaphognathite, absent in the types. Otherwise the two New Caledonian specimens agree with the types in the morphology of the carapace, the pereopods, the telson and uropods. It can be noted that, unlike other Acanthaxius species in which the dactylus, that of the smaller pereopod especially, is nearly 1.5–2 times longer than the propodal palm (see Kensley, 1996), in A. gadaletae n. sp., the pereopod 1 dactylus is only slightly longer than the palm,1.2–1.3 times longer in the small pereopod 1, and the New Caledonian specimens also agree with the types on this. They are assigned to the present species with a little doubt concerning the female for the differences mentioned above and the missing rostrum.

A. clevai n. sp. and A. gadaletae n. sp. are very close by having a similarly shaped rostrum and similar glabrous postcervical region of the carapace, pereopods, telson and uropods. The latter species is much smaller (holotype of tl. 35 mm vs. 62 mm in A. clevai n. sp.), yet does not include juveniles of the former but fully adults with gonopores wide open on the coxae of pereopods. The two species differ by:

1) Gastric region with median, submedian, lateral carinae; carinae hardly defined with large spines in A. clevai n. sp. (gastric region with two submedian carinae; carinae better defined with small spines in A. gadaletae n. sp.).

2) Maxilliped 3 with unarmed basis in A. clevai n. sp. (maxilliped 3 basis with large lower distal spine in A. gadaletae n. sp.)

3) Pereopod 1 stout compared to body; propodus and dactylus with three and two upper spines respectively in A. clevai n. sp. (pereopod 1 of moderate size, propodus and dactylus each with four spines in A. gadaletae n. sp.).

4) Abdominal pleura 3–5 ventrally rounded and unarmed in A. clevai n. sp. (slightly angled posteriorly with anterior spinule in A. gadaletae n. sp as in A. kirmilleri Kensley ).

Figures

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.