Richerellus moosai, Crosnier, 2003

Crosnier, Alain, 2003, A New Genus And Species Of Portunid Crab (Crustacea: Decapoda: Brachyura) From New Caledonia, South-West Pacific, Raffles Bulletin of Zoology 51 (2), pp. 315-321 : 316-321

Richerellus moosai , new species

( Figs. 1-5 )

Material examined. – Holotype – 1 male holotype, 11.5 x 16.8 mm ( MNHN-B 22837 ), New Caledonia, east lagoon, program Lagon , stn 672, 21 41.4’S, 166 23.2’E, 15-20 m, oyster shells with mud, 8 Aug.1986.

Paratypes – 1 juv., 4.7 x 6.2 mm ( MNHN-B 22839 ), New Caledonia, east lagoon, program Lagon , stn 656, 21 49.1’S, 166 32.5’E, 30-40 m, coarse sand and mud, coral rubble, foraminifers, 8 Aug.1986 ; 1 male, 10.3 x 14.4 mm ( ZRC2003.0595 ), New Caledonia, east lagoon, program Lagon , stn 662, 21 44.0’S, 166 32.0’E, 50 m, coarse sand, coral, 8 Aug.1986 ; 1 female, 10.6 x 14.2 mm ( MNHN-B 22840 ), New Caledonia, east lagoon, program Lagon , stn 663, 21 42.2’S, 166 30.5’E, 38-40 m, 8 Aug.1986 ; 1 male, 8.6 x 11.7 mm (MNHN- B 22838), New Caledonia, east lagoon, program Lagon , stn 851, 20 43.7’S, 165 08.3’E, 31 m, mud, stones with red algae, gorgonians, 11 Jan.1987 .

Size. – The largest specimen known is the male holotype (11.5 x 16.8 mm).

Description (based on holotype). – Carapace ( Fig. 2A ) wider than long (w/l = 1,46), slightly convex longitudinally and tranversally, smooth to naked eye, without pronounced regions or transverse rows of granules; a small and low protuberance at posterior part of protogastric regions and on each lateral side of urogastric region; a low weak groove along anterior and inner parts of branchial regions; another very weak groove joining the 2 protuberances of urogastric region; branchial and cardiac regions slightly swollen.

Front about one-third carapace width, slightly sinuous, with

a small notch medially. Internal orbital lobe indistinct. Upper orbital border with 2 fissures, very discrete, particularly the external one. Anterolateral margins of the carapace divided into 4 teeth; the first (exorbital angle) and the 2 following, directed forward, increasing in size distally; distal part of first tooth not very sharp, that of second slightly rounded, that of third very sharp; fourth tooth directed anterolaterally, smaller than third, more slender and acuminate. Posterior margin of carapace about three-quarters carapace width.

Lower orbital border sinuous with a fissure at base of external orbital angle and 2 low lobes on internal part ( Fig. 4A ). Basal antennal segment slender, twice as long as broad; antennal flagellum entering orbit.

Mouthparts represented on Fig. 3 . Anterolateral angle of third maxilliped merus slightly produced.

Chelipeds elongate, unequal (left one strongest), slightly longer than other pereiopods, smooth to naked eye, without granules except on anterior border of merus which bears 4 curved, sharp teeth that increase in size and interval from base to extremity of border. Carpus with 2 spiny teeth, one, strongest, at antero-internal extremity of upper surface, other at antero-external angle of lower surface. Chelae with no ornamentation on palm except for a very faint carina on external border of upper surface; fingers about four-tenths length of large chela and half length of small chela, with a longitudinal groove on external and internal surfaces; external groove of fixed finger extending slightly behind base of finger; dactylus (mobile finger) with a very faint, partial longitudinal groove; cutting margins of fingers with contiguous triangular teeth of variable sizes; a molariform tooth at base of dactylus.

Second to fourth pereiopods elongate (slightly shorter than chelipeds), smooth, glabrous, slender. Dactylus about 1.1 length of propodus.

Fifth pereiopod with propodus-dactylus modified as swimming paddle. Propodus and dactylus respectively 2.25 and 2.5 times as long as wide. Dactylus with a distal denticle.

Male abdomen triangular with a strong transversal carina on first and second segments. Greatest part of first segment hidden. Third to fifth segments fused, suture between them almost invisible. Lateral borders of sixth segment very slightly sinuous, strongly converging forward; ratio of anterior to posterior margin length 0.6. Telson triangular, as long as wide at base, as long as sixth segment, with lateral borders straight and distal part rounded ( Fig. 4B ).

First male pleopod not very long, sinuous, not becoming very slender distally; without setae but with some spinules in its bilobed distal part ( Fig. 5 A-D).

Second male pleopod smaller than first, slightly sinuous, with bifid extremity ( Fig. 5E).

Coloration. – Orange brown with anterior half of carapace slightly darker than posterior one, and with a straight narrow clear median line. On pereiopods large transversal bands separated by short clearer ones. Fingers of chelae distally whitish.

Variation. – The paratypes agree well with the holotype in

most characters. However, the front of the female paratype is more sinuous ( Fig. 2B ), the first tooth of the anterolateral margin of the carapace is sharper in the juvenile and the female paratype, and no external orbital lobes are visible in the specimens smaller than the holotype. On the other hand, in the juvenile, the second tooth of the anterolateral margin is not well separated from the first ( Fig. 2C ).

Etymology. – This species is dedicated to Mohammad Kasim Moosa, from Pusat Penelitian dan Pengembangan Oseanologi, LIPI in Djakarta, who has written many papers on the Indonesian Crustacea and, when staying at the Muséum national d’Histoire naturelle in Paris in 1994, recognized several of the specimens studied here as meriting interest.

Distribution. – New Caledonia: East lagoon at depths of 15- 20 and 50 meters on muddy or coarse sandy bottoms with many blocks and occasionally gorgonians or coral.

Remarks. – Taking into account the large number of samples collected in the lagoon, it is surprising to note that the species described here was found in only five samples, all from the same small area, on substrates which seem quite common in the lagoon.

Figures

Fig. 1. Richerellus moosai, new genus, new species, male holotype 11.5 x 16.8 mm (MNHN-B 22837).

Fig. 2. Richerellus moosai, new genus, new species. Carapace: A, male holotype 11.5 x 16.8 mm (MNHN-B 22837); B, female paratype 10.6 x 14,0 mm (MNHN-B 22840); C, juvenile paratype 4.7 x 6.2 mm (MNHN-B 22839). Scale = 1 mm.

Fig. 3. Richerellus moosai, new genus, new species, male paratype 8.6 x 11.7 mm (MNHN-B 22838). A, right mandible (with the tendon of inner adductor muscle); B, right maxillula; C, right maxilla; D, right first maxilliped; E, right second maxilliped; F, right third maxilliped (podobranch and epipodite not represented). Scale = 1 mm.

Fig. 4. Richerellus moosai, new genus, new species. A-E, male holotype 11.5 x 16.8 mm (MNHN-B 22837); F, female paratype 10.6 x 14.2 mm (MNHN-B 22840). A, antennula, antenna and orbit, ventral view; B, abdomen; C, left chela; D; right chela; E, right P5, dorsal view; F, right P5, carpus, propodus and dactylus, dorsal view. Scales: A, B = 2 mm; C, D = 5 mm; E, F = 2 mm.