Homolochunia menezi, Forges & Ng, 2008

Forges, Bertrand Richer De & Ng, Peter K. L., 2008, New western Pacific records of Homolidae De Haan, 1839, with descriptions of new species of Homolochunia Doflein, 1904, and Latreillopsis Henderson, 1888 (Crustacea: Decapoda: Brachyura), Zootaxa 1967, pp. 1-35 : 8-10

Homolochunia menezi n. sp.

( Figs. 4D, 5E, 6D, 7A–D, 8A, B)

Material examined. Solomon Islands: SALOMONBOA cruise, stn. CP 2846, 10°27.47’S 161°23.71’E, 533–612 m, 23 September 2007: 1 male holotype (17.4 x 12.3 mm) ( MNHN-B31283 ) .

Diagnosis. Small-size species (adult holotype male 17.4 mm carapace length). Carapace longer than wide, dorsal surface covered with numerous long spines, thick, short tomentum. Front with small sharp rostral spine and 2 very long pseudorostal spines, slightly shorter than carapace; pseudorostral spines with 2 accessory spines bifurcated at extremity. Gastric region with 4 strong spines; anterior protogastric spine longer than posterior one; mesogastric region with low tubercle; 2 short spines present just below gastric groove. Subhepatic region inflated, with 2 long spines, anterior one longest, pointing anteriorly, reaching level of rostrum. Pterygostomian region with 2 short spines. Posterolateral border with line of 3 long spines; first curved, oriented anteriorly, 2 others directed laterally; 2 small spines on lower part of lateral border of carapace. Antennule with basal article bulbous, 2 following articles cylindrical, of similar length. Antenna with prominent urinary article, antennae as long as pseudorostral spines. Eyes peduncles long, cornea distinct, rounded. Third maxilliped pediform, unarmed: merus enlarged on external corner, dactylus longer than propodus. Chelipeds of equal length, thin, not inflated, without spines or denticules. Ambulatory legs long, slender, cylindrical; P4 longest. Spines on superior borders of meri of legs arranged as follow: 0 on P5, 0 on P4, 3 on P3, 2 on P2; with terminal dorsal spine, especially long, sharp on P5; P5 subcheliform, with very long, curved spine starting from base of propodus and joining extremity of dactylus. Abdomen with 7 free somites including telson; several medial spines on somites 2 to 6; spine on somite 6 at distal border; telson short, triangular. G1 curved at extremity ( Fig. 8A, B).

Etymology. This species is dedicated to a good friend, the recently departed Dr. André Menez, former Président of the Muséum national d’Histoire naturelle in Paris, and an active collaborator of the National University of Singapore, in recognition of his many outstanding achievements in biology.

Remarks. There are only three species described in Homolochunia : H. valdiviae from the Indian Ocean, H. gadaletae from Japan and Taiwan, and H. kullar from the Tasman and Coral seas. Homolochunia kullar has a cheliform P5 which is completely different from that of the other two species ( Fig. 6B; Griffin & Brown 1976: 264, fig. 3 B). The two other species have the same pattern of carapace, horns and subcheliform P5 (cf. Guinot & Richer de Forges 1995: 430) but can easily be distinguished from each other by various carapace features as well as the structure of the P5 ( Figs. 4–6).

Comparing H. menezi n. sp. and H. valdiviae , the latter species appears to grow much larger; the relatively smaller specimen of H. menezi n. sp. being already an adult. In H. valdiviae , the carapace spines are relatively weaker and less numerous; there is only one accessory spine on the median part of the pseudorostral spine ( Figs. 4A, 5A, B) (versus two in H. menezi n. sp., Figs. 4D, 5E); the carapace is less spiny (two small spines on posterolateral margin [ Fig. 5A, B] versus three long spines in H. menezi n. sp. [ Fig. 5E); the P2-P5 are relatively stouter, with more numerous and larger spines; the P4 merus has four strong spines ( Fig.4A) (versus unarmed in H. menezi n. sp., Fig. 4D); the P3 merus has 4 strong spines ( Fig. 4A) (versus three small spines in H. menezi n. sp.¸ Fig. 4D); the P2 merus has 5 strong spines ( Fig.4A) (versus 3 spines on the left leg but only one on the right side in H. menezi n. sp., Fig. 4D); and the P5 carpus is relatively longer ( Fig. 4A versus Fig. 4D).

Compared to H. menezi n. sp., H. gadaletae differs in having two accessory spines on proximal half of the pseudorostral spines ( Figs. 4C, 5D) (more distal in H. menezi n. sp. Figs. 4D, 5E); the ambulatory legs are stronger, longer and more spiny in H. gadaletae (four spines on P4 merus [ Fig. 4C] versus none in H. menezi n. sp. [ Fig. 4D]; five spines on P3 merus [ Fig. 4C] versus three in H. menezi n. sp. [ Fig. 4D); five spines on P2 merus [ Fig. 4C] versus 1–3 in H. menezi n. sp. [ Fig. 4D]); and the spines on the carapace are proportionately much shorter than in H. menezi n. sp. ( Figs. 4C, 5D versus Figs. 4D, 5E).