Laomenes cornutus ( Borradaile, 1915 )

Marin, Ivan, 2009, Crinoid-associated shrimps of the genus Laomenes A. H. Clark, 1919 (Caridea: Palaemonidae: Pontoniinae): new species and probable diversity, Zootaxa 1971, pp. 1-49 : 11-13

Laomenes cornutus ( Borradaile, 1915)

( Fig. 7 )

Periclimenes cornutus Borradaile 1915: 211 ; 1917: 365, pl. 54 fig. 10a, b [type locality: Malé Atoll, Maldive Islands]. — Kemp 1922: 172. — Bruce 1978: 259, figs. 1C, 5.

Periclimenes amboinensis .— Tchesunov et al., 1989: 181, figs. 9, 10;

Laomenes cornutus . — Okuno & Fujita 2007: 119.

Material. 1 female, (pcl. 2.1 mm, without chelipeds), 3 males (pcl. 2.0,1.6, 1.5 mm), 3 juv. (pcl. 1.0, 1.2, 1.3 mm) (UO), Fiartu Island, North Nilandu Atoll, Maldive Islands, 3–15 meters, on crinoid № 23, 14.iii.1980, coll. A.V. Tchesunov, 9th cruise of c/v “ Academik Petrovsky ”.

Diagnosis. Carapace swollen, smooth, with antennal and hepatic teeth ( Fig. 7 A, B), hepatic tooth larger than antennal. Rostrum long, straight, deep and laterally compressed, with well developed dorsal carina bearing 6 or 7 teeth; ventral margin convex, with 1 or 2 teeth; lateral lamina feebly developed, continuous to orbital margin forming well developed sharp surpaocular teeth ( Fig. 7 A, B). Orbit well developed, inferior orbital angle non-produced. Abdominal somites smooth; pleura of abdominal somites I–V rounded ventrally. Telson about 3 times longer than wide in proximal part, gradually narrowing posteriorly, with 2 pairs of medium submarginal dorsal spines situated at 0.5 and 0.8 of telson length. Eyes large; eyestalk stout, as long as wide; central cornea with stout apical papilla ( Fig. 7 C). Antennule ( Fig. 7 E) well developed; basal segment about twice longer than wide, distolateral margin with acute distolateral tooth and rounded medial projection between tooth and the lateral margin of the intermediate segment; submarginal ventral tooth distinct, situated near medial border of basal segment. Mandible robust, without palp; incisor process well developed, broad, with 1 large and 8 small terminal teeth ( Fig. 7 D); molar process well developed, robust, with stout teeth distally. Pereiopod II unequal in females and males ( Fig. 7 F, H), with robust segments; carpus as long as maximal width, flared distally; major cheliped ( Fig. 7 F) with palm cylindrical, about 2.7 times longer than wide, about twice longer than fingers; fingers stout, about 2.5 times as long as wide, with large triangular teeth along cutting edges and acute, curved tips; minor cheliped ( Fig. 7 H) palm cylindrical, about 3 times longer than wide, about 1.5 times longer than fingers; fingers slender, about 4 times as long as wide, with 3 small triangular teeth along cutting edges and acute, with curved tips. Pereiopod III with unarmed segments; propodus with 3 or 4 distoventral teeth, with a row of long slender setae situated along distal margin; dactylus ( Fig. 7 J) slender, about twice as long as maximal width, with long, acute and curved unguis, small accessory tooth turned almost perpendicular to dactylus and tuft of 3 or 4 long slender setae at the middle of the dactylus. Appendix interna ( Fig. 7 K) longer than the appendix masculina, with numerous subterminal cincinnuli. Appendix masculina with 3 long terminal setae and 3 simple spines along lateral margin.

Coloration. Currently unknown. The identification of the specimens depicted by Debelius (1999: 182) needs confirmation.

Remarks. The holotype specimen of Periclimenes cornutus (UMZC, female, CL. 2.25 mm) described by Borradaile (1915) and re-described by Bruce (1978) clearly differs from specimens of Periclimenes amboinensis by a stouter eyestalk (length/width ratio is 1/ 1 in P. cornutus , and 1.7/ 1 in P. amboinensis ), presence of medial projection (lobe) between distolateral tooth and the lateral margin of the intermediate segment at distolateral margin of basal antennular segment (vs. produced lobe absent in P. amboinensis ( Fig. 2 E)). Pereiopod II are clearly unequal in males of P. c o r n u t u s ( Fig. 7 F, H) while they are almost similar and more slender in P. amboinensis ( Fig. 5 B, D); fingers of major pereiopod II of P. cornutus ( Fig. 7 G, I) stout, about 2.5 times longer than wide, curved, with large triangular teeth while fingers in P. amboinensis more slender, 4 times longer than wide, straight, with small teeth along cutting edges ( Fig. 5 C, E). Several rows of long setae along distoventral margin presents on propodus of P. a m b o i n e n s i s while only a single row of setae situated on distal margin of propodus present in P. c o r n u t u s. Based on these differences we suggest that P. cornutus (Borradaile) and P. amboinensis ( De Man) represent distinct species contrary to some authors (e.g., Bruce 1978; Tchesunov et al 1989) suggesting their conspecifity.

Periclimenes cornutus can be easily identified by the deep rostrum, short and stout eyestalk with small blunt apical papillae on central cornea of eyes, and robust, dissimilar chelae of pereiopods II. Host. Unknown.

Distribution. The presence of the species has been confirmed only from the type locality, Maldive Islands ( Borradaile 1915; Bruce 1978; Okuno & Fujita 2007; present study). Numerous pictures of spotty colored shrimps identified as “ Laomenes (Periclimenes) cornutus ” from other localities such as Indonesia and the Philippines published on the world-wide-web and in Debelius (1999: 182) may refer to Laomenes cornutus or further undescribed species with equal probability.

Figures

FIGURE 2. Laomenes amboinensis (De Man, 1888), ovigerous female. A, B, distal part of carapace and rostrum. C, eyes. D, antennule. E, same, distolateral margin of basal antennular segment. F, antenna. Scale 1 mm; E, without scale.

FIGURE 5. Laomenes amboinensis (De Man, 1888), male. A, distal part of carapace and rostrum. B, major pereiopod II. C, same, chela. D, minor pereiopod II. E, same, chela. Scale 1 mm.

FIGURE 7. Laomenes cornutus (Borradaile, 1915), ovigerous female (A—J), male (K). A, B, distal part of carapace and rostrum. C, eyes. D, distal margin of incisor process of mandible. E, antennule. F, major pereiopod II. G, same, chela. H, minor pereiopod II. I, same, chela. J, distal part of propodus and dactylus of pereiopod III. K, appendix masculina. Scale 1 mm.