Hippolyte sp.

Cédric, 2007, New records of Atlantic Hippolyte, with the description of two new species, and a key to all Atlantic and Mediterranean species (Crustacea, Decapoda, Caridea), Zoosystema 29 (1), pp. 183-207 : 198-200

Hippolyte sp.

( Fig. 11 )

MATERIAL EXAMINED. — West AFrica. Gulf of Guinea, Principe Island, Pedra da Galé, 1°43’N, 7°23’E, 45 m depth, from Antipathella , scuba diving, 18.II.2004, coll. Peter Wirtz, 2 small juveniles (MNHN-Na16268).

São Tomé Island, Diogo Vaz , 35 m depth, from Muriceopsis truncata , scuba diving, 13.II.2006, coll. Peter Wirtz, 1 ovigerous ♀ (incomplete: P1-P2 present, putative right P3 detached, left P5 present; other pereiopods missing) (MNHN-Na16269) .

DISTRIBUTION. — Tropical West Africa: Principe and São Tomé islands.

DESCRIPTIVE ACCOUNT

See Remarks

Colour pattern

Unknown.

Size

Total length up to 9 mm.

ECOLOGY

Although the three specimens examined were found in association with antipatharians and gorgonians, it is doubtful that Hippolyte sp. is an obligate commensal. Indeed it exhibits no modification of the spine pattern of its walking legs, as it is the case in all strictly commensal Hippolyte species known so far. It could be an ubiquitous species, which occasionally is found on cnidarians, just like its close relative H. varians .

REMARKS

Hippolyte sp. is morphologically similar to H. varians from the temperate northeastern Atlantic, to H. holthuisi Zariquiey Álvarez, 1953 from the Mediterranean sea, to H. kraussiana (Stimpson, 1860) from South Africa and Madagascar and to H. proteus Paulson, 1875 from the Red sea. The mature female Hippolyte sp. (total length 9 mm) has three dorsal rostral teeth. The two juveniles which are very small (total length 5.5 mm) have respectively one single dorsal rostral tooth on the middle of the rostrum, and two dorsal rostral teeth. The rostrum formulae of the juveniles may result from their small size and should not be considered as representative of the species. The occurrence of three dorsal rostral teeth in the mature female suggests that it is neither H. varians nor H. holthuisi , since these species almost always have two dorsal rostral teeth (d’Udekem d’Acoz 1996). Its conspecificity with the poorly known species H. kraussiana seems unlikely due to their wide geographical separation. Furthermore there are significant morphological differences. Barnard (1950) states that the sixth pleonite of H. kraussiana is 1.5 times as long as wide, whilst it is 2.6 times as long in the mature female Hippolyte sp. He also states that there are three to five spines on the merus of P3-P 4 in H. kraussiana , whilst there is only one in the mature female Hippolyte sp. However it must be borne in mind that South African Hippolyte kraussiana are much larger (up to 32 mm) than the illustrated specimen of Hippolyte sp. (9 mm), and in the genus Hippolyte the number of meral spines increases with size. It must be pointed out that Hippolyte sp. is distinct from the superficially similar West Atlantic species H. pleuracanthus (Stimpson, 1871) and H. zostericola (S. I. Smith, 1873) . The dactylus of P3-P5 of Hippolyte sp. has two terminal spines, of which the anterior is the longest, whilst in H. pleuracanthus and H. zostericola the dactylus of P3-P5 has three terminal spines, of which the anterior is significantly shorter than the next one (see illustrations by Chace 1972). With the very limited material at hand, it seems premature to name the species, although it is almost certainly a new one. Some illustrations of the mature female are given on Figure 11 . The dactylus of the left P5, which is still fixed on the specimen, is very similar to that of the putative right P3 which has been found detached in the vial and has been illustrated.

Figures

FIG. 11. — Hippolyte sp., ovigerous ♀, São Tomé: A, habitus in lateral view; B, carapace and cephalic appendages in dorsal view; C, putative right P3 (detached appendage); D, dactylus of the same. Scale bar: A, B, 1.24 mm; C, 0.42 mm; D, 0.10 mm.