Alcyonohippolyte, Marin, Ivan, Okuno, Junji & Chan, Tin-Yam, 2011

Marin, Ivan, Okuno, Junji & Chan, Tin-Yam, 2011, On the “ Hippolyte commensalis Kemp, 1925 ” species complex (Decapoda, Caridea, Hippolytidae), with the designation of a new genus and description of two new species from the Indo-West Pacific, Zootaxa 2768, pp. 32-54 : 33-34

Alcyonohippolyte gen. nov.

Type species. Alcyonohippolyte dossena sp. nov.; by present designation; gender feminine.

Species included. Alcyonohippolyte commensalis ( Kemp, 1925) comb. nov., A. dossena sp. nov.; A. maculata sp. nov.

Etymology. The name refers to the association of this genus with alcyonacean corals, the so called soft corals (Octocorallia, Alcyonacea ), and its similarity with the genus Hippolyte . The standard Japanese name for this genus is Kakure-moebi-zoku.

Diagnosis. Medium size shrimps with slender cylindrical body, sometimes with tufts of plumose setae. Carapace smooth, with dorsal margin normal or gibbous; with well developed supraorbital, antennal and hepatic teeth; antennal tooth situated below inferior orbital angle, hepatic tooth larger than antennal tooth, situated below and behind antennal tooth. Rostrum long, slender, unarmed dorsally; ventrally unarmed except for a single subapical tooth; proximal lateral rostral lamina well developed, armed with well marked supraorbital tooth at level of proximal margin of orbit. Orbit well developed, inferior orbital angle produced distally, blunt. Abdominal somites smooth; pleura of abdominal somites I–V rounded. Telson with 2 pairs of small submarginal dorsal spines, distal margin armed with 4 pairs of stout spines. Eyes large, normal, with subcylindrical eyestalk and subovate cornea, with ocellus. Antennule slightly reduced; basal antennular segment without ventromedial tooth, distolateral angle armed with large acute tooth which reaching distal margin of next segment. Antenna with basicerite armed with sharp triangular distoventral tooth; scaphocerite wide, with well developed acute distolateral tooth. Mandible without palp; with styliform incisor process; maxillula with well developed bilobed palp armed with long styliform rigid setae; wide upper lacinia and slender lower lacinia both covered with long simple setae; maxilla with simple blunt palp, endites completely fused, scaphognathite well developed. Maxilliped I with completely fused endites, well developed exopod bearing caridean lobe, with bilobed epipod. Maxilliped III with large arthrobranch and stout exopod; terminal segment with distal margin oblique, armed with row of strong spines distally. Pereiopods I similar, small, segments robust, fingers subspatulate, armed with some large acute teeth along lateral and distolateral margins. Pereiopod II relatively slender, segments unarmed, carpus subdivided into 3 subsegments; palm subcylindrical; fingers subspatulate, with straight smooth margins or armed with several teeth. Pereiopod III–IV similar; merus armed with large movable tooth distoventrally; propodus with ventral margin generally unarmed except in males, with distoventral margin of pereiopods III bearing 3 pairs of large spines; dactylus slender, simple, with elongate and curved main unguis, with or without accessory tooth. Segments of pereiopod V unarmed. Distolateral margin of uropodal exopod without fixed tooth, bearing slender movable spine only.

Remarks. The new genus is most closely related to the genus Hippolyte by the long slender rostrum, the presence of supraorbital, hepatic and antennal teeth on carapace, and the similar shape of mouthparts and ambulatory pereiopods (see Holthuis, 1993). However, the new genus differs from Hippolyte (the type species, H. varians Leach, 1814 , is re-described in d'Udekem d'Acoz 1996) in following combination of morphological characters: 1) rostrum dorsally unarmed, with single subapical tooth ventrally (vs. rostrum either armed dorsally or with several distinct ventral teeth in Hippolyte ); 2) incisor process of mandible reduced and styliform (vs. incisor process well developed and bearing several apical teeth in Hippolyte ); 3) basal antennular segment without ventromedial tooth (vs. well developed ventromedial tooth in Hippolyte ); 4) propodus of ambulatory pereiopods with single pair of movable spine at distoventral angle while merus and carpus of ambulatory pereiopods unarmed in females; males have several pairs of large spines along distoventral margin of propodus of pereiopod III (vs. meri, carpi and propodi of all ambulatory pereiopods armed with large distinct spines in both sexes in Hippolyte ); 5) ambulatory pereiopods with simple dactylus having single main unguis only (vs. dactylus with stout basal part and 2 large curved ungues as well as several sharp spines along ventral margin in Hippolyte ).

Presently defined genus Alcyonohippolyte gen. nov. can be readily separated from all other species of the genus Hippolyte in morphology and, more importantly, ecologically. All known species of Alcyonohippolyte gen. nov. are associated with soft corals ( Alcyonacea ) while no species in Hippolyte has such an association. Thus, Alcyonohippolyte gen. nov. likely represents a monophyletic group adapted as alcyonarian associates with its own diversification and evolutionary trends. An in deep phylogenetic analysis on the genus Hippolyte and its related genera will surely flow more lights to the actual status of Alcyonohippolyte gen. nov., as well as if the genus Hippolyte will need to be further subdivided.