Alcyonohippolyte brachycarpus, Marin & Chan, 2012

Marin, Ivan & Chan, Tin-Yam, 2012, Description of Alcyonohippolyte brachycarpus sp. nov., a further new hippolytid shrimp (Decapoda, Caridea, Hippolytidae) associated with soft coral from Taiwan, with the key to the species of the genus Alcyonohippolyte Marin,, Zootaxa 3534, pp. 53-60 : 54-59

Alcyonohippolyte brachycarpus sp. nov.

( Figs. 1, 2 a–f, 3 a–d, 4)

Material examined. Holotype: NTOU M00924 , ovigerous female ( PCL 2.1 mm, TL 10.0 mm), Badouzih , Keelung, northern Taiwan, 5–6 m, on “ Sinulari a sp.”, 07 July 2010.

Paratypes: NTOU M 00926 , 1 male ( PCL 1.4 mm), 1 non-ovigerous female ( PCL 1.6 mm), Maoao , Taipei County, northern Taiwan, 8–10 m, on “ Sinulari a sp.”, 30 June 2010 ; NTOU M00925 , 3 males, ( PCL 1.3–1.8 mm, illust.), Badouzih , Keelung, northern Taiwan, 5–6 m, on Sinulari a sp., 03 July 2010 ; NTOU M00927 , 1 ovigerous female ( PCL 2.0 mm, dissected, illust.), Badouzih , Keelung, northern Taiwan, 5–6 m, on “ Sinulari a sp.”, 09 July 2010 ; NTOU M00928 , 1 ovigerous female ( PCL 1.9 mm), 5–6 m, on “ Sinularia sp. ”, 09 July 2010 ; NTOU M 00929 , 1 male ( PCL 1.3 mm), 1 ovigerous female ( PCL 2.0 mm), Badouzih , Keelung, northern Taiwan, 5–6 m, on “ Sinulari a sp.”, 09 July 2010 .

Comparative material: Alcyonohippolyte maculata . NTOU M00931 , 1 ovigerous female ( PCL. 1.8 mm, illust.), 2 males ( PCL. 0.9, 0.6 mm, illust.), Badouzih , Keelung, northern Taiwan, 5–6 m, on “ Sinulari a sp.”, 03 July 2010 ; NTOU M 00930 , 3 males ( PCL 0.7-1.0 mm), Badouzih , Keelung, northern Taiwan, 10 m, on “ Sinulari a sp.”, 07 July 2010 .

Description. Paratype ovigerous female (NTOU M00927 ). Carapace ( Fig. 2 a, b) smooth, dorsal surface nongibbous, covered with single tuft of plumose setae situated dorsally and submedially near midlength of carapace; with well developed supraorbital, antennal and hepatic teeth; antennal tooth sharp, situated slightly below orbital angle; hepatic tooth sharp, larger than antennal tooth, slightly exceeding pterygostomial margin of carapace, situated below and slightly posterior to level of antennal tooth. Rostrum long, compressed, dorsally unarmed, with 1 subdistal ventral tooth; proximal lateral rostral lamina armed with 1 sharp supraorbital tooth situated above level of proximal orbital margin. Orbits well developed, inferior orbital angle slightly produced. Pterygostomial angle bluntly projected.

Abdominal somites smooth and unarmed, dorsal part of abdominal somites II, IV and VI covered with tufts of plumose setae; pleurae of abdominal somites I–V rounded ( Fig. 1). Telson ( Fig. 2 c) slender, about 3 times as long as proximal width, narrowing posteriorly, with 2 pairs of small dorsal submarginal spines at 0.45 and 0.7 of telson length; distal margin of telson armed with 4 pairs of spines including 1 pair of short stout lateral spines, 2 pairs of long slender intermediate spines and 1 pair of largest medial spines more or less as longer as intermediate spines.

Eyes normal, well developed, with subcylindrical eyestalk and subovate cornea; eyestalk about 1.5 times as long as wide; cornea suboval, without apical papilla.

Antennula well developed; basal segment about 1.5 times as long as wide, without ventromesial tooth, distolateral angle armed with acute distolateral tooth overreaching midlength of intermediate segment; stylocerite well developed, sharp, reaching distal margin of basal segment; intermediate segment stout, about twice wider than long, with slightly convex inner lateral margin; distal segment stout, about as long as wide.

Antenna normal, well developed, basicerite armed with sharp triangular spine distoventrally, slightly overreaching distal margin of segment; carpocerite stout, about as long as wide, reaching midlength of scaphocerite; flagellum well developed; scaphocerite wide, about 1.5 times as long as maximal width, far exceeding antennular peduncle, with well developed acute distolateral tooth.

Mouthparts characteristic for the genus.

Pereiopod I ( Fig. 2 d) with segments robust and unarmed; coxa with arthrobranch; basis with small lobe distoventrally; ischium stout, about as long as wide, with long simple setae along ventral margin; merus stout, about twice longer than wide; carpus stout, shorter than merus and equal to length of propodus, about as long as wide, flaring distally, distal margin overlapping carpo-propodal articulation, with row of stout plumose setae along distoventral margin; palm about as long as wide, subcylindrical, smooth; fingers stout, slightly longer than palm, subspatulated, about as long as wide, cutting edges armed with several large acute teeth.

Pereiopod II relatively slender, with segments unarmed ( Fig. 2 e); ischium about 2 times as long as wide, smooth; merus about 6 times as long as wide, with straight margins; carpus subdivided into 3 segments with ratio of about 1.3: 1: 1.5; palm subcylindrical, length equal to distal carpal segment, about 1.5 times longer than wide, with straight smooth margins; fingers robust, shorter than length of palm, about twice longer than wide, subspatulated, cutting edges armed with several large acute teeth.

Pereiopods III–V similar, with segments mostly unarmed. Pereiopod III ( Fig. 2f) with ischium about 2.5 times longer than wide; merus about 4 times as long as wide, with straight lateral margins and large movable spine at distoventral angle; carpus about 3 times as long as maximal width, flaring distally, with distodorsal margin overhanging proximal part of propodus; propodus about 6 times as long as wide, with straight and smooth margins, ventral margin unarmed, bearing 1 small spine at distoventral angle; dactylus slender, about 1.5 times as long as maximal width at basal part, swollen, with elongated and curved main unguis, and without accessory tooth. Pereiopod V similar to other ambulatory pereiopods, except for propodus and dactylus unarmed, without any accessory tooth.

Pleopods normal. Uropods slender, slightly exceeding telson; distolateral margin of exopod without fixed tooth, with long mobile spine distolaterally.

Male paratype (NTOU M 00925 ). Generally similar to females but smaller, about half size of females ( Fig. 1). Both carapace and abdominal somites smooth, without long setae; rostrum unarmed, styliform, pointed distally ( Fig. 3 a). Carpal segments of pereiopod II with relatively stout segments with proportion of about 1.5: 1: 2 ( Fig. 3b, c), distal segment about as long as wide; palm about 1.5 times longer than distal carpal segment. Propodus of pereiopod III with 3 pairs of distoventral spines, proximal pair about twice larger than others ( Fig. 3 d).

Measurements. The largest ovigerous female has PCL 2.1 mm, TL 10.0 mm; the largest male has PCL 1.8 mm, TL 9.7 mm.

Coloration. Carapace and appendages generally whitish and covered with greenish-brown bands. Antenna and antennula whitish, with transverse brown bands. Rostrum white. Carapace with 2 oblique transverse greenishbrown bands posterior to orbits and a broad greenish-brown transverse band at posterior part of carapace. Pereiopods white with wide transverse greenish-brown bands. Abdomen with dorsal surfaces and pleurae covered with wide greenish-brown bands. Tailfan generally brownish with white and reddish transverse bands (see Fig. 4 a–c). Bands less marked in smaller individuals and thus making the body being more whitish ( Fig. 4 d-g).

Variations. The specimens examined are generally similar in morphology. Some variations were found in the number of ventral rostral teeth in females and the armature of distoventral margin of propodus of pereiopod III similar to the situation in congeneric species (see Marin et al., 2011). Females usually have rostrum armed with one subdistal ventral tooth ( Fig. 2 b) but rarely two subdistal ventral teeth may be present. The number of large proximal spines along distoventral margin of propodus of pereiopod II varies from mostly one pair ( Fig. 3 d) to two pairs or one pair with an additional proximal spine as in A. maculata (see Fig. 3 g –j).

Habitat. The present specimens were collected from alcyoniid soft coral (Octocorallia, Alcyonacea , Alcyonariidae) identified as “ Sinularia sp. ” resembling both Sinularia polydactyla (Ehrenberg) and Cladiella digitulata (Klunzinger) . This soft coral species occurs in the algal zone between 2 and 8 m deep. Shrimps were found in groups consisting of several mature individuals per each host including a single large female and several males. The host coral species is also inhabited by A. maculata and portuniid crab Caphyra yokodai Sakai, 1933 ( Decapoda : Brachyura: Portunidae ) in the studied area (see Marin et al., 2010). Nevertheless, it has never been found that A. brachycarpus sp. nov. and A. maculata inhabit the same host together.

Etymology. The Latin “ brachycarpus ” refers to females of this species has a distinctly shorter carpal segments at the pereiopod II as compared to the other known species of the genus.

Distribution. The species is so far only known from the type locality, the northern Taiwan.

Taxonomic position. Alcyonohippolyte brachycarpus sp. nov. is most morphologically similar to A. maculata and A. tubiporae Marin, 2011 in having non-humped carapace and bearing tufts of setae on dorsal surface of abdomen in females. The new species differs from A. tubiporae by the presence of a tuft of setae on the dorsal carapace in females (vs. smooth carapace in A. tubiporae ), by the different coloration ( Fig. 4; Marin, 2011: Fig. 7) and host coral species ( A. tubiporae is known in association with hard organ pipe coral Tubipora sp. (Octocorallia: Tuboporidae)).

On the other hand, A. brachycarpus sp. nov. can be clearly separated from A. maculata by the banded coloration ( Fig. 4) (vs. spotted in A. maculata ; Marin et al, 2011: figs. 15B – H, 16C) and the relatively shorter carpal segments of pereiopod II (proximal carpal segment shorter than distal segment in females of A. brachycarpus sp. nov., while it is distinctly longer in A. maculata , Fig. 2 e, h)). In males, carpal segments of pereiopod II are stouter and shorter in A. brachycarpus sp. nov. and more slender in A. maculata ( Fig. 3 b, c, f). Moreover, there are three tufts of setae on the dorsal carapace in both sexes of A. maculata ( Figs. 2 g, 3 e), while there is only one tuft of dorsal carapace setae in females ( Fig. 2 b) and none in males of A. brachycarpus sp. nov. ( Fig. 3 a).

As no males have yet been known for the type species of the genus Alcyonohippolyte , A. dossena Marin, Okuno & Chan, 2010 , the following revised key for females of the genus is provided to accommodate the present new species.