Coralliocaris labyrintha, Mitsuhashi, Masako & Takeda, Masatsune, 2008

Mitsuhashi, Masako & Takeda, Masatsune, 2008, Identity of the coral-associated pontoniine shrimp species, Coralliocaris nudirostris (Heller, 1861) and C. venusta Kemp, 1922 (Crustacea: Decapoda: Palaemonidae), with descriptions of two new species, Zootaxa 1703, pp. 1-24 : 16-21

Coralliocaris labyrintha new species

(figs 1E, F; 6E, F, & 11–14)

Coralliocaris sp. Li & Bruce 2006: 629.

Material examined. Holotype: Urasoko Bay, Ishigaki-jima Island, Ryukyu Islands, coral reef, 2m depth, from Acropora sp., May 29, 1997, coll. Y. Takada and M. Mitsuhashi, ov.Ψ(CL 2.71 mm), NSMT-Cr 2002.

Paratypes: Japan: same locality data as in holotype, May 28, 1997, 1Ψ(CL 1.52 mm), 1ov.Ψ(CL 2.69 mm), NSMT-Cr 2004; Oct. 25, 1996, coll. Y. Takada, 1ɗ(CL 1.80 mm), 1ov.Ψ(CL 2.69 mm), NSMT-Cr 2009; Amitori Bay, Iriomote Island, Ryukyu Islands, reef edge, 2m depth, from Acropora elseyi (Brook) , Jul. 23, 1990, coll. H. Shimada, 1ɗ(CL 2.17 mm), 1ov.Ψ(CL 2.58 mm), NSMT-Cr 2010; Anadomari-mae, Kuroshima Island, Ryukyu Islands, 8m depth, from Acropora sp., Jun. 28, 1997, coll. K. Nomura and M. Mitsuhashi, 2Ψ(CL 1.69, 2.56 mm), NSMT-Cr 2003; in front of the Yaeyama Marine Park Research Station, Kuroshima Island, Ryukyu Islands, 2m depth, from Acropora sp., Jun. 15, 1999, coll. M. Mitsuhashi, 1ɗ(CL 2.24 mm), 1Ψ(CL 2.97 mm), NSMT-Cr 2005; Jun. 10, 1999, coll. M. Mitsuhashi, 1Ψ(CL 2.21 mm), NSMT-Cr 2007; off Nishinohama, Kuro-shima Island, Ryukyu Islands, 8 m depth, from Acropora sp., Jun. 14, 1999, coll. K. Nomura and M. Mitsuhashi, 1Ψ(CL 1.89 mm), NSMT-Cr 2008. Papua New Guinea: Laing Island, outside reef, 20m depth, from Acropora sp., coll. H. Wilkins, 1ov.Ψ(CL 2.44 mm), KBIN I.G. 28056/NAT86. Loyalty Islands: Lifou. Chateaubriand Bay, Wé Beach, stn 1474, 20°54.8’S, 167°16.1’E, 30m, fine sand and heads of Porites , Nov. 11, 2000, 1ov.Ψ(CL 2.25 mm) MNHN-Na 15439; Santal Bay, stn 1146, 36- 40m, 20°50.8’S, 167°09.7’E, Oct. 11, 2004, 1Ψ(CL 1.75 mm), MNHN-Na 15440; Gaatcha Bay, stn 1463, 20- 30m, 20°55.05’S, 167°03.35’E, Nov. 10, 2000, 1Ψ(CL 2.30 mm), MNHN-Na 15442; Northeast Chateaubriand Bay, Cila, stn 1456, 20°49.3’S, 167°10.4’E, slope, 25-30m, Nov. 26, 2000, 1ov.Ψ(CL 2.70 mm), MNHN-Na 15444. Australia: Heron Island, Capricorn Islands, Queens Lane, reef front, 18m depth, from Acropora sp., Sep. 20, 1976, coll. D. Fisk, 1Ψ(CL 1.84 mm), QM W 25600; lagoon, 0.5m depth, from Acropora sp., Sep. 20, 1976, coll. D. Fisk, 1ɗ(CL 2.01 mm), 1Ψ(CL 2.63 mm), QM W 25602.

Description of holotype. Relatively small-sized ovigerous female (CL 2.71 mm). General morphology resembling C. nudirostris and C. sandyi . Body (fig 11A) moderately depressed. Rostrum (fig 11A, B) slender, slightly shorter than distal segment of antennular peduncle; upper margin with 3 low but acute teeth, located anteriorly to eyes; lower margin with a small tooth near tip; few fine setae arising between rostral teeth; rostral midrib slightly developed; superorbital eave moderately convex, smoothly angled. Anterolateral angle of carapace rounded. Abdomen (fig 11A) forming large marsupium with first to third segments, with broadly rounded pleura. Telson (fig 11C) rather slender, armed with 2 pairs of dorsolateral spines; anterior pair situated slightly posterior than median length of telson, posterior pair at about posterior 1/3; posterior margin with 3 pairs of terminal spines, intermediate pair particularly thick, long, about 1/6 of telson length; innermost pair shorter than intermediate pair, with fine setae, outermost pair shortest, about 1/4 of intermediate spine in length; a simple, fine seta situated between innermost and intermediate spines. Eyes (fig 11A, B) moderately large; eyestalk cylindrical, slightly becoming narrower toward to cornea; posterior length of eyestalk 1.3–1.4 times as long as distal width. Antennular peduncle (fig 11B) reaching to 2/3 of lamella of scaphocerite; basal segment slender, medial margin length about 1.2 times of the greatest width; lateral margin moderately angular, terminating in long acute spine; stylocerite slender, reaching to 3/4 length of medial margin, projecting anterolaterally; basal segment ventrally with small acute spine at posterior 2/3 of its length; intermediate segment as long as wide; distal segment somewhat widened distally; upper flagellum biramous, fused part composed of 5 articles.

Antenna (fig 11B) with robust, long lateral spine on basicerite; scaphocerite almost 2.5 times as long as broad; lateral spine of scaphocerite not reaching distal end of scaphocerite. Mouthparts based on left side. Mandible (fig 12A) with distally tapering incisor process, armed with 4 teeth on its distal margin; innermost tooth slightly larger than others. Maxillula (fig 12B) with fine seta on tip of anterior lobe of palp; upper lacinia with several stout setae on distal margin; lower lacinia slender, with several setae. Maxilla (fig 12C) with single endite bearing a fine seta at tip; palp as long as endite. First maxilliped (fig 12D) with short, rounded endite; palp without seta on tip. Second and third maxillipeds (fig 12E, F) generally similar to those of C. nudirostris and C. sandyi sp. nov.; arthrobranch of third maxilliped with 8 lamellae.

First pereiopod (fig 13A, B) has elongated triangular fingers, without concavity on medial surface; palm 4/3 times as long as fingers, with several transverse rows of recurved dentate setae medioventrally; carpus slightly longer than merus, with a line of setae at distal part.

Second pereiopods (fig 13C, D) large, subequal. Chela slender, about twice as long as CL, slightly compressed laterally. Dactylus about half as long as palm, bearing longitudinal ridge along medial surface; cutting edge of dactylus with 2 triangular teeth on proximal half. Fixed finger with 3 subtriangular teeth on cutting edge corresponding to teeth on dactylus; proximal-most tooth dentate with 2 small teeth. Palm about twice as long as fingers, increasing broad to proximal part, 3 times as long as greatest width. Carpus short, about 1/3 times as long as palm, with a short, stout process on flexor margin; anterior margin with several indistinct, small processes. Merus half as long as palm, twice as long as carpus; distal end of flexor margin with flat triangular projection.

Third to fifth pereiopods (fig 13E) similar to each other; dactylus short, distally blunt with a strong hookshaped protuberance on extensor surface; propodus 4 times as long as dactylus, with 3 dense tufts of long, curly setae distoventrally; dorsal surface with scattered long setae; merus as long as propodus, 2.5 time as long as carpus. Pleopods and uropods similar to those of C. nudirostris and C. sandyi sp. nov. About 50-70 early developmental global ova present, measuring 0.49–0.61 mm along axis.

Notes of paratypes. Medium-sized females (CL 1.52–2.97 mm) and males (CL 1.8–2.24 mm). Body slenderer in males. Rostrum (fig 14A–C) situating distal end of intermediate segment to distal end of distal segment of antennular peduncle; dorsal margin with 1 to 5 shallow teeth, evenly situating anteriorly to orbital margin; ventral margin without or with 1 or 2 teeth distally ( Table 1 ).

First pereiopod (fig 6E) with slender fingers that are normally convex on medial surface; palm with several long setae near dactylus.

Second pereiopod, with chela slenderer in males.

Third to fifth pereiopods (fig 6F) each with 5 transverse rows of thick, strongly curly setae distally.

First pleopod short, elongated triangular in male paratypes; second pleopod of male (fig 14D) with small appendix masculina having 1 or 2 long apical setae.

Colour in life. Body is generally translucent white (fig 1E, F). The carapace and first to fourth abdominal segments are furnished with numerous fine longitudinal striations that are formed by yellow and red dots. The fifth and sixth abdominal segments, telson, eyestalks and appendages (antennular and antennal peduncles, first to fifth pereiopods and uropods) are coarsely scattered with relatively large deep red and yellow dots. The proximal half of palm of the second pereiopod is covered with scattered fine white dots. [Based on specimens: NSMT-Cr 2002, 2003, 2004.]

Remarks. This species resembles Coralliocaris nudirostris and C. sandyi sp. nov. in general morphology, but can be easily separated from the two species by the remarkable colour pattern having white longitudinal stripes and scrolls on the body, and bright yellow and reddish brown dots on the appendages. Coralliocaris labyrintha sp. nov. is rather similar to C. sandyi sp. nov. in lacking a concavity on the first pereiopod, but distinct in the following morphological features; usually more numerous rostral teeth (i.e. 1~5/0~2); somewhat angled supraorbital eave; basal segment of antennular peduncle with rather straight lateral margin; fingers of the first pereiopod slenderer than the other two species and being three times as long as proximal width (fig 14A, B, 6E); third to fifth pereiopod with dense, curly setae on distoventral part of the propodus (fig 6F).

This species may have been reported as C. venusta based on its morphological similarity (see remarks of C. sandyi sp. nov.).

Distribution. The specimens examined were collected from Ishigaki-jima Island and Kuro-shima Island in the Ryukyu Islands, and also from Heron Island in the Capricorn Islands, Queensland. Probably widely distributed in the Indo-West Pacific.

Etymology. The name labyrintha refers to the characteristic longitudinal stripe and scroll colour pattern on the carapace and abdomen that gives the impression of a labyrinth.

An updated key to the species of the genus Coralliocaris Stimpson, 1860 is given below including the revised characters of C. nudirostris and the two new species described above, as well as C. tridens Mitsuhashi, Takeda and Fujino, 2001 , and also the diagnostic characters of C. graminea and C. viridis , reported by Mitsuhashi (2000). The variation of the number of the teeth on the second pereiopod in C. brevirostris was reported by Patton (1966).