Philarius venustus, Kou & Li, 2016

Kou, Qi & Li, Xinzheng, 2016, A new palaemonid shrimp of the “ Philarius gerlachei (Nobili, 1905) species complex ” (Crustacea: Decapoda: Palaemonidae) from Hainan Island, South China Sea, Raffles Bulletin of Zoology 64, pp. 269-277 : 269-274

Philarius venustus , new species

( Figs. 1–6 )

Material examined. Holotype: 1 male, MBM 283036 (CL 2.8 mm, BL 9.2 mm), Houhai , Sanya, Hainan Island, China, 18°16’33”N, 109°43’40”E, 2–8 m depth, from Acropora sp., coll. X. Z. Li, 27 November 2014.

Description. Small-sized palaemonid shrimp with subcylindrical body form ( Figs. 1A , 6A, B ). Carapace ( Figs. 1 A–C, 2A) smooth, glabrous; supraorbital rim rounded; epigastric, hepatic, supraorbital spines absent; inferior orbital angle produced, rounded, reaching middle of antennal spine; antennal spine acute, marginal; pterygostomial angle bluntly produced anteriorly. Rostrum ( Figs. 1 A–C, 2A) well developed, compressed, slightly upcurved distally, not reaching distal margin of scaphocerite; dorsal carina with five teeth, posterior four teeth almost equidistant, acute, distalmost tooth separated from second tooth, posteriormost tooth inconspicuous, situated right above orbital margin; ventral carina with single acute tooth situated right beneath second anterior dorsal tooth; proximolateral carina without supraocular lobe.

Fourth thoracic sternite ( Fig. 2C ) with broad triangular median process; fifth thoracic sternite ( Fig. 2C ) with transverse ridge with median notch.

Abdominal somites ( Fig. 1A ) smooth, glabrous; pleura of first to third somites broadly rounded; fifth somite posteriorly produced, angled; sixth somite about 1.5 times of fifth somite.

Telson ( Fig. 2F ) about 1.8 times as long as sixth abdominal somite, tapering posteriorly, 2.1 times as long as greatest width; two dorsolateral spines situated at 0.53 and 0.83 of telson length on left side, three dorsolateral spines situated at 0.47, 0.63 and 0.80 of telson length on right side, dorsolateral spines slender, anteriormost spine on right side smallest.

Eyes ( Fig. 2B ) well developed, cornea globular, without accessory pigment spot; eyestalk about as long as wide, slightly wider than cornea.

Antennular peduncle ( Figs. 1B , 2G, H ) reaching to about level of fifth dorsal rostral tooth; stylocerite acute, with (right) or without (left) a subdistal tooth, reaching to middle of basal segment; distolateral spine of basal segment not overreaching to intermediate segment; submarginal ventral tooth distinct, small; intermediate segment about as long as wide; distal segment slightly wider than long; upper flagellum biramous, proximal 10 (left) or 9 (right) segments fused.

Antenna ( Figs. 1B , 2I ) with stout basicerite armed with sharp, triangular, distoventral tooth, overreaching distal margin of the segment; carpocerite extending to middle of scaphocerite; scaphocerite reaching to tip of rostrum, about 2.5 times as long as maximal width, lateral margin concave, distolateral tooth acute, overreaching distal margin of lamina, about 0.15 of scaphocerite length.

Epistome unarmed.

Mouthparts typical for genus. Mandible ( Fig. 3A ) without palp; molar process with four strong blunt teeth and several tiny teeth; incisor process robust, with three acute teeth. Maxillula ( Fig. 3B ) with single curved palp; upper lacinia slender, straight, distal margin armed with stout setae and about 10 articulate spines in two rows; lower lacinia tapering, with long simple setae. Maxilla ( Fig. 3C ) with simple palp, slender, tapering, with several plumose setae on lateral margin; basal endite simple, about 1.4 times longer than palp, with simple setae on distal margin; scaphognathite broad, with numerous marginal plumose setae. First maxilliped ( Fig. 3D ) with short palp, slender, medial margin with four short plumose setae; basal endite broad, with dense marginal setae, coxal endite without setae; exopod with well-developed flagellum, bearing long plumose setae along its distal borders; caridean lobe small; epipod large, triangular, feebly bilobed. Second maxilliped ( Fig. 3E ) with normal endopod; dactylar segment narrow, about 4.5 times longer than wide, medial margin slightly concave, with dense rows of simple spines medially; propodal segment with anteromedial margin bluntly produced, bearing long setae and several simple spines; carpus short, anteromedially angulate; merus distal slender; ischium and basis completely fused; exopod with well-developed flagellum; coxa inflated medially; epipod large, subrectangular, without podobranch. Third maxilliped ( Fig. 3F ) with slender endopod reaching to mid-length of scaphocerite; ischio-merus and basis almost fused, only separated by a notch in median margin; antepenultimate segment about three times as long as central width, medial margin with numerous long simple setae; penultimate segment about 0.6 of length of antepenultimate segment, tapering slightly distally, with three simple spines and groups of short stout setae medially; terminal segment tapering distally, about 0.9 of length of penultimate segment with transverse rows of stout setae; exopod with well-developed flagellum, distally with long plumose setae; coxal plate suboval, with several setae; arthrobranch absent.

First pereiopod ( Figs. 4A, B ) moderately slender, chela and distal half of carpus over-reaching distal margin of scaphocerite; palm ( Fig. 4B ) subcylindrical, slightly longer than dactylus, ventral and dorsal margin with sparse transverse rows of setae; dactylus and fixed finger tapering, fixed finger with dense setae and more scattered setae on outer surface, dactylus bearing sparse transverse rows of setae; cutting edges entire; carpus widening distally, about 2.4 times of chela length, about five times as long as distal width, with row of setae at subdistal margin; merus about twice length of chela, five times longer than width; ischium about 0.8 of chela length; basis and coxa without special features.

Second pereiopod ( Figs. 1A , 4 C–E, 5A–C) large, similar, subequal in size, about 1.6 times of BL, overreaching distal margin of scaphocerite by chela, carpus and half length of merus when extended anteriorly; left chela ( Fig. 4C ) about 2.5 times CL, right chela ( Fig. 4D, E ) about 2.6 times CL; palm smooth, glabrous, subcylindrical, not swollen proximally, about 1.1 times as long as dactylus, three times longer than deep; fingers slender, tapering, with robust hooked tip, outer aspect bearing several short setae; dactylus about five times longer than proximal depth, tapering distally, with well-developed hooked tip, proximal 2/3 of cutting edge of dactylus with six low, blunt teeth and long setae along cutting edge; fixed finger similar; carpus ( Figs. 4C, D , 5 A–C) slender proximally and expanded distally, cup-shaped, about 0.5 times as long as palm, distal margin not strongly flaring, without distal tooth or blunt projections but notched dorsally and with rounded lobe ventrally; merus about 1.2 times as long as carpus, 3.2 times as long as width, distoventral margin feebly angulate; ischium about 0.6 times as long as merus, twice as long as distal width.

Third pereiopod ( Figs. 1A , 4F ) robust, tip overreaching distal margin of scaphocerite when extended anteriorly; merus unarmed, about twice as long as carpus, 3.2 times as long as width; carpus unarmed, about 1.8 times as long as distal width; propodus smooth, about twice as long as carpus, five times as long as width, distal margin with groups of long setae, longest setae overreaching entire dactylus, distal 1/3 of ventral surface of propodus with tufts of long simple setae; dactylus about 0.35 of propodal length, simple, strongly curved, unguis distinctly demarcated. Fourth and fifth ( Fig. 4G, H ) pereiopods similar.

Pleopods well developed, first pleopod without appendix intema on endopod ( Fig.2D ), endopod about four times as long as width, half length of exopod; second pleopod ( Fig.2E ) with appendix masculina moderately stout, about 3.2 times as long as wide, about 0.8 length of appendix interna and bearing seven long setae, second to fifth pleopods with appendix interna about 0.4 times of endopod length, endopod 0.9 times as long as exopod.

Uropods ( Fig. 2F ) normal; protopodite unarmed laterally; exopod broad, overreaching distal margin of telson, about 1.8 times longer than wide, lateral margin straight, terminating in short distolateral tooth and small mobile spine; endopod about 0.9 times as long as exopod, 2.2 times as long as width. Colouration. Body generally semitransparent, whitish ( Fig. 6A, B ). Carapace sparsely covered with minute bronze spots. Abdomen and telson colourless, without stripes or patches. Eyes with cornea black. Dorsal margin of eyestalk with a yellowish longitudinal stripe. Antennular and antennal flagella semitransparent, colourless, without colour stripes. Second pereiopods mainly whitish, without lateral longitudinal colour stripes, finely speckled with bronze and black adjacent to joints, fingers with semitransparent, yellowish cutting edges. First and third to fifth pereiopods without longitudinal colour stripes, only with several minute unnoticeable blackish spots.

Host. The new species was found in association with slender-branched scleractinian corals, Acropora sp. ( Fig. 6C ). Specimens of Philarius imperialis ( Kubo, 1940) were collected from the same spot during the sampling.

Etymology. From Latin venustus , meaning elegant, indicating the whitish and glabrous body and the palms of the second pereiopods of the species.

Distribution. Currently only known from the type locality, Hainan Island at a depth of 2– 8 m.

Figures

Fig. 1. Philarius venustus, new species. Holotype, male (CL 2.8 mm). A, body, lateral; B, carapace and cephalic appendages, dorsal; C, carapace, lateral. Scale bar = 1 mm.

Fig. 2. Philarius venustus, new species. Holotype, male (CL 2.8 mm). A, anterior part of carapace, lateral; B, eye, lateral; C, fourth and fifth thoracic sternites and bases of first and second pereiopods; D, endopod of first pleopod, ventral; E, second pleopod, ventral; F, telson and uropods (setae omitted), dorsal; G, left antennule, lateral; H, right antennule, dorsal; I, left antenna, ventral. Scale bar = 1 mm.

Fig. 3. Philarius venustus, new species. Holotype, male (CL 2.8 mm). A, mandible, dorsal; B, maxillula, ventral; C, maxilla, ventral; D, first maxilliped, ventral; E, second maxilliped, dorsal; F, third maxilliped, ventral. Scale bar = 1 mm.

Fig. 4. Philarius venustus, new species. Holotype, male (CL 2.8 mm). A, right first pereiopod, ventral; B, same, chela, lateral; C, left second pereiopod, ventral; D, right second pereiopod, lateral; E, same, fingers, lateral; F, right third pereiopod, medial; G, left fourth pereiopod, lateral; H, left fifth pereiopod, lateral. Scale bars = 1 mm.

Fig. 5. Philarius venustus, new species. Holotype, male (CL 2.8 mm). A, right second pereiopod, carpus, ventral; B, same, dorsal; C, same, lateral. Scale bar = 1mm.

Fig. 6. Fresh colouration of the holotype male of Philarius venustus, new species [A, B] and the partial enlargement of its host coral [C]. A, dorsal view; B, lateral view; C, a branch of slender-branched coral Acropora sp.(Photographs by: Dong Dong, Yueyun Wang and Jixing Sui).