Hamodactylus macrophthalmus, Fransen, Charles H. J. M. & Rauch, Cessa, 2013

Fransen, Charles H. J. M. & Rauch, Cessa, 2013, Hamodactylus macrophthalmus spec. nov., a new coral-associated pontoniine shrimp (Decapoda, Caridea, Palaemonidae) from Indonesia, Zootaxa 3635 (3), pp. 286-296 : 288-293

Hamodactylus macrophthalmus spec. nov.

(figs. 1–4)

Material examined. 1 ovigerous female holotype (pocl. 1.5 mm) RMNH.CRUS.D.55048, stn LEM.23, Indonesia, N Sulawesi, Lembeh Strait, Tanjung Kuning, 1º23'10.788"N 125º10'23.2314"E, 11.ii.2012, depth 23.4 m, on Herpolitha limax (Esper, 1797) , collected by C. Rauch, field collection number S.172.

Comparative material examined. Hamodactylus aqabai Bruce & Svoboda, 1983: 1 ovigerous female holotype (pocl. 2.5 mm), RMNH.CRUS.D.33233, Aqaba, Jordan, depth 6 m, 24.ii.1976, on Litophyton arboreum Forskål, 1775 , collected by A. Svoboda (no. 2398). 1 ovigerous female (pocl. 2.2 mm) RMNH.CRUS.D.53969, stn SEM.09b, Malaysia, Semporna area, Ligitan reef N2, 04º14'57.5"N 118º37'54.0"E, depth 10 m, 1.xii.2010, on nephtheid alcyonarian, collected by Nina Ho. Hamodactylus boschmai Holthuis, 1952: 1 ovigerous female (pocl. 1.8) syntype, RMNH.CRUS.D.8999, Snellius Expedition, Indonesia, Ternate, depth 2–4 m, 6.vi.1930, divinghood. 1 ovigerous female (pocl. 3.1 mm), RMNH.CRUS.D.53786, stn SEM.47, Malaysia, Semporna area, Larapan Isl., 04º34'27.5"N 118º36'15.0"E, depth 18 m, 13.xii.2010, on red gorgonarian, collected by Bastian T. Reijnen. 1 female (pocl. 3.1 mm), RMNH.CRUS.D.53814, stn SEM.47, Malaysia, Semporna area, Larapan Isl., 04º34'27.5"N 118º36'15.0"E, depth 20 m, 13.xii.2010, on Ellisella spec., collected by C.H.J.M. Fransen. 1 female (pocl. 1.0 mm), RMNH.CRUS.D.53831, stn SEM.09, Malaysia, Semporna area, Ligitan Reef 1 S / Yoshi Point, 04º14'05.8"N 118º33'26.7"E, depth 20 m, 1.xii.2010, on red melitheid, collected by Bastian T. Reijnen. Hamodactylus noumeae Bruce, 1970: 1 ovigerous female (pocl. 2.2 mm), RMNH.CRUS.D.53812, stn SEM.20, Malaysia, Semporna area, Creach Reef, 04º18'58.8"N 118º36'17.3"E, depth 5 m, 5.xii.2010, on Ellisella spec., collected by Nina Ho.

Description. Very small sized, rather slender pontoniine shrimp (fig. 1A), with slender pereiopods.

Carapace smooth (fig. 1A). Rostrum short (fig. 1B), reaching to middle of basal segment of antennular peduncle; lamina deep, lateral carina indistinct, ventral margin slightly convex, toothless, proximally setose; dorsal margin convex, elevated, strongly compressed, with four subequal teeth, of which first situated above level of posterior margin of orbit. Supra-orbital and epi-gastric spines absent. Orbit obsolescent. Inferior orbital angle feebly produced, rounded in lateral view. Antennal tooth of moderate size, submarginal, situated below inferior orbital angle. Hepatic tooth as large as antennal tooth, situated well behind level of posterior orbital margin and slightly above level of antennal tooth. Antero-lateral angle of carapace blunt, not produced.

Abdominal segments smooth (fig. 1A). Third segment not produced posterodorsally. Pleura all broadly rounded. Posteroventral angle of sixth segment feebly produced, posterolateral angle feebly acute.

Telson 0.9 of length of sixth abdominal segment and 2.4 times longer than maximum width (fig. 1D); lateral margins converge posteriorly; two pairs of moderately sized submarginal dorsal spines present at 0.45 and 0.70 of telson length; posterior margin rounded, about half of anterior width, with three pairs of spines. Lateral spines short, about as long as dorsal spines. Intermediate spines about 0.13 of telson length, 1.3 times length of submedian spines.

Eyes twice as long as rostrum (fig. 1B, C). Cornea globular, obliquely set on stalks, with distinct accessory pigment spot posterodorsally. Eyestalks slightly more than twice as long as proximal width, slightly swollen proximally.

Antennular peduncle normal (fig. 1B, C), exceeding tip of rostrum by half length of proximal segment. Proximal segment long, slender, 2.8 times longer than wide; stylocerite slender, acute, reaching almost to middle of segment; disto-lateral margin straight, anterolateral margin slightly produced, with one distolateral tooth and row of setae; medial ventral margin with distinct acute tooth just before mid length of segment. Statocyst normally developed containing a granular statolith. Intermediate and distal segments short, together equal to 0.36 of proximal segment length. Upper flagellum biramous, with first 4–6 segments fused. Shorter free ramus unisegmented, longer rami incomplete. Few aesthetascs present. Lower flagellum slender.

Antennal basicerite (fig. 1B, C) without lateral tooth. Ischiocerite and merocerite normal. Carpocerite slender, reaching to 2/3 of scaphocerite. Scaphocerite long, rather narrow, with lamella almost reaching distal margin of antennular peduncle. Lateral border broadly convex, ending in an acute distolateral tooth. Lamella extending far beyond distolateral tooth, feebly angulated distomedially, about 2.7 times longer than broad, with greatest width at about one third of its length.

Fourth thoracic sternite unarmed.

Mandible (fig. 2A, B) with cylindrical molar process bearing a few brushes of setae distally. Incisor process rather slender, with four teeth distally, of which lateralmost slightly enlarged. Mandible without palp.

Maxillula lost during dissection.

Maxilla (fig. 2C) with tapering non-setose palp. Basal endite simple, short, stout and blunt, with about six simple setae distally. Coxal endite obsolete medial region slightly convex. Scaphognathite normal, widest centrally, about 2.8 times longer than broad, with marginal plumose setae.

First maxilliped (fig. 2D) with slender, tapering palp with one subdistal long seta. Basal region broad, not distinctly separated from coxal region. Median margin sparsely provided with setulose and slender simple setae. Caridean lobe distinct, with coarsely setulose plumose marginal setae. Flagellum of exopod well developed, with 4 long plumose terminal setae. Epipod small, indistinctly bilobed.

Second maxilliped (fig. 3A) with broadly triangular dactylar segment, about 3 times broader than long, slightly convex medially, bearing row of stout biserrulate spines. Propodal segment broader than dactylar segment, with subrectangular distomedial angle with few long serrulate setae. Carpus short. Merus partly fused to ischium. Ischium completely fused to basis. Basis without exopod. Coxa not produced medially, with small, rounded epipod laterally.

Third maxilliped (fig. 3B) with slender antepenultimate segment, about 5 times longer than proximal width. Basis completely fused with ischiomerus, junction indicated medially by small knob. Median margin of antepenultimate segment with few simple setae. Penultimate segment slender, 4.5 times longer than wide, 0.44 of length of antepenultimate segment, with few long slender setulose setae on medial border. Terminal segment 4.3 times longer than wide, slightly shorter than penultimate segment, with few serrulate and simple setae medially distally. Exopod absent. Coxa feebly produced medially, with rounded lateral lobe. Multilamellar arthrobranch present laterally.

First pereiopod slender (figs. 3C, 4A), reaching to end of scaphocerite. Chela with palm subcylindrical, slightly bowed, about 3.2 times longer than wide. Fingers 0.58 of palm length, feebly subspatulate with brushes of few setae in distal part. Cutting edges with very thin denticulate lamella laterally in distal 2/3. Tip of dactylus with distinct tooth. Cleaning setae present proximally on palm and distoventral end of carpus. Carpus 1.2 times length of chela, 5.5 times longer than wide. Merus 1.12 times longer than carpus and twice length of ischium. Coxa with very small medial setose process.

Second pereiopods (figs. 3D, 4B) greatly reduced, subequal and similar, only extending slightly beyond carpocerite. Chela atyid-like, with blunt fingers with brushes of distal curled setae, cutting edges not developed. Dactylus distinctly shorter than fixed finger, unguis not developed. Palm subcylindrical, 2.5 times longer than dactylus, 3.8 times longer than wide, unarmed. Carpus, merus and ischium also unarmed, their lengths ratio of 1.3, 1.8 and 1.5 times length of palm. Basis and coxa without special features.

Ambulatory pereiopods (fig. 4C, D) slender, similar, increasing in length from third to fifth. Dactylus slender, uniformly tapering, unarmed, with distinct slender unguis. Total length about five times width near base. Propodus about 9 times longer than wide, 3.6 times length of dactylus, devoid of spines. Carpus, merus and ischium 0.55, 1.1 and 0.65 of propodus length, unarmed.

Pleopods well developed. Marginal plumose setae of exopod and endopod coarsely serrulate.

Uropods (fig. 1D) slender just extending beyond tip of telson. Protopodite unarmed laterally. Exopod about 2.3 times longer than wide, about as long as endopod, with lateral border almost straight, entire, terminating in tooth with small mobile spine medially.

About 30 eggs of ca. 0.5 mm in length present under abdomen.

Colouration. Not recorded.

Etymology. The specific name macrophthalmus is a noun composed of the prefix macro- (Gr. makros), = long, and the suffix –opthalmus (Gr. opthalmos), = eye, referring to the eyes with the long eyestalks.

Host. Herpolitha limax (Esper, 1797) (Scleractinia) , identification confirmed by B.W. Hoeksema, Naturalis Biodiversity Center. The three previously known species of Hamodactylus have all been recorded as associated with Octocorallia. The closely related Hamodactyloides incompletus is only known from species of the hydrocoral Millepora (see Bruce 1976, 1978, 1981, 1983; Fujino 1973 (as Hamodactyloides ishigakiensis )). The new species is the first species of the genus Hamodactylus recorded in association with a scleractinian coral.