Pontonides maldivensis Borradaile 1915

Pontonides maldivensis (Borradaile, 1915)

( Figs. 6, 7, 10 A, 11A, B)

Pontonia maldivensis Borradaile, 1915: 213.

Pontonides maldivensis.— Borradaile, 1917: 387.— Heard, 1986: 481.—Müller, 1993: 125.—Li, 2000: 274.

Material examined. Vietnam, Nhatrang Bay: 5 ovig. females (pcl. 2.3, 2.5, 2.6, 2.8, 2.8 mm), 4 males (pcl. 1.7, 1.8, 2.0, 2.0), 2 juveniles (pcl. 1.6, 1.6 mm), Nok I., depth 15 m, on dendrophyllid coral Tubastrea micrantha, coll. I. Marin, 6 July 2006, ZMMU Ma 5487; 1 ovig. female (pcl. 1.8 mm), 1 male (pcl. 1.6 mm), Nok I., depth 10 m, on dendrophyllid coral Tubastrea micrantha, coll. I. Marin, 20 Aug 2006, ZMMU Ma 5488; 1 juvenile (pcl. 1.4 mm), Mun I., depth 10 m, on dendrophyllid coral Tubastrea micrantha, coll. I. Marin, 6 Oct 2006, ZMMU.

Diagnosis. Medium-sized pontoniine shrimps with dorsoventrally flattened body. Carapace smooth, not gibbous. Rostrum short, not reaching distal margin of basal antennular segment. Supraorbital margin well developed, convex, with small but distinct, tooth; orbits well developed. Eyestalk without dorsal tubercle. Fourth and fifth pleura rounded. Second and third maxillipeds without fusiform setae. First to fifth pereiopods with fusiform setae on ischia. Second pereiopods subequal, differing in shape of chela, and somewhat sexually polymorphic: female major chela covered with tiny tubercles, setose, with long curved simple setae along ventral and ventrolateral margins and shorter simple setae dorsally, fingers stout and curved; female minor chela setose, with long curved simple setae along ventral and ventrolateral margins and short simple setae dorsally, fingers 2–2.5 times as long as wide, with curved tips; male major chela similar to that of female; male minor chela with smooth stout palm, twice as long as wide; fingers long, about eight as long as wide, straight, with curved tips. Third pereiopods smooth, non-setose; dactylus simple, curved, distally acute.

Colouration. Body and appendages yellow-green, covered with minute yellow chromatophores (pattern well-adapted to host).

Size. Maximum length: ovigerous female, cl. 3.2 mm, pcl. 2.8 mm, tl. 10 mm; male, cl. 2.8 mm, pcl. 2.5 mm, tl. 9 mm. Eggs numerous; diameter 0.35 x 0.45 mm

Ecology. In Nhatrang Bay, P. m a l d i v e n s i s was found in association with dendroid colonies of Tubastrea micrantha Ehrenberg, 1834 (Scleractinia, Dendrophylliidae), usually in larger groups of adults (sometimes up to 15 adults per colony). Tubastrea corals are most common in areas exposed to currents, but P. maldivensis was found only near Nok Island and on the outer side of Mun Island, where currents are strongest in the bay. The presence of curved setae along the ventral margin of the second pereiopods suggests that shrimps may collect mucus secreted by the host coral for feeding.

Distribution. Widely distributed in the Indo-West Pacific; previously reported from the Maldives (type locality), Kenya, Japan, Hawaii (Li, 2000), and now, for the first time, from Vietnam.