Caridina cebuensis, Shokita, 2006

Shokita, Yixiong Cai Shigemitsu, 2006, Report On A Collection Of Freshwater Shrimps (Crustacea: Decapoda: Caridea) From The Philippines, With Descriptions Of Four New Species, Raffles Bulletin of Zoology 54 (2), pp. 245-270 : 250-253

Caridina cebuensis , new species

( Figs. 1 , 2 )

Materials examined. – Holotype: ovig. female, cl 2.9 mm, eggs 0.85 x 0.55 mm, NSMT, spring water to Sagay River , Cebu Island, Philippines.

Paratypes: 2 males, cl 2.1-2.5 mm, 4 females, cl 2.8-3.0 mm, ZRC , 13 males, cl 2.0- 2.6 mm, 19 females, cl 1.9-3.2 mm, UR, data same as holotype .

Description. – Rostrum ( Fig. 1A ) short, pointed, reaching to end of eye stalk or slightly beyond end of first segment of antennular peduncle. Unarmed mostly at both margins, occasionally armed ventrally with 1 small tooth. Antennal spine fused with inferior orbital angle. Pterygostomian margin subrectangular.

Third abdominal somite with moderately convex dorsal profile. Sixth abdominal somite about half length of carapace, 1.7 times as long as fifth somite, slightly shorter than telson. Telson ( Fig. 1B, C ) 2.8 times as long as wide, not terminating in a projection, with four pairs of dorsal spinules and one pair of dorsolateral spinules; lateral pair of distal spines distinctly longer than intermediate pairs of spiniform setae. Preanal carina lacking spine.

Eyes less developed, with short eye stalk, anterior end reaching only to 0.5 to 0.7 times length of basal segment of antennular peduncle. Antennular peduncle 0.7 times as long as carapace; basal segment of antennular peduncle as long as sum of second and third segment length, anterolateral angle reaching 0.27 length of the second segment, second segment distinctly longer than third segment. Stylocerite reaching 0.7 length of basal segment of antennular peduncle. Scaphocerite ( Fig. 1B ) 3.1 times as long as wide.

Incisor process of mandible ( Fig. 1E ) ending in irregular teeth, molar process truncated. Lower lacinia of maxillula ( Fig. 1F ) broadly rounded, upper lacinia elongated, with a number of distinct teeth on inner margin, palp slender. Upper endites of maxilla subdivided, palp short, scaphognathite tapering posteriorly with some long, curved setae at posterior end. Palp of first maxilliped ( Fig. 1G ) broadly triangular, with a pointed end; flagellum of caridean lobe short. Second maxilliped ( Fig. 1H ) typical of genus. Third maxilliped ( Fig. 1I ) reaching to end of antennular peduncle, with ultimate segment as long as penultimate segment.

Epipods on first four pereiopods. First pereiopod ( Fig. 1J ) reaching to end of basal segment of antennular peduncle; ischium as long as merus; merus 1.7 times as long as broad, shorter than carpus; carpus excavated anteriorly, shorter than chela, 1.6 times as long as high; chela 2.2 times as long as broad; fingers distinctly longer than palm. Second pereiopod ( Fig. 1K ) reaching beyond end of second segment of antennular peduncle; ischium as long as merus; merus shorter than carpus, 3.3 times as long as broad; carpus 1.1 times as long as chela, 4.4 times as long as high; chela 2.8 times as long as broad; fingers 1.6 times as long as palm. Third pereiopod ( Fig. 2A, B ) reaching to end of antennular peduncle, propodus 9.0 times as long as broad, 3.7 times as long as dactylus; dactylus 2.9 times as long as wide (spines included), with 4-7 accessory spines on its flexor margin. Fifth pereiopod reaching beyond end of second segment of antennular peduncle, propodus 11 times as long as broad, 3.0 times as long as dactylus, dactylus 3.7 times as long as wide (spinules included), with 39 spinules on its flexor margin.

Endopod of male first pleopod ( Fig. 2E ) subrectangular, one quarter length of exopod, no appendix interna. Appendix masculina of male second pleopod ( Fig. 2F ) half of endopod length, with appendix interna reaching base of distal onethird of appendix masculina.

Uropodal diaeresis ( Fig. 1L ) with 14-16 movable spinules.

Ovigerous females with egg sized 0.85 x 0.55 mm in diameter.

Habitat. – Caridina cebuensis , new species, was collected from the outlet of a spring water, headwater of a stream running into Sagay River, Cebu Island in central Philippines.

Etymology. – The new species is named after its type locality— Cebu Island, Philippines.

Remarks. – With respect to the short and sharp rostrum form, the large egg size, Caridina cebuensis , new species, most resembles the Taiwanese species, Caridina formosae Hung, Chan & Yu, 1993 . It, however, could be easily separated from the latter by the form of male first pleopod, which has no appendix interna (vs. has a distinct appendix interna in C. formosae ). Taking the egg size, the short rostrum, the male first pleopod which has no appendix interna and the form of telson into account, Caridina cebuensis , is similar to Caridina isaloensis Coutière, 1899 , from Madagascar (see Holthuis, 1965; Cai, 2005). It differs from C. isaloensis by the shape of the endopod of male first pleopod (Subrectangular vs. subtriangular), the more spinules on uropodal diaeresis (14- 16 vs. 7-12), and the position of the antennal spine which is fused with the inferior orbital angle (vs. lower than the inferior angle).

Distribution. – Philippines.

Figures

Fig. 1. Caridina cebuensis, new species, male, cl 2.5 mm, paratype, Cebu, Philippines: A, cephalothorax and cephalic appendages, lateral view; B, telson; C, distal portion of telson; D, scaphocerite; E, mandible; F, maxillula; G, first maxilliped; H, second maxilliped; I, third maxilliped; J, first pereiopod; K, second pereiopod; L, uropodal diaeresis. Scale bars: A = 1 mm; B, D-K = 0.5 mm; D, C = 0.1 mm; L = 0.2 mm.

Fig. 2. Caridina cebuensis, new species, male, cl 2.5 mm, paratype, Cebu, Philippines:A, third pereiopod; B, dactylus of third pereiopod; C, fifth pereiopod; D, dactylus of fifth pereiopod; E, endopod of male first pleopod; F, appendix masculina and appendix interna of male second pleopod. Scale bars: A, C = 0.5 mm; B, D-F = 0.1 mm.