Caridina macrodentata, Cai, 2006

Cai, Y., 2006, Atyid shrimps (Crustacea: Decapoda: Caridea) of the Ryukyu Islands, southern Japan, with descriptions of two new species, Journal of Natural History 40 (38 - 40), pp. 2123-2172 : 2156-2160

Caridina macrodentata , new species

( Figures 13 and 14 )

Caridina cf. Pareparensis: Cai and Ng 2001, p 666, fig. 2E, F.

Material examined

Holotype: Ovigerous female, cl 4.8 mm, eggs 0.25× 0.45 mm, NMST, 123 ° 51.849E 24 ° 23.659N, fast flowing water, about 200 m from sea, Omija River , Iriomote Island, Ryukyu Islands, coll. Y. Cai, N. K. Ng and T. Naruse, 15 June 2000 . Paratypes: One female, cl 4.8 mm, RUB, 1 ovigerous female, cl 4.8 mm, ZRC 2004.0583 , eggs 0.50× 0.30 mm, small river in Ohno , Ishigaki Island , Ryukyu Islands, coll. T. Naruse, 23 March 2001 .

Comparative material examined

One ovigerous female, cl 6.1 mm, NMMBA, Dongqing river, Lanyu Island, Taiwan, coll. C. C. Han, 19 April 2002 ; 1 damaged female, cl 5.2 mm, ZRC, Sungai Ifis , Halmahera, Indonesia, coll. D. Robb, September 1994 ; 1 ovigerous female, cl 4.7 mm, ZRC, Philippines, coll M. Kottelat, 1993 ; 1 female, cl 5.5 mm, SMF 947 a, Mariveles Island , Philippines, coll. Semper , 1876.

Description

Rostrum ( Figures 13A and 14A ) short, straight, with a pointed end, reaching middle of second segment of antennular peduncle; dorsal margin with 12–15 large teeth, two to three of them on carapace, ventral margin with three to five very small teeth; inferior orbital angle of carapace fused with antennal spine, sharp, long; pterygostomial angle broadly rounded.

Sixth abdominal somite 0.41 times as long as carapace, 1.2 times as long as fifth somite, slightly shorter than telson. Telson ( Figure 13B, C ) 2.8 times as long as wide, terminating in median projection; five to seven pairs of dorsal spinules, one pair of dorsolateral spines near distal end, one pair of spines and three pairs of subequal spiniform setae on distal margin; lateral spine slightly shorter than intermediate pairs of setae. Preanal carina high, without spine.

Eyes ( Figures 13A and 14A ) well developed, reaching to 0.8 times length of basal segment of antennular peduncle. Antennular peduncle stout, 0.6 times as long as carapace; basal segment of antennular peduncle longer than sum of second and third segment lengths of antennular peduncle, anterolateral angle reaching 0.2 times length of second segment; second segment slightly longer than third. Stylocerite reaching 0.9 times length of basal segment of antennular peduncle. Scaphocerite ( Figure 14B ) 2.8 times as long as wide.

Incisor process of mandible ( Figure 13D ) ending in irregular teeth, molar process truncated. Lower lacinia of maxillula ( Figure 13E ) broadly rounded, subtriangular, upper lacinia elongate, with a number of distinct teeth on inner margin, palp slender. Upper endites of maxilla ( Figure 13F ) subdivided, palp short, scaphognathite tapering posteriorly with numerous long, curved setae at posterior end. Palp of first maxilliped ( Figure 13G ) terminating in broad triangular end. Second maxilliped ( Figure 13H ) typical, arthrobranch well developed. Third maxilliped ( Figure 13I ) reaching to end of antennular peduncle, with ultimate segment shorter than penultimate segment.

Epipods on first four pereiopods. First pereiopod ( Figure 14C ) stout, reaching to end of basal segment of antennular peduncle, merus 2.0 times as long as broad, slightly longer than carpus; carpus strongly excavated anteriorly, shorter than chela, 1.2 times as long as high; chela 2.0 times as long as broad; fingers as long as palm. Second pereiopod ( Figure 14D ) reaching end of second segment of antennular peduncle, merus slightly longer than carpus, 4.4 times as long as broad; carpus slightly longer than chela, 3.8 times as long as high; chela 2.5 times as long as broad; fingers 1.7 times as long as palm. Third pereiopod ( Figure 14E, F ) reaching end of third segment of antennular peduncle, propodus distinctly shorter than merus, 8.5 times as long as broad, 4.3 times as long as dactylus; dactylus ending in two strong claws; 2.5 times as long as wide (spines included), with three accessory spines on flexor margin. Fifth pereiopod ( Figure 14G, H ) reaching to end of basal segment of antennular peduncle, propodus distinctly longer than merus, 11 times as long as broad, 4.7 times as long as dactylus; dactylus 2.4 times as long as wide, ending in two large claws, with 26 spinules on flexor margin.

Uropodal diaeresis ( Figure 14J ) with 19–20 spinules. Eggs 0.25–0.30× 0.45–0.50 mm in diameter.

Habitat

The holotype specimen was caught from a fast flowing stream, hiding under vegetation at the edge of the stream. The collection site is about 200 m from the sea.

Etymology

The name is derived from Latin, macro, large, and dentata, toothed, alluding to the large teeth on the dorsal margin of the rostrum.

Remarks

With regard to the form of the rostrum, the large number of uropodal spinules and the form of various pereiopods, Caridina macrodentata should be referred to the C. weberi species group. In the group, it is most similar to C. weberi papuana , which, however, can be separated from C. weberi papuana by its longer rostrum, the larger rostral teeth and the biunguiculate dactylus of the fifth pereiopod.

The new species is also close to C. okinawa , new species. The rostral formula, the form of the preanal carina, and pereiopods are shared only by these two species in the Ryukyus. Caridina okinawa was found from subterranean water in Okinawa, central Ryukyus, while C. macrodentata was caught from epigean waters in Iriomote, southern Ryukyus. Caridina macrodentata differs from C. okinawa by its well developed eyes, larger teeth on the dorsal margin of the rostrum, the relatively broad scaphocerite (2.5 time as long as wide vs. 2.8 times); the longer fingers of the first pereiopod (as long as palm vs. 0.6 times), the longer fingers of the second pereiopod (1.7 times as long as palm vs. 1.3 times) and the shorter stylocerite (does not reach the end of basal segment of antennular peduncle vs. reaching).

Cai and Ng (2001) doubtfully referred a damaged specimen from Halmahera, Indonesia, to Caridina pareparensis De Man, 1892a . According to the available characters, especially the rostrum and the first pereiopod, it most probably belongs to the present new species, and is formally referred to it here.

Distribution

Japan, Taiwan, Philippines and Indonesia (Halmahera).

Figures

Figure 13. Caridina macrodentata, new species. A, cephalothorax and cephalic appendages, B. telson, C. distal portion of telson, D. mandible, E. maxillula, F. maxilla, G. first maxilliped, H. second maxilliped, I. third maxilliped, J. diaeresis. Scales: A51 mm; B, D–I50.5 mm; C, J50.2 mm (ovigerous female, cl 4.8 mm, ZRC 2004.0583).

Figure 14. Caridina macrodentata, new species. A, cephalothorax and cephalic appendages, lateral view; B, scaphoceite; C, first pereiopod; D, second pereiopod; E, third pereiopod; F, dactylus of third pereiopod; G, fifth pereiopod; H, dactylus of fifth pereiopod. Scales: A, B51 mm; C, D, E, G50.5 mm; F, H50.2 mm (ovigerous female, cl 4.8 mm, holotype, NSMT).