Neocaridina ishigakiensis ( Fujino and Shokita, 1975 )

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 : 2160-2165

Neocaridina ishigakiensis ( Fujino and Shokita, 1975)

( Figures 15–17 )

Caridina denticulata ishigakiensis Fujino and Shokita, 1975, p 93 , figs. 3, 4 [type locality: Ishigaki Island , Ryukyu Islands, Japan].

Caridina denticulata ishigakiensis: Shokita 1976, p 1 .

Neocaridina ishigakiensis: Shokita 1979, p 200 ; 2002, p 164; 2003, p 249, figs. 18K, 19R, 20B; 2005d, p 195; 2006g, p 51, pl 3 (up, left); Shokita et al. 2003a, p 101.

Neocaridina palmata ishigakiensis: Cai 1996, p 145 .

Not Neocaridina denticulate ishigakiensis: Liang 2004, p 84 , fig. 42.

Material examined

Twenty six males, cl 3.3–4.4 mm, 8 females, cl 3.0– 5.2 mm, ZRC 2004.0584 , 124 ° 12.749E 24 ° 25.199N, freshwater stream connected to Sokobaru Dam Reserve , Ishigaki Island , Ryukyu Islands, coll. Y. Cai, N. K. Ng and T. Naruse, 13 June 2000 ; 1 ovigerous female, cl 4.9 mm, ZRC 2004.0585 , 124 ° 09.869E 24 ° 25.009N, fast flowing tributary of Nagura River , below a reservoir, Ishigaki Island , Ryukyu Islands, pH 7.2, coll. Y. Cai and T. Naruse, 13 June 2000 ; 1 male, cl 4.0 mm, ZRC, 123 ° 51.219E 24 ° 18.249N, freshwater, very small, shallow stream, headwater of Nakama River , Iriomote Island , Ryukyu Islands, pH 7.4, coll. Y. Cai, N. K. Ng and T. Naruse, 15 June 2000 ; 9 males, cl 3.5–5.0 mm, 8 females, cl 4.0– 5.2 mm, ZRC 2004.0586 , 124 ° 12.649E 24 ° 25.989N, river below Sokobaru Dam Reserve , Ishigaki Island , Ryukyu Islands, pH 7.5, coll. Y. Cai and T. Naruse, 13 June 2000 .

Description

Rostrum ( Figures 15A and 17A ) narrow, straight, reaching to middle of second segment of antennular peduncle, or slightly beyond end of this segment, rostral formula: 1– 2+1+10(mode 5–7)/0–4(mode 1–2). Antennal spine fused with inferior orbital angle; pterygostomian margin with a spine.

Sixth abdominal somite 0.49 times length of carapace, 1.4 times as long as fifth somite, as long as telson. Telson ( Figure 16A, B ) 3.0 times as long as wide, terminating in a projection, with five to six pairs of dorsal spinules and one pair of dorsolateral spinules; distal end with about four to five pairs of spines, lateral pair as long as or slightly longer than intermediate pairs, sublateral pair shortest. Preanal carina (Figure 20K) without spine.

Eyes well developed, anterior end reaching to 0.8 times length of basal segment of antennular peduncle. Antennular peduncle 0.57–0.63 times as long as carapace; basal segment of antennular peduncle longer than sum of second and third segment lengths, anterolateral angle reaching 0.25 times length of the second segment, second segment distinctly longer than third segment. Stylocerite reaching to 0.85–0.9 length of basal segment of antennular peduncle. Scaphocerite ( Figure 15B ) 2.8 times as long as wide.

Incisor process of mandible ( Figure 15C ) ending in irregular teeth, molar process truncated. Lower lacinia of maxillula ( Figure 15D ) broadly rounded, upper lacinia elongate, with a number of distinct teeth on inner margin, palp slender. Upper endites of maxilla ( Figure 15E ) subdivided, palp short, scaphognathite tapering posteriorly with numerous long, curved setae at posterior end. End of palp of first maxilliped ( Figure 15F ) truncate. Podobranch of second maxilliped ( Figure 15G ) well developed. Third maxilliped ( Figure 15H ) reaching to end of scaphocerite, with ultimate segment as long as or slightly shorter than penultimate segment.

Epipods present on first four pereiopods. First pereiopod ( Figures 16C and 17B ) reaching to distal end of basal segment of antennular peduncle; merus 2.6–2.7 times as long as broad, slightly longer than carpus; carpus excavated anteriorly, shorter than chela, 1.6– 1.8 times as long as high; chela 2.1–2.3 times as long as broad; fingers 1.1–1.4 times as long as palm. Second pereiopod ( Figures 16D and 17C ) reaching to end of antennular peduncle; merus slightly shorter than carpus, 5.1–5.3 times as long as broad; carpus 1.15– 1.25 times as long as chela, 5.0–5.1 times as long as high; chela 2.6–2.9 times as long as broad; fingers 1.4–1.7 times as long as palm. Third pereiopod ( Figures 16E, F and 17D, E ) reaching to end of scaphocerite, propodus incurved strongly in male but straight in female, 7.4–8.4 times as long as broad, 3.4–4.2 times as long as dactylus; dactylus 2.0 times as long as wide in male and 2.6 times in female (spines included), terminating in two claws, with three to four accessory spines on flexor margin. Fifth pereiopod ( Figures 16G, H and 17F, G ) reaching beyond end of basal segment of antennular peduncle, propodus 8.6–10 times as long as broad, 3.1–3.3 times as long as dactylus, dactylus 3.0–3.3 times as long as wide (spinules included), terminating in one claw, with 25–46 spinules on flexor margin.

Endopod of male first pleopod ( Figure 16I ) inflated at distal three-quarters into palmshape, with numerous tiny spinules on distal portion of dorsal surface; appendix interna at base of endopod, small, elongate, or reduced, 1.5 times as long as wide, 0.7 times length of exopod. Appendix masculina of male second pleopod ( Figure 16J ) cylindrical, reaching to half length of endopod, armed with numerous stout spines on surface, with appendix interna reaching to distal quarter of appendix masculina or near its distal end.

Uropodal diaeresis ( Figure 16K ) with 19–20 movable spinules.

Eggs 1.1× 0.7 mm in diameter.

Habitat

Mountain streams.

Remarks

Fujino and Shokita (1975) described it as a subspecies of Caridina denticulata (De Haan, 1849) , on the basis of specimens from Ishigaki Island. Shokita (1979) raised it to a full species, Neocaridina ishigakiensis . In his revision of the genus Neocaridina, Cai (1996) treated it as a subspecies of N. palmata (Shen, 1948) , as the sexual appendages are very similar to the nominal subspecies. Apart from the differences in the rostrum, the appendix interna of the male first pleopod is also shorter than that of N. palmata . While N. ishigakiensis is morphologically closer to N. palmata than N. denticulata (cf. Cai 1996), we nevertheless follow Shokita (1979) in regarding it as a distinct species as recent investigations have shown that it is restricted to Ishigaki Island, and there are no intermediate forms, and no range overlap in the distributions of N. ishigakiensis and N. palmata .

Liang (2004) recently reported the occurrence of Neocaridina denticulata ishigakiensis from Wenling, Zhejiang Province. His drawing ( Liang 2004, fig. 42) shows that sexual appendages of his specimens are much more like those of Neocaridina sinensis than N. ishigakiensis .

Distribution

Several localities on Ishigaki Island.

Figures

Figure 15. Neocaridina ishigakiensis. A, cephalothorax and cephalic appendages; B, scaphocerite, C. mandible; D. maxillula, E. maxilla; F. first maxilliped; G. second maxilliped; H. third maxilliped; I. preanal carina. Scales: A, B51 mm; C–I50.5 mm (male, cl 4.7 mm, ZRC 2004.0584).

Figure 16. Neocaridina ishigakiensis. A, telson; B, distal portion of telson; C, first pereiopod; D, second pereiopod; E, third pereiopod; F, dactylus of third pereiopod; G, fifth pereiopod; H, dactylus of fifth pereiopod; I, male first pleopod; J, male second pleopod; K, diaeresis. Scales: A, C–E, G50.5 mm; B, F, H–K50.2 mm (male, cl 4.7 mm, ZRC 2004.0584).

Figure 17. Neocaridina ishigakiensis. A, cephalothorax and cephalic appendages; B, first pereiopod; C, second pereiopod; D, third pereiopod; E, dactylus of third pereiopod; F, fifth pereiopod; G, dactylus of fifth pereiopod. Scales: A51 mm; B–D, F50.5 mm; E, G50.2 mm (female, cl 4.1 mm, ZRC 2004.0584).