Caridina impensa, Cai & P.K.L.Ng, 2001

Ng, Y. Cai and P. K. L. & Ng, Cai P. K. L., 2010, revision of Caridina yunnanensis and its allied species (Crustacea: Decapoda: Caridea: Atyidae) from Yunnan, southern China, with description of one new species, Journal of Natural History 35, pp. 213-227 : 223-226

Caridina impensa , new species

(®gures 8, 9)

Material examined

HOLOTYPE:, l cl. 4.7 mm ( IZAS), Xilong Tang (Pond), Chengjiang County, Yunnan, leg. B. Sket, 27 April 1997.

PARATYPE: Twelve ll, cl. 3.3±5.4 mm, one m, cl. 4.6 mm, two m (ovigerous), cl. 5.5±6.1 mm ( ZRC.1998.906-92 0); two ll, cl. 4.6±4.7 mm, one m (ovigerous), cl. 5.3 mm ( IZAS) ; two ll, cl. 4.6±4.8 mm, one m, cl. 5.1 mm ( RMNH); two ll, cl. 4.5±4.6 mm, one m, cl. 6.8 mm ( UVL).

Description

Rostrum straight, slightly turning upwards distally, reaching to base or end of third segment, rostral formula: 3±7 (mode 5±6) 1 3±9 (mode 6±7)/1±5 (mode 2±3). Suborbital angle acute, completely fused with antennal spine. Pterygostomian margin broadly rounded.

Abdomen with sixth somite 0.5 times as long as carapace, 1.4 times as long as ®fth somite. Telson (not including marginal spines) slightly longer than sixth somite, tapering posteriorly, ending in a posteromedian projection. Lateral pair of distal spines subequal to or slightly longer than intermediate pairs.

Eyes well developed. Antennular peduncle 0.55±0.65 times as long as carapace, basal segment of antennular peduncle slightly longer than half length of antennular peduncle (from posterior margin of orbit to distal end of its third segment), second segment distinctively longer than third segment. Stylocerite not reaching end of basal segment of antennular peduncle. Scaphocerit e oval, 3.0 times as long as wide. Branchial formula normal, with arthropod of second maxilliped less developed. Epipods on ®rst four pereiopods. Third maxilliped reaching end of second segment of antennular peduncle, ending in single terminal claw; exopod reaching anterior quarter of penultimate segment, ultimate segment slightly longer than penultimate segment.

First pereiopod short, reaching end of ®rst segment of antennular peduncle, chela 2.1 times as long as broad, ®ngers 1.6 times as long as palm, carpus 1.5 times as long as high, merus 3.6 times as long as broad, 1.4 times as long as palm. Second pereiopod slender, reaching end of second segment of antennular peduncle, chela 2.5 times as long as broad; ®ngers 2.0 times as long as palm. Carpus slightly longer than chela, 4.1 times as long as high; merus distinctively longer than carpus, 5.5 times as long as broad. Third pereiopod reaching distal end of scaphocerite, dactylus terminating in two spines, with ®ve spines on posterior margin; propodus 10 times as long as broad, 3.1±3.5 times as long as dactylus (terminal claw included), with numerous spinules on posterior margin. Fifth pereiopod reaching slightly beyond end of second segment of antennular peduncle, dactylus ending in a curved clawlike tip, with a row of 36±39 closely packed spinules, propodus 11 times as long as broad, 3.2±3.7 times as long as dactylus (terminal claw included).

Endopod of male ®rst pleopod sub-rectangular, 3.0 times as long as wide at base, extending to 0.7 times length of exopod; appendix interna distinctively reaching beyond distal end of endopod by 0.3 times length. Appendix masculina of male second pleopod extending to 0.8 times length of endopod, armed on its inner margin with two rows of very strong spines, 3.6 times as long as appendix interna. Uropodal diaeresis with 13 or 14 spinules. Eggs large 1.35± 1.5 Ö 0.80±0.85 mm in diameter.

Habitat

The specimens were caught from a karst spring (B. Sket, personal communication).

Distribution Known only from the type locality in Chengjiang County, Yunnan (®gure 1).

Etymology

The name is derived from the Latin word `impensus ’, for`large’ and`strong’, alluding to the form of the appendix masculina of the male second pleopod, which has two rows of very large and strong spines.

Remarks

Caridina impensa is referred to C. yunnanensi s species group on the basis of the structure of the sexual appendages. Within the group, C. impensa can be distinguished from C. yunnanensi s by the form of rostrum which is slightly upturned distally; fewer ventral rostral teeth (one to ®ve (mode 2±3) vs two to ten (mode 3±7) in C. yunnanensi s); the stouter carpus on the ®rst pereiopod (1.5 times as long as broad vs 2.0 times); the propodus of the third pereiopod being 3.1±3.5 times as long as the dactylus (vs 4.0±4.5 times in C. yunnanensi s); the propodus of the ®fth pereiopod being 3.2±3.7 times as long as the dactylus (vs 3.8±4.5 in C. yunnanensi s); and the larger egg size (1.35± 1.5 Ö 0.80±0.85 mm vs 1.20± 1.28 Ö 0.75±0.85 mm in C. yunnanensi s). Caridina impensa diOEers from C. mongziensis in the longer rostrum, which reaches to the base of the third segment of the antennular peduncle or to the end of this segment (vs reaches to the middle of second segment or slightly beyond it in C. mongziensis ) and its form which is upturned along its anterior half (vs straight in C. mongziensis ); the more slender antennular peduncle which is 5.5±6.5 times as long as the carapace (vs 0.50 times in C. mongziensis ); the propodus of the ®fth pereiopod being 3.2±3.7 times as long as the dactylus (vs 4.0± 4.1 in C. mongziensis ). Caridina impensa can be easily seperated from C. disparidentata by the endopod of the male ®rst pleopod which is 3.0 times as long as broad (vs 3.5 times) and the spinules on the uropodal diaeresis 13±14 (vs 15±18). It can also be distinguished from C. dianchiensis by the rostral formula: 3±7 (mode 5±6) 1 3±9 (mode 6±7)/1±5 (mode 3±4) vs 6±10 1 7±8/4±7 (mode 6) in C. dianchiensis ); the form of endopod of the male ®rst pleopod which is 3.0 times as long as wide (vs 2.3±2.7 times in C. dianchiensis ); and the larger egg size 1.35± 1.50 Ö 0.80±0.85 mm (vs 0.99± 1.16 Ö 0.66±0.77 mm).