Macrobrachium niphanae Shokita & Takeda, 1989

Hanamura, Yukio, Imai, Hideyuki, Lasasimma, Oulaytham, Souliyamath, Pany & Ito, Sayaka, 2011, Freshwater prawns of the genus Macrobrachium Bate, 1868 (Crustacea, Decapoda, Palaemonidae) from Laos, Zootaxa 3025, pp. 1-37 : 16-18

Macrobrachium niphanae Shokita & Takeda, 1989

( Fig. 9 )

Macrobrachium niphanae Shokita & Takeda, 1989: 147 , figs. 1, 2, pl. 1; Cai et al. 2004: 609. Macrobrachium secamanense Dang, 1998: 1 , fig. 1.

Material examined. Vientiane Capital: Nong Niew Market, 1 male (CL 11.0 mm), 30 Aug 2007, coll. H. Ikenoue. Khammouane Province: Theun River, 1 female (CL 10.8 mm), 13 July, 2009, hand net, coll. Ito et al. Champasak Province: Khone Island, 1 male (CL 8.5 mm), 5 females (CL 5.3–8.2 mm), 3 ovig. females (CL 7.0– 8.5 mm), 1 juv. (CL 4.3 mm), set net, 10 July 2009, coll. S. Ito & Y. Niimura; Det Island, 2 males (CL 7.4 mm, 10.4 mm), 21 July 2009, set net, coll. Y. Niimura; Det Is., 1 male (CL 12.0 mm), 21 July 2009, set net, coll. Y. Niimura.

Diagnosis. Rostrum ( Fig. 9 a) barely reaching anterior end of antennal scale, weakly curving dorsad, dorsal margin with somewhat widely spaced 8–10 teeth, including 1–3 placed posterior to orbital margin, ventral margin with 3 or 4 teeth; antennal spine sub-marginal, apex barely reaching end of antennal lobe and antennal spine supported by moderately long carina extending backward to near hepatic spine, latter situated at approximately same level of antennal spine.

Sixth abdominal somite 1.4–1.6 times as long as fifth; pre-anal carina well marked as elevated thin carina. Telson 1.4–1.8 times as long as sixth abdominal somite, posterior margin sub-triangular with 2 pairs of ordinary subterminal spines, 2 pairs of dorsolateral spines, anterior pair of latter spines situated on mid-length of telson.

Antennal scale 0.7–0.75 times as long as carapace, 3.0–3.5 times as long as wide. Epistome composed of 2 lobes with shallow transverse median groove.

Second pereopods ( Fig. 9 a–c) almost equal in length, slightly longer than total body length, extending beyond antennal scale by four-fifths of carpus and onwards, ischium, merus, carpus, and propodus covered with short velvety setae; carpus slightly longer than merus and again slightly longer than palm; fingers 0.65–0.70 times as long as palm, with 18–20 tuberculate teeth on entire margin of cutting edges. Third pereopod ( Fig. 9 d, e) with propodus 3.2–3.8 times as long as dactylus.

Appendix masculina ( Fig. 9 f) about twice length of appendix interna, with moderately long setae along anterolateral margin as well as mesial surface. Exopod of uropod slightly longer than endopod, movable spine on diaeresis ( Fig. 9 g) slightly longer than lateral projection.

Egg. Eggs small in numbers and moderately large in size, measuring 1.0–1.1 x 1.4–1.5 mm.

Remarks. The present specimens basically agreed with the original description by Shokita &Takeda (1989), although some minor differences were found. Our specimens have comparatively fewer teeth on the cutting edges of the second pereopod (see also Cai et al. 2004). The second pereopod of our specimens collected from the Khammouane and Champasak Provinces was found to have velvety setae on the carpus, while, in other specimens, the merus is nearly naked or occasionally with such setae only on its anterior part. These are regarded as intraspecific variations.

Cai et al. (2004) suggested that M. secamanense Dang, 1998 , reported from the southern part of Laos, could be a junior synonym of this species.

Distribution. Thailand and southern and central Laos (Cai et al. 2004; present study).

Figures

FIGURE 9. Macrobrachium niphanae, male (CL 11.0 mm) collected from Vientiane Capital, Laos: a, entire body; b, right second pereopod, mesial view; c, chela of left second pereopod, lateral view; d, right third pereopod, lateral view; e, dactylus of same leg; f, appendix masculina, mesial view; g, uropodal diaeresis, lateral view.