Macrobrachium mieni Dang, 1975

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 : 14-16

Macrobrachium mieni Dang, 1975

( Fig. 8 )

Macribrachium mieni Dang, 1975: 68 , fig. 2: Dang 1980: 389, fig. 223; Cai et al. 2004: 613, fig. 11.

Material examined. Luang Prabang Province: Ou River, Ngoi District, 2 males (CL 11.3 mm, 15.0 mm), Sept 2000, coll. O, Lasasimma; Xuang River, Na Pho Village, St. 3, 2 males (CL 10.5 mm, 12.5 mm), 20 Oct 2007, hand net, coll. S. Ito et al.; Xuang River, Na Pho Village, St. 2, 1 male (CL 17.0 mm), 1 female (CL 8.8 mm), 28 Dec 2008, hand net, coll. S. Ito et al.; Xuang River, Na Pho Village, St. 2, 1 male (CL 15.2 mm), 27 Apr 2008, hand net, coll. S. Ito et al.; Xuang River, Na Pho Village, St. 3, 1 male (11.5 mm), 25 May 2008, hand net, coll. S. Ito et al. Vientiane Province: Kasi District, 1 female (CL 12.0 mm), 22 May 2008, hand net, coll. S. Ito et al.; Kasi District, 1 female (CL 16.0 mm), 30 Jan 2009, hand net coll. S. Ito et al.; Kasi District, 2 males (CL 19.9 mm, 20.0 mm), 1 Nov 2009, hand net, coll. S. Ito et al. Vientiane Capital: Nong Niew Market, 2 ovig. females (CL 10.8 mm, 11.5 mm), 31 Aug 2007, coll. H. Ikenoue. Champasak Province: Det Island, 1 male (CL 9.5 mm), 11 July 2009, set net, coll. S. Ito & Y. Niimura; Det Island, 1 male (CL 9.8 mm), 1 female (CL 6.2 mm), 23 July 2009, set net, coll. Y. N i i m u r a.

Diagnosis. Rostrum ( Fig. 8 a) straight or slightly directed ventrad, 0.35–0.4 times as long as carapace and usually falling slightly short of anterior end of antennular peduncle, dorsal margin armed with 9–15 teeth including 2– 5 situated posterior to orbital margin, ventral margin with 2–4 teeth; antennal lobe moderately developed, antennal spine placed just behind lateral margin, apex extending slightly beyond antennal lobe; hepatic spine smaller than antennal spine, situated posteriorly, distinctly below level of antennal spine.

Abdomen with sixth somite 1.3–1.4 times as long as fifth, pre-anal carina represented by obtuse ridge; anterior 3 abdominal sternites each with moderately developed median tooth, third one smaller than precedent ones. Telson 1.5–1.6 times as long as sixth abdominal somite, posterior margin sub-triangular, possessing 2 pairs of ordinary sub-terminal spines and 2 pairs of dorsolateral spines, anterior pair of latter spines placed slightly posterior to midlength of telson.

Antennal scale 0.4–0.6 times as long as carapace, 2.6–3.2 times as long as wide. Epistome ( Fig. 8 b) normally without anteromedian projection (bi-lobed).

First pereopods extending beyond antennal scale by carpus and onwards, fingers about 0.75 times as long as palm. Second pereopods ( Fig. 8 c, d) equal or slightly unequal in length, extending beyond antennal scale by almost whole length of carpus and onwards, sub-equal in length to total body length; merus slightly longer than carpus, with numerous spinules on entire surface; carpus as long as or slightly shorter than palm, covered by numerous spinules on entire surface; palm nearly smooth except for several short setae scattered on surface; fingers as long as or slightly shorter than palm, not gaping when closed, armed with less than 10 small teeth at most on basal twothirds. Propodus of third pereopod ( Fig. 8 e) 2.9–3.5 times as long as dactylus, with 5–8 well spaced spines on posterior margin.

Appendix masculina ( Fig. 8 f) 0.5–0.7 times as long as appendix interna, with numerous stiff setae on anterolateral margin as well as mesial surface. Uropodal exopod ( Fig. 8 g) as long as or slightly longer than endopod, movable spine on diaeresis noticeably shorter than lateral projection.

Remarks. Macrobrachium mieni resembles M. yui Holthuis, 1950 , in general appearance, but it could be distinguished from the latter species by having a movable spine on the diaeresis of the uropodal exopod ( Fig. 8 g) as opposed to no spine in M. yui in specimens larger than 15 mm in carapace length ( Fig. 17 d) (see also “Remarks” under the latter species). In fully grown males, the second pereopod of M. mieni ( Fig. 8 a) is comparatively smaller than that of M. yui ( Fig. 16 ).

In fresh specimens of M. mieni , a yellowish stripe running along the dorsal margin of the entire length of the abdominal somites was observed.

Distribution. This species has been reported with reasonable certainty from northern Vietnam, Thailand, and Laos ( Dang 1980; Cai et al. 2004; present study).

Figures

FIGURE 8. Macrobracium mieni, male (CL 19.9 mm) from Kasi District, Vientiane Province (a, e), male (CL 20.0 mm) (c, d, f, g) collected from Kasi District, Vientiane Province, and male (CL 17.0 mm) (b) collected from Xuang River, Luang Prabang Province, Laos: a, entire body; b, epistome; c, left second pereopod, lateral view; d, basal part of chela of same leg, lateral view; e, propodus and dactylus of left third pereopod, lateral view; f, appendix masculina, mesial view; g, uropodal diaeresis, lateral view.

FIGURE 16. Macrobrachium yui, male (CL 31.5 mm) collected from Xuang River, Luang Prabang Province, Laos: entire body, lateral. Scale bar = 10 mm.

FIGURE 17. Macrobrachium yui, male (CL 31.3 mm) (a), male (CL 29.0 mm) (b), male (CL 30.0 mm) (c, d), and early juvenile (CL 1.9 mm) (e – g) collected from Xuang River, Luang Prabang Province, Laos: a, basal part of fingers of right second pereopod, mesial view; b, propodus and dactylus of left third pereopod, lateral view; c, appendix masculina, mesial view; d, right uropodal diaeresis, lateral view; e, juvenile anterior part of carapace and cephalic appendages, lateral view; f, juvenile distal end of telson, dorsal view; g, juvenile left uropodal diaeresis, lateral view.