Macrobrachium mieni Dang, 1975

Cai, Y., Naiyanetr, P. & Ng, P. K. L., 2004, The freshwater prawns of the genus Macrobrachium Bate, 1868, of Thailand (Crustacea: Decapoda: Palaemonidae), Journal of Natural History 38 (5), pp. 581-649 : 613-615

Macrobrachium mieni Dang, 1975

(figure 11)

Macrobrachium mieni Dang, 1975: 68 , figure 2 [type locality: Hoa Binh, northern Vietnam]; Dang , 1980: 389, figure 223.

? Macrobrachium asperulum Lumubol, 1980: 503 , figure.

Material examined

Central Thailand. Three WW, cl 15–17.5 mm ( ZRC 2000.2718 ), Phetchabun, central Thailand, 8 January 1981 .

North-east Thailand. Four WW, cl 10.1–14.2 mm, 4 XX, cl 8.5–11.5 mm (two ovigerous, eggs 1.5× 1.2 mm) ( ZRC 2000.2656 ), coll. P. Naiyanetr, 29 March 1976 .

Diagnosis

Rostrum straight, reaching to or slightly beyond distal end of antennular peduncle. Rostral formula: 2–5+5–7/1–3, third tooth situated just above postorbital margin, teeth placed more widely posteriorly than anteriorly. Antennular peduncle 0.55 times as long as carapace. Scaphocerite 3.0 times as long as wide. First pereiopod reaching with entire chela beyond end of scaphocerite, fingers as long as palm; chela 0.5 times as long as propodus. Second pereiopods of males slightly longer than body (excluding rostrum), equal in length, similar in form, reaching with one-third of carpus beyond distal margin of scaphocerite; carpus shorter than merus, about twothirds length of palm. Palm cylindrical, broader than carpus; fingers slightly shorter than palm, with 8–10 small teeth at proximal half of cutting edges. Third pereiopod reaching with dactylus beyond distal margin of scaphocerite, propodus 10 times as long as broad, 3.4 times as long as dactylus; dactylus with very short claw, four times as long as broad. Uropodal diaeresis with a spine slightly shorter than outer angle. Ovigerous females with eggs 1.5× 1.2 mm in diameter.

Remarks

Macrobrachium mieni closely resembles M. yui , but can be distinguished by its longer rostrum which reaches to distal end of scaphocerite (versus not beyond end of antennular peduncle); the form of the second pereiopods (equal in length versus unequal); the longer antennular peduncle (0.55 times as long as carapace versus 0.4 times); the scaphocerite 3.0 times as long as wide (versus 2.6 times); the third pereiopod with a propodus 10 times as long as broad (versus eight times); and the dactylus has a short claw (versus long, slender claw). Macrobrachium mieni is also similar to M. thai sp. nov., but it can be separated by having fewer teeth on the cutting edges of the second pereiopod, relatively shorter propodus of the third pereiopod and a shorter movable spine on the uropodal diaeresis (see Remarks for M. thai ).

Macrobrachium yui is commonly found in fast-flowing waters in the mountains of southern China, northern Thailand and Vietnam, while M. mieni seems to replace M. yui in the Mekong basin, living in relatively slower-flowing water.

The present Thai material differs from the original description and figures in the number of postorbital rostral teeth, which is two or three (mode three), rather than four or five in the types. This may be due to variation. We can discern no other differences. As the types are almost certainly lost (H. T. Dang, personal communication) and we do not have any Vietnamese material of this species on hand, we prefer to use the name M. mieni for the Thai material for the time being .

Lumubol (1980: 503) reported M. asperulum (Von Marten) from Khon Kaen. M. asperulum , however, has so far been reported only from mainland China and Taiwan. On the basis of his figure which shows 12 dorsal rostal teeth (three of them postorbital) and the carpus of the second pereiopod being shorter than palm, Lumubol’s specimens are probably M. mieni instead.