The freshwater prawns of the genus Macrobrachium Bate, 1868, of Thailand (Crustacea: Decapoda: Palaemonidae) Author Cai, Y. Author Naiyanetr, P. Author Ng, P. K. L. text Journal of Natural History 2004 2004-10-10 38 5 581 649 http://www.tandfonline.com/doi/abs/10.1080/0022293021000033238 journal article 10.1080/0022293021000033238 1464-5262 5258702 Macrobrachium malayanum (Roux, 1934) Palaemon (Macrobrachium) pilimanus malayanus Roux, 1934: 32 [ type locality: Lasah , Plus valley , Perak , Malaysia ]. Macrobrachium geron Holthuis, 1950: 258 , figure 52 [ type locality: Banka island off Sumatra , Indonesia ]; Holthuis , 1980: 91; Johnson , 1961: 57. Macrobrachium malayanum : Chong and Khoo, 1987b: 903 ; Ng and Choy, 1990: 13; Ng, 1992: 793. Material examined South Thailand . Two ovigerous XX , cl 12.0– 14.3 mm , eggs with eye spot, 1.3× 0.9 mm , ( ZRC 2000.2645 ), Narathiwat Province , Nam Tok Sipo , downstream area, 6°16.06∞N, 101°38.65∞E, coll. H. H. Tan et al ., 24 October 1998 . Diagnosis Rostrum straight, reaching to or slightly beyond end of scaphocerite; rostral formula: 3–4+5–8/3–6 (mode 3–4). Male second pereiopods unequal in length, dissimilar in form; carpus shorter than merus and chela, fingers shorter than palm; two teeth present on cutting edges of fingers, with two to three smaller ones posterior of proximal large teeth; palm inflated; entire chela of large leg covered with dense carpet of soft, short velvety pubescence; small spinules present on surface of palm; movable spine on uropodal diaeresis longer than outer angle. Ovigerous females with eggs 1.3× 0.9 mm in diameter. Remarks Only two ovigerous Thai specimens were available. The specimens agree well with the description by Chong and Khoo (1987b). This is the northernmost record for M. malayanum , and also a new record for Thailand . Macrobrachium malayanum is distributed throughout the Malay Peninsula, Borneo and Sumatra (Roux, 1934; Holthuis, 1950; Chong and Khoo, 1987a; Ng and Choy, 1990; Ng, 1992), and its presence in southern Thailand is not unexpected.