On a new species of Macrobrachium Spence Bate (Decapoda: Palaemonidae) from Ayeyarwady River, Myanmnar

Abstract

Macrobrachium myanmarum sp. nov. was found from near Min Kun (local name Min Gon) at Mandalay, Ayeyarwady (Irrawaddy) River (22.043N & 96.043E), Myanmar. It is a small-sized prawn showing close relation with Arachnochium kulsiense (Jayachandran et al. 2007) and A. mirabile (Kemp 1917). This species can at once be identified from both the species by the characters: medium-sized and highly-elevated and arched rostrum, extending as far as distal segment of antennular peduncle or behind, upper margin with 11–15 teeth of which three (rarely 4) teeth post-orbital; ventral margin without teeth (rarely one); second chelate legs unequal, right leg larger (sometimes left); major leg in which carpus with proximal part narrow and distal end broadened, subequal to merus, palm and fingers; propodus slightly more than the combined length of merus and carpus; fingers very slender, almost equal to palm, fixed finger a bit shorter than movable finger, cutting edges with 2–6 weak denticles at proximal cutting edges, distal denticle situated at about 1/3rd distance from base; ischium, merus, carpus, propodus, palm and dactylus in the ratio 9.62: 19.25: 24.06: 47.06: 23.53: 23.53, respectively (related to the total length of pereopod); minor leg with minute tubercles in larger specimens; ischium, merus, carpus, propodus, palm and fingers in the ratio 13.1: 23.68: 22.37: 40.8: 15.8: 25.0, respectively (related to total length of pereopod); palm slightly swollen and shorter than fingers, fingers slender and curved with a wide gap when closed. Maximum size recorded for the species is 56mm male and 44mm female.