Some Aspects of the Biology of 5 Freshwater Crabs in Lower Southern Part of Thailand

Some biological features of 5 freshwater crabs in southern of Thailand, Pattani Yala and Narathiwat provinces were studies by collecting freshwater crab samples by crab trap and hand with net, turning stone and wood in the natural resources: mountain, waterfall, stream, canal, deep pool, paddy field, swamp and river during August 2015 - April 2017. There were 348 items of freshwater crabs found in this study. Parathelphusa maculata De Man, 1879 (21 items) and Heterothelphusa fatum Ng, 1997 (189 items) were only observed to distribute in Narathiwat province.  In addition, Heterothelphusa insolita Ng & Lim, 1986 (64 items) was distributed in Pattani and Narathiwat. Moreover, Sayamia sexpunctata (Lanchester, 1960) (60 items) and Stoliczia panhai Ng & Naiyanetr, 1986) (14 items) were observed to distribute in all three provinces. Sex ratio (M:F) in Stoliczia panhai was difference between the sexes in high level, while that in Heterothelphusa insolita was 1:1. Sayamia sexpunctata was the biggest freshwater crab with the weight average at 18.67±7.12 g, the carapace width average at 31.45±3.64 mm and the carapace length average at 37.47±4.69 mm. In addition, the difference between the carapace width and carapace length of this crab was 6.02±1.28 mm and the carapace width was 0.84±0.02 time of the carapace length by average. H. insolita was the smallest crab with the weight average at 2.24±1.69 g, the carapace width average at 16.93±4.79 mm and the carapace length average at 14.75±4.22 mm. Moreover, the difference between the carapace width and carapace length of this crab was 2.18±1.12 mm and the carapace width was 1.15±0.10 time of the carapace length by average. Relationships carapace width and body weight of P. maculata represented                  W = 2.6608CW 0.3175 , W = 2.6263CW 0.3328 of H. insolita , W = 2.6815CW 0.3076 of H. fatum , W = 2.5392CW 0.3153 of                         S. sexpunctata and S. panhai represented W = 2.5884CW 0.3415 . The biological data of 5 freshwater crabs from this study will be the basis of environmental quality in the future which is affected by the agriculturist’s behavior in                 the area. Keywords : freshwater crab, southern Thailand, crustacean, decapods