author(s)
Md. Latiful Islam, Mollah NS Mamun Siddiky and Khairun Yahya

abstract
The present study was conducted to elucidate the age at sexual maturity and transformation of secondary organs of male mud crab. Five crabs were dissected at 15 days interval; testes were collected and preserved in Davidson’s fixatives for 24 hours, then transferred to 50% ethanol. Samples were chronologically dehydrated in 70% to 100% ethanol at 10% intervals; embedded, sectioned at 6 µm, stained with Haematoxylene-Eosin and observed under stereo microscope. Present observation revealed three distinct sexual maturation stages of male mud crab (Scylla paramamosain) with first sexual maturation in four months of age. Internal carapace width (ICW) showed discrete relation with external morphological features at ICW of 10.20 cm at pubertal molting. Asynchronies maturation was noticed with first fully sexually matured crab (20%) in 5^th month of age and the median sexual maturity (MA₅₀) occurs in 6.5 month of age. Findings of the present study suggested to being ready for captive mating of mud crab within 4 months of age after crab instars.