Relative Growth, Sexual Dimorphism and Morphological Sexual Maturity of the Freshwater Prawn Macrobrachium rude (Heller, 1862) (Decapoda: Palaemonidae)

Macrobrachium rude is an autochthonous prawn species of Bangladesh, with a wide distribution across southern Asia and parts of eastern Africa. This study aims to analyse the relative growth of morphometric characters of this species in order to evaluate the sexual dimorphism and to estimate the onset of morphological sexual maturity. A total of 637 individuals were examined to measure carapace length (CL), body length (BL), rostrum length (RL), brood chamber width (BCW), cheliped propodus length (CPL) and second pleuron length (SPL). Females exhibited significantly larger body size and other body dimensions than males, indicating pronounced sexual dimorphism. Allometric shifts between demographic categories were best demonstrated by the relationships of RL versus CL, BCW versus CL and CPL versus CL, with transition points occurring at 8.1, 8.9 and 9.6 mm CL, respectively. The estimated size at the onset of morphological sexual maturity (CL 50 ) of female M. rude was 8.9 mm. Overall, these findings enhance understanding of the species’ morphological and reproductive aspects and provide valuable insights for assessing the conservation status of the studied population.