Comparative analysis of morphology, growth performance and gonadal development between the hybrid crab ( <i>Scylla serrata</i> ♀ ×  <i>S. paramamosian</i> ♂) and <i>S. serrata</i>

Abstract Interspecific hybridization, through integrating genetic resources across distinct species, serves as a pivotal strategy for improving yield, stress resistance, and quality in aquacultural species. To evaluate the performance of hybrid crab ( Scylla serrata ♀ × S. paramamosain ♂), this study systematically compared morphological traits, growth performance, and gonadal development between the hybrid crab ( S. serrata ♀ × S. paramamosain ♂) and its maternal parent S. serrata . The results show that the hybrids exhibit morphological traits similar to S. serrata , including high, blunt frontal lobe spines, contrasting with the moderately tall, sharply pointed spines of S. paramamosain . However, morphological differences also exist between hybrid crab and S. serrata , primarily reflected in the internal carpal spine (ICS). At the 2 months (M2) and 3 months (M3) stages, the ICS degeneration rates in hybrids (36.36% and 35.56%, respectively) exceeded those in S. serrata (13.85% and 17.65%). As the cultivation progressed, the number of significant differences in the 27 morphological ratios between the hybrid crab and S. serrata gradually decreased, from 15 in the M2 stage to 8 in the M4 stage. The hybrid crab exhibited superior weight gain rate (142.98%) from M2 to M3 stage compared with S. serrata (112.42%). However, the growth advantage of the hybrids decreased during the M3–M4 period, and their advantage at the M4 stage was mainly reflected in the total edible yield. The hybrid crab can produce germ cells; however, its overall gonadal development remains limited. Further studies are needed to determine whether the hybrids are capable of successful mating and whether their ovaries can develop normally after mating. This study provided new insights into the hybrid mud crab that would be beneficial for the aquaculture industry.