Growth, sexual maturity and size dimorphism in the Amazonian freshwater shrimp Macrobrachium chryseus (Decapoda: Palaemonidae)

Morphometric studies have been widely used to understand growth patterns, sexual dimorphism, and morphological sexual maturity in decapod crustaceans. Macrobrachium chryseus is a small-sized species associated with Amazonian blackwater environments, for which detailed biological information is still scarce. In this study, we analyzed the onset of morphological sexual maturity, sexual size dimorphism, and relative growth in M. chryseus. The onset of morphological sexual maturity was estimated at 4.4 mm of carapace length for males and 5.2 mm for females. Sexual size dimorphism was observed, with females exhibiting a larger body size than males across all analyzed structures. The analyses indicated negative allometric growth patterns for both juveniles and adults of both sexes, considering both body structures and cheliped articles. The results of this study expand the knowledge of the biology of M. chryseus and provide a basis for comparisons with congeneric species, contributing to ecological and evolutionary interpretations of freshwater shrimps in Amazonian ecosystems.