Exploring sexual dimorphism and growth patterns in Aegla aff. castro (Crustacea: Aeglidae): insights into reproductive and competitive strategies

Abstract

This study, conducted on an isolated population of Aegla aff. castro in Avaré (São Paulo, Brazil), provides new insights into body growth patterns between males and females throughout life stages, as well as a detailed analysis on the growth relationship between the dactyl and the propodus. Morphological measurements included carapace length (CL), abdomen width (AW), propodus length (PL), and dactyl length (DL), performed for morphometric, heterochely and laterality analyses. No significant differences in carapace length (CL) were observed between males and females. (Wilcoxon, p > 0.05). Morphometric maturity was estimated at 12.9 mm CL for males and 12.7 mm CL for females. Females exhibited pronounced allometric growth in abdominal width (AW), while males developed larger propodus (PL). Both sexes exhibited heterochely and predominantly left laterality, with the latter more pronounced in males, suggesting functional adaptations in the lever system of the chela. The dactyl to propodus relationship displayed isometric growth, for all chelae except for female´s left chelae. These findings corroborate previous studies in which distinct energy allocation strategies between sexes and life stages: females prioritize reproductive traits, while males invest in competitive features. These growth patterns reflect the selective pressures that shape energy allocation and resource use, which are linked to the reproductive and competitive roles of each sex.