Allometry, Sexual Maturity and Intraspecific Morphological Variations in <i>Aegla jacutinga</i> Marçal and Teixeira, 2020 (Crustacea, Anomura)

ABSTRACT Crustaceans of the genus Aegla represent a taxonomically challenging group, with numerous morphologically similar species. This study investigates the growth patterns, morphological maturity and sexual dimorphism in Aegla jacutinga , through allometric analyses of 661 specimens. The results revealed three ontogenetic stages in males (young, adult Morphotype I and Morphotype II) and two in females (young and adult), with significant differences in relative growth. Morphometric maturity was reached at similar sizes between sexes (males: 8.34 mm; females: 8.43 mm), but with marked sexual dimorphism: adult males showed marked positive allometry in the chelipeds, while females exhibited greater abdominal growth. The species demonstrated significant heterochely ( p &lt; 0.05) and laterality with predominance of the left chela in both sexes (73% of males; 71% of females). Analyses of intraspecific morphological variation identified modifications in diagnostic characters throughout development, with only 30%–40% of the characteristics remaining stable between demographic groups. These findings highlight the need to integrate ontogenetic series into taxonomic descriptions and reinforce the importance of combining morphological, molecular approaches and geographical distribution for species delimitation in this genus with cryptic species. The study provides unprecedented bases for the identification of life stages and dimorphism in A. jacutinga , in addition to evidencing limitations of traditional morphological characters.