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Sexual dimorphism and morphometric maturity in males of Ucides occidentalis (Ortmann, 1897) (Brachyura, Ocypodidae) in the Gulf of Guayaquil, Ecuador

Abstract:

Sexual dimorphism was established in Ucides occidentalis (Ortmann, 1897) in the Gulf of Guayaquil, Ecuador on the basis of the size and dimensions of the chelar propodus (CP); whether the CP can be used as an indicator of sexual maturity in males was also evaluated. Morphological differences were also established in individuals by inspecting CP variability. Morphotypes were identified as homochelous (HmC, having a similar CP) or heterochelous (HtC, having one CP larger than the other), and varieties were established by the differences in the CP dimensions of each morphotype. The Kruskal-Wallis test was used to determine whether significant size differences based on the length and height of the major chelar propodus for each morphotype exist between the sexes. The largest sizes were determined in males (p<0.01), and there was a significant difference (p<0.01) in length and height when the males of each morphotype were compared. This study established that U. occidentalis exhibits allometric CP growth, because the small sizes in successive molts do not allow the observation of evident differences between the developmental stages (juveniles and adults). Therefore, sexual maturity cannot be estimated in males using the CP, and it is necessary to use other structures (e.g., the pleopods) or methodologies (e.g., physiological) to estimate sexual maturity.