Differentially expressed morphological characters depend on sex and ontogenetic stage in the crab Goniopsis cruentata (Crustacea: Grapsidae)

Abstract

The hypothesis of this study was that significant variations in the growth rates of Goniopsis cruentata are related to intersexual and age-related characteristics, particularly in areas identified as secondary sexual (pleon, carapace and chelipeds). From February 2019 to January 2020, a total of 713 individuals were captured, 378 males and 335 females, with a carapace width ranging from 0.42 to 6.59 cm. Males and females showed negative allometry (β0<1) for all linear morphometric relationships, with an ontogenetic difference (p=0.0001) for all comparisons. In geometric morphometry, the dorsal view showed a significant difference in sexual comparisons (p=0.0001), in which males were wider in the posterior region than females. Furthermore, there was a significant difference in the abdominal region between young and adult females (p=0.0001), with the young ones being triangular and the adults oval, a characteristic brachyuran behaviour. We observed morphological separation in cheliped shape in sexual comparison (F×M) and laterality (R×L) (p=0.0001), with no ontogenetic variations (A×J). Goniopsis cruentata showed a noteworthy ontogenetic and sexual dimorphism. In addition, the discovery of cheliped variation was recorded for arboreal species that do not show a high degree of heterochely. Understanding these ontogenetic variations is crucial for effective conservation strategies because it allows specific life stages and their corresponding needs to be identified.