Sexual and size dimorphism in two deep-water hermit crabs (Decapoda: Parapaguridae) from the Western Atlantic Ocean

Author(s)

Adriane Candiotto ^[1] ; Caio S. Nogueira ^[2] ; Laura Schejter ^[3] ; Alexandre R. da Silva ^[4]

Affiliation

^[1] Universidade Estadual do Norte do Paraná. Centro de Ciências Humanas e da Educação - Brasil

^[2] Universidade Estadual Paulista. Faculdade de Ciências. Departamento de Ciências Biológicas - Brasil

^[3] Instituto Nacional de Investigación y Desarrollo Pesquero. Instituto de Investigaciones Marinas y Costeras. Consejo Nacional de Investigaciones Científicas y Técnicas - Argentina

^[4] Universidade Estadual Paulista. Instituto de Biociências. Departamento de Ciências Biológicas e Ambientais - Brasil

• Document type: Journal article
• Source: Nauplius; v. 31, 2023-12-04.

Abstract

Abstract The Parapaguridae comprises hermit crabs that inhabit deep-water environments. In these environments, shell availability can be limited, mostly consisting of small and fragile-shelled gastropods. Thus, different strategies have evolved to mitigate this limited shell supply. Sympagurus dimorphus (Studer, 1883) lives in association with a zoanthid cnidarian that creates a pseudo-shell that grows with the hermit crab. In contrast, Oncopagurus gracilis (Henderson, 1888) inhabits small, calcified gastropod shells. Therefore, we selected these two species as models to test sexual dimorphism and shape patterns of their chelipeds and cephalothoracic shield, due to their different shelter acquisition methods. We photographed the animals and digitized the images to employ comparative geometric morphometric techniques. We tested the differences in shape between the sexes within each species, and also tested sexual size dimorphism based on centroid size. For O. gracilis, we found shape differences for the chelipeds and cephalothoracic shield, however, we only observed sexual size dimorphism for the chelipeds. For S. dimorphus, an inverse pattern was found, in which females presented more robust chelipeds, and sexual size dimorphism was present in which males were larger. These differences can be reasonably explained by their shelter acquisition methods, in which O. gracilis depends on small shells that limit growth, while S. dimorphus grows with its cnidarian pseudo-shell. The robustness found in the shape patterns may also be related to their behaviors, e.g., in addition to competition for shells, they also fight during mating. However, we emphasize that future studies with other populations of these species are needed for comparative purposes. (AU)

• FAPESP's process: 19/00661-3 - A comparative interdisciplinary analysis between the prawns Macrobrachium amazonicum (Heller, 1862) and Macrobrachium pantanalense (dos Santos, Hayd & anger, 2013) support the interspecific differentiation?
• Grantee: Caio dos Santos Nogueira
• Support Opportunities: Scholarships in Brazil - Doctorate
• FAPESP's process: 23/01445-8 - Ultrastructure of spermatozoa of the caridean shrimps of Brazil: a modern taxonomic approach through morphological and phylogenetic integration
• Grantee: Caio dos Santos Nogueira
• Support Opportunities: Scholarships in Brazil - Post-Doctoral