Morphometric analyses of Mithraculus forceps (Brachyura: Mithracidae): linear and geometric approaches in a no-take marine reserve population

ABSTRACTMithraculus forceps is a common species on islands in Brazil, and investigations of their sexual and population structures provide insights into their life cycle. Our aim was to analyze relative growth, estimate morphological sexual maturity, and investigate sexual dimorphism in a population inhabiting the Alcatrazes Archipelago. Sampling was conducted using artificial refuge and active capture methods. Five body structures were analyzed for relative growth and morphological sexual maturity estimation: carapace and abdomen width, propodus length and height, and gonopod length in males. Sexual dimorphism was observed in carapace and propodus shape. Morphological sexual maturity was estimated at 10.12 mm carapace width for males and 10.66 mm carapace width for females. Some variations in morphometric aspects were observed in the analyzed population when compared to other populations of M. forceps inhabiting unprotected areas. Crabs from Alcatrazes may reach larger sizes due to their protected habitat. This underscores the crucial role of a marine conservation unit in preserving significant ecological processes and highlights the importance of management plans for other locations and environments facing anthropogenic pressures.KEYWORDS: AllometryAlcatrazes ArchipelagoDecapodarelative growthreproduction AcknowledgmentsWe would like to express our gratitude to the entire LABCAM and LABIAQUA teams for their assistance during the animal collection. CSN thanks for its doctoral and postdoctoral scholarships (FAPESP 2019/00661-3 and 2023/01445-8). We also thank ICMBio (Instituto Chico Mendes de Biodiversidade) and IBAMA (Instituto Brasileiro de Meio Ambiente e dos Recursos Naturais Renováveis) for granting permission to sample and transport in situ wild fauna for scientific purposes, in accordance with the State and Federal regulatory framework SISBIO (Sistema de Autorização e Informações em Biodiversidade) n° 69588-4/2020.Data availability statementThe data that support the findings of this study are available from the corresponding author, CSN, upon reasonable request.Disclosure statementNo potential conflict of interest was reported by the author(s).Additional informationFundingThis work was funded by the São Paulo Research Foundation (FAPESP) [Fundação de Amparo à Pesquisa do Estado de São Paulo] [grant numbers 2018/13685-5 for RCC, 2018/00739-0 and 2022/08605-8 for RCS]; National Council for Scientific and Technological Development (CNPq) [Conselho Nacional de Desenvolvimento Científico e Tecnológico] [grant numbers 306672/2018-9 and 304368/2022-9 for RCC]; Coordination for the Improvement of Higher Education Personnel (CAPES) [Coordenação de Aperfeiçoamento de Pessoal de Nível Superior] [grant number 88887.604989/2021-00 for GVMRG].