Sperm competition and ultrastructural characteristics of spermatozoa: are there synapomorphic characteristics of the reproductive system of Inachidae or in the common ancestor of Inachidae and Inachoididae?

• Grant number: 25/13156-6
• Support Opportunities: Scholarships in Brazil - Scientific Initiation
• Start date: September 01, 2025
• End date: August 31, 2026
• Field of knowledge: Biological Sciences - Morphology - Histology
• Principal Investigator: Fernando Jose Zara
• Grantee: Ayra Maria Tebaldi Capelane
• Host Institution: Faculdade de Ciências Agrárias e Veterinárias (FCAV). Universidade Estadual Paulista (UNESP). Campus de Jaboticabal. Jaboticabal , SP, Brazil
• Associated research grant: 18/13685-5 - Integrative analysis of the Brazilian fauna of decapod crustaceans: taxonomy, phylogenetic systematics, spermiotaxonomy, morphology of post-embryonic development, ecology and conservation, AP.BTA.TEM

Abstract

The morphology of the male reproductive system (MRS) of Brachyurans is quite diverse. The MRS consists of a pair of testicles (lobular or tubular) connected to the vas deferens (VD). The sperm produced in the testicles are released into the seminiferous tubules and transported by the VD, which are divided into three regions, each with a specific function for the production of seminal fluid and the assembly and storage of spermatophores: anterior (AVD), middle (MVD) and posterior (PVD). In Brachyura, it is very common to observe differences in the regions of the VD where seminal fluid production and storage of spermatophores occur in certain groups or families. For females, mating will not guarantee the use of only the sperm of a specific male, which may lead to a cryptic choice of the female, that is, sperm competition. Recently, certain species belonging to the superfamily Majoidea, such as the spider crab Stenorhynchus seticornis Inachoididae, had their SRM in the female reproductive system properly described and analyzed. However, certain families such as Inachidae remain poorly studied. In this sense, obtaining knowledge about the morphology of the SRM and sperm competition in individuals of the family Inachidae is necessary to understand the reproductive structure, the process of sexual maturation and the reproductive strategies that allow species of the genera Podochela Stimpson, 1860 and Ericerodes Rathbun, 1897 to present sperm competition. Thus, the objective will be to perform the morphological, anatomical, histological, histochemical and ultrastructure analysis of the spermatozoa and thus characterize, in detail, the SRM of Ericerodes gracilipes and Podochela brasiliensis, to verify whether or not sperm competition exists in Inachidae as well as to seek morphological and sperm synapomorphies for the family and also compare them with the phylogenetically sister family, Inachoididae.