Sperm competition, plug formers or just semen mixers: what happens in the monophyletic clade of Heterotremata from the families Aethridae, Calappidae, Cancridae, Leucosiidae, Menippidae and Parthenopidae?

• Grant number: 24/13610-6
• Support Opportunities: Scholarships in Brazil - Scientific Initiation
• Start date: October 01, 2024
• End date: September 30, 2025
• Field of knowledge: Biological Sciences - Zoology - Morphology of Recent Groups
• Principal Investigator: Fernando Jose Zara
• Grantee: Maria Júlia Geraldo Dias
• 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

Sperm competition, characterized by the formation of packages and its absence due to the formation of sperm plugs, occurs in some species of Brachyura, specifically in Heterotremata crabs. Spider crabs form sperm packages, while swimming crabs form sperm plugs. Plug-forming Portunids are paraphyletic to the group containing Aethridae, Calappidae, Cancridae, Leucosiidae, Menippidae, and Parthenopidae, whose male reproductive systems (MRS) have been poorly studied. Thus, this project will verify, through the reconstruction of the ancestral state of MRS characters, whether the presence or absence of sperm competition is more frequent in Heterotremata. For this, the MRS of eight key species from the six families of this monophyletic clade will be studied through anatomical, histological, and histochemical analyses. Based on the available literature for other Heterotremata clades and the information obtained here, the ancestral character state will be inferred using the latest molecular phylogenies. Thus, it will be verified whether the most commonly recorded morphological pattern is correlated with sperm competition by package formation, random gamete fertilization, or absence of competition. For this, a data matrix will be created, containing the following characters: i) presence of accessory glands and absence of spermatophores in the posterior region of the vas deferens (PVD), i.e., package-forming, ii) absence of glands and presence of spermatophores in the PVD, i.e., random fertilization, and iii) very voluminous MRS, with "outpocket" type glands and absence of spermatophores in the PVD, i.e., absence of competition by sperm plug formation.