Evolution of the male reproductive system in Penaeoidea (Dendrobranchiata): Integrating morphological and molecular data

Penaeoidea shrimps exhibit substantial diversity in reproductive morphology, but the evolutionary history of the male reproductive system (MRS) and its congruence with molecular phylogenies remain poorly understood. This study characterized MRS morphology across Penaeoidea and used these morphological data, together with a molecular phylogeny of the species analyzed herein, to reconstruct the ancestral states of MRS traits and investigate their evolutionary patterns and taxonomic implications. The MRS of 11 species was examined using histological methods, and phylogenetic analysis was conducted. In Benthesicymidae and Aristeidae, as well as in Solenoceridae and Penaeini, the median vas deferens (MVD) bears accessory and spermatic ducts, representing a synapomorphic trait and the putative plesiomorphic condition for Penaeoidea. In contrast, Trachypenaeini, Parapenaeini, and Sicyoniidae share a single duct in the MVD. Within Penaeini, the accessory gland is simple in Farfantepenaeus species but highly complex, with multiple glandular chambers, in Litopenaeus schmitti , supporting the separation of these lineages and arguing against treating Penaeus as a single genus. Benthesicymidae, Aristeidae, Solenoceridae, and Sicyoniidae lack accessory glands, representing a homoplastic condition, whereas Trachypenaeini and Parapenaeini exhibit a simplified accessory gland. The plesiomorphic spermatophore condition appears to be morphologically complex. Phylogenetic analyses recovered Penaeidae as paraphyletic, and substantial differences in MRS morphology among tribes support the hypothesis that these lineages may warrant elevation to family rank.