Protandric Simultaneous Hermaphroditism in Salmoneus Carvachoi Anker, 2007 (decapoda: Alpheidae): a New Sexual System in Alpheid Shrimps

In caridean shrimps, sexual systems vary from gonochorism to various forms of hermaphroditism. The shrimp Salmoneus carvachoi has been reported to exhibit both male (appendix masculina) and female (brooding embryos) anatomical characteristics simultaneously. Our aim was to examine the sexual system of S. carvachoi and to test the hypothesis of protandric simultaneous hermaphroditism (PSH) in this species. We analysed internal and external features using microscopy and histology techniques. Our analyses support the hypothesis of PSH in S. carvachoi and enabled the identification of male-phase and hermaphroditic individuals. All individuals exhibit a well-developed appendix masculina on the endopods of the second pleopods; however, small male-phase individuals possess only male gonopores, whereas larger hermaphroditic individuals possess both female and male gonopores. Hermaphrodites exhibit both male and female germinative cells in various stages of development, as well as an androgenic gland. Our study describes a novel sexual system for alpheids and provides a detailed description of anatomical traits in S. carvachoi. Studies that describe sexual systems in Alpheidae may shed light on the evolutionary history of gender expression in carideans and how environmental conditions favour sex allocation in decapods and other invertebrates.