Sexual plasticity of Hippolyte inermis Leach (Crustacea, Decapoda): Gene expression of vitellogenin and insulin-like androgenic gland hormone.

Hippolyte inermis is a protandric hermaphroditic shrimp widespread in most Mediterranean seagrass meadows. It has a complex life cycle, because an unknown compound present in benthic diatoms (Cocconeis spp.) induces an early sex reversal in its post-larvae upon ingestion. This change occurs due to the disruption of the androgenic gland (AG) germ cells. To elucidate the molecular mechanisms behind this unique example of sexual plasticity, we isolated sex-specific genes from the transcriptomes of shrimp collected at various stages of their life cycle. Using Real-Time qPCR, we measured, in wild adults, the expression levels of the Insulin-like Androgenic Gland hormone (Hi-IAG), Vitellogenin-1 (Hi-VG1), two uncharacterized male and female genes (Hi-UCM and Hi-UCF), and two uncharacterized male and female eyestalk genes (Hi-UCMe and Hi-UCFe). Further, the expression of these genes was evaluated in shrimp cultured in the laboratory, after the ingestion of bioactive diatoms, to identify potential molecular markers. Only Hi-VG1 and Hi-UCM showed a consistent relationship with the phenotype of adults, according to their sex. Subsequently, we investigated the physiological and developmental expression patterns of Hi-VG1 and Hi-UCM, along with several Vitellogenin variants, across a range of developmental stages, to reveal the mechanisms of sex regulation. While the results revealed complex response patterns, they lay the groundwork for understanding the link between key gene expression and sexual determination and maturation in decapod crustaceans.