Abstract
Hermaphrodite systems offer unique opportunities to study sexual differentiation, due to their high degree of sexual plasticity and to the fact that, unlike gonochoristic systems, the process is not confined to an early developmental stage. In protandric shrimp species, such as Hippolyte inermis and Pandalus platyceros, male differentiation is followed by transformation to femaleness during adulthood. The mechanisms controlling sexual differentiation have not been fully elucidated in crustaceans, but a key role has been attributed to the insulin-like hormone (IAG) produced by the androgenic gland (AG), a crustacean masculine endocrine organ. To uncover further transcriptomic toolkit elements affecting the sexual differentiation of H. inermis, we constructed eye and whole body RNA libraries of four representative stages during its protandric life cycle (immature, male, young female and mature female). The body libraries contained transcripts related to the reproductive system, among others, while the eye libraries contained transcripts related to the X-organ-sinus gland, a central endocrine complex that regulates crustacean reproduction. Binary pattern analysis, performed to mine for genes expressed differentially between the different life stages, yielded 19,605 and 6,175 transcripts with a specific expression pattern in the eye and body, respectively. Prominent sexually biased transcriptomic patterns were recorded for the IAG and vitellogenin genes, representing, respectively, a key factor within the masculine IAG-switch, and a precursor of the yolk protein, typical of feminine reproductive states. These patterns enabled the discovery of novel putative protein-coding transcripts exhibiting sexually biased expression in the H. inermis body and eye transcriptomes of males and females. Homologs to the above novel genes have been found in other decapod crustaceans, and a comparative study, using previously constructed transcriptomic libraries of another protandric shrimp, P. platyceros, showed similar sexually biased results, supporting the notion that such genes, mined from the H. inermis transcriptome, may be universal factors related to reproduction and sexual differentiation and their control in other crustaceans. This study thus demonstrates the potential of transcriptomic studies in protandric species to uncover unexplored layers of the complex crustacean sex-differentiation puzzle.
Highlights
Occurring sexual shifts during hermaphrodite life cycles offer unique opportunities to study sexual plasticity and sexual differentiation
Sexual differentiation processes are confined to early developmental stages – from embryogenesis to early post-larvae – while in hermaphrodite species they occur during adult stages (Levy et al, 2018; Benvenuto and Weeks, 2020; Levy and Sagi, 2020)
In the present study, thousands of genes were recorded as differentially expressed and sexually biased during the life cycle of the protandric shrimp H. inermis, and homologs to representative genes were found in P. platyceros and other decapod crustaceans
Summary
Occurring sexual shifts during hermaphrodite life cycles offer unique opportunities to study sexual plasticity and sexual differentiation. Important examples of sexual plasticity may be found among the crustaceans (Pandian, 2016), an ancient highly diverse group of animals in which a variety of reproductive strategies are represented, including gonochorism (separate sexes) (Juchault, 1999), intersexuality (combination of male and female features within a gonochoristic species) (Goldschmidt, 1938; Reinboth, 1975; Sagi et al, 1996; Abdel-Moneim et al, 2015; Levy et al, 2020c), asexual reproduction (e.g., parthenogenesis) (Scholtz et al, 2003; Martin et al, 2007), and different types of hermaphroditism (Levy et al, 2018; Benvenuto and Weeks, 2020) The last of these strategies constitutes a means of reproduction in which a particular individual bears both ovarian and testicular tissues [ovotestis (Hoffman, 1972; Stentiford, 2012)] and produces gametes of both sexes (Benvenuto and Weeks, 2020). Of relevance to this study, hermaphroditism may be exploited as a valuable model system for studying sexual plasticity, since the sex-differentiation process does not occur as a single event limited to the early developmental stages of the organism
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
