Seasonal environmental change and sex change in a cnidarian

Here, we investigated the effect of seasonal temperature fluctuations on the expression of sex-related genes and sex change in the gonochoristic freshwater cnidarian, brown hydra (Hydra oligactis). Individuals of this species reproduce clonally throughout much of the year but switch to sexual reproduction when the temperature decreases in autumn. After sexual reproduction, some individuals can revert to clonality again. We found that clonal offspring derived from these individuals had a relatively high rate of female-to-male transition. The sexual stage was most differentiated in terms of gene expression, with a large number of genes involved in cellular differentiation and gametogenesis differentially expressed between males and females undergoing gamete production, while asexual individuals belonging to the male and female strains were transcriptomically nearly identical following sexual reproduction.