Temperature manipulation stimulates gonadal maturation and sex steroid production in Senegalese soleSolea senegalensisKaup kept under two different light regimes

Abstract

This study evaluates the influence of temperature manipulation on circulating levels of sex steroids and gonadal maturation in F1 generation Senegalese sole Solea senegalensis breeders kept under either continuous light (LL) or natural photoperiod (NP). Under LL, progressive water temperature reduction during early winter [treatment MT (modified temperature)] significantly elevated [compared with exposure to LL and constant temperature (CT)] plasma steroid levels in females (January–February) and males (January) and proportion of females initiating maturation (January), suggesting a modulatory role of decreasing temperature in the early phases of sole gonadal recrudescence. Under NP, treatment MT did not stimulate female gonadal maturation despite the significantly higher plasma testosterone levels (February) compared with exposure to NP and CT, which may indicate that females at early-intermediate phases of ovarian development, the predominant stages of maturation at early winter, were less responsive to the treatment. Conversely, treatment MT significantly enhanced male androgen production from January onwards, together with an increase in proportions of running individuals (March), indicating that males were also responsive to this treatment at mid-late phases of testicular development. Our data further support the strong influence of water temperature on the overall control of gonadal maturation in Senegalese sole.