EFFECT OF PHOTOPERIOD ON ENDOCRINE PROFILES IN EUROPEAN EELS ANGUILLA ANGUILLA DURING ARTIFICIALLY INDUCED OVARIAN DEVELOPMENT

Artificial reproduction in eels is very challenging due to their peculiar life cycle. No information is yet available on the influence of photoperiod on the sexual development of wild silver eels in captivity. Previous studies have demonstrated the photoperiod to influence sexual maturation of eels showing that dark conditions lead to a better reproductive performance in terms of a greater gonadal maturation and a higher egg production and spawning record. This study aimed to investigate the physiological mechanisms leading to different outcomes in light or dark conditions on the gonadal steroidogenesis in wild female European silver eels during pituitary extract treatment. The variation of the body weight index and gonadosomatic index suggested a positive effect in dark conditions. Sexual steroids (androgens and estrogens) showed a significant difference in plasmatic concentration in the animals kept in the dark suggesting a better wellness reproductive situation in this particular housing condition.