Environmental control of the annual gonadal cycle of Fundulus heteroclitus L.: The pineal organ and eyes

Female fish collected in winter, spring, or summer were subjected to pinealectomy, eye enucleation, or both, and maintained on short days (LD 9:15) or long days (LD 15:9) at 20°C. Sexual maturity (gonadosomatic index and occurrence of vitellogenesis) was determined after 6 weeks of exposure to the experimental light regimes. The fish subjected to surgical manipulations were capable of perceiving stimulatory or inhibitory photoperiods regardless of whether they were blinded, pinealectomized, or both. Pinealectomized fish did not remain sexually active when exposed to short days. From these results we conclude that an extraretinal nonpineal photoreceptor can influence seasonal reproduction in Fundulus heteroclitus. We were unable to demonstrate an essential photoreceptive or endocrine role of the pineal organ in reproduction in this species.