Environmental control of the annual gonadal cycle ofFundulus heteroclitus L.: The pineal organ and eyes
✍ Scribed by Day, Jonathan R. ;Taylor, Malcolm H.
- Publisher
- John Wiley and Sons
- Year
- 1983
- Tongue
- English
- Weight
- 519 KB
- Volume
- 227
- Category
- Article
- ISSN
- 0022-104X
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✦ Synopsis
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 159) 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 a n essential photoreceptive or endocrine role of the pineal organ in reproduction in this species.
Vertebrates use various mechanisms to perceive and respond to the changes in daily photoperiod which synchronize seasonal reproduction. In mammals, day length is perceived via the lateral eyes, but the pineal appears to be necessary for gonadal regression in response to short-day stimuli (Reiter, '74). In birds, neither the lateral eyes nor the pineal organ is necessary for the animal to perceive changes in photoperiod (Benoit, '64; Menaker et al., '70). According to Benoit ('64) and Yokoyama et al. ('781, a light-sensitive area of the hypothalamus is the site of the photic input which controls the seasonal reproductive cycle in birds.
Reptilian reproduction may be influenced by photoperiod through several pathways. Some reptiles, like Sceloporus occidentalis, possess a n extracranial "third eye" or parietal eye that histologically bears an obvious resemblance to mammalian retinal receptor cells (Eakin and Westfall, '60). Since the parietal eye, like the pineal organ, is embryologically derived from the diencephalon, it is not surprising that in the anole, the pineal organ itself has a photoreceptive function that can influence reproduction (Underwood, '81). Electrophysiological and morphological evidence (Meissl and Ueck, '80; Oksche and Hartwig, '75; Hartwig and Korf, '78) suggests that photoreception by the pineal organ