Abstract
Photosensitive white-throated sparrows were transferred from a nonstimulatory LD 8:16 light cycle to either a stimulatory LD 13:11 or LD 20:4 light cycle on Day O. While some birds remained on these stimulatory photoperiods throughout the study, other birds were transferred from LD 13:11 to LD 20:4 on Day 50, or from LD 20:4 to LD 13:11 on Day 30 after the testes had reached a width of about 4.0 mm. The testes of birds continuously exposed to LD 13:11 grew more slowly, reached a larger maximum size, and spontaneously regressed later than the testes of birds continuously maintained on LD 20:4. Spontaneous testicular regression occurred at the same time (between Days 90 and 120) in sparrows that were transferred from LD 13:11 to LD 20:4 on Day 50 as in sparrows that were maintained continuously on LD 13:11. Following testicular growth in sparrows that were exposed initially to LD 20:4, the transfer to a presumably photostimulatory LD 13:11 cycle induced rapid testicular regression suggesting that LD 13:11 was no longer being interpreted as a long day. These results suggest that in nature, the timing of spontaneous testicular regression which occurs after a prolonged exposure to photostimulatory long days may be (1) programmed by the LD cycle the bird is exposed to during gonadal growth, and/or (2) due to a decrease in day length after the summer solstice even though the length of the day is still longer than that which previously initiated testicular growth.
Original language | English (US) |
---|---|
Pages (from-to) | 124-129 |
Number of pages | 6 |
Journal | General and Comparative Endocrinology |
Volume | 46 |
Issue number | 1 |
DOIs | |
State | Published - Jan 1982 |
Funding
This research was supported by a Richter Research Grant from Northwestern University (M.O.H.), U.S. Public Health Service Research Grants (HD-09885, HD-12622), and U.S. Public Health Service Research Career Development Award (F. W.T.) HD-00249 from the National Institute of Child Health and Human Development. We thank Brian Follett and Trevor Nicholls for their valuable comments on an earlier draft of this manuscript.
ASJC Scopus subject areas
- Animal Science and Zoology
- Endocrinology