Search Results
You are looking at 1 - 2 of 2 items for
- Author: M. S. Boulakoud x
- Refine by access: All content x
Search for other papers by M. S. Boulakoud in
Google Scholar
PubMed
Search for other papers by A. R. Goldsmith in
Google Scholar
PubMed
Photorefractory male starlings (Sturnus vulgaris) were transferred from a photoperiodic schedule of 18 h light:6 h dark to 8 h light:16 h dark for 2, 4, 6 or 10 weeks, and then photostimulated by exposure to 18 h light:6 h dark. Testicular dimensions were measured at regular intervals by laparotomy. There was no change in testicular volume in birds photostimulated after 2 weeks under a photoperiod of 8 h light:16 h dark, but a cycle of testicular growth followed by regression occurred in the other groups. Testicular volume was increased significantly by 20 days under 18 h light:6 h dark in all three groups; regression began after 45, 65 and 75 days in birds pre-exposed to 8 h light:16 h dark for 4, 6 and 10 weeks, respectively. These results are discussed in relation to other evidence for the progressive development of photosensitivity.
Search for other papers by M. S. Boulakoud in
Google Scholar
PubMed
Search for other papers by A. R. Goldsmith in
Google Scholar
PubMed
Photorefractory castrated male starlings were transferred from a photoperiodic schedule of 18 h light:6 h dark to 1 h light:23 h dark, 5 h light:19 h dark, 8 h light:16 h dark or 11 h light:13 h dark. Plasma concentrations of LH were measured in blood samples taken at regular intervals, to give an indication of the reacquisition of photosensitivity under these schedules. Concentration of plasma LH increased after 35, 38, 35 and 63 days, respectively; there was a steady increase in LH in all groups, but the increase under 11 h light:13 h dark was much slower than in the other groups. In contrast, birds held under 18 h light:6 h dark showed no increase in LH. Thus, starlings became photosensitive at a similar rate under fixed photoperiods of 8 h light:16 h dark or shorter, but took longer to acquire photosensitivity under 11 h light:13 h dark.
