- Email: [email protected]
Termination of breeding in weaver bird: role of photoperiod and gonadal hormones
1534
H17 SERUM TESTOSTERONE AND SEMEN PRODUCTION IN THE TURKEY DURING TWO BREEDING CYCLES. Helene C. Cecil* and Murray R. Bakst, USDA-ARS, Beltsville, MD 20705. Ejaculate volume, ejaculate sperm concentration, and serum testosterone were followed in 4 male breeder turkeys from 28 to 80 weeks of age. Semen volume for the first breeding cycle was at a maximum at 28 wks, remained high until 49 (Turkey l), 54 (Turkey 2), 59 (Turkey 3), and 61 weeks (Turkey 4), declined for the following 4 weeks, and then remained at zero for 20 (Turkey l), 12 (Turkey 2), 11 (Turkey 3), and 6 weeks (Turkey 4). The semen volumes for the second cycle reached a maximum at 72 (Turkey l), 73 (Turkey 2), 76 (Turkey 3), and 74 weeks (Turkey 4) and were comparable to volumes in the first cycle. Serum testosterone fluctuated from lows of <.2 ng/ml to highs >2.2 ng/ml throughout the experiment. There was no correlation of semen production with serum testosterone.
H18 TERMINATION OF BREEDING IN WEAVER BIRD: ROLE OF PHOTOPERIOD AND GONADAL HORMONES. Krishna Chakravorty* and Asha Chandola, Dept. of 2001 Banaras Hindu University, Varanasi *Garhwal University, Srinagar, 246174, U.P. INDIA. Gonadal regression in the photoperiodic tropical Weaver bird (Ploceus philippinus) occurs in late summer although the ambient day-length is still stimulatory. Earlier studies suggested that termination of reproduction in Weaver bird is not due to the development of a 'classical' photorefractoriness since gonadal reEression is abolished in daylengths longer than the longest day (at 25 N). Experiments were conducted to determine the role of photoperiod, in the seasonal decline in photosensitivity. Birds were transferred from natural daylength to nonstimulatory 6L:18D during two different times of the year viz. March and May. These 6L-stock birds were then transferred to stimulatory 13L: 11D two (May) and four (July) months later. Results indicate that birds that were maintained on 6L since March retained their photosensitivity whereas birds transferred to 6L in May, became refractory like the birds held on 13L:llD or NDL. Furthermore, birds maintained in 12L:12D eventually became refractory to this daylength although they were sensitive to daylengths longer than 12L. It seems that a) longdays program the refractoriness during late summer b) Birds became refractory to the daylengths including LL as in many photoperiodic passerine species. Gonadal hormones also seem to be involved in seasonal regression. Most likely photoperiod program the decline in photosensitivity by an interaction at the level of sex steroid sensitive centres in the hypothalamus.
H17 SERUM TESTOSTERONE AND SEMEN PRODUCTION IN THE TURKEY DURING TWO BREEDING CYCLES. Helene C. Cecil* and Murray R. Bakst, USDA-ARS, Beltsville, MD 20705. Ejaculate volume, ejaculate sperm concentration, and serum testosterone were followed in 4 male breeder turkeys from 28 to 80 weeks of age. Semen volume for the first breeding cycle was at a maximum at 28 wks, remained high until 49 (Turkey l), 54 (Turkey 2), 59 (Turkey 3), and 61 weeks (Turkey 4), declined for the following 4 weeks, and then remained at zero for 20 (Turkey l), 12 (Turkey 2), 11 (Turkey 3), and 6 weeks (Turkey 4). The semen volumes for the second cycle reached a maximum at 72 (Turkey l), 73 (Turkey 2), 76 (Turkey 3), and 74 weeks (Turkey 4) and were comparable to volumes in the first cycle. Serum testosterone fluctuated from lows of <.2 ng/ml to highs >2.2 ng/ml throughout the experiment. There was no correlation of semen production with serum testosterone.
H18 TERMINATION OF BREEDING IN WEAVER BIRD: ROLE OF PHOTOPERIOD AND GONADAL HORMONES. Krishna Chakravorty* and Asha Chandola, Dept. of 2001 Banaras Hindu University, Varanasi *Garhwal University, Srinagar, 246174, U.P. INDIA. Gonadal regression in the photoperiodic tropical Weaver bird (Ploceus philippinus) occurs in late summer although the ambient day-length is still stimulatory. Earlier studies suggested that termination of reproduction in Weaver bird is not due to the development of a 'classical' photorefractoriness since gonadal reEression is abolished in daylengths longer than the longest day (at 25 N). Experiments were conducted to determine the role of photoperiod, in the seasonal decline in photosensitivity. Birds were transferred from natural daylength to nonstimulatory 6L:18D during two different times of the year viz. March and May. These 6L-stock birds were then transferred to stimulatory 13L: 11D two (May) and four (July) months later. Results indicate that birds that were maintained on 6L since March retained their photosensitivity whereas birds transferred to 6L in May, became refractory like the birds held on 13L:llD or NDL. Furthermore, birds maintained in 12L:12D eventually became refractory to this daylength although they were sensitive to daylengths longer than 12L. It seems that a) longdays program the refractoriness during late summer b) Birds became refractory to the daylengths including LL as in many photoperiodic passerine species. Gonadal hormones also seem to be involved in seasonal regression. Most likely photoperiod program the decline in photosensitivity by an interaction at the level of sex steroid sensitive centres in the hypothalamus.