Zur Kontrolle von Fortpflanzungszyklen bei Vögeln

摘要: Under the natural light conditions of Kiel maximal AChE-activity pars distalis male bramblings (group N) is correlated with highest testes weight, widest diameter seminiferous tubules, darkest bill color, and seminal vesicles (Fig. 1, Fig. 2). AChE-cells first appear at end Jan. almost completely disappear beginning photorefractory period. At this time large amounts lipids can be observed in tubules interstitial tissue. These gradually during fall winter. Feb. fat droplets are selectively deposited differentiating Leydig-cells. constant longday (20L4D, group L, October) tubule as they did N. The characteristics refractory period (no AChE-cells, minimal testicular vesicles, yellow color) maintained over 13 months until experiment 3, 4). Only 3 out 51 birds showed a gonadal cycle. shortday (8L 16D, K, no essential differences to groups N L bee seen 5). By January AChE-positive cells develop distalis, weight increase slowly, Leydig-cells differentiate incorporate lipids. From July steady state 6). about numerous May N, but smaller more irregularly shaped. 4 times heavier than winter, reach only 1% No testosterone secretion indicated by sexhormone dependent structures. Photosensitive males rapidly prematurely stimulated longdays undergo alterations spring. Castrated photosensitive react spectacular hyperplasia hypertrophy AChE-cells. This reaction evidence that these have gonadotropic function. Castration treatment (beginning do not lead hyperplastic hypertrophic AchE-cells May. indicates existence negative feedback between hypo-thalamo-pituitary system even when recognized Treatment causes which developed under disappear. Several observations (ultrastructural localization AChE, parallelism gonadotropin content AChE-activity, high together undeveloped gonads) indicate AChE involved hormone synthesis release controlled separately. While may occur long-days necessary for release. Testosterone inhibit GTH-synthesis In K circannual oscillations could detected. Therefore seasonal changes day length must considered cause annual reproduction rhythm bramblings. An hour glass model constructed uses circadian photosensitivity phases their threshold-shifts connect endogenously exogenously rhythms.