A QUANTITATIVE EXAMINATION OF OVARIAN GROWTH IN THE WHITE-CROWNED SPARROW

¹ Laboratories of Zoophysiology, Department of Zoology Washington State University, Pullman, Washington

1. Ovarian development in Zonotrichia leucophrys gambelii subjected to long daily photoperiods is a logarithmic function of time until a weight of approximately 50 mg. is attained. Although there is a slight non-photoperiodic ovarian growth especially in first-year birds, it is clear that long daily photoperiods are essential for normal ovarian growth and constitute the basic environmental information used in the control of the ovarian cycle.

2. The photoperiodic control mechanism in the female differs from that of the male in that the logarithmic growth phase brings the ovary to only approximately one-tenth of its maximum weight, whereas the logarithmic growth phase of the testes in photostimulated males brings them to about one half of maximum (See TABLE II in Source Pdf) weight. In addition, the female differs from the male in that complete gonadal development can be induced only rarely in captivity with either artificial or natural photoperiodic stimulation, whereas sufficiently long daily photoperiods invariably result in the complete development of the testes of photosensitive males in captivity.

3. Until an ovarian weight of approximately 50 mg. is attained the gonadotropic performance of the anterior pituitary of the female in captivity appears to be similar to that of photostimulated males.