Biology of Reproduction, Vol 6, 179-192, Copyright © 1972 by Society for the Study of Reproduction

Observations on the Ultrastructure and Differentiation of Leydig Cells in the Testis of the Japanese Quail (Coturnix coturnix japonica)

¹ Department of Biological Sciences, Northern Illinois University, DeKalb, Illinois 60115

Testicular growth and development in Japanese quail was controlled by artificial regulation of photoperiod. It was found that in the undeveloped testes of birds subjected to a short photoperiod (6 hr of light per day) the interstitial region contained only fibroblast-like cells. When birds were subjected to 20 hr of light per day, fibroblast-like elements in the more central regions of the interstitial zone differentiated into Leydig cells similar to those of mammals in ultrastructure. Initial changes, particularly an increase in size and complexity of the Golgi apparatus, a rounding of the nucleus, and an increase in cytoplasmic volume, could be first detected 3 days after initiation of the long-photoperiod regime. Later, increased quantities of membrane were observed in the cytoplasm, portions of which were associated with ribosomes while others were agranular. The mitochondria increase considerably in size during the differentiative stages, becoming somewhat more spherical in shape, while the cristae increase in number and appear to change from a lamellar to a cylindrical configuration. Apparently mature Leydig cells were present after 10 days of subjection to long photoperiods. These contain a spherical nucleus, numerous mitochondria, large quantities of tubular smooth membrane, little granular endoplasmic reticulum, and variable numbers of lysosomes and lipid droplets. The Golgi complex does not appear to be extensive. It is suggested that the Leydig cells may secrete androgens.