Changes in the tubular compartment of the testis of Gallus domesticus during development.

1. The aim of the present study was to analyze histological and stereological changes in the tubular compartment in Gallus domesticus testes, as well as the variations in the number and size of their cells, from the start of morphological differentiation of the gonads (8-d chick-embryo) until the adult reproductive stage (28 weeks old). 2. In embryonic chick testes, the total volume occupied by the interstitial tissue is greater than that occupied by the tubular compartment, but in the post-hatched chick the total volume of tubular compartment exceeds that of the interstitial tissue. 3. From day 1 until 28 weeks of age, the seminiferous tubules increased in total volume, diameter, and epithelial height, which was directly related to the increase in the number of Sertoli and germ cells and the size of Sertoli cells. 4. In the testes of one-day- and 6-week-old chicks, Sertoli cells were the most abundant cell type in the seminiferous tubules due to hyperplasia, but in 28-week-old birds the germ cells were the most abundant cell type. Hypertrophy rather than hyperplasia of Sertoli cells appears to be responsible for the increase in the total volume of seminiferous tubules. 5. There are marked age-dependent changes in the tubular compartment of chick testes that help to understand the histological and stereological events occurring during normal development.