1998 Volume 44 Issue 4 Pages 377-383
Developmental changes of horse testis were examined morphologically. Spermatogenesis initiated in the spring of 2-year-olds, and spermatogenic activity appeared to increase age dependently up to 9 years old. The characteristic feature of fetal testis is its large interstitial mass. The interstitial region revealed no proportionate change during the fetal period, but gradually decreased with age-dependency from birth to 9 years old. On the other hand, the area of seminiferous tubules showed no changes up to 1 year old. Most characteristic feature during development is the appearance/disappearance of pigmented cells. These cells first appeared in 3-day-old individuals and gradually increased in volume up to 1 year old (sampled in spring). The number of cells reached maximum at 2 months old, gradually decreased, and completely disappeared after 3 years old. The pigmented cells possessed large and small round bodies with various electron densities in the cytoplasm.
