Histological changes in trout testis produced by injections of salmon pituitary gonadotropin

Abstract

The histological changes produced in testes of immature trout (Salmo gairdneri) by biweekly injections of salmon pituitary gonadotropin have been studied. The hormone injections quickly induced spermatogenesis and mature sperm were present 12 weeks later. Sperm precursor cells formed in orderly progression and large numbers of cells at the same stage of development were present at each week during the cycle. At no time, however, after the first 2 weeks was a pure population of a single germ cell type present throughout the testis. Sertoli cells were identified for the first time in trout testis. The results revealed no significant differences in morphology of germ cells in the accelerated system from that previously described during normal maturation of trout testis. Therefore, hormonally accelerated spermatogenesis in trout appears to be an ideal system for biochemical analysis of the factors regulating and contributing to sperm maturation.