Age-related changes in testicular histology and androgen levels of the immature spiny-tailed lizard, Uromastix hardwicki

Abstract

Age-related changes in testicular histology and androgen levels have been studied during the first 16 weeks of life of the immature spiny-tailed lizard ( Uromastix hardwicki). In the young lizards which emerge from eggs in late June to early July, until approximately 3 months of age, the seminiferous tubules contain only two types of cells: gonocytes and pre-Sertoli cells. Subsequently, in the month of October (age: 12–16 weeks) there is a marked proliferation of germ cells accompanied by an increase in the diameter of the seminiferous tubules and weight of the testis. The interstitial cells which are markedly differentiated even in the earliest phase of posthatching development are considerably hypertrophied in early August (age: 4–5 weeks). Plasma titers of testoslerone, as measured by radioimmunoassay, showed an initial rise in August followed by a second major peak at the end of October. Testicular testosterone concentrations expressed per milligram of tissue were lowest in July and maximal in August. A significant increase in testosterone concentration in both the plasma and the testicular tissue was also observed following administration of FSH and LH to immature lizards. It is suggested that, in the immature spiny-tailed lizard, androgenesis resulting in detectable levels of testosterone in peripheral plasma and testicular tissue precedes gamatogenic activity. Furthermore, the steroidogenic tissue in this species has been shown to be responsive to exogenous gonadotropins even in the earliest phase of posthatching development.