DETERMINATION OF TESTIS TEMPERATURE RHYTHMS AND EFFECTS OF CONSTANT LIGHT ON TESTICULAR FUNCTION IN THE DOMESTIC-FOWL (GALLUS-DOMESTICUS)

There is a wide range of opinions regarding the operating temperature of the testis in the domestic fowl. We used physiological monitoring t echniques to investigate testis and body temperature over daily period s and under various light regimes to elucidate body temperature gradie nts in the fowl. We confirm that the operating temperature of the adul t fowl's testes is equivalent to core body temperature (40-41 degrees C). Long-term continuous temperature monitoring showed that there was no difference between the temperature of the testis, liver, and perito neum during a 24-h period either in a normal light:dark cycle or under constant light conditions. However, there was a slight decrease in al l temperatures at subjective night in each case, a decrease that does not appear to be sufficient to influence spermatogenesis. Birds mainta ined under constant light throughout two cycles of the seminiferous ep ithelium (28 days) still exhibited normal testis function and structur e, even when ''nightly'' testis temperature decrease was the lowest. T hug by undergoing spermatogenesis at an elevated temperature, the dome stic fowl system is unique among the homeothermic animal systems studi ed to date.