COMPARATIVE DIMENSIONS OF TESTES, EPIDIDYMIDES AND SPERMATOZOA OF AUSTRALIAN DINGOES (CANIS-FAMILIARIS-DINGO) AND DOMESTIC DOGS (CANIS-FAMILIARIS-FAMILIARIS) - SOME EFFECTS OF DOMESTICATION

The dimensions of testes, epididymides and spermatozoa of Australian d ingoes (Canis familiaris dingo) and a sample of domestic dogs (Canis f amiliaris familiaris), chosen to lie within the range of dingo body we ights, were compared. There were no significant differences for body w eight or testis weight but total epididymal weight, the caput + corpus weights and sperm numbers in the cauda epididymidis were significantl y larger in dogs. Dimensions of the spermatozoa were similar for dogs and dingoes except for a small but significantly larger head length in dingoes. Seminiferous tubule diameters were significantly larger in d ingoes and epididymal tubule diameters were similar in dogs and dingoe s except for significantly wider tubules in the cauda of dogs. The est imated length of tubules in the total epididymis and in the cauda was significantly greater in dogs than in dingoes. Greater size of the epi didymis and especially of the cauda epididymidis probably reflect sele ction for larger sperm stores in free-ranging domestic dogs where ther e is a greater chance of intermale sperm competition. Two possible hyb rids (determined by skull morphometry) were intermediate between dogs and dingoes for some of these dimensions.