Abstract:
Many mammals use the change in day-length to time physiological and
behavioural activities on a seasonal basis. Particularly mammals from temperate regions use
photoperiod to regulate reproductive functions; however, information on the role of
photoperiod in small mammals from the tropics and sub-tropics is scarce. We studied the
response of the reproductive system of male eastern rock sengis (Elephantulus myurus) from
southern Africa to photoperiods of differing length. Elephantulus myurus breeds seasonally
during the spring and summer months of the southern hemisphere despite its subtropical
distribution. It is one of only three sengi species known to breed seasonally. Fourteen male
E. myurus were subjected to either long-day (LD; 16L:8D) or short-day (SD; 8L:16D)
photoperiods and the photoperiodic effects on the testes, testosterone concentration and
body mass were examined. Testicular volume and mass, seminiferous tubule diameter as
well as body mass were not significantly different between LD and SD conditions. However,
plasma testosterone concentration was significantly lower in males on LD compared to SD
photoperiods. Male E. myurus may not use photoperiod as a cue to control seasonal
reproductive changes. Other environmental factors such as temperature, rainfall, food
abundance or social factors are possibly influencing seasonal reproduction in this species.
