Abstract:
Seasonal reproduction is a common characteristic of many small mammals which
inhabit seasonal environments in temperate regions, the sub-tropics as well as the
tropics. It is important for an animal to reproduce during the most favourable time of
the year to ensure the survival of the young and maximize reproductive success. In
southern Africa, female spiny mice (Acomys spinosissimus) breed during the warm
and wet spring and summer months, whereas the reproductive pattern of males is
unknown although an opportunistic breeding pattern has been implicated. We
investigated testes mass and volume, seminiferous tubule diameter,
spermatogenesis and plasma testosterone concentrations in a South African
population of male spiny mice on a 2-monthly basis over one year. Testes mass and
volume started to increase in July/August and was high from September until
December. Seminiferous tubule diameter and spermatogenesis increased during the
same months. Plasma testosterone concentration was elevated from July/August to
November/December. Development of the reproductive characteristics of male spiny
mice was correlated with high rainfall and high ambient temperatures, but
reproductive development had already started during the dry season and the coldest
months. This shows that reproductive development in males may not be dependent
on climatic conditions, and other factors, such as photoperiod, may trigger the onset
of reproduction. The data, however, suggest that A. spinosissimus is a true seasonal
breeder with reproduction confined to the spring and summer months in southern
Africa.
