Seasonal changes in reproductive development in male spiny mice (Acomys spinosissimus) from South Africa

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.

Assessment of Reproductive Function in Southern African Spiny Mice (Acomys spinosissimus) using Faeces as Hormone Matrix

“…The males exposed to a long photoperiod, simulating the austral summer, had elevated FAM levels compared to the males that were exposed to the short photoperiod, simulating the austral winter, which confirmed the findings of Medger et al (2012a) regarding an existing seasonal pattern in plasma testosterone concentrations for Acomys spinosissimus males. Based on their findings, Medger et al (2010) concluded that spiny mice are seasonal breeders with the breeding season coinciding with the summer months when the rainfall is maximal in the Limpopo province of South Africa.…”

Seasonal reproduction in the Arabian spiny mouse, Acomys dimidiatus (Rodentia: Muridae) from Saudi Arabia: The role of rainfall and temperature

“…This could partially be attributed to the recruitment of a new generation into the population (Medger et al, 2010(Medger et al, , 2012a. However, laboratory studies have shown that food limitation as well as increases in dietary salinity may result in reductions in body mass of arid adapted A. russatus, but not mesic adapted A. cahirinus, particularly in females (Wube, Fares & Haim, 2008a;Bukovetzky et al, 2012).…”

“…Most species of Acomys inhabit arid habitats in the Middle East and northern, eastern and southern Africa (Wilson and Reeder, 2005). A great diversity of reproductive patterns has been reported for members of the genus Acomys ranging from seasonal to aseasonal breeding (Happold, 1966;Neal, 1984;Delany and Farook, 1989;Fleming and Nicolson, 2002;Medger et al, 2010Medger et al, , 2012a. Several studies have been undertaken on species of Acomys in countries that border with a peak in reproduction during the months with the highest rainfall (Al-Khalili and Delany, 1986;Kivanç et al, 2013).…”

The pattern of ovulation in the southern African spiny mouse (Acomys spinosissimus)

“…Both systems favour spontaneous ovulation as access to females is relaxed and male competition is low (Larivière and Ferguson, 2003). Although most Acomys species show some tendency towards seasonal reproduction such as A. spinosissimus (Medger et al, 2010;2012b), A. cahirinus (Young, 1976) and A. minous (Dieterlen, 1978), other species breed throughout the year (A. subspinosus: Fleming and Nicolson, 2002;A. percivali and A. wilsoni: Neal, 1983).…”

“…A number of recent studies have concentrated on the reproductive physiology of A. spinosissimus. Medger et al (2010;2012b) established that A. spinosissimus breeds seasonally during the warm and wet spring and summer months in South Africa. In addition, the males are reproductively photoresponsive and show increased reproductive development under long-day photoperiods (Medger et al, 2012a).…”