Is reproduction of male eastern rock sengis (Elephantulus myurus) from southern Africa affected by photoperiod?

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.

Analysis of gonadotrophin‐releasing hormone‐1 and kisspeptin neuronal systems in the nonphotoregulated seasonally breeding eastern rock elephant‐shrew (Elephantulus myurus)

“…Under natural conditions, eastern rock elephant‐shrews show seasonal development of the gonads and, as previously reported (Medger et al, ), an associated rise in circulating testosterone and progesterone in, respectively, males and females. Reproduction in this species does not appear to be a photoregulated phenomenon: neither the testes nor seminiferous tubules differ in size between short‐ and long‐day housed eastern rock elephant‐shrews (Medger et al, ). Nevertheless, the large increases in the density of kisspeptin‐ir processes in the RP3V and arcuate nucleus in the breeding season and the positive correlations between the density of those processes and gonadal mass seem in keeping with changes previously reported for reproductively photoresponsive species, namely increases in: kisspeptin mRNA expressing cell bodies in the AVPV and arcuate nucleus in male and female Syrian hamsters (Ansel et al, ; Revel et al, ), kisspeptin mRNA in tissue containing the AVPV and arcuate nucleus in male Libyan jirds (seasonally reproducing desert rodents; Boufermes et al, ), kisspeptin‐ir process density, kisspeptin‐ir cell bodies and kisspeptin mRNA expression in the arcuate nucleus in wild‐captured male jerboas (results for the AVPV were not reported; Janati et al, ; Talbi et al, ), kisspeptin‐ir cell bodies in the AVPV (but not in the arcuate nucleus) in male and female Siberian hamsters (Greives et al, ; Mason et al, ) and kisspeptin‐ir cell bodies in the arcuate nucleus in ewes, female Abedeh goats (an Iranian seasonally breeding ecotype), and male and female red deer (Barrell et al, ; Jafarzadeh Shirazi et al, ; Smith et al, ).…”

“…Recently, we have reported (Medger, Chimimba, & Bennett, ) that males of this species do not appear to use photoperiod to regulate reproductive onset. Thus, males exposed for 3 to 4 months to either a short‐ or long‐day photoperiod show no difference in the size of the testes or the diameter of the seminiferous tubules (Medger et al, ). These findings suggest that environmental factors other than photoperiod regulate their reproduction.…”

“…Prominent seasonal changes affect their habitat; food availability is especially low during the winter (Andrews & O'Brien, 2000). Recently, we have reported (Medger, Chimimba, & Bennett, 2016) that males of this species do not appear to use photoperiod to regulate reproductive onset. Thus, males exposed for 3 to 4 months to either a short-or long-day photoperiod show no difference in the size of the testes or the diameter of the seminiferous tubules (Medger et al, 2016).…”