Social and photoperiod effects on reproduction in five species of Peromyscus

Abstract

At temperate latitudes, mammals and birds use changes in day length to time their reproductive activities to coincide with seasonal fluctuations in the environment. Close to the equator, however, conditions permissive of breeding do not track changes in day length as well, so other cues may be more important than photoperiod. In a variety of vertebrates, social interactions regulate breeding condition. We hypothesized that individuals of different species of Peromyscus mice found closer to the equator would respond more strongly to housing with an opposite sex conspecific than they would to photoperiod. To test this hypothesis, we compared the effects of long and short day lengths versus 8 days of pair housing with a female on reproductive tissue weights and testosterone (T) concentrations in five species of Peromyscus (P. aztecus, P. eremicus, P. maniculatus, P. melanophrys, and P. polionotus). After 13 weeks of short days (8L:16D), P. maniculatus, P. melanophrys, and P. polionotus significantly reduced relative testes mass compared to long day (16L: 8D) housed animals. Social housing, however, had no effect on tissue weights in any species. However, male P. polionotus paired with females for 8 days increased T concentrations compared to single-housed males, whereas paired P. maniculatus reduced T. These data suggest that mechanisms of photoperiodic and social regulation of reproductive function are mediated by different physiological mechanisms among closely-related species and that both phylogeny and environmental factors contribute to patterns of reproductive plasticity.

Rapid effects of estrogens on behavior: Environmental modulation and molecular mechanisms

“…Some species and strains may be unaffected. For example, photoperiod had no effect on aggressive behavior or estrogen receptor expression in outbred CD-1 mice [63]. On the other hand, some common laboratory strains could be strongly affected.…”

Reproductive patterns in the Baluchistan gerbil, Gerbillus nanus (Rodentia: Muridae), from western Saudi Arabia: The role of rainfall and temperature

“…A seasonal change in photoperiod is the one of the most classic of environmental cues used for timing reproduction at higher latitudes (El-Bakry et al, 1998, Medger et al, 2011,Trainor et al, 2006. However, photoperiod does not play such an important cue in desert and semi-desert environments where the correlation between photoperiod and food availability is often not so clear cut (Henry andDubost, 2012, Breed andLeigh, 2011).Deserts experience extreme ranges in daily and seasonal ambient temperatures, with little or no rainfall, intense solar radiation and have a minimal primary productivity (Schmidt-Nielsen, 1964).…”

Rapid effects of estradiol on male aggression depend on photoperiod in reproductively non-responsive mice

“…In Syrian hamsters (Mesocricetus auratus) (Garrett and Campbell, 1980;Jasnow et al, 2002;Caldwell and Albers, 2004), Siberian hamsters (Phodopus sungorus) (Jasnow et al, 2000;Demas et al, 2004;Wen et al, 2004), beach mice (Peromyscus polionotus) (Trainor et al, 2007a), and deer mice (Peromyscus maniculatus) (Trainor et al, 2007b), males are more aggressive in a resident-intruder test when tested in short days (8L: 16D) as opposed to long days (16L:8D). This effect has been considered paradoxical, because in each of these species housing in short days causes regression of testes and a corresponding decrease in testosterone (Jasnow et al, 2000(Jasnow et al, , 2002Trainor et al, 2006c). In Siberian hamsters there is evidence that the effect of photoperiod on aggression is independent of gonadal responses .…”