Control of reproductive and energetic status by environmental cues in a desert rodent, Shaw's jird

The photoperiod is the controller of reproductive cycles in temperate clima tes for most mammalian species. Several nonphotoperiodic cues appear to con trol reproductive status at lower latitudes. We tested the roles of the pho toperiod or water availability on the reproductive status of the desert-dwe lling Shaw's jird (Meriones shawi) trapped from a moderately temperate clim ate (similar to 30 degrees N in Egypt). Males and females were transported to the laboratory and, in Experiment 1, were housed in either the longest ( LDs) or shortest (SDs) photoperiod that occurs naturally at this latitude ( 14 h light, 10 h dark, and 10 h light, 14 h dark, respectively). In Experim ent 2, LD-housed male jirds were subjected to a water availability schedule that inhibits reproductive status in a closely related species (Meriones u nguiculatus). Specifically, one group had no free water, but had lettuce av ailable once a week for 24 h (control jirds received free water for 10-60 m in/day). Neither photoperiod nor free-water deprivation affected reproducti ve status of male or female jirds. That is, neither testes mass nor spermat ogenetic activity (males), nor uterine mass nor folliculo-genesis (females) were affected by either condition. In addition, photoperiod did not affect body or white adipose tissue (WAT) masses, although SDs decreased carcass lipid in males. Free-water deprivation decreased body and WAT pad masses, a nd all carcass components. Collectively, these results suggest that changes in day length or water availability alone do not affect reproductive statu s in Shaw's jird. (C) 1999 Elsevier Science Inc.