Control of Reproductive and Energetic Status by Environmental Cues in a Desert Rodent, Shaw’s Jird

Abstract

EL-BAKRY, H. A., W. M. ZAHRAN AND T. J. BARTNESS. Control of reproductive and energetic status by environmental cues in a desert rodent, Shaw’s jird. PHYSIOL BEHAV 66(4) 657–666, 1999.—The photoperiod is the controller of reproductive cycles in temperate climates for most mammalian species. Several nonphotoperiodic cues appear to control reproductive status at lower latitudes. We tested the roles of the photoperiod or water availability on the reproductive status of the desert-dwelling Shaw’s jird ( Meriones shawi) trapped from a moderately temperate climate (∼30°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 Experiment 2, LD-housed male jirds were subjected to a water availability schedule that inhibits reproductive status in a closely related species ( Meriones unguiculatus). Specifically, one group had no free water, but had lettuce available once a week for 24 h (control jirds received free water for 10–60 min/day). Neither photoperiod nor free-water deprivation affected reproductive status of male or female jirds. That is, neither testes mass nor spermatogenetic activity (males), nor uterine mass nor folliculogenesis (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, and all carcass components. Collectively, these results suggest that changes in day length or water availability alone do not affect reproductive status in Shaw’s jird.