EFFECTS OF PHOTOPERIOD HISTORY AND TEMPERATURE ON MALE COLLARED LEMMINGS, DICROSTONYX-GROENLANDICUS

Adult collared lemmings, Dicrostonyx groenlandicus (87 days of age), t ransferred from long (20L:4D) to short (8L:16D) photoperiod showed an increase in body mass, while those transferred from 8L:16D to 20L:4D s howed a decrease in body mass. Exposure to short photoperiod resulted in an increase in length of body relative to exposure to long photoper iod. Temperature affected body mass only under 20L:4D with animals hou sed at 5-degrees-C being significantly heavier than lemmings housed at 18-degrees-C. Temperature did not affect length of body. Changes in b ody mass in response to photoperiod exposure primarily were due to the deposition or loss of fat-free dry mass and water. The mass of the re productive organs (testes and seminal vesicles) was significantly incr eased in lemmings maintained at 5-degrees-C relative to animals house at 18-degrees-C. Mass of reproductive organs at 87 days of age was not affected by the photoperiod experienced during the subadult stage. Ho wever, at 167 days of age, lemmings originally housed under 8L:16D con ditions (from weaning to 87 days of age) had significantly heavier mas s of reproductive organs than did lemmings maintained on 20L: 4D from weaning to 87 days of age, regardless of secondary photoperiod exposur e (87-167 days of age). Photoperiod conditions seen early in life may have long-term effects on mass of reproductive tissues in this species .