Meeting Abstract

P3.87  Monday, Jan. 6 15:30  Respiratory and Cutaneous Water Loss in Egyptian Fruit-bats (Rousettus aegyptiacus) WALCEK, A*; PINSHOW, B; KORINE , C; Mitrani Department of Desert Ecology, The Jacob Blaustein Institutes for Desert Research, Ben-Gurion University of the Negev; Mitrani Department of Desert Ecology, Ben-Gurion University of the Negev; Mitrani Department of Desert Ecology, Ben-Gurion University of the Negev walcame@bu.edu

The sum of respiratory and cutaneous evaporative water losses (REWL, CEWL) make up total evaporative water loss (TEWL) in endothermic animals. Compared to non-volant mammals of similar body mass, bats have as much as six times greater surface-to-volume ratio, ostensibly resulting in relatively large CEWL, especially when they fly. In Israel, most microchiropteran bats (7-35 g) save water and energy by entering torpor daily or by hibernating. In torpor REWL drops with decreasing resting metabolic rate (RMR); consequently, the CEWL:REWL ratio is also reduced. Although sympatric in Israel with many microchiropteran species, the Egyptian fruit bats, Rousettus aegyptiacus a130 -150 g Pteropodid, do not become torpid, but must nevertheless survive the winter shortage of nutritious food and the hot, dry summers. In summer, fruit bats are unlikely to be energy or water stressed since their fruit diet contains 70-90% water; in winter, their food has lower water and nutrient content and they must drink regularly. This being complicated by lower ambient temperatures (T_as) that induce high metabolic rates; in turn, increasing REWL. We tested the prediction that at low T_as (in winter), the ratio of CEWL to REWL in R. aegyptiacus decreases, due to subcutaneous vasoconstriction. Using an open-flow respirometry system we are measuring the changes in CEWL and REWL over a wide range of T_as (10, 20, 30, 35, and 40 °C) for both summer and winter acclimatized animals. To do this, we constructed a latex bat face-mask to separate CEWL and REWL. Our initial results support our prediction that CEWL in resting R. aegyptiacus is reduced in the cold.