Meeting Abstract

P3.77  Thursday, Jan. 6  Metabolic Cost of Pregnancy and Lactation in the Nine-Banded Armadillo LENGYEL, M.S.*; SPENCER, M.A.; RIGGS, G.; BECKET, A.; MOORE, F.B.G.; BAGATTO, B.; The University of Akron msl26@zips.uakron.edu

The nine-banded armadillo (Dasypus novemcinctus) has a unique reproductive physiology. Armadillos are the only known mammals to exhibit obligate polyembryony, and D. novemcinctus can have periods of embryonic diapause lasting several years. In addition, D. novemcinctus has an unusually low body temperature (~34.5^oC) and basal metabolic rate (BMR) (~50% lower per g) when compared to other mammals. There is a trend in other mammals for the non-mass-specific BMR to increase significantly during pregnancy and lactation. This study investigates the metabolic costs of pregnancy and lactation in armadillos by calculating BMR in pregnant, lactating, and non-pregnant individuals using flow-through respirometry. BMR was calculated from both O₂ consumption and CO₂ excretion. Comparison of BMR between pregnant and non-pregnant animals indicates that a metabolic cost of pregnancy exists. Differences in BMR persisted five weeks after neonates were removed, which included the lactation period, after which pregnant and non-pregnant animals had similar BMRs. Pregnant armadillos exhibited a decrease in BMR as early as two weeks after neonate removal, with an average decrease of 86% by day 35. Not surprisingly, pregnant armadillos were an average of 23% heavier than non-pregnant armadillos. Pregnant armadillos had lower mass-specific BMRs before and up to parturition, possibly indicating that weight gained during pregnancy had low metabolic activity. Other mammals commonly gain adipose tissue prior to pregnancy to buffer the daily costs of fetal growth, so it is likely a similar mechanism is used by D. novemcinctus. These data along with additional energy budget data further elucidate the effects of energetically costly conditions on the ecology and evolution of this species.