Respiration PhyJir.!ugy, 85 (199!) IS: 1991 Elsevier Science Publishers BY 003+568791,503.50 RESP 01.809 Arrhythmic breathing in torpid pipistrelle bats, Pipistrellus pipistrellus G. C. Hays, P. L Webb and J. R. Speakman •.L ..... Department of Zoology, University of Aberdeen. Aberdeen AB9 2 TN. U.K. (Accepted 22 April 1991) Abstr:act. The arrhythmic breathing pattern of torpid female pipistrelle bats tPipistrellus pipistrellusi was monitored using Doppler radar. A total of 98 h of radar measurements were made on II individuals over 17 experiments.during which time 974 apneic intervals were monitored, over ambient temperatures (Ta, 'C) ranging from - 1 to 14 'c. and body masses rangmg from 4.6 to 7.'\ g. As Ta declined. a greater proportion of all breaths occurred in discrete breathing bouts. Apneic intervals lengthened at lower Ta, but were not related to body mass. Mean apneic length, averaged over 1 'C intervals, was best described by the least squares fit regression equation: In (apneic length in s) = 7.07-0.8111n (Ta + I), (r 2 = 0.96, P< 0.01). Ventilation frequency (breaths- min - '). averaged over a breathing bout and the subsequent apnea, increased as Ta increased, and was not related to body mass. Mean ventilation frequency If), averaged over I 'C intervals, was best described by the least squares fit regression equation: f= 0.812 + 0.499 Ta (r: = P < 0.011. Using previously published values for 0: consumption rv0,) in torpid pipistrelles, and tidal volume 0: extraction efficiency at .. 'C in torpid bats of the same mean size (6.2 g). we calculated tbt ,il4 'C ventilation would, on avenge, supply only of Y This suggests that in torpid O o ' pir-istrelles :he glottis :lOa,. remain open dunng apnea, allowing a significant diffusive influx of 0: into the lungs. Diffusive transport, torpid bat; \lammai. bat Pipistrellus pipistrellus; Pattern of breathing, torpid bat; Torpidity. arrhythmic breathing in bat Torpor in mammals is often accompanied by intermittent breathing bouts separated by periods of apnea, this pattern being termed 'Cheyne-Stokes respiration' (e.g. Malan. I '.,)82) or 'arrhythmic breathing' (e.g. Milsorn. 1988). Arrhythmic breathing has been recorded in a range of mammals such as golden mantled ground squirrels (Cirel/us hedgehogs (Erinaceus dealbatas and E. europaeus], dormice (GUs glis and quercinus], and microchiropteran bats (see lyman, 1982. and Malan, 1982, for reviews). Oxygen uptake may. however. not be confined solely to breathing bouts. since, if the glottis remains open during apnea. 0: will diffuse down the respiratory tract. In torpid marmots (Marmora marmora) the glottis remains open during apnea (Malan, Correspondence 10: G.c. Hays, Dept. Zoology, university of Aberdeen, Aberdeen AB9 2TN, U.K.