Oxygen supply of the heart and electrocardiogram potentials with reversed polarity in sleeping and resting honey bees
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A novel active ventilatory mechanism of the dorsal air sacs in the abdomen of forager honey bees is described. These air sacs supply the heart with oxygen. During sleep and rest, the air sacs undergo frequent volume changes. The dilation of the air sacs is caused by the activity of hitherto unidentified muscles. Their subsequent collapse is probably due to elastic components in the walls of the sacs. The volume changes also occur when, during discontinuous resting ventilation, ventilatory movements of the abdomen are absent. They are always combined with an increase in heart rate. The heart thus receives oxygen when it needs it and can therefore function effectively during sleep, to supply the brain with nutrients necessary for energy-demanding sleep-specific functions. During sleep, rest, and induction of chill coma, periodic heartbeat reversals were also discovered. The biological significance of these heartbeat reversals remains to be elucidated.
Keywordshoney bee sleep heart function oxygen supply electrocardiogram
The constructive criticism provided by the referees is gratefully acknowledged. One of us (W.K.) thanks the Max-Planck-Institut für Verhaltensphysiologie (now Max-Planck-Institut für Ornithologie) for its hospitality during several stays as guest researcher. He is also grateful to Peter Dancker (Heidelberg) for numerous valuable suggestions to the manuscript. The experiments on animals reported here have been registered with the appropriate authority.
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