Meeting Abstract
At cold temperatures, insects enter a reversible state of paralysis known as chill coma. Chill coma onset (CCO) represents a key physiological and ecological threshold where insects become unable to move and therefore cannot feed, reproduce or evade predation. Maintenance of muscle function at cold temperatures may therefore allow populations to invade and persist in colder climates. Bumble bees are broadly distributed in cold climates at high latitudes and altitudes. Recent work has shown that high altitude Bombus vosnesenskii have lower CCOs than their low altitude counterparts. We used electrophysiological recordings to directly measure the effect of temperature on the activity of flight muscle fibers in worker bumble bees (B. vosnesenskii) reared in common garden conditions from queens collected at high (1619m) and low (70m) altitudes. Intracellular recordings using sharp microelectrodes revealed tonic discharge of muscle action potentials (MAPs) at room temperatures and during the onset of cold temperatures. Near CCO, bursting became more irregular, and there was a complete cessation of MAPs at CCO. These data may lead to a better understanding of the key mechanistic differences in muscle physiology underlying variation in cold tolerance among bumble bee populations.
