Meeting Abstract
Chill coma recovery time (CCRT) is an ecologically-relevant metric of cold tolerance that is correlated with geographic distributions of diverse insects. When exposed to low temperatures insects enter chill coma, a reversible state in which they are alive but unresponsive. The ability to quickly recover neuromuscular function after chill coma likely affects fitness, particularly in cold climates—insects in chill coma are incapable of feeding or reproducing and make easy prey. Bumblebees (genus Bombus) are broadly distributed in diverse climates where they may be regularly exposed to temperatures low enough to induce chill coma. Yet they are adept at regulating body temperature and workers (females) spend nights in temperature-regulated nests. In contrast, male bumblebees do not return to the nest after emerging and thus must contend with daily cold exposure. We therefore predicted that male bumblebees would recover more quickly from chill coma than females. We measured CCRT of male and female Bombus vosnesenskii collected from nests established from field-caught queens and reared under common garden conditions. We held bees in chill coma at -4 °C for 2 hours and then placed them at 22 °C and measured time elapsed before they displayed coordinated muscle movement. Contrary to our prediction, female bumblebees recovered from chill coma ~1 minute faster than did males. This difference was robust to differences in body mass and consistent across nests from queens collected from diverse geographic locations.
