Rapid cold-hardening, which occurs within minutes or hours, confers protection from injury during sudden chilling. Recently, we demonstrated that rapid cold-hardening occurs during ecologically-based thermoperiods and functions to decrease the temperature at which flies enter cold torpor. However, the evolutionary significance of this process, as it relates to reproduction, has been little studied. In this study, we demonstrated that rapid cold-hardening preserves normal reproductive behaviors in the fruit fly, Drosophila melanogaster. Once group of flies was rapidly cold-hardened by step transfer of the flies from 23°C to 16°C. We video taped pairs of rapidly cold hardened (RCH) flies (exposed to 16°C for 2 h) and pairs of control flies (transferred directly from 23°C) at 16°C, and measured whether they courted, the duration of courtship, and whether they mated. More RCH pairs than control pairs were able to court (17 vs. 11 pairs) and to mate (11 vs. 0 pairs). The courtship events of the RCH flies averaged 19.0±3.5 min, which was significantly longer than that of control pairs (9.5±2.2 min). We also repeated these tests at 23°C and found no significant difference between RCH and control groups in the number of pairs courting or mating. However, the event durations of the control flies (7.9±1.2 min) were significantly longer than those of the RCH pairs (4.9±0.7 min).
Species 1: Diptera Drosophilidae Drosophila melanogaster
Keywords: thermoperiod
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