Induction of rapid cold hardening by cooling at ecologically relevant rates in Drosophila melanogaster

• Published in: Journal of insect physiology Vol. 45; no. 8; pp. 719 - 726
• Main Authors: Kelty, Jonathan D, Lee, Jr, Richard E
• Format: Journal Article
• Language: English
• Published: England Elsevier Ltd 01-08-1999
• Subjects: ambient temperature; Cold shock; cold stress; cold tolerance; cooling rate; critical thermal minimum; CT min; Drosophila melanogaster; fecundity; mortality; Rapid cold-hardening; Cold shock; Drosophila melanogaster; Rapid cold-hardening; CT min
• ISSN: 0022-1910; 1879-1611
• DOI: 10.1016/S0022-1910(99)00040-2

Over a decade ago it was hypothesized that the rapid cold hardening process allows an organism's overall cold tolerance to track changes in environmental temperature, as would occur in nature during diurnal thermal cycles. Although a number of studies have since focused on characterizing the rapid cold hardening process and on elucidating the physiological mechanisms upon which it is based, the ecological relevance of this phenomenon has received little attention. We present evidence that in
Drosophila melanogaster rapid cold hardening can be induced during cooling at rates which occur naturally, and that the protection afforded in such a manner benefits the organism at ecologically relevant temperatures.
Drosophila melanogaster cooled at natural rates (0.05 and 0.1°C min
−1) exhibited significantly higher survival after one hour of exposure to −7 and −8°C than did those directly transferred to these temperatures or those cooled at 0.5, or 1.0°C min
−1. Protection accrued throughout the cooling process (e.g., flies cooled to 0°C were more cold tolerant than those cooled to 11°C). Whereas
D. melanogaster cooled at 1.0°C min
−1 had a critical thermal minimum (i.e., the temperature at which torpor occurred) of 6.5±0.6°C, those cooled at an ecologically relevant rate of 0.1°C min
−1 had a significantly lower value of 3.9±0.9°C.