THE Effect of acclimation upon the survival of ptinus tectus and tenebrio molitor when exposed to low temperatures
1970
NUTTALL, R.M.
Ptinus tectus and Tenebrio molitor adults were acclimated for 24 hours to 15°, 25° and 35°. Evidence of acclimation was given by measurement of the chill coma point, heart beat and respiration rates. The respective chill coma points for insects acclimated to 15°, 25° and 35° were 2.9°, 3.7° and 4.7° for P. tectus, and 5.4°, 6.9° and 8.3° for T. molitor. The rates of heart beat and oxygen intake showed that P. tectus could acclimate from 25° to 15° but not to 35°, whilst T. molitor could acclimate from 25° to 35° but not to 15°. Acclimation also affected the undercooling point and fat content, but not the water content. The acclimated insects were exposed to a range of low temperatures for varying periods of time and allowed to recover at 15°, 25° or 35°. The dosage mortality data produced were subjected to probit analyses. In both species mortality varied with the time and temperature of exposure. In P. tectus there was a zone of resistance to freezing extending from 0° (L.D.₅₀ = 1820h) to --9° (L.D.₅₀ = 49--76h) and acclimation affected the terminal region (--9° to --12°) of this zone by altering the undercooling point. Resistance to freezing was minimal in T. molitor and was unaffected by acclimation. The time taken to recover in both species varied with the recovery temperature and the quantity and intensity of cold, but was unaffected by acclimation.
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