Journal
COMPARATIVE BIOCHEMISTRY AND PHYSIOLOGY B-BIOCHEMISTRY & MOLECULAR BIOLOGY
Volume 143, Issue 2, Pages 171-179Publisher
ELSEVIER SCIENCE INC
DOI: 10.1016/j.cbpb.2005.11.005
Keywords
chill tolerance; cold-acclimation; ion gradients; equilibrium potentials; Dictyoptera; Insecta
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Adults of warm- and cold-acclimated tropical cockroaches, Nauphoeta cinerea were exposed to low temperatures of 0 or 5 degrees C for various time intervals (hours to days). Development of chilling-injury (defects in crawling and uncoordinated movements) and mortality during the exposure were assessed and correlated with the changes in concentrations of metal ions (Na+, K+ and Mg2+) in the haemolymph and coxal muscle tissue. Warm-acclimated insects entered chill-coma at both low temperatures. In their haemolymph, the [Na+] and [Mg2+] linearly decreased and [K+] increased with the increasing time of exposure. The rate of concentration changes was higher at 0 than at 5 degrees C. The concentration changes resulted in gradually dissipating equilibrium potentials across the muscle cell membranes. For instance, E-K decreased from -49.8 to -20.7 mV during 7 days at 5 degrees C. Such a disturbance of ion homeostasis was paralleled by the gradual development of chilling-injury and mortality. Most of the cockroaches showed chilling-injury when the molar ratio of [Na+]/[K+] in their haemolymph decreased from an initial of 4.4 to 2.1-2.5. In contrast, the cold-acclimated cockroaches did not enter chill-coma. They maintained constant concentrations of ions in their haemolymph, constant equilibrium potentials across muscle cell membranes and the development of chilling-injury was significantly suppressed at 5 degrees C for 7 days. (C) 2005 Elsevier Inc. All rights reserved.
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