Eur. J. Entomol. 93 (3): 405-418, 1996
Regulation of supercooling and ice nucleation in insects
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Since most insects are unable to survive internal ice formation a key factor in their overwintering survival is the regulation of the temperature at which they spontaneously freeze, termed the supercooling point or temperature of crystallization. Most insects enhance their supercooling capacity during the winter by eliminating endogenous ice nucleators, accumulating low-molecular-weight polyols and sugars, and synthesizing hemolymph antifreeze proteins. In the absence of heterogeneous ice nucleators, small body size promotes supercooling to temperatures 25°C or more below the freezing point of their body fluids. Although susceptibility to inoculative freezing is clearly detrimental for most species, in some insects it is required for freeze tolerance. Some freeze-tolerant species produce ice-nucleating proteins or lipoproteins that initiate freezing at relatively high subzero temperatures. Insoluble crystalloid deposits, such as calcium phosphate, present in a variety of insects, represent a newly-discovered class of endogenous ice nucleators. During the last few years, a number of research groups have reported ice-nucleating-active bacteria and fungi as normal flora in the gut of overwintering insects. Since these ice-nucleating-active microorganisms markedly reduce the supercooling capacity of insects when ingested or applied topically, they may offer a novel means for the biological control of insect pests during the winter.
Keywords: Supercooling, ice nucleation, insect, inoculative freezing, cold-hardiness, ice nucleating microorganisms, biological control
Accepted: June 10, 1996; Published: September 30, 1996 Show citation
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