Nucleating agents in the haemolymph of insects tolerant to freezing

Abstract

MANY insects that survive the winter in cold, exposed habitats in arctic or temperate regions are sensitive to freezing. These insects usually have supercooling points below −15°C, and their capacity for supercooling has been shown to increase considerably with increasing concentrations of glycerol in their body fluid¹. On the other hand, adult insects that are tolerant to freezing (‘freeze tolerant’) seem to freeze invariably at high subzero temperatures (from −6 to −10°C), without regard to the concentration of glycerol and other polyols in their body fluid^2–4. We report here that haemolymph from freeze-tolerant adult beetles contains a substance, which induces freezing in the haemolymph at about −6.5°C. Haemolymph from freeze-sensitive species seems to lack this substance. Such substances probably constitute the physical basis of the remarkably high supercooling points of freeze-tolerant adult insects.