EFFECT OF TEMPERATURE AND ANOXIA ON HAEMOLYMPH COMPOSITION AND SUPERCOOLING IN 3 OVERWINTERING INSECTS

Supercooling points in diapausing larvae of a grain moth (Nemapogon personellus (P. and M.)) and of the tortricid Laspeyresia strobilella (L.) were lowered during anoxia or storage at low temperatures. In pupae of Pieris brassicae (L.) only small changes in supercooling points were found during storage at 2[degree] C from Dec. to April. Transfer to 20[degree] C resulted in decreased ability to supercool, both during and after diapause, whereas increased supercooling was observed following anoxia or exposure -6[degree] C after diapause was broken. Freezing-point depressions in haemolymph of N. personellus and P. brassicae were smaller than the corresponding supercooling-point depressions. Concurrent with increased ability to supercool, increases in concentrations of various solutes in the haemo-lymph were observed in all species. In L. strobilella glycerol was formed during storage at low temperatures but not during anoxia. Glycerol was not produced in P. brassicae and only after long periods of anoxia in N. personellus. Depending on species and kind of treatment, the main substances in which concentration changes were observed included sorbitol, trehalose, lactate, and alanine. The relation between supercooling-point depression and haemolymph composition in various insects, including 2 glycerol-forming species, is treated statistically in the discussion. With increased concentrations of solutes in the haem-olymph, significantly larger depressions of supercooling points than of freezing points were found in species with and without glycerol. It is concluded that the effect on supercooling exhibited by glycerol is not unique, but that a number of solutes in the haemolymph may have a similar effect.