EFFECT OF TEMPERATURE ON COLD-HARDINESS AND TISSUE ICE FORMATION IN THE ADULT CHRYSOMELID BEETLE MELASOMA-COLLARIS L

The freeze-tolerant chrysomelid beetle Melasoma collaris overwinters i n plant litter on windswept ridges or covered with snow for 8-9 months in the Norwegian alpine region. Lower lethal temperature, supercoolin g and melting point depression were correlated to accumulation of glyc erol. The lower limit of freeze tolerance was associated with the free zing of 73-75% body water, About 23-15.5% of the body water was osmoti cally inactive, and the highest percentage was revealed in individuals depleted of glycerol at 21 degrees C. A shift in cooling rate from 1 degrees C min(-1) to 1 degrees C every 13.5 min lowered nucleating tem perature markedly. The alteration in nucleating activity probably aris es from the structure of the haemolymph nucleating agent that function s to slow embryo growth at the slow cooling rate. An enhanced supercoo ling is particularly beneficial in autumn before M. collaris has accum ulated glycerol, since supercooled individuals accumulate glycerol in higher concentrations than frozen ones. Freezing at higher temperature s is probably a better survival strategy during brief intervals with p ronounced decrease in air temperature. (C) 1997 Elsevier Science Ltd.