COLD SHOCK AND RAPID COLD-HARDENING OF PHARATE ADULT FLESH FLIES (SARCOPHAGA-CRASSIPALPIS) - EFFECTS ON BEHAVIOR AND NEUROMUSCULAR FUNCTIONFOLLOWING ECLOSION

Little is known about the nature of injury due to cold shock, or its p revention by rapid cold-hardening, in insects. To understand these phe nomena better at the system level, physiological and behavioural compa risons were made between control, cold shock injured, and rapidly cold -hardened flesh flies, Sarcophaga crassipalpis Macquart (Diptera, Sarc ophagidae). Cold shock impaired the proboscis extension reflex in resp onse to 0.125, 0.5 and 1.0 M sucrose solutions. Cold shock-injured fli es were unable to groom effectively and spent only 12.5% of the first 5 min following general dust application producing ineffectual leg mov ements. in contrast, control and rapidly cold-hardened flies exhibited normal grooming behaviour spending 92.4% and 94.1% of the first 5 min following generalized dust application grooming. Cold shock also decr eased the mean resting membrane potential of tergotrochanteral muscle fibres from -65.9 mV in control flies to -41.6 mV. Conduction velociti es of the three motor neurone populations innervating the tergotrochan teral muscle were all significantly lower in cold-shocked flies than i n control or rapidly cold-hardened flies. Finally, cold shock impaired neuromuscular transmission as evidenced by a lack of evoked end plate potentials.