COLD TOLERANCE OF A NEW-ZEALAND ALPINE COCKROACH, CELATOBLATTA-QUINQUEMACULATA (DICTYOPTERA, BLATTIDAE)

Ecophysiological features, including survival and recovery from freezi ng and determination of the freezable water content, are reported for a cold-adapted cockroach Celatoblatta quinquemaculata Johns 1966 (Dict yoptera, Blattidae) inhabiting alpine communities at altitudes greater than 1300 m a.s.l. in mountains of Central Otago, New Zealand. Nymphs ranged from 15 to 51 mg live weight of which 67% was water. Cockroach es had a mean supercooling point temperature of -5.4 +/- 0.1 degrees C ; with recovery from freezing close to this temperature being rapid, b ut no recovery was observed when frozen at -9 to -10 degrees C. The du ration of exposure to freezing conditions and the time allowed for rec overy (24-96 h) both influenced individual recovery and subsequent sur vival. Comparison of supercooling point data and survival shows that t his species possesses a few degrees of freeze tolerance, and individua ls have been found frozen in the held when subzero temperatures occur. Differential scanning calorimetry showed approximate to 74% of body w ater froze during cooling and between 24 and 27% of total body water w as osmotically inactive (unfreezable under the experimental conditions ). Carbohydrates, other than glucose at 7.5 mu g/mg fresh weight, were in low concentrations in the body fluids, suggesting little cryoprote ction. No thermal hysteresis from antifreeze protein activity was dete cted in haemolymph samples using calorimetric techniques. It is sugges ted that slow environmental cooling rates, together with high individu al supercooling points, confer a small amount of freezing tolerance on this species enabling it to survive low winter temperatures. This has allowed it to colonize and maintain populations in alpine habitats >1 300 m a.s.l. in New Zealand.