Cold tolerance of a New Zealand alpine cockroach, Celatoblatta quinquemaculata (Dictyoptera, Blattidae)
1998
Block, W. | Wharton, D.A. | Sinclair, B.J.
Ecophysiological features, including survival and recovery from freezing and determination of the freezable water content, are reported for a cold-adapted cockroach Celatoblatta quinquemaculata Johns 1966 (Dictyoptera, 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. Cockroaches had a mean supercooling point temperature of -5.4 +/- 0.1 degrees C; with recovery from freezing close to this temperature being rapid, but no recovery was observed when frozen at -9 to -10 degrees C. The duration of exposure to freezing conditions and the time allowed for recovery (24-96 h) both influenced individual recovery and subsequent survival. Comparison of supercooling point data and survival shows that this species possesses a few degrees of freeze tolerance, and individuals have been found frozen in the field when subzero temperatures occur. Differential scanning calorimetry showed approximately 74% of body water froze during cooling and between 24 and 27% of total body water was osmotically inactive (unfreezable under the experimental conditions). Carbohydrates, other than glucose at 7.5 micrograms/mg fresh weight, were in low concentrations in the body fluids, suggesting little cryoprotection. No thermal hysteresis from antifreeze protein activity was detected in haemolymph samples using calorimetric techniques. It is suggested that slow environmental cooling rates, together with high individual 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 > 1300 m a.s.l. in New Zealand.
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