ISSN:
1432-136X
Keywords:
Key words Cold tolerance
;
Free amino acids
;
Ions
;
Cryoprotectants
;
Insect
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
,
Medicine
Notes:
Abstract The microclimate in the habitat of the New Zealand alpine weta Hemideina maori is very variable with winter temperatures down to −6 °C under the rocks where the insects are found. Subfreezing temperatures may in winter prevail for up to 17 days but diurnal cycles of freezing and thawing are common, as is also the case in summer. Rates of temperature change can be very high and up to −7.20 °C/h. During winter, humidity was high for extended periods ranging from 70% to 100% relative humidity (RH). In the summer, humidity ranged from 30% RH during the day to 100% RH at night. The supercooling point of the haemolymph was approximately −8 °C year round, caused by a heat labile substance. The supercooling point of the haemolymph of an insect of the same genus, Hemideina femorata not regularly exposed to subfreezing temperatures, was ca. −16.5 °C. Thermal hysteresis was not detected in the haemolymph of H. maori. Haemolymph osmolality varied from 380 mOsm (summer) to 700 mOsm (winter). Body water content was ca. 75% all year round. Total concentrations of sodium, potassium and chloride in haemolymph varied from 170 mM (winter) to 250 mM (summer). The total concentration of free amino acids varied from 58 mM (summer) to 263 mM (winter). This variation was mostly due to proline which varied from ca. 15 mM (summer) to ca. 100 mM (winter). The freeze-tolerant weta H. maori is exposed to a highly variable and cold environment all year round and several properties of its haemolymph composition can be attributed to these climatic conditions, e.g. the presence of ice-nucleating agents and an increase in the concentration of proline during cold hardening in the autumn.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/s003600050215
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