Cold hardiness

 

Ø Cold hardiness describes the ability of insects to survive exposure to low temperatures.

Ø Insects tolerate winter temperatures if they first undergo a physiological preparedness that may take several weeks to develop.

Ø The acclimatization process occurs when insects are first exposed to low temperatures, which trigger the accumulation of the cryoprotectants.

Ø A short-term exposure to cold temperatures can also protect some insects from subsequent lethal temperatures. 

Ø Insects that are characterized as being freeze tolerant are able to withstand the formation of extracellular ice crystals.

Ø They synthesize ice nucleating proteins that raise the supercooling point of body fluids and serve as catalysts for the nucleation of ice in safe extracellular areas. Water moves from the cells to these extracellular areas, preventing intracellular freezing from occurring.

Ø This gives the cells time to adjust to the osmotic changes that result from the formation of ice crystals and reduces the likelihood of intracellular freezing.

Ø Freeze-avoiding species produce hemolymph cryoprotectants that allow the insect to supercool and remain in a liquid state without the formation of ice crystals.

Ø These species can often supercool to as low as −35°C. The cryoprotectants that are produced include glycerol, sorbitol, trehalose, and mannitol often in concentrations approaching 25% of the insect’s total body weight.

Ø In addition to preventing the formation of ice, these components may stabilize enzymes and cell membranes.