Sorgmantlar

Aldrig sett så många som denna vår. Bara igår ett 20-tal efter skogsvägarna. Kollade hur de klarat sig undan vinterkylan och fann följande:

Arctic insects can manage down to -55·C. How do they do this? The freeze avoidance strategy has three main parts.

First, special antifreeze proteins are produced and circulated in the blood. These proteins are specially designed so that they bind to the surface of embryonic ice crystals and prevent them from growing any further. So, any ice that forms stays in tiny crystals that can't do any harm to tissues.

Secondly, the animals build up extremely high concentrations of sugars or sugar alcohols in their blood and tissues and this lowers the freezing point of their body water. More commonly, however, a related chemical called glycerol is used which is much less toxic. By midwinter, the amount of glycerol in an insect's body is so high that it often makes up 20-25% of its entire body weight!

The third part of the freeze avoidance strategy is to prevent contact with molecules that can act as "ice nucleators", molecules that "seed" the formation of ice in body fluids. Ice itself is the most potent ice nucleator and so animals take steps to avoid contact with environmental ice. Some insects do this by wintering in very dry places, but most rely on wrapping themselves in water-proofing. This can be done by increasing the thickness of the waxy cuticle on an insect's body or by spinning a water-proof cocoon. Potential nucleators inside the insect's body are also eliminated such as by emptying the gut to get rid of foreign particles and bacteria and by seasonal changes to the types of proteins present in their blood to remove any whose structure could stimulate ice crystallization.