Research Progress in Insect Cold Hardines
昆虫耐寒性研究

Climate change will often lead to the fluctuation of insect populations,because insect is poikilothermic animals.Cold hardiness becomes a crucial strategy of insects.It largely determines the distribution,abundance and developmental rates of insect population.Here we summarize the literature about insect cold hardiness in order to make others convenient to know this field.The supercooling point(SCP)is perhaps the most common index of invertebrate cold hardiness and is often the first measurement to be made when the cold tolerance of a given species is to be investigated.Underlying the assumption that the SCP is an accurate indicator of cold hardiness,the strategies adopted by insects to survive at low temperature were classified into two types:freezing avoidance and freezing tolerance.In recent years,many scientists have questioned the validity of this viewpoint,because more insect mortality occurred well above the SCP.Therefore,it was suggested that the SCP should not be used as a unique and completely reliable index in determining the cold hardiness of insects.The current freezing avoidance/tolerance classification system has also been extended from two types to five types.The cold hardiness of insect is a reflection of insect adaptation to its environement.In temporal and spatial scales,the seasonal climate change results in the seasonal difference in cold hardiness,and the latitudinal difference also leads to geographical variation in cold hardiness.Low temperature acclimation before cold stress significantly increases the old hardiness of insects.In addition,the physiological and biochemical process in response to low temperature enhance insect's adaptation to extreme low temperature,which makes it possible to survive in the harsh winter climate.Both the degrees of freezing tolerance and supercooling increase by the accumulation of Low\|molecular\|weight cryoprotectant substances,e.g.glycerol.Ice nucleating agents have special functions in freezing tolerant insects,but have to be removed or biochemically masked in freezing intolerant species.Antifreezing proteins stabilize the supercooled state of insects and may prevent the inoculation of ice from outside through the cuticle.Current research progress has given the explanation to the cold hardiness concerning about the molecular stucture of antifreezing proteins,which will promote the cold hardiness studies at molecular level.Moreover,a better understanding of the cold hardiness of individual species requires the consideration of factors that are involved in life history strategies of insects.