Research progress in Nematode cold tolerance
线虫耐寒性研究进展

In order to have normal development and better existence,nematodes should overcome the challenges of winter cold in the temperate and frigid areas.Therefore,the research on nematode cold tolerance assumes greater significance. The present status of knowledge alongwith the methods to study nematode cold tolerance,its strategies and mechanisms are reviewed in this paper.Research methods for nematodes cold tolerance are similar to that of insects,including measurement of supercooling points and assessment of survival;but the detailed experimental technique for nematodes has its own characteristics.The F_(50) has been shown as a valid measure of the degree of supercooling.Cold tolerance strategies have been mainly divided into freezing tolerance and freeze avoidance.Freeze tolerance is widespread among nematodes but not all nematode species are freezing tolerant.As the sheath or eggshell can prevent inoculative freezing,some nematodes can survive by freeze avoidance.In nematodes,these two strategies are not mutually exclusive as in found in case of arthropods.Nematodes are also able to optimize their strategy in response to changes in the environment.Nematodes have adopted various cold tolerance mechanisms.In many parasitic nematodes,which spend part of their life cycle in a protected and favourable environment(i.e.the host),only particular developmental stage has adopted these mechanisms.Cold acclimation before cold stress significantly increases the cold hardiness of nematodes.In addition,other mechanisms of cold stress include the synthesis of cryoprotectants,antifreezing proteins and heat shock proteins.Further,it has been suggested that the nematode cold tolerance must also be investigated from other aspects,such as chill susceptibility,cold tolerance of parasitic stages and the effect of cross-stresses.