Cold Tolerance in the House Spider, Achaearanea tepidariorum (Araneae : Theridiidae)
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概要
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The cold tolerance strategy of the house spider, Achaearanea tepidariorum, consisted of at least two components, freezing avoidance by supercooling and chilling tolerance. The former ability varied with season and latitude. The northern population with severe winters lowered the supercooling point (SCP) in winter, but the southern population with mild winters did not. A prime factor limiting the supercooling ability of this spider was the presence of ice nucleators in the gut. The SCP depression, therefore, can be achieved at least in part by excretion or inactivation of gut ice nucleators. Chilling tolerance also showed a seasonal cycle, but the underlying mechanism seems to be different from the mechanism regulating supercooling ability. Both supercooling ability and chilling tolerance were associated with the diapause programme. The relationship between the two, however, differed geographically. The cool-temperate diapause enhanced both supercooling ability and chilling tolerance, but the subtropical diapause enhanced only chilling tolerance. This interpopulation difference in the relationship between diapause and cold hardiness provides an indication of the pathway of evolution. It would follow that the ancestral diapause of this spider evolved first with chilling tolerance, but not with an ability to lower SCP. The latter ability would have evolved secondarily as the spider expanded its distribution from subtropical to cool-temperate regions.
- 日本昆虫学会の論文
- 1999-12-25