Cold adaptation of the terrestrial isopod,Porcellio scaber,to subnivean environments |
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Authors: | K. Tanaka T. Udagawa |
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Affiliation: | (1) Laboratory of Applied Zoology, Faculty of Agriculture, Hokkaido University, 060 Sapporo, Japan;(2) Present address: Zoological Section, Institute of Low Temperature Science, Hokkaido University, 060 Sapporo, Japan;(3) Present address: Fish and Shellfisch Section, Resource Enhancement Devision, Hokkaido National Fisheries Research Institute, 085 Kushiro, Japan |
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Abstract: | The terrestrial isopod, Porcellio scaber, was susceptible to subzero temperature: both freezing and chilling were injurious. The level of cold hardiness against chilling and freezing showed different patterns in their seasonal variation. The lower lethal temperature causing 50% mortality, an indicator of the tolerance to chilling, ranged from-1.37°C in August to-4.58°C in December. The whole body supercooling point, the absolute limit of freeze avoidance, was kept at about-7°C throughout the year. The winter decrease in lower lethal temperature was concomitant with an accumulation of low molecular weight carbohydrates which are possible protective reagents against chilling injury, whereas the less seasonally variable supercooling point seemed to be associated with the year-round presence of gut content. Food derivatives may act as efficient ice nucleators. The different trend in seasonal changes between lower lethal temperature and supercooling point may be related to the microclimate of the hibernacula in subnivean environments, where the winter temperature became lower than the lower lethal temperature in the summer active phase, but remained higher than the summer supercooling point.Abbreviations LLT50 lower lethal temperature inducing 50% mortality - SCP supercooling point - Ta ambient air temperature - Ts soil surface temperature |
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Keywords: | Supercooling point Lower lethal temperature Cryoprotectants Gut contents Isopod, Porcellio scaber |
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