Zachariassen K E, Li N G, Laugsand A E, Kristiansen E, Pedersen S A
Laboratory of Ecophysiology and Toxicology, Department of Biology, Norwegian University of Science and Technology, 7491 Trondheim, Norway.
J Comp Physiol B. 2008 Nov;178(8):977-84. doi: 10.1007/s00360-008-0284-6. Epub 2008 Jun 18.
The strategy for cold-hardiness and water balance features of two closely related families of Coleoptera, Cerambycidae and Chrysomelidae, were investigated. Cerambycids were freeze-avoiding with low supercooling points, whereas chrysomelids froze at high temperatures and were tolerant to freezing. Hence, the two families have adopted different strategies for cold-hardiness. Due to their low trans-cuticular water permeability, the cerambycids have low rates of evaporative water loss. Chrysomelids have much higher trans-cuticular water permeability, but freezing brings their body fluids in vapour pressure equilibrium with ice and prevents evaporative water loss. The differences in cold-hardiness strategies and rates of water loss are likely to reflect the water content of the diets of the two families. Cerambycids feed on dry wood with low water content, causing a restrictive water balance. Chrysomelids feed on leaves with high water content and may use evaporation through the cuticle as a route of water excretion. Haemolymph ice nucleators help chrysomelids to freeze at a high temperature and thus to maximize the period they spend in the water saving frozen state. The diet-related differences in water balance may be the reason why the two families have developed different strategies for cold-hardiness.
研究了鞘翅目两个近缘科（天牛科和叶甲科）的抗寒策略和水分平衡特征。天牛科昆虫通过低过冷却点来避免结冰，而叶甲科昆虫在高温下结冰且能耐受冷冻。因此，这两个科采取了不同的抗寒策略。由于天牛科昆虫的经皮水分渗透率较低，其蒸发失水率也较低。叶甲科昆虫的经皮水分渗透率要高得多，但结冰使它们的体液与冰处于蒸气压平衡状态，从而防止了蒸发失水。抗寒策略和失水率的差异可能反映了这两个科食物的含水量。天牛科以含水量低的干燥木材为食，导致水分平衡受到限制。叶甲科以含水量高的叶子为食，可能通过角质层蒸发作为水分排泄途径。血淋巴冰核有助于叶甲科昆虫在高温下结冰，从而使它们在节水的冷冻状态下停留的时间最大化。与食物相关的水分平衡差异可能是这两个科发展出不同抗寒策略的原因。
