Zoophysiology, Department of Biosciences, Aarhus University, C. F. Møllers Alle 3, Building 1131, DK-8000 Aarhus, Denmark.
J Exp Biol. 2013 May 1;216(Pt 9):1630-7. doi: 10.1242/jeb.081141. Epub 2013 Jan 24.
Chill tolerance of insects is defined as the ability to tolerate low temperature under circumstances not involving freezing of intracellular or extracellular fluids. For many insects chill tolerance is crucial for their ability to persist in cold environments and mounting evidence indicates that chill tolerance is associated with the ability to maintain ion and water homeostasis, thereby ensuring muscular function and preventing chill injury at low temperature. The present study describes the relationship between muscle and haemolymph ion homeostasis and time to regain posture following cold shock (CS, 2 h at -4°C) in the chill-susceptible locust Locusta migratoria. This relationship was examined in animals with and without a prior rapid cold-hardening treatment (RCH, 2 h at 0°C) to investigate the physiological underpinnings of RCH. CS elicited a doubling of haemolymph [K(+)] and this disturbance was greater in locusts pre-exposed to RCH. Recovery of ion homeostasis was, however, markedly faster in RCH-treated animals, which correlated well with whole-organism performance as hardened individuals regained posture faster than non-hardened individuals following CS. The present study indicates that loss and recovery of muscular function are associated with the resting membrane potential of excitable membranes as attested by the changes in the equilibrium potential for K(+) (EK) following CS. Both hardened and non-hardened animals regained movement once K(+) homeostasis had recovered to a fixed level (EK≈-41 mV). RCH is therefore not associated with altered sensitivity to ion disturbance but instead is correlated to a faster recovery of haemolymph [K(+)].
昆虫的耐寒性定义为在不涉及细胞内或细胞外液体冻结的情况下耐受低温的能力。对于许多昆虫来说，耐寒性对于它们在寒冷环境中生存的能力至关重要，越来越多的证据表明，耐寒性与维持离子和水稳态的能力有关，从而确保肌肉功能并防止低温损伤。本研究描述了易受寒地区蝗虫 Locusta migratoria 肌肉和血淋巴离子稳态与冷休克（CS，-4°C 下 2 小时）后恢复姿势时间之间的关系。在有和没有预先快速冷驯化处理（RCH，0°C 下 2 小时）的动物中检查了这种关系，以研究 RCH 的生理基础。CS 引起血淋巴 [K(+)] 的两倍增加，而在预先暴露于 RCH 的昆虫中这种干扰更大。离子稳态的恢复明显更快在 RCH 处理的动物中，这与整体动物表现很好地相关，因为硬化个体在 CS 后比非硬化个体更快地恢复姿势。本研究表明，肌肉功能的丧失和恢复与兴奋膜的静息膜电位有关，这可以从 CS 后 K(+)（EK）的平衡电位的变化得到证明。一旦 K(+)稳态恢复到固定水平（EK≈-41 mV），硬化和非硬化动物就会恢复运动。因此，RCH 与离子扰动的敏感性改变无关，而是与血淋巴 [K(+)] 的更快恢复相关。
