Data from: Preservation of potassium balance is strongly associated with insect cold tolerance in the field: a seasonal study of Drosophila subobscura

There is interest in pinpointing genes and physiological mechanisms explaining intra- and interspecific variations in cold tolerance, because thermal tolerance phenotypes strongly impact the distribution and abundance of wild animals. Laboratory studies have highlighted that the capacity to preserve water and ion homeostasis is linked to low temperature survival in insects. It remains unknown, however, whether adaptive seasonal acclimatization in free-ranging insects is governed by the same physiological mechanisms. Here, we test whether cold tolerance in field-caught Drosophila subobscura is high in early spring and lower during summer and whether this transition is associated with seasonal changes in the capacity of flies to preserve water and ion balance during cold stress. Indeed, flies caught during summer were less cold tolerant, and exposure of these flies to sub-zero temperatures caused a loss of haemolymph water and increased the concentration of K+ in the haemolymph (as in laboratory-reared insects). This pattern of ion and water balance disruption was not observed in more cold-tolerant flies caught in early spring. Thus, we here provide a field verification of hypotheses based on laboratory studies and conclude that the ability to maintain ion homeostasis is important for the ability of free-ranging insects to cope with chilling.

学界一直致力于精准定位解释耐寒性种内与种间变异的基因与生理机制，因为热耐受表型对野生动物的分布与种群丰度具有强烈影响。已有实验室研究证实，昆虫维持水分与离子稳态的能力与其低温存活能力密切相关。然而，野外自由生存昆虫的适应性季节驯化是否由相同的生理机制调控，目前仍不清楚。本研究以野外捕获的暗果蝇（Drosophila subobscura）为研究对象，旨在验证两项科学假设：其一，早春捕获的个体耐寒性较强，而夏季捕获的个体耐寒性较弱；其二，这种季节间的耐寒性转变，与果蝇在低温胁迫下维持水分与离子平衡的能力的季节变化相关。实验结果确实显示，夏季捕获的果蝇耐寒性更弱；将此类果蝇暴露于零下低温环境后，其血淋巴水分流失，且血淋巴中钾离子（K+）浓度升高，这一现象与实验室饲养昆虫的表现一致。而早春捕获的耐寒性更强的果蝇，则未出现这种离子与水分平衡紊乱的现象。综上，本研究为基于实验室研究提出的假说提供了野外验证，并得出结论：维持离子稳态的能力，是野外自由生存昆虫应对冷胁迫的关键能力。