Xiao Quan-Hong, He Zhe, Wu Rong-Wei, Zhu Dao-Hong
Laboratory of Insect Behavior and Evolutionary Ecology, College of Life Science and Technology, Central South University of Forestry and Technology (CSUFT), Changsha, China.
College of Physical Education, Central South University of Forestry and Technology (CSUFT), Changsha, China.
Front Physiol. 2022 Nov 2;13:1031654. doi: 10.3389/fphys.2022.1031654. eCollection 2022.
The swallowtail butterfly, Gray, is endemic to East Asia, has high ornamental value but faces an increased risk of extinction. To understand the overwintering strategies of this species, the dynamic changes in supercooling point (SCP) and water and biochemical contents of diapause-destined and non-diapause pupae were investigated. The SCP of laboratory-reared diapause pupae was as low as -26°C compared to -24°C in diapause pupae in the field. Although there was no significant difference in total water content between diapause-destined and non-diapause pupae, the free water of diapause-destined pupae was significantly lower, and the bound water was significantly higher, than that of non-diapause pupae. Lipid, glycogen, and protein contents of diapause-destined pupae showed a downward trend, whereas the total sugar content showed the opposite trend after pupation. The glycogen content decreased rapidly during the initial stage of pupation, whereas the lipid content decreased significantly after 30 days of pupation, suggesting that diapause-destined pupae deplete glycogen stores during the pre-diapause period and then switch to using lipids during the diapause maintenance phase. Trehalose levels in diapause-destined pupae increased significantly and remained high after pupation. Meanwhile, the trehalose content of overwintering pupae during the diapause maintenance period was significantly higher than that of diapause termination pupae in the field. These results suggest that trehalose is the main cryoprotectant for overwintering pupae. Thus, diapausing pupae appear to be freeze avoidant, accumulate trehalose as a cryoprotectant, and reduce the free water content to decrease the SCP, enhancing their cold tolerance.
凤蝶（Papilio xuthus）是东亚特有的物种，具有很高的观赏价值，但面临着日益增加的灭绝风险。为了解该物种的越冬策略，研究了滞育蛹和非滞育蛹的过冷却点（SCP）以及水分和生化成分的动态变化。实验室饲养的滞育蛹的SCP低至-26°C，而野外滞育蛹的SCP为-24°C。尽管滞育蛹和非滞育蛹的总含水量没有显著差异，但滞育蛹的自由水显著低于非滞育蛹，而结合水显著高于非滞育蛹。滞育蛹的脂质、糖原和蛋白质含量呈下降趋势，而化蛹后总糖含量呈相反趋势。糖原含量在化蛹初期迅速下降，而脂质含量在化蛹30天后显著下降，这表明滞育蛹在滞育前期消耗糖原储备，然后在滞育维持阶段转而利用脂质。滞育蛹中的海藻糖水平显著升高，化蛹后保持较高水平。同时，滞育维持期越冬蛹的海藻糖含量显著高于野外滞育结束蛹的海藻糖含量。这些结果表明，海藻糖是越冬蛹的主要抗冻剂。因此，滞育蛹似乎是避免结冰的，积累海藻糖作为抗冻剂，并降低自由水含量以降低SCP，从而增强其耐寒性。
