Department of Zoology and Entomology, University of the Free State, Bloemfontein, South Africa.
Tugwi-Mukosi Multidisciplinary Research Institute, Midlands State University, Gweru, Zimbabwe.
Bull Entomol Res. 2023 Aug;113(4):449-455. doi: 10.1017/S0007485323000111. Epub 2023 Apr 4.
In this era of global climate change, intrinsic rapid and evolutionary responses of invasive agricultural pests to thermal variability are of concern given the potential implications on their biogeography and dire consequences on human food security. For insects, chill coma recovery time (CCRT) and critical thermal minima (CT), the point at which neuromuscular coordination is lost following cold exposure, remain good indices for cold tolerance. Using laboratory-reared (Lepidoptera: Noctuidae), we explored cold tolerance repeated exposure across life stages of this invasive insect pest. Specifically, we measured their CT and CCRT across four consecutive assays, each 24 h apart. In addition, we assessed body water content (BWC) and body lipid content (BLC) of the life stages. Our results showed that CT improved with repeated exposure in 5th instar larvae, virgin males and females while CCRT improved in 4th, 5th and 6th instar larvae following repeated cold exposure. In addition, the results revealed evidence of cold hardening in this invasive insect pest. However, there was no correlation between cold tolerance and BWC as well as BLC. Our results show capacity for cold hardening and population persistence of in cooler environments. This suggests potential of fall armyworm (FAW) to withstand considerable harsh winter environments typical of its recently invaded geographic range in sub-Saharan Africa.
在全球气候变化的时代，入侵农业害虫对热变异性的固有快速和进化反应引起了人们的关注，因为这可能对它们的生物地理学产生影响，并对人类食品安全产生严重后果。对于昆虫来说，冷昏迷恢复时间（CCRT）和临界热最小值（CT），即冷暴露后神经肌肉协调性丧失的点，仍然是耐寒性的良好指标。本研究使用实验室饲养的（鳞翅目：夜蛾科），探索了这种入侵性害虫在其生命各阶段的反复暴露对耐寒性的影响。具体来说，我们在四个连续的试验中测量了它们的 CT 和 CCRT，每个试验相隔 24 小时。此外，我们评估了生命阶段的身体含水量（BWC）和身体脂肪含量（BLC）。研究结果表明，5 龄幼虫、处女雄虫和雌虫的 CT 在反复暴露后得到提高，而 4 龄、5 龄和 6 龄幼虫的 CCRT在反复低温暴露后得到提高。此外，研究结果还表明这种入侵性昆虫具有冷驯化的证据。然而，耐寒性与 BWC 和 BLC 之间没有相关性。本研究结果表明，在较冷的环境中具有冷驯化和种群生存的能力。这表明秋粘虫（FAW）有能力抵御其最近入侵的撒哈拉以南非洲地理范围内典型的相当恶劣的冬季环境。
