Pullock Dylan A, Malod Kévin, Manrakhan Aruna, Weldon Christopher W
Department of Zoology and Entomology, University of Pretoria, Pretoria, South Africa.
Citrus Research International, Mbombela, South Africa.
Front Insect Sci. 2023 Mar 28;3:1122161. doi: 10.3389/finsc.2023.1122161. eCollection 2023.
Temperature fluctuations are important for the distribution and survival of insects. Rapid hardening, a type of phenotypic plasticity, is an adaptation that can help individuals better tolerate lethal temperatures because of earlier exposure to a sublethal but stressful temperature. Nutrition and sex are also known to influence a species ability to tolerate thermal stress. This study determined the effects of larval diet, adult diet, sex and hardening on the thermal tolerance of (Walker) (Diptera: Tephritidae) at lower and upper lethal temperatures.
Larvae were raised on either an 8% torula yeast (high) or a 1% torula yeast (low) larval diet and then introduced to one of three dietary regimes as adults for thermal tolerance and hardening assays: no adult diet, sugar only, or sugar and hydrolysed yeast diet. Flies of known weight were then either heat- or cold-hardened for 2 hours before being exposed to a potentially lethal high or low temperature, respectively.
Both nutrition and hardening as well as their interaction affected tolerance of stressful temperatures. However, this interaction was dependent on the type of stress, with nutrient restriction and possible adult dietary compensation resulting in improved cold temperature resistance only.
The ability of the insect to both compensate for a low protein larval diet and undergo rapid cold hardening after a brief exposure to sublethal cold temperatures even when both the larva and the subsequent adult fed on low protein diets indicates that have a better chance of survival in environments with extreme temperature variability, particularly at low temperatures. However, there appears to be limitations to the ability of to cold harden and the species may be more at risk from long term chronic effects than from any exposure to acute thermal stress.
温度波动对昆虫的分布和生存至关重要。快速硬化是一种表型可塑性，是一种适应性特征，由于更早暴露于亚致死但有压力的温度下，它可以帮助个体更好地耐受致死温度。营养和性别也已知会影响一个物种耐受热应激的能力。本研究确定了幼虫饮食、成虫饮食、性别和硬化对地中海实蝇（Walker）（双翅目：实蝇科）在较低和较高致死温度下热耐受性的影响。
幼虫用8%的圆酵母（高）或1%的圆酵母（低）幼虫饲料饲养，然后作为成虫引入三种饮食方案之一进行热耐受性和硬化试验：无成虫饮食、仅糖或糖和水解酵母饮食。已知体重的果蝇在分别暴露于潜在致死的高温或低温之前，先进行2小时的热硬化或冷硬化。
营养和硬化及其相互作用均影响了对压力温度的耐受性。然而，这种相互作用取决于应激类型，营养限制和可能的成虫饮食补偿仅导致耐寒性提高。
即使幼虫和随后的成虫都以低蛋白饮食为食，该昆虫仍有能力补偿低蛋白幼虫饮食，并在短暂暴露于亚致死低温后进行快速冷硬化，这表明地中海实蝇在温度极端变化的环境中，特别是在低温环境中有更好的生存机会。然而，地中海实蝇的冷硬化能力似乎存在局限性，该物种可能更容易受到长期慢性影响的风险，而不是任何急性热应激暴露的影响。
