柑桔大实蝇越冬蛹的滞育强度调控及其能量代谢机制

Differentiation of diapause intensity is the bet-hedging strategy for diapause insects which is regulated by genetic diversity and diapause conditions, but less is known about the physiological mechanisms of diapause intensity regulated by environmental cues. We use the important citrus insect pest Bactrocera minax (Enderlein) to examine how environmental conditions affect the differentiation on pupal developmental duration and overwintering death through energy storage and metabolism. Firstly, we use the larvae which collected from the dropped citrus fruits to detect the effects of pre-winter temperature and food supply on pupal energy reserves by measuring the carbohydrate and fat contents with pupal weight, and establish 4 to 6 artificial populations with significant diversity of energy storages. Secondly, we use those artificial populations to investigate the effects of pre-diapausing energy reserves, overwintering temperature during diapause maintenance phase and higher-lower temperature stress during diapause initiation phase on the diapause intensity and their variance coefficient, then to explore the respiratory metabolism characteristics by periodly monitoring CO2 production and energy consumption of each artificial population during different diapause phases. Based on the above studies, we hope to conclude the energy metabolic mechanism on the diapause intensity regulation of B. minax pupa that will improve our understanding of the energy allocation theory and the bet-hedging strategy during insect diapause, and to promote establishing of the forcast system of B. minax (Enderlein).

滞育强度分化是滞育昆虫分散风险的生活史策略，由物种的遗传多样性和滞育环境调控，但环境因子对滞育强度调控的生理机制鲜为人知。本项研究以柑橘重大害虫柑桔大实蝇为研究对象，以能量储备与代谢为切入点，探讨环境因子对越冬蛹自然死亡和历期分化的调控效应。首先以落果幼虫为材料，明确越冬前温度和食物供给对滞育蛹能量储备的影响，从而构建4-6个能量储备差异明显的人工种群；然后以人工种群为材料，分别考察滞育前能量储备差异、滞育持续期温度和滞育初期高-低温刺激对蛹滞育强度的影响，并定期监测滞育蛹的呼吸代谢率与能量物存量，明确各人工种群的呼吸代谢特征、滞育强度及其变异系数，揭示柑桔大实蝇越冬蛹滞育强度分化的调控因子及其效应，并阐明其滞育维持与解除的能量代谢机制。研究结果有助于完善昆虫滞育的风险分散策略和能量分配机制，促进柑桔大实蝇测报体系的建立。

柑桔大实蝇是高致害性的柑桔果实害虫，以蛹在果园内外土壤中滞育越冬，其发生期和发生量预测是科学防控的前提。本项研究以柑桔大实蝇蛹的发育调控为切入点，探讨了落果期温度、蛹期温度、蛹期土壤含水量等因子对滞育蛹发育和存活率的影响，结果表明：1）落果期温度对柑桔大实蝇化蛹质量和蛹发育历期（蛹滞育强度）存在显著影响，当温度上升至16℃时，柑桔大实蝇化蛹质量最高，虽然温度与化蛹质量间的关系较混乱，但随温度的升高，蛹滞育强度越大，蛹滞育强度（D）=252.084－441.852/X（R2=0.924，P=0.039＜0.05）；2）越冬蛹的能量积累（蛹重）与蛹滞育强度间呈直线相关关系，滞育强度（D）= 0.361×W（mg）＋193.7（R2 = 0.967，P = 0.003＜0.01），说明滞育前的能量积累提高了滞育强度；3）10℃冷藏时间越长，蛹滞育强度越高，滞育强度增加量y = 0.4135x–2.1222（x为低温处理天数，R2 = 0.7616），说明低温降低了滞育期的能量消耗，但随着冷藏时间的延长，蛹存活率下降；4）柑桔大实蝇蛹滞育的能量储存以脂肪为主，碳水化合物储存较少（10%）且以海藻糖储存为主；柑桔大实蝇蛹滞育期消耗的主要能量物质也是脂肪，但在蛹滞育深度期发生了一次明显的能量调整过程；5）滞育期间的呼吸强度与滞育解除后差异不明显，但滞育期间可见2次明显的呼吸高峰，再次证实蛹滞育期存在明确的能量调整期；处于含水量高的土壤中，柑桔大实蝇蛹的呼吸强度一致性提高，且滞育中期的呼吸强度达到幼虫期，证实水淹胁迫可显著提高滞育蛹的呼吸代谢速率。现有研究揭示的越冬蛹发育环境调控效应及其生理基础，为柑桔大实蝇测报技术体系建立积累了大量基础数据。