Cold tolerance of laboratory-reared Asian longhorned beetles

Area of Science:

• Entomology
• Ecology
• Climate Change Biology

Background:

• The Asian longhorned beetle (Anoplophora glabripennis) is an invasive pest impacting hardwood trees in North America and Europe.
• Understanding its cold tolerance is vital for predicting invasive population success and distribution.
• Native populations experience diverse climates, necessitating study of overwintering survival strategies.

Purpose of the Study:

• To systematically characterize the cold tolerance strategies and lethal limits of Asian longhorned beetle eggs, larvae, and pupae.
• To investigate the physiological mechanisms of cold hardiness in diapausing larvae.
• To assess the impact of low temperatures on developing pupae.

Main Methods:

• Measurement of supercooling points and LT90 (lethal temperature for 90% of individuals) for eggs and larvae.
• Analysis of hemolymph osmolality and glycerol concentrations in diapausing larvae exposed to chilling.
• Observation of sublethal effects in pupae after low-temperature exposure prior to freezing.

Main Results:

• Eggs are freeze-avoidant (supercooling point: -25.8°C); larvae are freeze-tolerant (LT90: -25°C).
• Freeze-tolerant larvae exhibited increased hemolymph osmolality (811 mOsm) and glycerol (232 mM) during chilling.
• Pupae were chill susceptible, experiencing sublethal effects before freezing.

Conclusions:

• Asian longhorned beetle eggs and larvae possess significant cold tolerance, enabling overwintering survival.
• Larval freeze tolerance is mediated by cryoprotectants like glycerol.
• These findings are critical for refining species distribution models and invasive risk assessments.