Low temperature thresholds: are chill coma and CT(min) synonymous?

Area of Science:

• Insect physiology and behavior
• Low-temperature ecophysiology
• Insect cold hardiness

Background:

• Sub-lethal low temperatures significantly impact insect foraging, mating, and survival.
• Understanding insect responses to cold is crucial for predicting species distribution and climate change impacts.
• Current research faces challenges due to inconsistent terminology for temperature thresholds and physiological responses.

Purpose of the Study:

• To review and clarify the nomenclature and physiological basis of insect responses to low temperatures.
• To elucidate the correct sequence of behavioral and physiological responses to cold exposure.
• To propose standardized terminology for insect chill coma and associated temperature thresholds.

Main Methods:

• Literature review of studies on insect cold tolerance and chill coma.
• Analysis of physiological and electrophysiological data related to low-temperature responses.
• Comparison of terminology used in insect and vertebrate cold physiology research.

Main Results:

• Chill coma is a reversible state defined by absent electrophysiological activity.
• The onset of chill coma involves a sequence of thresholds: cessation of movement, loss of coordination, and entry into coma.
• Confusion arises from the varied use of 'onset of chill coma' and the adoption of vertebrate terminology (CT(min)).

Conclusions:

• Standardized terminology is essential for accurate interpretation of insect cold stress research.
• Clear definitions of physiological and behavioral thresholds improve our understanding of insect cold tolerance.
• Adopting a consistent nomenclature will enhance future research on insect responses to climate change.