How do fleas tolerate cold? - briefly
Fleas survive low temperatures by entering a dormant diapause and synthesizing cryoprotectant compounds that depress the freezing point of their body fluids. They also remain on insulated hosts or within protected microhabitats until warmth returns.
How do fleas tolerate cold? - in detail
Fleas survive low temperatures through a combination of physiological adaptations, behavioral strategies, and life‑stage timing.
Physiological mechanisms
- Production of cryoprotectant compounds such as glycerol and trehalose, which lower the freezing point of body fluids and stabilize cellular membranes.
- Up‑regulation of heat‑shock proteins that refold denatured proteins and prevent aggregation under cold stress.
- Alteration of membrane lipid composition, increasing unsaturated fatty acids to maintain fluidity at reduced temperatures.
Behavioral responses
- Migration to insulated microhabitats: adult fleas seek cracks, bedding, or animal fur where temperature fluctuations are dampened.
- Aggregation within host nests or burrows, creating a communal microclimate that remains above lethal thresholds.
- Reduced activity levels, entering a state of torpor that conserves energy and minimizes exposure to freezing conditions.
Life‑stage adaptation
- Eggs and pupae exhibit greater cold tolerance than adults; pupal cocoons contain a silken matrix that insulates developing insects.
- Developmental arrest (diapause) may be induced by photoperiod cues, halting progression until ambient temperature rises.
- Seasonal timing ensures that the most vulnerable stages coincide with the warmest periods, while more resilient stages persist through winter.
Environmental factors influencing survival
- Relative humidity: higher moisture levels facilitate glycerol synthesis and reduce desiccation risk, enhancing cold resilience.
- Substrate temperature: contact with warm surfaces (e.g., mammalian hosts) can offset ambient cold, allowing adult fleas to remain active.
- Presence of antifreeze proteins in some flea species, which bind to ice crystals and inhibit growth, further protecting tissues.
Collectively, these biochemical, behavioral, and developmental tactics enable fleas to endure temperatures that would otherwise be lethal, ensuring population persistence across seasonal cycles.