When less means more: dehydration improves innate immunity in rattlesnakes

Area of Science:

• Physiological Ecology
• Immunology
• Herpetology

Background:

• Immune function is often studied in relation to energy resources, with limited focus on water's role.
• Water limitation can alter physiological processes, potentially affecting immune responses.
• Seasonal water availability varies greatly for species like the western diamond-backed rattlesnake (Crotalus atrox).

Purpose of the Study:

• To investigate the relationship between hydration status and immunocompetence in Crotalus atrox.
• To determine if dehydration affects innate immune function.
• To understand the impact of seasonal water fluctuations on snake immunity.

Main Methods:

• Field study: Collected blood samples from free-ranging Crotalus atrox across different seasons (spring, hot-dry, hot-wet).
• Laboratory study: Experimentally dehydrated Crotalus atrox for up to 16 weeks, monitoring blood osmolality and immune function.
• Measured innate immune parameters: lysis, agglutination, and bacterial growth inhibition.

Main Results:

• Crotalus atrox experienced significant dehydration during the hot-dry season.
• Innate immune function in Crotalus atrox was strongly correlated with osmolality.
• Both natural dehydration and experimentally induced dehydration affected immune function.

Conclusions:

• Hydration state is a critical factor influencing innate immune function in Crotalus atrox.
• Dehydration, whether seasonal or experimental, compromises immune defenses.
• Future research should consider water balance when assessing immune function in vertebrates.