Sex-specific immune component contribution to Escherichia coli killing ability in Trachemys scripta elegans

Area of Science:

• * Comparative immunology
• * Wildlife physiology
• * Reptile immune systems

Background:

• * Organisms face resource limitations, necessitating trade-offs between physiological processes like reproduction and immunity.
• * The innate immune system, composed of various cells and proteins, has components with potentially unequal costs.
• * Understanding within-immune system trade-offs is crucial for comprehending immune function in variable environments.

Purpose of the Study:

• * To investigate the differential contributions of innate immune components in red-eared slider turtles (Trachemys scripta elegans) during the nesting season.
• * To examine how acute stress (capture) affects these innate immune components.
• * To identify potential sex-specific differences in immune response and resource allocation.

Main Methods:

• * Blood samples were collected from wild turtles at multiple time points post-capture to measure corticosterone levels.
• * Immune components (cells, complement, heat-labile proteins) were systematically removed from serum and buffy layer samples.
• * Functional microbial killing assays using Escherichia coli were performed on manipulated serum+buffy layer samples.

Main Results:

• * Corticosterone levels increased post-capture, confirming a stress response.
• * Complement and heat-labile proteins were upregulated during the acute stress response.
• * Females exhibited a shorter duration of elevated protein-based immunity compared to males.

Conclusions:

• * The innate immune system exhibits trade-offs, with specific components being prioritized under stress.
• * Sex-specific differences in immune response duration suggest females may face greater energetic constraints during the nesting season.
• * This study enhances the understanding of reptile immunity and the physiological costs associated with stress and reproduction.