Figure 1.

Hypothesized and predicted relationships among mercury concentrations, body condition, active infection and antibody detection. Dashed blue arrows represent negative relationships between variables and solid orange arrows represent positive relationships. Grey ovals are variables that are important mechanistically but were not measured directly in this study. In pathway A, MeHg immunotoxicity compromises the innate immune response to infection, leading to a higher probability of active infection, more antibody production and an increased probability of antibody detection. In B, MeHg immunotoxicity compromises the adaptive immune response, reducing antibody detection but increasing the probability of active infection. In C, MeHg toxicity reduces host body condition, reducing the energy available to mount an immune response and increasing infection probabilities. In pathway D, MeHg toxicity reduces host body condition, altering physiologic conditions for viral replication and decreasing the probabilities of both active infection and antibody detection. Feedbacks complicate these relationships, including disease-induced reductions in body condition following influenza infection and effects of body condition on MeHg concentrations (due to concentrating of body MeHg with mass loss). (Online version in colour.)