Ecological factors mediate immunity and parasitic co-infection in sea fan octocorals

The interplay among environment, demography, and host-parasite interactions is a challenging frontier. In the ocean, fundamental changes are occurring due to anthropogenic pressures, including increased disease outbreaks on coral reefs. These outbreaks often include multiple parasites, calling into question how coral immunity functions in this complex milieu. Corals provide an interesting model to study ecological immunity during co-infection, being highly sensitive to environmental change, susceptible to many diseases, and defended by the innate immune system. Our work investigates the interplay of factors influencing coral co-infection using metrics of the innate immune response: levels of cellular immunity and the expression of candidate immune genes. We used existing copepod infections and live pathogen inoculation with Aspergillus fungus to test the effect of sequential co-infections in a laboratory experiment. We profile significant increases in the expression of the immune recogn...