Subsidies of essential nutrients from aquatic environments correlate with immune function in terrestrial consumers

Subsidies across aquatic-terrestrial boundaries can alter consumer distributions and physiology. The importance of subsidies is a function of export quantity and of their physiological significance and relative scarcity in the recipient system. Aquatically derived long-chain polyunsaturated fatty acids (LC-PUFAs) are physiologically essential, relatively rare in terrestrial habitats, and can enhance immune function. We explored fatty-acid profiles and immune function of Tigrosa georgicola wolf spiders in wetland and upland habitats. Wetland spiders had higher tissue levels of aquatically derived LC-PUFAs and elevated immune function (measured as encapsulation of parasites) compared to upland spiders. Whether increased encapsulation activity translates into greater survival is unclear, but our results suggest that aquatically derived nutrients, such as LC-PUFAs, may benefit organisms exploiting freshwater habitats. Furthermore, these patterns suggest that such aquatic-terrestrial subsidies may shape parasite-host interactions in surrounding ecological communities.