Alien vs predator play hide and seek: How habitat complexity alters parasite mediated host survival

Abstract

Parasites can greatly affect the behavior of their hosts, influencing how they respond to biotic and abiotic factors within their communities. Some parasites are particularly impactful, causing significant reproductive and behavioral changes in hosts relative to uninfected conspecifics. In eastern North America, a non-native parasitic barnacle, Loxothylacus panopaei (Gissler, 1884), has severe reproductive impacts on native panopeid mud crab hosts, resulting in castration. Moreover, the parasite has been documented to induce significant behavioral changes, such as reducing mud crab activity, influencing predator-prey relationships, and enhancing hiding behaviors in infected host crabs. Yet much remains to be understood regarding the host's ability to escape predators in heterogeneous environments. We investigated the effects of L.panopaei parasitism on mud crab (flatback mud crab, Eurypanopeus depressus (Smith, 1869)) survival in simple versus complex habitats. In lab mesocosm experiments, habitat heterogeneity was manipulated using oysters and gravel, and predatory pressures came from two common predatory crabs in southeast Atlantic estuaries: the Atlantic mud crab, Panopeus herbstii (H. Milne Edwards 1884) and the stone crab, Menippe mercenaria (Say, 1818). We found L.panopaei-infected E. depressus crabs to have the lowest survival rates in the simple gravel habitat, while the crabs with the highest survival were uninfected crabs in the complex oyster habitat. Moreover, we detected differences between uninfected and infected crabs in habitat usage (oyster versus gravel) within the complex habitat. This study demonstrates the complexity of predator-prey dynamics in the face of impactful parasitism and global change, including the introductions of species to new communities where they may have strong impacts on host populations and community interactions.