ZOMBIE HIDE & SEEK: INVASIVE PARASITE’S INFLUENCE ON HOST PREDATORY HIDING BEHAVIOR IN MUD CRABS

Abstract

Parasites are known to affect behavior and physiology of hosts, influencing how hosts interact with biotic and abiotic factors of the community. An invasive castrating parasitic barnacle, Loxothylacus panopaei (L. panopaei), has been documented to alter the behavior of its host, and is adapted to infect panopeid (mud) crabs. These crabs are important food sources for several commercial fisheries, includinghake, white catfish, blue crabs, and stone crabs. L. panopaei infection has been found to reduce mud crab activity, causing indirect effects on predator-prey relationships, and it has also been found to increase hiding behaviors in infected versus uninfected host crabs. The purpose of my research was to determine how salinity and temporal gradients influenced L. panopaei parasitism in this ecologically-important group of native mud crabs in North Carolina estuaries. Collected crabs were sub-sampled and examined for external and internal parasites, most notably L. panopaei, using a compound microscope. Overall and species-specific parasite prevalence were recorded and analyzed across salinity and temporal gradients. Behavior of infected versus uninfected crabs was observed in the presence of predatory pressures in different habitats to determine how the parasites affect the hosts’ behavior. Simple and complex habitat variables were manipulated using oysters and gravel, and predatory pressures came from two larger native predatory crabs (the Atlantic mud crab and the stone crab). Increasing salinity was found to correlate with a general increase in infection prevalence. Furthermore, L. panopaei-infected crabs had lower survival rates than uninfected crabs in simple habitats and were found to prefer hiding in oyster as opposed to gravel. Research on L. panopaei can also tell us more about a related barnacle, Loxothylacus texanus that infects the blue crab. Future studies aim to compare behavioral differences between “feminized” L. panopaei male crabs and gravid female crabs, and explore relationships between habitat and salinity.