Non‐native parasite enhances susceptibility of host to native predators



Parasites often alter host physiology and behavior, which can enhance predation risk for infected hosts. Higher consumption of parasitized prey can in turn lead to a less parasitized prey population (the healthy herd hypothesis). Loxothylacus panopaei is a non-native castrating barnacle parasite on the mud crab Eurypanopeus depressus along the Atlantic coast. Through prey choice mesocosm experiments and a eld tethering experiment, Jeb Byers and his team investigated whether the predatory crab Callinectes sapidus and other predators preferentially feed on E. depressus infected with L. panopaei. He found that C. sapidus preferentially consumed infected E. depressus 3 to 1 over visibly uninfected E. depressus in the mesocosm experiments. Similarly, infected E. depressus were consumed 1.2 to 1 over uninfected conspeci cs in eld tethering trials. He evaluated a mechanism behind this skewed prey choice, specically whether L. panopaei affects E. depressus movement, making infected prey more vulnerable to predator attack. Counter to his expectations, infected E. depressus ran faster during laboratory trials than uninfected E. depressus, suggesting that quick movement may not decrease predation risk and seems instead to make the prey more vulnerable. Ultimately, the preferential consumption of L.panopaei-infected prey by C. sapidus highlights how interactions between organisms could affect where novel parasites are able to thrive.