HOSTS MANIPULATED BY ONE PARASITE INCUR ADDITIONAL COSTS FROM INFECTION BY ANOTHER PARASITE

Manipulation of host phenotype by parasites often serves to increase t he predation rate of definitive hosts on intermediate hosts. For inter mediate hosts, the indirect consequences of manipulation may extend be yond the direct increase in predation, however. Metacercariae of the t rematode Curtuteria australis encyst in the foot of New Zealand cockle s, Austrovenus stutchburyl, and stunt its growth, rendering cockles in capable of burrowing into the sediments. Here, we show that cockles ma nipulated by C. australis are 5 times more likely to be infected by th e castrating sporocysts of another trematode than normal, nonmanipulat ed cockles. Our results indicate that the consequences for C. australi s-manipulated cockles are far more important than a simple increase in the risk of predation and that indirect repercussions of manipulation can be as severe as direct ones.