Meeting Abstract
In most host-parasite systems it would be difficult or impossible to decouple the cost of parasite reproduction from the cost of the parasites presence within its host. However, rhizocephalans have a stage within their reproductive cycle, the virgin externa, which decouples infection from reproduction. The virgin externa is produced by a female parasite that has developed an internal network of tissue but is not yet reproductively mature. The virgin externa must have a male parasite recruit, and then it matures into a reproductive externa. Most infections are perpetrated by a single parasite with a single externa, but multiple externa are found. Multiple externa can either be a single interna with multiple reproductive organs or two interna each with its own externa. Either will lead to an increase in reproductive burden. I examined survival rate of crabs parasitized with either a virgin externa, a reproductive single externa, or a double externa of the rhizocephalan Loxothylacus panopaei which infects the mud crab Eurypanopeus depressus in Savannah, Georgia. Crabs were exposed to a range of temperature experienced in the field; 5, 10, 15, 20, 25, 30 and 35° C for 110 days. Parasite and host mortality occurred simultaneously for each parasitized crab. Double externa had significantly lower survival rates at extreme temperatures. There was high survival at intermediate temperatures, but double externa still had a trend towards lower survival. Surprisingly, there was no significant difference in survival rate between the immature virgin externa and mature single infections at any temperature. This suggests that the increase in mortality at extreme temperatures is driven by the mere physical presence of the parasite within the host.
