What constrains the geographic and host range of the rhizocephalan Loxothylacus texanus in the wild?

Abstract

In the Gulf of Mexico, the rhizocephalan barnacle Loxothylacus texanus parasitizes members of the genus Callinectes. In the past, research has primarily focused on the interaction between L. texanus and its blue crab host Callinectes sapidus. Only recently investigators have begun to examine the association that this parasite shares with other Gulf of Mexico hosts and little is known about interactions outside of the Gulf of Mexico. In the current study, settlement of L. texanus on a variety of potential hosts was examined. Settlement of L. texanus occurred not only on C. sapidus but also on the congener Callinectes similis, the grapsid Sesarma cinereum and the xanthid Rhithropanopeus harrisii collected from the Gulf of Mexico. L. texanus also settled on C. sapidus from Delaware Bay and Callinectes ornatus from Brazil. A carbohydrate-based cue appears to be the trigger for settlement in all cases. These results suggest that larval settlement may not play as important a role in determining host specificity as is often assumed. In fact, this type of nonspecific settlement may over evolutionary time lead to establishment of the parasite on new host species. Other factors such as physical barriers and immune response may aid in the control of such parasitic infections.