Prevalence of the invasive Rhizocephalan parasite Loxothylacus panopaei in Eurypanopeus depressus in South Carolina and genetic relationships of the parasite in North and South Carolina.

The rhizocephalan barnacle Loxothylacus panopaei is a parasitic castrator of xanthid crabs that has invaded the U.S. Atlantic coast. It was transported to the Chesapeake Bay in the mid-1960s with mud crabs associated with Gulf coast oysters and has since spread north to Long Island Sound, New York, and south to Cape Canaveral, Florida. Here we report parasite prevalence at 3 South Carolina sites--2 from which the parasite had not been previously reported--and examine the genetic relationships of North and South Carolina L. panopaei populations relative to Gulf of Mexico and other Atlantic coast parasite populations. Total L. panopaei prevalence was 24.2% among all 3 sites, with monthly prevalence as high as 51.6% at Waties Island, South Carolina. Sequence analyses of North and South Carolina specimens revealed the presence of 4 cytochrome c oxidase subunit I haplotypes--3 commonly found in other invasive populations and 1 new haplotype found in a single specimen from the Rachel Carson Reserve in Carteret County, North Carolina--and indicate that the Carolina populations are a result of range expansion from the original Atlantic coast invasion.