Acanthocephalans from crabs in the southeastern U.S., with the first intermediate hosts known for Arhythmorhynchus frassoni and Hexaglandula corynosoma.

Cystacanths of Hexaglandula corynosoma were discovered in the fiddler crabs Uca spinicarpa and Uca rapax collected in Mississippi and Florida. Adults were present in yellow-crowned night herons, Nyctanassa violacea, collected in Florida. Cystacanths are very similar to adults, varying only in size and state of development. This is the first record of H. corynosoma from the United States and the first record of an intermediate host for any species of the genus. Cystacanths of Arhythmorhynchus frassoni were present in U. rapax from Florida. The proboscis size, shape, and armature of the cystacanths are identical to those of adults from clapper rails (Rallus longirostris) collected in several southeastern states. This is the first report of an intermediate host for A. frassoni. Profilicollis altmani cystacanths were collected from mole crabs (Emerita talpoida) at Atlantic Beach, North Carolina. These specimens, together with adults obtained from shore birds in Louisiana and Mississippi, are consistent with the view that P. altmani, Profilicollis kenti, and Profilicollis texensis are synonyms, with P. altmani having nomenclatural priority.