A NEW SPECIES OF THELOHANELLUS KUDO, 1933 (MYXOZOA: BIVALVULIDA) INFECTING SKELETAL MUSCLE OF BLACKTAIL SHINER, CYPRINELLA VENUSTA GIRARD, 1856 (CYPRINIFORMES: CYPRINIDAE) IN THE CHATTAHOOCHEE RIVER BASIN, GEORGIA, USA.

Thelohanellus magnacysta n. sp. (Bivalvulida: Myxobolidae) infects the skeletal muscle of blacktail shiner, Cyprinella venusta Girard, 1856 (Cypriniformes: Cyprinidae) in Bull Creek, Chattahoochee River Basin, eastern Georgia. Although numerous members of Thelohanellus Kudo, 1933 have overlapping myxospore dimensions with the new species, it differs from all nominal congeners by polar filament coil number and polar capsule width as well as by lacking a mucous envelope, iodinophilic vacuole, and sutural markings. Using novel primers for Myxozoa, a phylogenetic analysis of the small subunit ribosomal DNA (SSU rDNA) suggests that the new species shares a recent common ancestor with a clade of cyprinid-infecting species of Myxobolus Butschli, 1882 (Bivalvulida: Myxobolidae) and Thelohanellus . In addition, and consistent with other published research concerning the systematics of Thelohanellus , this result suggested that Thelohanellus and Myxobolus are polyphyletic and need revision. Histological sections of infected blacktail shiners confirmed that myxospores were only found within a plasmodium and only infected skeletal muscle and that plasmodia were encapsulated by a granuloma comprising varying degrees of acute granulomatous inflammation. The new species is the fourth of Thelohanellus reported from North America and first reported from Cyprinella as well as the first myxozoan described from the blacktail shiner.