Freshwater Mussels of Florida

Pyganodon cataracta

Species of Hypothetical Occurrence 400 Pyganodon cataracta (Say 1817) eastern Floater Pyganodon cataracta – Length 105 mm, UF 359783. Lake Marion, Santee National Wildlife Refuge, Clarendon County, South Carolina, 7 October 2002. Photograph by James D. Williams. Description Size: length to 170 mm. Shell: thin to moderately thick; smooth; inflated, width usually 30%–45% of length; outline oval to elliptical; anterior margin rounded; posterior margin rounded; dorsal margin straight to slightly convex; ventral margin straight to slightly convex; posterior ridge rounded; posterior slope moderately steep dorsally, flat to slightly concave; umbo broad, inflated, elevated above hinge line; umbo sculpture moderately thick, double-looped, nodulous ridges; umbo cavity moderately wide, deep. teeth: pseudocardinal and lateral teeth absent; hinge often thickened posterior to umbo. Nacre: white to bluish white, occasionally with pinkish tint in umbo cavity. Periostracum: small individuals shiny, large individuals dull to clothlike; small individuals yellowish to greenish brown, occasionally with green rays, large individuals yellowish brown to dark brown. General Distribution Pyganodon cataracta is native to the Atlantic Coast basins of North America, ranging from the St. Lawrence River, Canada, south to the Altamaha River, Georgia (Johnson 1970). In Gulf Coast basins, Pyganodon cataracta was reported in Apalachicola River in Alabama, Florida, and Georgia (Brim Box and Williams 2000) and a reservoir on Tallapoosa River in Alabama, which appears to be a recent introduction (Williams et al. 2008). Habitat Pyganodon cataracta inhabits creeks, rivers, ponds, lakes, and reservoirs. It is usually found in backwater areas with little or no current but can also be found along stream banks in sheltered areas in moderate current in mud, sandy mud, sand, and occasionally gravel substrates. Species of Hypothetical Occurrence 401 Reasons for Inclusion Pyganodon cataracta was reported from Apalachicola River in Florida by Brim Box and Williams (2000) based on shell morphology of specimens used in a genetic analysis from reservoirs in Georgia. There are no reliable differences in shell morphology that distinguish P. cataracta from Pyganodon grandis. Samples from Apalachicola and Chipola Rivers exhibited shell morphology that graded imperceptibly between the extremes of the two species (Brim Box and Williams 2000). The Apalachicola basin P. cataracta populations may have resulted from introduction of glochidia-infested host fishes (e.g., Morone saxatilis) from an Atlantic Coast reservoir. An introduced population of Pyganodon cataracta was discovered in the Suwannee River basin in 2002 in Warrior Creek, a tributary of Withlacoochee River (northern), Colquitt County, Georgia, and appears to be recruiting. ...