Freshwater Mussels of Florida

Genus Ptychobranchus

Accounts for Genera and Species 308 Genus Ptychobranchus Simpson 1900 Five species were recognized in Ptychobranchus by Turgeon et al. (1998). An additional species, Ptychobranchus foremanianus, from the eastern portion of the Mobile basin was elevated from synonymy by Williams et al. (2008), bringing the total recognized species in the genus to six. Ptychobranchus jonesi was described as a species of Lampsilis where it remained until a gravid female was examined, and the unique folded outer gill (Figure 10.77) was observed, confirming its placement in Ptychobranchus (Fuller and Bereza 1973). Ptychobranchus is found in Mississippi River and Great Lakes basins and eastern Gulf Coast rivers from Louisiana to Florida. Conglutinates produced by gravid females of Ptychobranchus are interesting mimics of insect larvae, fish eggs, and fish larvae (Hartfield and Hartfield 1996; Watters 1999). The same species are known to produce multiple types of conglutinates (Hartfield and Hartfield 1996; Haag and Warren 1997; Watters 1999). type Species Unio phaseolus Hildreth 1828 = Ptychobranchus fasciolaris (Rafinesque 1820) Diagnosis Shell moderately thin to moderately thick; smooth; outline elliptical to triangular; female shell with oblique depression internally; male and female shells very similar externally, sexual dimorphism very subtle to nonexistent; periostracum shiny to dull; pseudocardinal and lateral teeth typically thick, 2 in left valve, 1 in right valve; umbo cavity very shallow. Inner lamellae of inner gills completely connected to visceral mass or connected only anteriorly; mantle margin weakly modified ventral to incurrent aperture; mantle bridge separating supra-anal and excurrent apertures short; outer gills marsupial; entire marsupium developed into short parallel folds (Figure 10.77), extended beyond original gill margin when gravid; glochidia held in ventral portion of gill; conglutinates variable, in form of insect larvae, fish eggs, or fish larvae; glochidium outline subspatulate to subelliptical, without styliform hooks (Simpson 1900a, 1914; Ortmann 1912; Hartfield and Hartfield 1996; Watters 1999). Figure 10.77. Ptychobranchus foremanianus gravid female. Note folded outer marsupial gill. Photograph by James D. Williams. 309 Genus Ptychobranchus Ptychobranchus jonesi (van der Schalie 1934) Southern Kidneyshell Ptychobranchus jonesi – Upper image: length 61 mm, UF 65567. Conecuh River, Bozeman’s Landing near Crenshaw County line, Covington County, Alabama, 1 July 1915. © Richard T. Bryant. Middle image: length 52 mm, ANSP 139374 (paratype). Pea River, Andrew’s Fish Trap, Barbour County, Alabama, November 1915. Photograph by James D. Williams . Lower image: length 34 mm, UMMZ 234878. Yellow River at State Highway 55, 7 miles northwest of Lockhart, Covington County, Alabama, 28 October 1963. © Richard T. Bryant. Description Size: length to 72 mm, in Florida to 55 mm. Shell: moderately thin; smooth; moderately inflated, width 30%–40% of length; outline elongate oval; anterior margin rounded; posterior margin narrowly rounded; dorsal margin straight to slightly convex; ventral margin straight to slightly convex; posterior ridge triangulate, prominent dorsally, with slight radial depression between ridges; posterior slope moderately steep, flat to slightly convex; umbo broad, elevated slightly above hinge line; umbo sculpture moderately thick ridges; umbo cavity wide, shallow. teeth: pseudocardinal teeth low, triangular, 2 divergent teeth in left valve, anterior tooth moderately compressed, crest almost parallel to shell margin, 1 tooth in right valve; lateral teeth moderately long, straight, 2 in left valve, 1 in right valve; interdentum moderately long, narrow. Nacre: bluish white. Accounts for Genera and Species 310 Periostracum: typically shiny, occasionally dull; small individuals greenish yellow to olive, occasionally with faint green rays, large individuals olive brown to black, obscuring rays. Glochidium Description Outline subspatulate; length 155–163 µm; height 191–212 µm; width 98–126 µm (Figure 10.78). Figure 10.78. Scanning electron micrographs of glochidial valves of Ptychobranchus jonesi from West Fork Choctawhatchee River, Blue Springs State Park, Barbour County, Alabama, April 2007—(A) external view; (B) surface sculpture ; (C) lateral view; and (D) internal view. Similar Sympatric Species Ptychobranchus jonesi most closely resembles Hamiota australis but is more inflated , has a more rounded posterior margin, and the ventral margin is typically straighter. Also, the posterior ridge of P. jonesi is typically triangulate distally with a shallow radial sulcus between the ridges. Gravid individuals of P. jonesi have swollen and folded outer gills, while the marsupia of Hamiota are swollen but not folded. Ptychobranchus jonesi may resemble Elliptio pullata but is typically much more inflated, has a more rounded posterior margin, and posterior ridge that is typically triangulate distally with a shallow radial sulcus between the ridges. 311 Genus Ptychobranchus Distribution in Florida Ptychobranchus jonesi occurs in Choctawhatchee...