Freshwater Mussels of Florida

Genus Reginaia

Accounts for Genera and Species 330 Genus Reginaia Campbell and Lydeard 2012 Reginaia was recently described based on a phylogenetic analysis of the genera of the subfamily Ambleminae (Campbell and Lydeard 2012a). They removed three species from Fusconaia and assigned them to Reginaia. Their analysis established the distinctiveness of Reginaia; however, it was not clearly assignable to any recognized tribe within the subfamily Ambleminae (Campbell and Lydeard 2012a). Reginaia is distributed in Mississippi River basin and Gulf Coast rivers from Louisiana to Florida. type Species Unio ebenus Lea 1831 = Reginaia ebenus (Lea 1831) Diagnosis Shell thick; smooth; outline oval to round; umbo moderately to highly inflated, elevated slightly to well above hinge line; umbo sculpture a few weak ridges; posterior ridge rounded; periostracum shiny or dull, brown to black, without rays; pseudocardinal and lateral teeth well developed, 2 in left valve, 1 in right valve; umbo cavity deep; nacre white. Inner lamellae of inner gills only connected to visceral mass anteriorly; excurrent aperture smooth or with crenulations or small papillae; mantle bridge separating excurrent and supra-anal apertures very short or absent; all 4 gills marsupial; glochidia held across entire gill; marsupium not extended beyond original gill margin when gravid; ova and embryos bright pink, becoming white as glochidia mature; glochidium depressed subelliptical, without styliform hooks (Williams et al. 2008; Campbell and Lydeard 2012a). 331 Genus Reginaia Reginaia apalachicola (Williams and Fradkin 1999) Apalachicola ebonyshell Reginaia apalachicola – Upper image: length 34 mm, UF 358659 (left valve only; outside image reversed). Mouth of Omusee Creek [Chattahoochee River,] Omusee Park, Houston County, Alabama. © Richard T. Bryant. Lower image: length 40 mm, UF archaeological collection (left valve only; outside image reversed). Archaeological Site 8LI76, 500 meters east of Apalachicola River (T1N; R8W; SE ¼ Sec. 1) near river mile 88, about 5 miles north of Bristol, Liberty County, Florida. © Richard T. Bryant. Description Size: length to 50 mm. Shell: moderately thick; smooth; compressed; outline round; anterior margin broadly rounded; posterior margin broadly rounded; ventral margin broadly rounded; dorsal margin rounded; posterior ridge rounded, indistinct; posterior slope flat to slightly convex ; umbo broad, moderately inflated, elevated slightly above hinge line; umbo sculpture unknown; umbo cavity moderately wide, deep. teeth: pseudocardinal teeth thick, low, triangular, 2 divergent teeth in left valve, 1 tooth in right valve; lateral teeth short to moderately long, straight to slightly curved, 2 in left valve, 1 in right valve; interdentum short, wide. Accounts for Genera and Species 332 Nacre: unknown. Periostracum: unknown. Glochidium Description The glochidium of Reginaia apalachicola is unknown. Similar Sympatric Species Reginaia apalachicola may resemble young Glebula rotundata but can be distinguished by the presence of a wide interdentum, deep umbo cavity, and pseudocardinal teeth that are thick and triangular, not radially arranged serrate ridges. Distribution in Florida Reginaia apalachicola is known only from Apalachicola River (Figure 10.87). Figure 10.87. Distribution of Reginaia apalachicola. ecology and Biology All archaeological excavations containing Reginaia apalachicola are adjacent to large rivers with moderate current in the Apalachicola basin. Currently, substrates in these rivers consist of a mixture of clay, silty sand, sand and gravel, and occasionally bedrock. Reginaia apalachicola was likely a short-term brooder based on what is known about a related species, Reginaia ebenus. Glochidial hosts for R. apalachicola are unknown . Conservation Status Reginaia apalachicola was recently described and has not been previously evaluated . It was considered to be extinct by Williams and Fradkin (1999) and Williams et al. (in review). 333 Genus Reginaia Remarks Reginaia apalachicola was originally placed in Fusconaia. Phylogenetic analysis of the Pleurobemini by Campbell and Lydeard (2012a, 2012b) recovered a clade containing Fusconaia ebenus and Fusconaia rotulata outside of the remainder of Fusconaia. Based on this, the new genus Reginaia was erected for F. ebenus and F. rotulata. Similarity of apalachicola shell characteristics to the other two Reginaia species led to its placement in the new genus. Based on shell morphology R. apalachicola appears to be most closely related to Reginaia rotulata, an Escambia River basin endemic (Williams et al. 2008). Reginaia apalachicola was apparently endemic to large rivers inApalachicola River basin. In Florida the species is known only from three archaeological sites along Apalachicola River in Gadsden, Jackson, and Liberty counties. Archaeological samples were from the Weeden Island culture period and ranged in age from A.D. 500–1000. There is no reason to believe that R. apalachicola was not extant when Europeans arrived in North America. Extinction of...