N35 2013 Southeastern Naturalist Notes Vol. 12, No. X J.S. Tiemann, W.R. Posey, K.S. Cummings, K.J. Irwin, and B. Turner First Occurrences of Lithasia armigera and Lithasia verrucosa (Gastropoda: Pleuroceridae) in the Mississippi River Jeremy S. Tiemann1,*, William R. Posey2, Kevin S. Cummings3, Kelly J. Irwin4, and Bryan Turner5 Abstract - Lithasia armigera (Armored Rocksnail) historically occurred in the Cumberland, Ohio, and Tennessee river drainages of eastern North America, whereas Lithasia verrucosa (Verrucose Rocksnail) is known from the Ohio, Tennessee, and Black river drainages. Prior to our 24–27 September 2012 surveys, neither species had been recorded from the Mississippi River. We discovered Armored Rocksnail near the Mississippi River–Missouri River confluence in the St. Louis metropolitan area, and both Armored Rocksnail and Verrucose Rocksnail 5 linear miles east-northeast of Osceola, AR. Freshwater snails are an understudied group, and basic information on species distribution is not well documented (Brown et al. 2008, Lynse et al. 2008). In addition, some aquatic gastropods are microhabitat specialists with highly patchy distributions, and populations are scattered among the mosaic of microhabitats created by flow regimes and sediment types (Strong et al. 2008). We began investigating the status of gastropods in Illinois and Arkansas by conducting literature reviews, examining museum collections, and qualitatively collecting snails throughout both states. We conducted independent freshwater mollusk surveys in the Mississippi River on 24–27 September 2012. The historically low water levels in the middle and lower sections the Mississippi River (e.g., between its confluences with the Missouri and Ohio rivers, and downstream of its confluence with the Ohio River, respectively) allowed us to search for aquatic mollusks in many areas of the river that were previously inaccessible. The results of our surveys yielded two rocksnail species (Gastropoda: Pleuroceridae) that had not been previously documented in the Mississippi River mainstem: Lithasia armigera (Say) (Armored Rocksnail) and Lithasia verrucosa (Rafinesque) (Verrucose Rocksnail). We deposited specimens collected as part of the surveys in the Illinois Natural History Survey (INHS) Mollusk Collection, Champaign, IL . Armored Rocksnail is historically known from the Cumberland, Ohio, and Tennessee river drainages of eastern North America (Burch 1989, Goodrich 1940, Minton et al. 2005). Specifically, the snail has been recorded from the Ohio River; lower Wabash River; Cumberland River upstream of Burnside, Pulaski County, KY, to streams in Trigg County, KY; and the Tennessee River in the vicinity of Florence, Lauderdale County, AL (Fig. 1). Armored Rocksnail is typically found in sandy gravel areas, on cobble rip-rap, or on woody debris (authors’ pers. observ.). Johnson et al. (2013) recently assessed the conservation status of North American freshwater snails and ranked Armored Rocksnail as vulnerable (a species that is imminently likely to become threatened throughout all or a significant portion of its range). We here report Armored Rocksnail at two locations in the Mississippi River: 1) near its confluence with the Missouri River in the St. Louis metropolitan area, and 2) near Osceola, AR. The Illinois population was found on rip-rap throughout a five-mile stretch of the Mississippi River in Madison County, from river mile 195, across from its confluence with the Missouri River at Lewis and Clark State Memorial Park, 1 linear mile 1Illinois Natural History Survey, Prairie Research Institute at the University of Illinois, 1816 South Oak Street, Champaign, IL 61820. 2Arkansas Game and Fish Commission, PO Box 6740, Perrytown, AR 71801. 3Illinois Natural History Survey, Prairie Research Institute at the University of Illinois, 1816 South Oak Street, Champaign, IL 61820. 4Arkansas Game and Fish Commission, 915 Sevier Street, Benton, AR 72015. 5St. Louis Community College, Florissant Valley, 3400 Pershall Road, Ferguson, MO 63135. *Corresponding author - jtiemann@illinois.edu. Notes of the Southeastern Naturalist, Issue 12/4, 2013 2013 Southeastern Naturalist Notes Vol. 12, No. X N36 J.S. Tiemann, W.R. Posey, K.S. Cummings, K.J. Irwin, and B. Turner upstream of the Chain of Rocks Canal entrance (38.80529°N, 90.11574°W; INHS #43832), to river mile 189.5, the first wing-dam downstream of the Chain of Rocks dam (38.74756°N, 90.17827°W; INHS #43861) by J.S. Tiemann, K.S. Cummings, and B. Turner. Snail densitities were less than 5 individuals/m2, except for on the boulders in Chain of Rocks dam at river mile 190.3 (38.75596°N, 90.17205°W; INHS #43859), where density was about 100 individuals/ m2. We failed to find Armored Rocksnail at 27 sites in the Mississippi River between river mile 184.5, at the end of Gabaret Island, Madison County (38.68976°N, 90.19269°W) to the river’s confluence with the Ohio River at Fort Defiance State Park near Cairo, Alexander County (36.98308°N, 89.13912°W). We also failed to find the snail upstream of river mile 195 to Lock and Dam 26 (38.86582°N, 90.14231°W). The Arkansas population of Armored Rocksnail was found in the Mississippi River at river mile 791, along Kate Aubrey Towhead, 5.5 linear miles east-northeast of Osceola, Mississippi County, AR (35.74404°N, 89.87894°W; INHS #43433) by W.R. Posey and K.J. Irwin. Unlike the Illinois specimens, the Arkansas specimens were all empty shells found on a gravel bar in concentrated, wave-swept piles along the water’s edge. The nearest documented population of Armored Rocksnail to the newly discovered Illinois and Arkansas sites occurs in the Ohio River at river mile 974, Mound City, Pulaski County, IL (37.07804°N, 89.16529°W; INHS #32727; Tieman et al. 2011), which is a distance of 197 river miles from the Illinois population near St. Louis, and 169 river miles from the Arkansas population (noting that the Mississippi River’s mile markers change at its confluence with the Ohio River). Figure 1. Distribution map of Lithasia armigera. Two new locations on Mississippi River are indicated with a star. N37 2013 Southeastern Naturalist Notes Vol. 12, No. X J.S. Tiemann, W.R. Posey, K.S. Cummings, K.J. Irwin, and B. Turner Verrucose Rocksnail is historically known from the Ohio, Tennessee, and Black river drainages of North America (Burch 1989, Goodrich 1940, Minton and Lydeard 2003). Specifically, the snail has been recorded from the Ohio River; lower Wabash River; Tennessee River from eastern Tennessee to Marshall County, KY; and Black and Spring rivers, AK (Fig. 2). As with the Armored Rocksnail, the Verrucose Rocksnail is typically found in sandy gravel areas, on cobble rip-rap, or on woody debris (authors’ pers. observ.). Johnson et al. (2013) ranked Verrucose Rocksnail as currently stable (species populations not currently at risk). Empty shells of Verrucose Rocksnail were found with Armored Rocksnail in concentrated, wave-swept piles along the water’s edge of a gravel bar in the Mississippi River at river mile 791, along Kate Aubrey Towhead, 5.5 linear miles east-northeast of Osceola, Mississippi County, AR (35.74404°N, 89.87894°W; INHS #43434) by W.R. Posey and K.J. Irwin. Although the Black River population is closer in terms of linear distance (approximately 70 miles), in terms of river miles, the nearest documented population of Verrucose Rocksnail occurs in the Ohio River at Mound City (INHS #32728; Tiemann et al. 2011), which is a distance of 169 river miles. Minton and Lydeard (2003) suggested that Verrucose Rocksnails from the Black River drainage, in Arkansas, are genetically distinct from the lower Ohio River populations. Neither Armored Rocksnail nor Verrucose Rocksnail had been documented in the Mississippi River mainstem prior to our survey (e.g., Baker 1906, 1928; Burch 1989; Dawley 1947; Goodrich 1939; Stewart 2006; Wu et al. 1997). It is beyond the scope of our study Figure 2. Distribution map of Lithasia verrucosa. New location on the Mississippi River is indicated with star. 2013 Southeastern Naturalist Notes Vol. 12, No. X N38 J.S. Tiemann, W.R. Posey, K.S. Cummings, K.J. Irwin, and B. Turner to determine if these populations are native or introduced. Given the distance to the next known population, these Mississippi River populations could represent unique genetic stocks. Future studies could utilize other methods (e.g., trawling or diving) to assess the snail populations in the middle and lower Mississippi River, and examine genetics to determine the origin of the populations (e.g., Hayes et al. 2007). Acknowledgments. Funds were provided in part by a grant from the Illinois Department of Natural Resources’ Wildlife Preservation Fund (#13-031W) and the Illinois Department of Transportation, Springfield, IL. B. Dabney, H. Dunn, S.M. Jaworski, B. Lubinski, J.E. Petzing, and D. Shasteen assisted in collecting Illinois specimens, and J. Harris assisted in collecting Arkansas specimens. J.L. Sherwood assisted in map creation. A.J. Baldinger, the Museum of Comparative Zoology, Cambridge, MA; P. Callomon, the Academy of Natural Sciences of Drexel University, Philadelphia, PA; D.Ó. Foighil, the University of Michigan Museum of Zoology, Ann Arbor, MI; J. Gerber, Field Museum of Natural History, Chicago, IL; T. Pearce, the Carnegie Museum of Natural History, Pittsburgh, PA; D. Roberts, Chicago Academy of Science, Chicago, IL; J. Slapcinsky, the University of Florida Museum of Natural History, Gainesville, FL; and G.T. 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