> Ferrissia fragilis (Tryon 1863)

> Habitat & Distribution
F. fragilis ranges throughout North America, from Florida and Texas to southern Canada.  It is common in calmer waters of the southern Atlantic Piedmont and Coastal Plain, on vegetation and woody debris.

> Ecology & Life history
Like all freshwater limpets, the diet of F. fragilis seems to be especially high in diatoms (Blinn et al 1989).   Jokinen (1985) reported three generations per year for an F. fragilis population in Connecticut (Life cycle Esis).  The statewide distribution of F. fragilis in Connecticut reported by Jokinen (1983) suggested to Dillon (2000: 360-363) that the species might show Stress-tolerant life history adaptation.

> Taxonomy & Systematics
Ferrissia hendersoni is a synonym, according to Basch.  Nor am I altogether convinced that F. fragilis is specifically distinct from F. rivularis.  The shell of F. fragilis is indeed thinner than that of F. rivularis, but shell thickness could easily result from a phenotypically plastic response to current speed or substrate type (Russell-Hunter et al. 1967).  A population genetic survey to cast additional light on this question would be especially welcome.

American Ferrissia fragilis has apparently been introduced into Europe and east Asia, where it has been given a variety of genus and species names, including F. wautieri and F. clessiniana (Walther et al. 2006). 

> Maps of Ferrissia distribution
Click the small map to enlarge it, or download the state-specific PDFs



North Carolina (PDF)

South Carolina (PDF)

Georgia (PDF)

> References
Basch, P. (1963)  A review of the recent freshwater limpet snails of North America. Bull. Mus. Comp. Zool. Harvard, 129, 399-461.  Blinn, D., R. Truitt, & A. Pickart. (1989)  Feeding ecology and radular morphology of the freshwater limpet Ferrissia fragilis. J. N. Am. Bentho. Soc., 8: 237-242.  Dillon, R. T., Jr. (2000)  The Ecology of Freshwater Molluscs.  Cambridge University Press, United Kingdom.  509 pp.  Hubendick, B. (1964) Studies on Ancylidae, The subgroups.  Meddelanden Fran Goteborgs Musei Zoologiska Avendelining, 137.  (Goteborgs Kungl. Vetenskaps-Och Vitterhets-Samhalles Handlingar.  Sjatte Foljden. Ser. B.) 9, 1-72  Jokinen, E.  (1983)  The freshwater snails of Connecticut. Hartford, Connecticut, State Geol. Nat. Hist. Survey Bull. 109. 83 p.  Jokinen, E.  (1985)  Comparative life history patterns within a littoral zone snail community. Verh. Internat. Verein, Limnol., 22: 3292-3399.  Walther, A. C., T. Lee, J. B. Burch, and D. O'Foighil (2006)  Confirmation that the North American ancylid Ferrissia fragilis (Tryon 1863) is a cryptic invader of European and East Asian freshwater ecosystems.  J. Moll. Stud. 72: 318 - 321.