> Ferrissia rivularis (Say 1817)

>Habitat & Distribution
F. rivularis ranges throughout North America, being found attached to rocks, cobbles, macrophytes, leaves, woody debris, pop bottles and beer cans in rivers, streams, and northern lakes.  It seems to require well-oxygenated water, and is especially characteristic of low-nutrient streams with good water quality.  In the southern Atlantic drainage it does not occur in swamps or lentic environments generally, seeming to require at least low levels of flow.

> Ecology & Life history
This little limpet was one of the most herbivorous of the macrobenthos studied by Coffmann (1971) dining almost entirely upon diatoms (Blinn et al. 1989).  It shows great variation in life cycle, Burky (1971) reporting a simple annual life cycle in one population and two generations per year in a second.  Jokinen (1985) reported three generations per year for a Ferrissia population in Connecticut (Life cycle Esis).  Generation times of less than six weeks have been documented in the laboratory (Dillon & Herman 2009).  

The statewide distribution of Ferrissia in Connecticut reported by Jokinen (1983) suggested to Dillon (2000: 360-363) that the species might show Stress-tolerant life history adaptation.  But both of Burky’s populations posted reproductive efforts in line with their adult sizes, suggesting that they are Undifferentiated in their life history strategy (Dillon 2000: 126-135).

The allozyme data of Dillon & Herman (2009) suggest that Ferrissia populations may be obligately self-fertilizing.  Self fertilization has been well-documented in the European freshwater limpet Ancylus fluviatilis (Stadler et al. 1995).

> Taxonomy & Systematics
Basch (1963) recognized five species in the genus Ferrissia - F. rivularis from stones, F. fragilis from vegetation and organic debris in flowing water, F. parallela on narrow-bladed plants in lentic environments, F. walkeri on broad-leaved plants in lentic environments, and F. mcneilli endemic to Alabama.  Walther (pers. comm.) combined these taxa into two lineages, broadly correlated with the rivularis and fragilis morphologies and life habits, on the basis of DNA sequence data.  Dillon & Herman (2009) reported that all the morphological criteria by which fragilis and rivularis have been distinguished seem to be the result of ecophenotypic plasticity (Russell-Hunter et al. 1967), unifying all the American Ferrissia under the single nomen F. rivularis.  See Essay #1 below.

American Ferrissia  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).


> Essay #1
I reviewed the research findings of Dillon & Herman suggesting that North America is inhabited by just a single species of Ferrissia on 10Jun09.  The essay includes a couple nice figures and a PDF download of the paper.

> 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.   Burky, A. (1971)  Biomass turnover, respiration, and interpopulation variation in the stream limpet Ferrissia rivularis (Say). Ecol. Monog., 41: 235-251.  Coffman, W. (1971)  Energy flow in a woodland stream ecosystem: I. Tissue support trophic structure of the autumnal community. Arch. Hydrobiol., 68: 232-276.  Dillon, R. T., Jr. (2000)  The Ecology of Freshwater Molluscs.  Cambridge University Press, United Kingdom.  509 pp.  Dillon, R. T., & J. J. Herman (2009)  Genetics, shell morphology, and life history of the freshwatear pulmonate limpets Ferrissia rivularis and Ferrissia fragilis.  J. Freshwat. Ecol. 24: 261 - 271.  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.   Keating, S.T. & Prezant, R.S. (1998)  Effects of stream chemistry on the distribution, growth, and diatom colonization of the freshwater limpet, Ferrissia rivularis.  J. Freshwat. Ecol. 13: 67-77.  Russell-Hunter, W.D., M. L. Apley, A. J. Burky, & R. T. Meadows (1967)  Interpopulation variations in calcium metabolism in the stream limpet, Ferrissia rivularis (Say)  Science 155: 338-340.  Russell-Hunter, W.D., Burky, A.J. & Russell-Hunter, R.D. (1981)  Interpopulaton Variation in Calcareous and Proteinaceous Shell Components in the Stream Limpet, Ferrissia rivularis.  Malacologia 20: 255-266.  Stadler, T., S. Weisner, & B. Streit (1995) Outcrossing rates and correlated matings in a predominantly selfing freshwater snail.  Proc. R. Soc. Lond. B 262: 119-125.   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.