> Habitat & Distribution

Baker (1911) gave the range of L. catascopium (together with 20 - 30 synonyms) as extending through Eastern Canada, west to North Dakota, and south to northern Ohio and Maryland.  And indeed, museum collections do confirm that L. catascopium was at one time common in the Delaware River at Philadelphia (its type locality), extending through Maryland to the vicinity of Washington, DC.  But today L. catascopium is very rarely recorded below the glacial maximum, at the approximate latitude of New York City.  The species is peripheral in our 15-state study area, FWGNA incidence rank I-3p.

Populations of L. catascopium seem to reach maximum abundance on the firm (often rocky) bottoms of large, permanent, northern lakes, at depths as great as 6 – 9 m in some cases (Laman et al 1984).  They can also be found in larger rivers, typically on rocks and organic debris, again usually at some depth.  Until quite recently, conventional wisdom held that populations of L. catascopium are not characteristic of swamps, marshes, ponds or ephemeral habitats, nor typical of shallow, muddy or organic bottoms.  But research on the "cryptic stagnicoline" populations of NW Pennsylvania (Brady & Turner 2010), together with the thesis work of Flowers (2013) has revolutionized our understanding of the biology of this enigmatic lymnaeid group in North America.  See my essay of 3Sept15 from the link below for more.

> Ecology & Life History

Given its propensity for solid substrates, one might not be surprised by the findings of Aloi & Bronmark (1991) that L. catascopium is an effective grazer on periphyton.  Lymnaea catascopium was the most common species in Baker’s (1918) samples from the diverse bottom types of Oneida Lake, NY, as analyzed by Dillon (1981).  The reanalysis of Dillon (2000: 417-419) suggested that a significant positive association between L. catascopium, Gyraulus parvus, and Marstonia lustrica may account for the striking community structure demonstrated by that remarkable fauna.

The five populations of L. catascopium studied by Pinel-Alloul and Magnin (1979) included three demonstrating a simple annual life cycle (type A of Dillon 2000: 156-162) and two populations with two generations per year (type Bis).

> Taxonomy & Systematics

Basommatophoran gastropods of the worldwide family Lymnaeidae are characterized by striking conchological diversity but anatomical uniformity.  The mounting evidence that much of the shell morphological variation upon which lymnaeid systematics have been based seems to arise from ecophenotypic plasticity (e.g., Bronmark et al. 2011, 2012, Terry & Duda 2021) has led to a great deal of taxonomic churn.

Thomas Say described Lymnaeus catascopium in 1817 a few years earlier than his L. elodes, stating as he did that catascopium “inhabits the Delaware River and many other waters of the United States” (see my post of 14July15 below).  F. C. Baker (1911) collected the pale, fat “stagnicoline” populations of lakes and rivers into a “Group of catascopium” with 12 taxa and a “Group of emarginata” with 19 taxa.  Hubendick (1951) lumped all 31 of these nomina (except arctica) under either catascopium or emarginata, but could not bring himself to synonymize the two guidepost species, even though he could find “no features distinctly separating” them.  

Both Baker and Hubendick preserved the distinction between pale, obesely-shelled stagnicoline populations of lakes and rivers and the dark, slender-shelled populations of vernal ponds and swamps.  But Walter (1969) had no such scruples, lumping all the New World stagnicolines, including both the slender elodes-types of ponds and marshes and the fat catascopium-types of lakes under the single nomen L. catascopium.

Burch (1989) reverted to a modification of the Baker (1911) system, recognizing 16 species in his “Stagnicola emarginata/catascopium group,” including the two guidepost species as well as 14 others of a more regional character.  Modern molecular phylogenies seem to support the Walter (1969) viewpoint, however, generally failing to return much genetic divergence among any of the nominal stagnicoline taxa of North America.  Intriguingly, molecular studies also seem to support Walter’s suggestion of a connection between New World stagnicoline populations and populations identified as L. occulta in Eastern Europe or L. tarebra in Russia (Correa et al. 2010).  See my essays of 23Apr12 and 4June12 from links below for more.

Most recently, the observations of Brady & Turner (2010), together with the MS thesis of Flowers (2013) and the phenotypic plasticity studies of Terry & Duda (2021), have supported a a two-species model for the North American stagnicolines, best identified as L. elodes and L. catascopium.  Populations of both species seem to bear pale, fat shells in large lakes and dark, slender shells in vernal ponds.  See my essay of 3Sept15 for more.

> Maps and Supplementary Resources

• Lymnaea catascopium distribution in Atlantic drainages (2023)
• Lymnaeid distribution in the drainages of The Ohio (2019)
• Although bearing dark, slender shells, Brady & Turner's "V2" stagnicoline population from Hartstown Marsh seems best identified as L. catascopium.  See 10May12 & 3Sept15 below.
  

> Essays

• See my post to the FWGNA blog of 28Dec06 for a review of The Classification of the Lymnaeidae.
• The taxonomy of the Old World stagnicoline lymnaeids has long been entangled with that of the New.  In my post of 23Apr12 I reviewed the work of Jackiewicz and others on the cryptic species of Lymnaea palustris, and the light this research may shed on the evolutionary relationships of the North American stagnicoline fauna in general.  See “The Lymnaeidae 2012: Tales of L. occulta.”
• See my post of 10May12 for a review of some largely unpublished (but nevertheless fascinating) observations on the shell morphology of marsh-dwelling lymnaeid populations from NW Pennsylvania, “The Lymnaeidae 2012: Tales from the cryptic stagnicolines.”  One of these populations (called V2 by Brady & Turner 2010) ultimately proved (in 2013) to be a population of L. catascopium bearing the dark, slender shell morphology associated with L. elodes.  See my essay of 3Sept15 from the link below for more.
• On 9July12 I reviewed a paper by Bronmark and colleagues (2011) offering a marvelous insight into shell phenotypic variance of the sort I had just featured on 10May12: “The Lymnaeidae 2012: A clue.”
• As of 4June12 a stack of 21 molecular phylogenetic studies of the Lymnaeidae worldwide had accumulated on my desk.  Here’s my effort to make sense of it all: “The Lymnaeidae 2012: Stagnalis yardstick.”
• See my post of 26Sept14 for good, comparative figures illustrating "The egg masses of freshwater pulmonate snails."
• See my post of 14July15 for an exciting expedition up the 19th-century Delaware River in search of "The type locality of Lymnaea catascopium."
• And on 29July15 I described a second (much milder) adventure, hunting The Type Locality of Lymnaea emarginata up in Maine.  Say's emarginata (1821) is almost certainly a synonym of his catascopium (1817).   This particular essay featured a scan of Say's lovely (1830ish) figure comparing the shell morphology of both species.
• On 3Sept15 I reviewed The Lost Thesis of Samantha Flowers, at long last bringing a bit of clarity to the tangled systematics of the North American stagnicoline lymnaeids, if you have the patience to wade through it.

> References

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Baker, F. 1911. The Lymnaeidae of North and Middle America, Recent and Fossil. Special Publication No. 3., Chicago: Chicago Academy of Natural Sciences.
Baker, F. 1918. The Productivity of Invertebrate Fish Food on the Bottom of Oneida Lake, NY, with Special Reference to Mollusks. Technical Publication 9. NY State College of Forestry, Syracuse. 264p.
Bovbjerg, R. 1968. Responses to food in lymnaeid snails. Phys. Zool. 41: 412-423.
Brady, J. K & A. M. Turner 2010.  Species-specific effects of gastropods on leaf litter processing in pond mesocosms.  Hydrobiologia 651: 93-100.
Bronmark, C., T. Lakowitz, and J. Hollander. 2011. Predator-induced morphological plasticity across local populations of a freshwater snail. PLoS ONE 6(7): e21773.
Bronmark, C., T. Lakowitz, P. Nilson, J. Ahlgren, C. Lennartsdotter, and J. Hollander. 2012. Costs of inducible defense along a resource gradient. PLoS One 7(1): e30467.
Burch, J. B. 1989.  North American Freshwater Snails.  Malacological Publications, Hamburg, MI.  365 pp.
Clarke, A. H.  1981.  The Freshwater Molluscs of Canada.  Ottawa: National Museums of Canada.  445 pp.  
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Cuker, B. 1983b. Competition and coexistence among the grazing snail Lymnaea, Chironomidae, and microcrustacea in an arctic epilithic lacustrine community. Ecology 64: 10-15.
Dillon, R. T., Jr. 1981. Patterns in the morphology and distribution of gastropods in Oneida Lake, NY, detected using computer-generated null hypotheses. Amer. Natur. 118: 83-101.
Dillon, R. T., Jr. 2000.  The Ecology of Freshwater Molluscs.  Cambridge University Press 509 pp.
Flowers, S. L. 2013.  Inferences into species delimitation of Nearctic Stagnicola (Gastropoda: Lymnaeidae) using geometric morphometric and phylogenetic methods.  M.Sc. Thesis, University of Michigan, Ann Arbor.
Hershey, A. 1990. Snail populations in artic lakes: competition mediated by predation? Oecologia 82: 26-32.
Hershey, A. 1992. Effects of experimental fertilization on the benthic macroinvertebrate community of an arctic lake. J. NABS 11: 204-217.
Hubendick, B. 1951. Recent Lymnaeidae.  Their variation, morphology, taxonomy, nomenclature, and distribution. Kungl. Svenska Vetensk. Akad. Handl., 3, 1-223.  
Hunter, R. 1975. Growth, fecundity, and bioenergetics in three populations of Lymnaea palustris from upstate New York. Ecology 56: 50-63.
Jokinen, E. 1983. The Freshwater Snails of Connecticut. State Geol. Nat. Hist. Survey Bull. 109, Hartford, Connecticut. 83 p.
Laman, T., N. Boss, and H. Blankespoor. 1984. Depth distribution of seven species of gastropods in Douglas Lake, Michigan. Nautilus 98: 20-24.
Lodge, D., M. Kershner, J. Aloi, and A. Covich. 1994. Effects of an omnivorous crayfish (Orconectes rusticus) on a freshwater littoral food web. Ecology 75: 1265-1281.
Pinel-Alloul, B. & E. Magnin. 1979.  Cycle de developpement, croissance et fecondite de cinq populations de Lymnaea catascopium catascopium (Gastropoda, Lymnaeidae) au Lac Saint-Louis, Quebec, Canada.  Malacologia 19: 87-101.
Terry, C.H. and T.F. Duda 2021.  Consequences of captive-rearing and exposure to cures from potential predators on shell sizes and shapes of North American stagnicoline gastropods (Family Lymnaeidae).  American Malacological Bulletin 38: 1 - 9.
van der Schalie, H., and E. Berry. 1973. The effects of temperature on growth and reproduction of aquatic snails. Sterkiana 50: 1-92.
Walter, H. 1969. Illustrated biomorphology of the "angulata" lake form of the basommatophoran snail Lymnaea catascopium Say. Malacological Review 2: 1-102.