> Planorbula armigera (Say 1821)

> Habitat & Distribution
Planorbula armigera populations reach maximum abundance in smaller ponds and intermittent lentic habitats including marshes and wetlands, especially associated with submersed macrophytes and decomposing vegetation (Pip 1985, Jokinen 1992, Jokinen 2005, Stewart and Dillon 2004, Stewart 2006). In Canada, Clarke (1979) considered populations of P. armigera to be characteristic of older eutrophic ponds or swamplike ecosystems. The species is found less commonly in streams, rivers, and lakes. Dillon (2000:363) considered Connecticut populations of P. armigera to be R-adapted, typically associated with rich but unpredictable habitats. The species ranges from New Brunswick and James Bay west to Saskatchewan, northwest to the Mackenzie River system, south to Florida and west to Nebraska (Burch 1989, Jokinen 1992).

> Ecology & Life history
Planorbula armigera populations seem adaptable to a variety of water chemistries and have the physiological capability of aestivation if habitats dry (McKillop 1985, Jokinen 1992, Jokinen 2005). Jokinen (1987) considered P. armigera to be a good disperser, and therefore a frequent early colonizer of newly available sites. Like pulmonates generally, the species is monecious and capable of both cross- or self-fertilization. The gelatinous, transparent, colorless and sausage-shaped egg masses contain numerous yellow eggs (Clarke 1981). Populations typically display at least two breeding cycles annually, individuals not living for more than one year (McKillop 1985, Brown 2001). This is life history C or H(s) of Dillon (2000:156 – 162) .

> Taxonomy & Systematics
The classification of the Planorbidae proposed by the tag team of Baker (1945) and Hubendick (1955) remains, after 50 years, the basis for our understanding of this large and diverse family of pulmonates worldwide.  See Essay #2 below.  Synonyms of Planorbula armigera include Planorbella armigera, Planorbis armigera, Planorbis armigerus, Planorbula jenksii, Segmentina armigera, and Segmentina wheatleyi (Stewart and Dillon 2004, Stewart 2006).

> Essay #1
North Carolina populations Planorbula were mentioned in my essay of 17Nov05 on the aerial dispersal of freshwater gastropods.

> Essay #2
The Classification of the Planorbidae.  1 Figure.

> Hubendick (1955)
classification of the Planorbidae, applied to North America.

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



North Carolina (PDF)

>References
Baker, F. C. (1945) The Molluscan Family Planorbidae. Urbana: University of Illinois Press.  Baker, H. B. (1946) Index to F.C. Baker's "The Molluscan Family Planorbidae." Nautilus, 59, 127-41. Brown, K.M. 2001. Mollusca: Gastropoda. In: J.H. Thorp and A.P. Covich, eds., Ecology and Classification of North American Freshwater Invertebrates, Academic Press, New York. Pp. 297-329. Burch, J.B. 1989. North American Freshwater Snails. Malacological Publications, Hamburg, Michigan. Clarke, A.H. 1979. Gastropods as indicators of trophic lake stages. Nautilus 93:138-142. Clarke, A.H. 1981. The Freshwater Molluscs of Canada. National Museum of Natural Sciences, National Museums of Canada, Ottawa, Canada. Dillon, R.T., Jr. 2000. The Ecology of Freshwater Molluscs. Cambridge University Press, Cambridge, United Kingdom.   Hubendick, B. (1955)  Phylogeny in the Planorbidae.  Trans. Zool. Soc. London 28: 453-542.  Jokinen, E.H. 1987. Structure of freshwater snail communities: species-area relationships and incidence categories. Amer Malac Bull 5:9-19. Jokinen, E.H. 1992. The Freshwater Snails (Mollusca: Gastropoda) of New York State. NY State Mus Bull 482, Albany, New York. Jokinen, E.H. 2005. Pond molluscs of Indiana Dunes National Lakeshore: then and now. Amer Malac Bull 20:1-9. McKillop, W.B. 1985. Distribution of aquatic gastropods across the Ordovician dolomite – Precambrian granite contact in southeastern Manitoba, Canada. Can J Zool 63:278-288. Pip, E. 1985. The ecology of freshwater gastropods on the southwestern edge of the Precambrian Shield. Can Field-Nat 99: 76-85. Stewart, T.W., and R.T. Dillon, Jr. 2004. Species composition and geographic distribution of Virginia’s freshwater gastropod fauna: a review using historical records. Amer Malac Bull 19:79-91. Stewart, T.W. 2006. The freshwater gastropods of Iowa (1821-1998): species composition, geographic distributions, and conservation concerns. Amer. Malac. Bull. 21: 59–75.