Sinistral, deeply biconcave, shells, whorls strongly keeled at whorl shoulder with a flat spire in juveniles but whorls become more rounded and spire becomes sunken in adults. Umbilicus deep and funnel-like. Animal brown to reddish with a strongly mottled mantle and thin tentacles.
The distinct angle on the top of the whorl (particularly in juveniles) and deeper, overlapping whorls distinguish this species from the similar Planorbarius corneus which is generally flatter and with a more open whorl spiral. The spire whorls are also flatter in Planorbella duryi.
Planorbella duryi (Wetherby, 1879)
Common name: Seminole Rams Horn
Original name: Planorbis (Helisoma) duryi Wetherby, 1879. Wetherby, A. G. 1879. Notes on some new or little known American Limnaeidae. Journal of the Cincinatti Society of Natural History 2: 93-100.
Type locality: Florida, USA.
On water weeds etc. in aquaria and small ponds in urban areas. On water weeds etc., in ponds, swamps and aquaria in urban areas. Feed on algae and detritus. Egg mass a jelly strip containing small eggs. Development direct.
Introduced from North America to a few scattered localities near urban centres around Australia, most likely from aquaria.
This species is often referred to as Helisomia duryi. It is encountered in the aquarium trade and has established in a few ponds in urban centres around Australia.
Kershaw (1991) suggested this species may be Helisoma anceps. The distinct angle on the top of the whorl (particularly in juveniles) and deeper, overlapping whorls distinguish this species from Planorbarius which is generally flatter and with a more open whorl spiral.
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Beesley, P. L., Ross, G. J. B. & Wells, A., Eds. (1998). Mollusca: The Southern Synthesis. Parts A & B. Melbourne, CSIRO Publishing.
Hubendick, B. (1955). Phylogeny in the Planorbidae. Transactions of the Zoological Society of London 28: 453-542.
Iredale, T. (1943). A basic list of the fresh water Mollusca of Australia. Australian Zoologist 10: 188-230.
Iredale, T. (1944a). Guide to the freshwater shells of New South Wales. Part 2. Australian Naturalist (Sydney) 11: 113–127.
Kershaw, R. C. (1991). Snail and Slug Pests of Tasmania, Queen Victoria Museum and Art Gallery.
Ng, T.H., Tan, S.K., Wong, W.H., Meier, R., Chan, S-Y., Tan, H.H. and Yeo, D.C.J. 2016. Molluscs for Sale: Assessment of Freshwater Gastropods and Bivalves in the Ornamental Pet Trade. PLOS One. DOI:10.1371/journal.pone.0161130.
Smith, B. J. and Kershaw, R. C. (1979). Field guide to the non-marine molluscs of south eastern Australia. Australian National University Press, Canberra, Australia.
Smith, B. J. & Kershaw, R. C. (1981). Tasmanian Land and Freshwater Molluscs. Hobart, University of Tasmania.