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Banff Springs snail

Banff Springs snail
Banff snail.jpg
Physella johnsoni
Scientific classification
Kingdom: Animalia
Phylum: Mollusca
Class: Gastropoda
(unranked): clade Heterobranchia
clade Euthyneura
clade Panpulmonata
clade Hygrophila
Superfamily: Planorboidea
Family: Physidae
Subfamily: Physinae
Tribe: Physellini
Genus: Physella
Species: P. johnsoni
Binomial name
Physella johnsoni
(Clench, 1926)

The Banff Springs snail (Physella johnsoni) is a species of small air-breathing freshwater snail in the family Physidae.

Based on molecular research, it appears that Physella johnsoni separated out as a species from Physella gyrina about 10,000 years ago.

These aquatic pulmonate gastropod mollusks are approximately the size of unpopped corn kernels. The largest ones are only about one centimetre long, and like all of the Physidae, the shells are sinistral or coiled left-handed. The snails' diet consists of periphyton.

The Banff Springs snail was first identified in 1926 in the nine sulphurous hot springs of Sulphur Mountain in Banff National Park, Alberta, Canada, and has been found nowhere else. It is very unusual because it is adapted to life in thermal springs where the water is low in oxygen and high in hydrogen sulfide, an environment too harsh for most animals to survive in. Since its discovery, its range has shrunk to just five of the nine hot springs.

The reduction in Banff Spring snail population and range is likely attributable to human use of the hot springs, although fluctuating water temperature is also a factor. In April 1997 it became the first living mollusc to be placed on Canada's national list of species at risk. In 2000 it was classified as endangered by COSEWIC and the Canadian Species at Risk Act listed it in the List of Wildlife Species at Risk as being endangered in Canada.


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