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Acroloxus coloradensis (J. Henderson, 1930)
Rocky Mountain Capshell
Family: Acroloxidae


© Hugh Clifford     (Photo ID #10976)


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Distribution of Acroloxus coloradensis in British Columbia in British Columbia

Species Information

The Rocky Mountain capshell is a a tiny species of freshwater limpet (gastropod). It has a flat, brown shell, 5 mm in length, 2.7 mm wide. The apex of the shell is pointed backwards, and to the left (dextral). Shell sculpture includes both radial striae and growth lines (Anderson 2005).


This species is tolerant of a wide temperature range (Anderson 2005). Like other types of limpets, this species moves as it grazes using its muscular foot. This species grazes on algae. According to Anderson (2005), this species “lays yellowish egg masses of two to three eggs (Clarke 1970). Individual eggs measure approximately 1 mm (0.039 in) long and 0.5 mm (0.02 in) wide (Clarke 1970)”.


In the US, this species is found in cold boreal lakes with rocky substrate (Anderson 2005). In BC, it has been found on several substrates, including the undersides of rocks in shallow water, submerged wood, decaying (cattail) leaves (Lee and Ackerman 2000). It has also been found in slow-moving rivers (Anderson 2005).


Global Distribution

This is the only species of the family Acroloxidae found in North America. It exhibits a disjunct distribution in North America, which may represent rarity or relictual populations. ( Lee and Ackerman 2000). As of 2000, there were 14 reported stations for it in Canada, with nine records reported from Canada (BC, Alberta, Ontario, Quebec).
Distribution in British Columbia

This species is found only in the east-central region of the province. It is known from Purden Lake, Shane Lake (Prince George), Carp Lake, Gataiga Lake, Babine Lake pond, Topley rest area pond, and Decker Lake.

Status Information

Origin StatusProvincial StatusBC List
(Red Blue List)
NativeS3S4BlueNAR (Nov 2001)

BC Ministry of Environment: BC Species and Ecosystems Explorer--the authoritative source for conservation information in British Columbia.

Additional Range and Status Information Links

Species References

Anderson, Tamara. 2005. Rocky Mountain Capshell Snail (Acroloxus coloradensis): A Technical Conservation Assessment. Prepared for the USDA Forest Service, Rocky Mountain Region, Species Conservation Project.

Lee, Jacqueline and Josef Daniel Ackerman. 2000. IN L. M. Darling, editor. 2000. Proceedings of a Conference on the Biology and Management of Species and Habitats at Risk, Kamloops, B.C., 15 - 19 Feb.,1999. Volume One. B.C. Ministry of Environment, Lands and Parks, Victoria, B.C. and University College of the Cariboo, Kamloops, B.C. 490pp.

Aquatic invertebrates of Alberta online guide.

General References