Tag Archives: BC

Crepidula convexa

Crepidula convexa; Boundary Bay, BC.

Crepidula convexa (Say, 1824) is a northwest Atlantic slipper-snail long known to be introduced in San Francisco Bay. This marine snail species arrived on the West Coast by accident, having been transported with Eastern Oysters, Crassostrea virginica (Gmelin, 1791) (Hanna 1966). I found this species for the first time in Boundary Bay, British Columbia, in 1984, southern Strait of Georgia, British Columbia, although its first appearance in BC must have been many years prior when Eastern Oysters were being “planted” in the Bay for the commercial oyster industry.

The native range is Atlantic Canada to Georgia (Colin 2002).

Crepidula convexa is polymorphic: the shell varies considerably in colour. Many shells are creamy white or light brown with darker reddish brown spots and streaks. Others are solid purplish brown or grayish brown with darker spots that are not always clearly evident. Shell form varies as well, depending upon the substrate to which the animal was attached. Larger, oval shells (such as shown here) come from stones and other relatively flat surfaces. Narrowed, higher examples live on snail shells. In Boundary Bay living Batillaria atramentosa (G.B. Sowerby II, 1855) are often infested with C. convexa. Diminutive individuals live on eelgrass (Zostera marina).

  • Collin R (2002) Another last word on Crepidula convexa with a description of U. ustulatulina n. sp. (Gastropoda: Calyptraeidae) from the Gulf of Mexico and southern Florida. Bulletin of Marine Science 70: 177–184.
  • Hanna GD (1966) Introduced mollusks of western North America. Occasional Papers of the California Academy of Sciences (Series 4) 48: 1–108, pls 1–4.

Aegopinella nitidula

Aegopinella nitidula; Queen Elizabeth Park, Vancouver, BC (diameter: 7.2 mm).

Aegopinella nitidula (Draparnaud, 1805) is yet another terrestrial land snail introduced into Canada. This species, which bears some resemblance to the also introduced species of Oxychilus, was first noticed in BC (and North America) by myself and friends around the Vancouver area. Since then, I am unaware of any finds outside of this regions. It would be of interest to learn of additional occurrences anywhere in the region, or beyond. Oddly, no one has yet to find it elsewhere in Canada or the USA.

Further reading:

Forsyth RG, Hutchinson JMC, Reise H (2001) Aegopinella nitidula (Draparnaud, 1805) (Gastropoda: Zonitidae) in British Columbia—first confirmed North American record. American Malacological Bulletin 16: 65–69. PDF here.