The leafy hornmouth is a predatory marine rock snail that is found in the East Pacific Ocean from Sitka (Alaska) to San Diego, where it occurs on rocky faces near bivalves and barnacles (which it feeds on). In British Columbia, it is known from along the BC Coast, including the Queen Charlotte Islands, in the waters around Vancouver Island (including Botanical Beach, Bamfield and many records from the Victoria area), Gibsons and West Vancouver.
The leafy hornmouth shell Ceratostoma foliatum is of special interest because of its predominant varices or flanges. Are these for camouflage, stability, defense, or perhaps other things? After considerable research, mainly at the Bamfield Marine Sciences Centre, British Columbia, there is convincing evidence that the varices play a dual role in the life of the snail. Thus, they act both as destabilising devices to favour aperture-down landings during accidental falls through the water column, and also in providing defense from both shell-crushing crabs and swallowing-type sea stars. For more on Ceratostoma and its varices, go to A SNAIL'S ODYSSEY.
Note Author: Tom Carefoot, Department of Zoology, University of British Columbia.
