Atlantic Dogwhelk

The dog whelk shell is small and rounded with a pointed spire and a short, straight siphonal canal (a groove on the underside of the shell) and a deep anal canal. The overall shell shape varies quite widely according to the degree of exposure to wave action of the shore on which a particular population lives but the body whorl (the largest section of the shell where the majority of the visceral mass is located) is usually around 3/4 of the total length of the shell. The aperture is usually crenulated in mature dog whelks, less often in juveniles.

The shell surface can be fairly smooth interrupted only with growth lines, or when the snail is living in more sheltered areas the shell surface can be somewhat rough and lamellose. The surface is spirally corded. The outer lip is dentate and ridged within. The columella is smooth.

This species is found around the coasts of Europe and in the northern west Atlantic coast of North America. It also can be found in estuarine waters along the Atlantic coasts. This species prefers rocky shores, where it eats mussels and acorn barnacles.

Its adaptations include a modified radula (a toothed chitinous structure) to bore holes in the shells of prey, complemented by an organ on the foot which secretes a shell-softening chemical. When a hole has been formed paralysing chemicals and digestive enzymes are secreted inside the shell to break the soft body down into a 'soup' which can be sucked out with the proboscis. The plates of barnacles can be pushed apart with the proboscis, and the entire individual is eaten in about a day, although larger animals such as mussels may take up to a week to digest.

The dog whelk lives on rocky shores, and in estuarine conditions. Climatically it lives between the 0 °C and 20 °C isotherms.

Predators of the dog whelk include various species of crabs and birds. Protection against predation from crabs which attempt to pull the soft body out through the shell aperture can be afforded by growing teeth around the edge of the aperture. Many predators cannot smash the strong shell of an adult dog whelk, but juveniles are vulnerable to attack from many predatory species. Eider ducks and various other birds simply swallow the entire body with its shell, while oystercatchers and various crustaceans are often capable of crushing or breaking the shells. In the winter they endure more predation from purple sandpipers and similar wading birds, but in the summer crabs represent a greater threat. In general, the dog whelk can be thought of as being vulnerable to birds when emersed, and to crabs when immersed.

The dog-whelk can be used to produce red-purple and violet dyes, like its Mediterranean relations the spiny dye-murex Bolinus brandaris, the banded dye-murex Hexaplex trunculus and the rock-shell Stramonita haemastoma which provided the red-purple and violet colours that the Ancient World valued so highly. Bede mentions that in Britain "whelks are abundant, and a beautiful scarlet dye is extracted from them which remains unfaded by sunshine or rain; indeed, the older the cloth, the more beautiful its colour."