Dogwhelk, Atlantic dogwinkle
The dog whelk, dogwhelk, or Atlantic dogwinkle (Nucella lapillus ) is a species of predatory sea snail, a carnivorous marine gastropod in the family Muricidae, the rock snails.
Nucella lapillus was originally described by Carl Linnaeus in his landmark 1758 10th edition of Systema Naturae as Buccinum lapillus (the basionym).
"Dog whelk" can also refer to the Nassariidae.
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.
The external shell colour is usually a whitish grey, but can be a wide variety of orange, yellow, brown, black, or banded with any combination of these colours. They can even, occasionally, be green, blue, or pink.
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.
The dog whelk lives on rocky shores, and in estuarine conditions. Climatically it lives between the 0 °C and 20 °C isotherms.
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.
Feeding only occurs when conditions are conducive to such an activity, and during these times the dog whelk consumes large quantities of food so that the gut is always kept as full as possible. This allows shelter until more food is required, when foraging resumes. If waves are large or there is an excessive risk of water loss the dog whelk will remain inactive in sheltered locations for long periods.
Mussels have developed a defensive strategy of tethering and immobilising with byssus threads any dog whelks invading their beds, leading to the whelks' starvation.
