Channeled Whelk and Knobbed Whelk
Whelks are large marine snails (gastropods) with spiral shells. Whelks are often confused with Conchs- both are large marine snails similar in appearance. However, conchs live in warm tropical water and are herbivores that feed on vegetation and whelks live in more temperate waters and are carnivores whose diet is mostly meat. The Knobbed Whelk is the official state shell of NJ. Most whelks (as well as most snails) are right handed or dextral. If the shell is held upright, with the spire up and the aperture facing the observer, then the aperture is on the right side. The opposite, much less common, condition is sinistral, in which the aperture is on the left of the central axis.
Whelks are subtidal animals, meaning they live only below the low tidemark in sandy or muddy bottoms because their operculum does not tightly seal the opening of the shell so it cannot survive being exposed to the air as some intertidal animals (like mussels) can.
When hunting prey, they travel along the bay bottom using their strong foot and use their nose (or proboscis) to find these buried animals by sensing the stream of water flowing out of the clam’s feeding tubes. Once its prey is located the whelk digs down into the bay bottom to capture it. Whelks use their shell’s lip to chip and pry the valves of bivalves (clams) apart by holding it with its foot so that the ventral edges of the prey’s valves are under the outer lip of the whelk’s shell. This is similar to using a clam knife to shuck (open) a hard clam. Slow chipping continues until an opening occurs to allow the whelk to wedge its shell between the clam’s valves.When there is sufficient room, it extends its proboscis (with mouth at the end) to begin feeding. Another method of getting at a food source (especially if the victim is not a bivalve) is that once the prey is immobilized, the whelk extends its proboscis which is equipped with a mouth and a tooth-like radula at the end. The whelk has a gland that secretes a chemical that softens calcium carbonate so the radula can efficiently be used to bore a hole in the shell of the prey. When the drilling process is completed, the whelk extends its proboscis into the prey and begins feeding.
Whelks reproduce by sexual reproduction with internal fertilization. Some, like the channeled and knobbed whelk, produce a string of egg capsules that may be 2-3 feet long, and each capsule has 20-100 eggs inside which hatch into miniature whelks. The egg capsule allows the young whelk embryos to develop and provides protection. Once they have developed, the eggs hatch inside the capsule, and the juvenile whelks leave via an opening.
Whelks grow by using their mantle to produce calcium carbonate to extend their shell around a central axis or columella, producing turns, or whorls, as they grow. A whorl is each spiral of the shell. The final whorl, and usually the largest, is the body whorl that terminates, providing the aperture into which the snail can withdraw.
One of the whelks natural predators are the blue crab. They are also a popular human food and are often caught as bi-catch in the fisheries industry and are collected for the sea shell trade.