Whelks are a diverse group of carnivorous sea snails, recognized by their distinct swirling, tapered shells. These marine gastropods inhabit a wide range of aquatic environments globally, from shallow intertidal zones to the depths of the ocean. Whelks are active predators and scavengers within these ecosystems.
Primary Food Sources
Whelks are predominantly carnivorous, preying on marine invertebrates. Their diet frequently includes bivalves such as clams, oysters, and mussels. Beyond bivalves, whelks also consume other sea snails, barnacles, crustaceans, and marine worms like polychaetes.
Many whelk species also function as opportunistic scavengers. For instance, the common whelk often includes polychaete worms in its diet, which can constitute a significant portion of its stomach contents. Whelks possess a keen sense of smell, utilizing chemoreceptors and a siphon to detect the presence of prey or carrion in the water, allowing them to locate food sources efficiently.
How Whelks Consume Their Prey
Whelks employ specialized anatomical features and complex behaviors to access their food. A key tool is their proboscis, a tube-like mouthpart, which houses a rasping organ called the radula. The radula is a chitinous ribbon equipped with rows of teeth, functioning like a drill or scraper.
To penetrate the protective shells of their bivalve prey, many whelks secrete an acidic substance from an accessory boring organ (ABO) located on their foot. This chemical secretion softens the shell material, allowing the radula to effectively scrape away loosened particles. Once a hole is drilled, the whelk injects digestive enzymes that liquefy the prey’s soft tissues, which are then consumed by sucking out the resulting “soup.” Some whelks also use the muscular foot to hold prey securely or even wedge the lip of their own shell between the valves of a bivalve to pry it open.
Dietary Variations Among Whelk Species
The diet of whelks can vary considerably among different species, influenced by their specific habitats, the availability of prey, and unique physical adaptations.
The common whelk (Buccinum undatum) is an active predator and scavenger, consuming bivalves, crustaceans, other molluscs, and sea urchins. It also attacks fish caught in nets. In contrast, the lightning whelk (Busycon contrarium or Sinistrofulgur perversum), prevalent in the North American Atlantic, primarily feeds on bivalves such as oysters, clams, and scallops. This species can forcibly pry open bivalve shells using its own shell lip or grind through them to reach the soft body inside.
The dog whelk (Nucella lapillus), commonly found on rocky shores, mainly preys on mussels and barnacles, but also consumes periwinkles and cockles. Dog whelks utilize both chemical secretions and drilling to access their prey. They tend to avoid dense mussel beds, where the mussels’ byssus threads can trap them, leading to starvation.