knobbed whelk, busycon carica

Knobbed Whelk – Busycon Carica

By far the most common whelk found on our beach is the knobbed whelk, busycon carica. Live whelks can be found in the tidepools on the front beach at low tide, cruising the silty shallows for clams and other prey. They can force the edge of their foot between the shells of gastropods and then use a radula (tooth-like tongue) to eat away at the prey. Whelk shells can be found in many stages of deconstruction, and they provide habitat for large numbers of other sea creatures. Their egg cases frequently wash ashore in the tide wrack. The snail lays the eggs in the sandy substrate, where they are anchored at one end. There are many tiny snails in each capsule, which may cannibalize each other before emerging through the central hole. Knobbed whelks are similar to channeled whelks and lightning whelks. Channeled whelks don’t have knobbed protrusions on the shell, and lightning whelks open to the left side.

knobbed whelk, busycon carica, Dewees Island
The operculum can close the shell to keep the snail safer from predators. Live whelks can be found on the island at low tide.

knobbed whelk, busycon carica, in tidepool

egg case of knobbed whelk, buyscon carica
knobbed whelk egg case

Twice a year, in September/October and April/May, when the water reaches about 68 degrees fahrenheit, the snails lay strings of eggs in the sand.  The first few capsules serve as anchors in the sand and do not include eggs. The string will likely have 35 eggs per capsule and about 100 capsules per string.   The eggs develop slowly, hatching in 3-13 months.  At least one scientific source  describes them as protandric hermaphrodites: they start off as males when small and change into females as they grow and age.

Whelks feed on bivalves like oysters, clams, and incongruous arks.

busycon carica with thin striped hermit crab
Hermit crabs can move in after the snail dies


knobbed whelk shell that has been engulfed by boring sponge and encrusting bryozoan

busycon carica

In his lovely book of essays about growing up in the Lowcountry, Porcher’s Creek: Lives Between the Tides
John Leland surmises that the local Native Americans (the Sewee and those who preceded them) dined on whelks (which he calls conchs) by drilling through the top and removing the snails.

To read more, try the following books:
Life along the Inner Coast: A Naturalist’s Guide to the Sounds, Inlets, Rivers, and Intracoastal Waterway from Norfolk to Key West, p.169

Tideland Treasure, p.104

Living Beaches of Georgia and the Carolinas, p.90-91

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