Wondrous Whelks: From Case to Creature

By Katharine Hart, Summer 2024 Intern

Whelk shell and egg case side by side

At first glance, the long spiraling case of a Whelk, a common find on the shores of beach accesses like the Shoals here on Bald Head, may not stand out as an island treasure. However, the external stack of yellow disks does not yet reveal the impressive intricacies inside. At BHI Conservancy’s NC Coastal Explorers program, participants use scissors and digital microscopes to uncover the case’s residents: hundreds of tiny, unhatched Whelk eggs.

Protoconchs next to a whelk egg case. If you look closely, you can see more protonochs inside the egg case!

Whelks are sizable marine snails that lay up to one hundred eggs in each small pouch of their egg case spiral, producing up to thirty inches of casing. When laying eggs, a mother Whelk will anchor one end of the case to the ocean floor to ensure that it stays wet and does not come ashore. The embryonic fluid inside the pouches sustains the eggs until they develop into protoconches (the first stage of whelk development), at which point the young Whelks crawl out of their cases.

Protoconch and adult whelk size comparison.

Unlike hermit crabs, a whelk does not search for a shell; it grows one. Whelks grow radially, widening their shell by adding self-produced calcium carbonate around the shell’s center. They can grow up to sixteen inches in width, and as they expand, they produce spirals called whorls. A close look at a whelk reveals the lines on its shells, representative of how much a whelk grows in a season (wider lines correspond to more growth). One might expect that a whelk’s size represents its age, but rather, it indicates its appetite: hungrier whelks are larger. This carnivorous organism particularly enjoys eating clams, consuming its meals with its sharp, tongue-like radula (different from us, whelks have no need for chewing!).

Knobbed whelks like this one will fit on your right hand with your palm facing toward you. If it fits on your left hand, it’s a lightning whelk!

There are multiple species of Whelks to find around Bald Head Island. You can identify lightning whelks by their leftward opening. Conversely, knobbed and channeled whelk shells open on the right side. Knobbed whelks have a more spiky appearance, named for the protruding knobs on their shells. Channeled whelks are smoother and are named after the channels visible in their spirals.

This knobbed whelk lives in the touch tank in the Fleming Education Building!

You can learn more about whelks (and even touch a live one!) at BHI Conservancy’s NC Coastal Explorer program, which highlights the impressive array of organisms that live in the island’s intertidal zone!