Saturday morning’s low tide revealed dozens of Northern Moon Snail sand collars on the flats at Cape Hedge Beach. Perhaps the storm released the collars from the ocean floor.
There are hundreds of species of moon snails, so named because they are round like the Moon. The sand collars we see locally and all along the northern Atlantic Coast are made by the beautiful Northern Moon Snail (Euspira heros).
Moon snails are marine gastropods that live in the intertidal zone. We often find their shells washed ashore but rarely see living ones. When you find a clam or mussel shell, or even another moon snail shell, with a perfectly drilled hole, chances are it was eaten by a moon snail.
Piping Plover chick and Northern Moon Snail
The beautiful sculptural sand collars at Cape Hedge Beach are Northern Moon Snail egg cases. When you find a collar, and it is soft, and flexible, it is comprised of thousand eggs. Please don’t remove the collar from the beach. Toss it back into the water, which will also help prevent other folks from collecting.
How the female Moon Snail constructs the egg collar is nothing short of spectacular. When a female is ready to lay her eggs, at low tide, she begins preparing her egg collar by secreting mucus. During high tide, she digs down to begin forming the collar with mucus and sand. She spreads out the front part of her foot (the propodium) so that it covers her shell. She collects grains of sand with tiny cilia that cover her foot. Creating a sort of egg “sand”- wich, she combines a layer of mucus with thousands (and even hundreds of thousands) of released eggs and then cements all with another layer of mucus to form the flexible egg case.
The snail lies at the center of the collar as she creates it, so the hole in center of the collar gives an indication of the size of the mother snail. When finished building the collar she has to escape from her egg case sitting on the ocean floor. She digs straight down using her foot and burrows away from the collar.
The collars are pushed to the surface and, during low tide, are visible on the beach. The egg cases stay on the beach as the water from the incoming tide washes over them.
The eggs hatch before the collar falls apart. so while it is still flexible and rubbery there are thousands of tiny Northern Moon Snail larvae swimming in the mucus matrix of the collar.
Piping Plover chick and Northern Moon Snail collar