This spiraling structure is a fairly common find on our beach.
Kids see this and immediately recognize it: the skeleton of an exotic sea snake! These round rubbery things with the frilly edges, though…
…these are harder to identify. If a kid picks one up and asks me what it is, I’ll have them carry it for a bit so I can talk to the whole group about it the next time we stop.
The first photo, in case you haven’t guessed, actually has nothing to do with snakes. It’s the egg case of a whelk, which some people apparently call a “mermaid’s necklace.” The second one is the egg mass of a moon snail, which is commonly referred to as a “sand collar,” because whole ones resemble old-fashioned detachable shirt collars. To make a sand collar, the female moon snail cements grains of sand together with mucous, embedding her tiny eggs in the matrix. Which means that, after making the kid who picked it up carry it for several minutes, I get to wind up my explanation with “…so basically you’re holding snail snot” and see the look on their face.
Isn’t outdoor education grand?
One must-discuss mollusk (say that ten times fast) during every beach class I teach is the moon snail (family Naticidae). What middle school student – heck, what person – wouldn’t be fascinated by an animal that uses its tongue to drill holes in the shells of other animals and eat them alive? And sometimes practices cannibalism? The life history of this critter, identified by its round, smooth, spiral shell, is guaranteed to earn wide eyes and “Wow!”s from any group of sixth-graders.
The telltale sign that a moon snail has been up to its mischief is a clam shell with a small round beveled hole drilled through its end.
When I was a kid, I found a shell like this and strung it on a length of red yarn to turn it into a necklace. Never did I pause to wonder how the heck the hole got there. When I finally learned about moon snail predation a couple months ago it was like I was a cartoon character with a light bulb going off above my head. Aha!
Moon snails, you see, have a long, minutely toothed, tongue-like appendage called a radula, which (in combination with acid secretions) they use to drill a hole through the shell of their bivalve prey. Then they insert their proboscis into the hole to consume the fleshy animal inside. Alive. Whoa!
Better still, they don’t limit their ravenous rampages to clams. No, big moon snails are quite happy to eat small moon snails. Finding a little moon snail shell with the telltale hole during beach class is a guaranteed crowd-pleaser.
Cannibalism! Acid secretions! Drilling holes with its tongue! It’s like a horror movie monster, washed up right here on our beach. Who knew there was so much drama in the world of seashells?