|Little Tykle Cove, (Olympia, WA)|
|Shirley Patterson, circa 1930|
One of my all time favorite shells are the Slipper Shells. These are pretty odd shells, fairly ordinary on top but when you turn them over, you see a thin half shelf inside. They were uncommon on Uncle Wilmot’s beach, but I learned to find them in one particular place right on the edge of the Little Tykle Creek as it emerged into the gravel-mud beach. To me these shells were profoundly magical: I thought of them as Faery shoes. Sometimes we also called them cradle shells and I imagined the Faery, packing their youngsters into these shells and floating them off under the starlight night...
I have joined the beach naturalists and am currently in training. We were asked to pick a “critter” and do a talk on it. I immediately jumped on the slipper shells. Here is what I found:
They are a kind of mollusk, known as a gastropod (stomach foot). They start out life as tiny larvae swimming in the plankton, but after about three -five weeks in the sea, they drop down to the sea floor, living in the deep sub tidal waters where we are unlikely to find them except in the lowest tides. Here they attach to some hard surface, growing into the snail that lives in this unique shell. And where they drop out is is generally where they spend the rest of their lives. They may live up to 10 years.
|Slipper shells on a Moonsnail|
They attach to all kinds of hard surfaces: rocks, floats, pilings and other shells. Here is picture of several of them attached to a Moon Snail, another common marine animal on our beaches.
There are several species in Puget Sound. Probably the most common is one from the Atlantic beaches that was introduced with non-native oysters. This one with a white chalky outer shell is called Crepidula fornicata, a highly suggestive name which refers to their life habit as sequential hermaphrodites. The way it appears to work is that a female lands on the hard surface first. A male then comes along and attaches to her.
|Cluster of Slipper shells, off Cooper Point, (Olympia WA)|
Then other males may come along as well, attaching in turn until you can see quite a large pile of slipper shells. This system works well for reproduction: the animal has everything it needs right there and doesn’t have to move. However, if the female on the bottom of the dog pile dies, the other slipper shells have the ability to change sex! This is remarkable system.
The Atlantic species C. fornicata is quite numerous along the eastern seaboard. While they live in the deep intertidal waters, once they die their shells are cast up on the beach. Here is a photo published by "Maggie's Farm" from along the Connecticut seacoast, where literally thousands of slipper shells have washed ashore.
|Slipper shells on a Connecticut beach, cast up by winter storms. |
Resources: South Sound Estuary Association http://sseacenter.wordpress.com/
Photo of cluster of slipper shells by Wendy Eklund
* South Sound Estuary Association is a local jewel. They have lots of wonderful (free) education about our local estuaries. They offer regular summer low tide walks, staffed by volunteer beach naturalists. They lead monthly Pier walks at Boston Harbor marina, where at night a light is lowered off the dock: all kinds of amazing creatures are drawn to the light. There are local experts and volunteers who answer questions about what is seen.
They also have a small building down by the Farmer’s Market at 608 Washington NE, Olympia. Here for a small entrance fee you can visit this "estuarium" and see the salt water tanks, full of the wonderful creatures of Puget Sound. Highly recommended.
They are planning on moving to a larger facility on State Street, probably later this summer. They are in the process of raising money and donations are always welcome. You can check their webpage at http://sseacenter.wordpress.com/ to find beach walk schedules, Pier night schedules, Estuarium hours and ways to donate.