Wednesday, August 28, 2013

A bubble in the hand . . .

is worth any number in the eelgrass.

It's interesting, how once you've gotten familiar with the shape and movements of a critter, that you see them in places where you looked before, without finding any. Like the bubble shell snails; I've waded knee-deep in the eelgrass beds at low tide in Boundary Bay many times, and all I saw were crabs and isopods. This last time, I recognized the bubble shells, dozens of them.

They're easy to catch; they hang out on the eelgrass blades, and when they're disturbed, they just let go and float down to the next blade. And they're just as content to land on my hand.

I got this one still on his eelgrass. He's upside-down, twisting up to get a look at me.

Setting out to explore. Isn't he a cutie?

"Hi, there!"

These snails are incredibly fragile; their shells are paper-thin, and as brittle as eggshell porcelain. Other snails have thick, sturdy shells, essential for survival in crab country. Even so, I find many empty shells, peeled back by crabs to get at the tasty meat inside. How do the bubble shells, without that protection, manage to live?

Watching them on the eelgrass, it all became clear. As long as the eelgrass in underwater, it stands upright, swaying in the current. The crabs scuttle along underneath, but only the smallest climb the eelgrass; it won't support the weight of the larger ones. Up at the top of the bed, there are no hard edges, no stones, no crabs, nothing to squeeze or bang those fragile shells.

When a bubble shell drops to the sand, he buries himself immediately. I've been watching in my tank, as they just ooze down between the sand grains and disappear, in seconds. The next time I see them, they're climbing an eelgrass stalk, up to safety.

Bubble shell egg ribbon, on eelgrass

I have seen these egg ribbons many times, but didn't know which snails they belonged to. Now I do: I've watched the bubble shells laying them, gluing them to the eelgrass blades near the top of my tank.

There must be thousands of eggs in one ribbon, and a bubble shell will lay several ribbons over the course of a few days. Few of them survive, or we'd be wading through a mass of bubble shells. Hermit crabs love them; fish eat them, so do nudibranchs. Even in the gentle eelgrass beds, life is precarious.

2 comments:

  1. I never heard of this critter. Thanks for introducing us. Every time I think about how we begin to see what we grow familiar with, I remember how someone sat in my sister's kitchen and pointed out at her tomatoes, fifty feet away, and said: "I see you got the hornworms." The what? We went out there and could not see a one. Then she started pointing them out. Enormous green caterpillars four inches long and an inch thick, and we couldn't see them.

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  2. Four inches long and an inch thick? Yikes!

    But that's just how it is; we don't see what's right in front of our eyes until we learn what we're seeing.

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