Friday, September 12, 2014

A never-ending supply

Val, the big burrowing anemone eats snails. Eats them and spits out the shells for the hermit crabs to wear. Or glues them to her column.

But it's not just any snail that she likes; she prefers the upper intertidal periwinkles that climb to the top of the tank and occasionally drop straight into her mouth. One gulp, and they're gone.

She'll reject the Asian mud snails, as if the longer, sharper shell gets stuck in her throat. Or maybe she just doesn't like the taste.

And I've never seen her eat a little Nassa, but somehow there's always a supply of new empty shells; she must nibble on them at night, when I'm not watching.  And somehow, although I don't bring Nassas home with me, when I clean out the tank, I find dozens of these snails plowing through the sand. They're breeding here.

The Japanese Nassa, Nassarius fraterculus.

I've watched them mating often; one snail chases down another. When he catches up, there's a quick writhing and twisting interaction, and then they both hurry away. I've never seen their eggs; they lay them in the sand, in small capsules containing two or three eggs each, and the juveniles are as small as the sand grains. (Here's a video of mating Nassas, the eggs, and emerging juveniles.)

The recent pump disaster didn't seem to worry them at all; they're as active and numerous as ever.

This may be Nassarius fostatus. Or maybe not.

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