Friday, June 29, 2012

I promised you snail orgies.

We found the tide almost at its minimum at Crescent Beach, and I waded out through inch-deep tidepools, trying to get to the drop-off before the water rose again.
Looking back at the shore from half-way out.

The eelgrass comes in patches in this section of the beach. The sand was mostly bare, but where there was eelgrass, there were snails.

The invasive Eastern mud snails, Ilyanassa obsoleta, in eelgrass.

This snail has just about driven out our other invasive, the mudflat snail, Batillaria attramentaria, that we see in the millions on the opposite side of the bay, at Centennial Beach. I saw a couple or three only among these herds of mud snails.

"Hurry, hurry! You're late to the party!"

The snails were in full mating frenzy, piled several deep, hundreds of them to a pile, writhing and rolling, a mass of squirming black bodies and grungy shells. Every so often one flipped completely upside down, stretching out to show her white underside, waving her siphon excitedly. What with all the gunk on their shells, the stirred-up sand, and the curtain of eelgrass, it becomes difficult to distinguish individual snails.

And along with the fun, comes the work. Once they have mated, the females find a hard surface and start to lay eggs. Here, the surface is usually an eelgrass blade, where they line up the eggs in rows.

Eelgrass with snail egg "beads". And snails three-deep beneath them.

Each transparent egg capsule contains from 30 to 300 yellowish eggs. They are firmly glued to the eelgrass, and feel like a cold, hard lump of jelly.

A closer view of some eggs. The furry stuff is probably a colony of hydroids.

Close-up of some capsules I brought home in 2008, showing the individual eggs.

A couple of snail heaps were not interested in sex. No writhing, no sand-stirring, no coupling, no egg-laying; they had something else on their minds. In both cases, the molted remains of a crab lay on the sand, with a tidy mass of snails around and under it. They're algae eaters, but they also love a scavenged meal of animal flesh.

A little after-orgy snack?

1 comment:

  1. Well, you have to get your strength back up after all that!

    What great photos and what a great sighting!

    Musdnail egg capsules also have that lovely faceted shape that you captured in your picture.

    Thanks for sharing a day of gastropod romance with us!


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