Rock houses

Anemones are squishy. Touch one (not the tentacles; sometimes they sting). Touch the stalk; it feels like watery Jello. It leaks tears at your touch, and shrinks. Now it's regular Jello texture, still springy, still soft.

They have no teeth, no rasping mechanisms, no scratchy outer shell. So how do they excavate holes in rock?

Sandstone boulder, Willow Point. With ancient anemone homes around the edge.

Another boulder, another set of holes. This is rock, not sand.

Sometimes the holes line up along the edge of a flat rock. Sometimes the whole rock is pock-marked. And the next rock, of the same material, is smooth, without a hole to be seen.

Some holes are just that; old holes. I poke at them with a finger. There's nothing there but rock, hard and dry.

Some holes are occupied. The surrounding rock is hard, but if I touch the centre of a hole, it shrinks away from my finger, leaking tears, exposing a flash of yellow or green jelly.

Anemones in their rocky holes, unhappy because I poked them.

The beach life is layered.  Here, crabs, limpets, and snails in shallow pools, a seaweed level (sea cauliflower and red algae), barnacles on the bottom of a flat rock, and a rim of holes around the upper side. And more barnacles and algae on the top. Crouch and look up at the underside of the rock; there may be a starfish or three.

Why are the holes so often lined up along the edge of flat rocks? Could it be something to do with the currents bringing foods, the way the anemones in my aquarium congregate near the top of the tank, sometimes half out of the water? Do they line up because new babies move only a little way from their parent?

Why do they choose one rock, and not the next? Why is one rock smooth, its neighbour completely pock-marked, and the next one free of holes except for one edge?

Are some of those holes ancient limpet beds, hollowed out by years of tidewaters? Is there a way to tell the difference?

And in my tank, why do the few pink-tipped green anemones who choose to stay at the bottom park themselves mostly on oyster shells, almost never on stone?

I ask them, but they never answer.