A multi-species community

These are a few of the larger intertidal critters from the aquarium, photographed in the course of a tank census:

Three different shells; from right to left, Nassa snail, Asian mud snail, and barnacle.

Barnacles usually live attached to rocks or other solid materials. When they break off, the base gets left behind and the barnacle dies. Occasionally, one detaches from the rock without breaking. This one has most of the base intact, so it is still alive and feeding. Look closely to see the pale tentacles at the mouth.

The Nassa shell, on the right, has several round holes drilled through it, the work of a carnivorous snail, such as a whelk. Once the hole penetrates the flesh, the whelk injects paralyzing and digestive enzymes, which dissolve the snail inside. Often, once the shell is vacant, I discover the tentacles of worms waving from these holes.

Rockweed isopod, about an inch long. The flash makes the red seaweed glow in neon reds. Under normal lights, it is a bit paler than the burgundy Turkish towel that the isopod is feeding on.

The second isopod. Look closely; on the back, it is carrying a small shelled animal, probably a limpet.

Head of a polychaete worm, out looking for a meal. They rarely leave the sand completely, and retract almost instantaneously at any disturbance..

One of the round algae-eating periwinkles, with an amphipod taking a short break.

At least four species of snails live in my tank: Nassas, mud snails, periwinkles, and the tiny lacunas; these last may be so small that even with a lens, I am hard put to determine whether they are snails or sand grains until they move. Their eggs often come home with me on blades of eelgrass.

Underside, through the glass, of a very small anemone. 

This anemone sat for weeks on a stone, and then went wandering about. It has now hidden itself. I have never seen that "petal" effect on the base before.

The youngest crab, raised in the tank from babyhood. 

And my new mascot, found in a thrift store. $0.50; I couldn't resist.