Baby slipper

This hooked slipper snail turned up in my aquarium three weeks ago, on a hermit crab's shell.

Crepidula, either fornicata or adunca

Shortly after he arrived, he moved to this snail shell. A few days later, he was on the thermometer, where he has stayed ever since, crawling up and down the face of it. Either he likes the glass, the algae growing on it, or the current in that location.

Slipper snails are born male, but after a couple of months, they start turning to females. Once they're full grown, they breed, and raise their young under the shell. (UPDATE: adunca only; fornicata releases the larvae. Thanks, Olivia!) When the youngsters are like miniature adults, the mothers push them out into the water, where they sink to the ground and start looking for a new home.

They usually attach themselves to other snails, most often to other slipper snails. Often they are found piled one on top of the other, in tall towers, the larger ones at the bottom. I've only seen stacks of three or four, on Crescent Beach. This one came from Boundary Bay, where they're not so common.

Hermit with two slipper snails, from a muddy spot on Boundary Bay. The large one would be female; the one on top is probably still male.

They grow to about 1 inch across. This one is a youngster, then, only about a quarter inch long, and probably still a male. I hope I find him another male by the time he's female; I'd love to see babies.