Metamorphosis: a photo essay

Watching these snails metamorphose is one of my favorite parts of rearing them in the lab. If you catch them at the right points, you can actually see their characteristic larval trait, the velum, falling off and falling apart. And the juvenile snails are just too much fun to watch under the microscope. Their shells are still transparent, so you can see all of their internal parts for a while.

Today I spent some time checking my larvae to see if they are ready to metamorphose (competent). I also got some microscope pictures. So here is a photo essay of Crepidula metamorphosis.

A larval C. fornicata with intact ciliated velum, used for capturing algae.
Picture at 100X. Photo credit A. Cahill

A just-metamorphosed C. fornicata. On the right is the disintegrating velum. On the left, attached to the shell, is a colony of protozoans that has contaminated my cultures (see below). Picture at 40X. Photo credit A. Cahill

Closeup of the disintegrating velum.
Picture at 1000X. Photo credit A. Cahill

Juvenile C. fornicata, no velum present. It must now use its ctenidium to feed on algae.
Picture at 40X. Photo credit A. Cahill

In the second picture up there, you can see today’s drama. There appears to be a colonial protozoan (identified as Vorticella) that has gotten into my cultures. It’s not as bad as it could be – these are not ciliates, other protozoans that eat my larvae. Certainly the larva in the picture has metamorphosed just fine, even with all that extra baggage to carry around. Still, it’s time to clean everything in the lab and take better care when filtering my water!

Closeup of the Vorticella colony on the snail’s shell. Picture at 1000X. Photo credit A. Cahill