Operculum: snail door

Today’s word: operculum. From Wikipedia: “The operculum (from Latin operculum 'cover, covering'; pl. opercula or operculums) is a corneous or calcareous anatomical structure like a trapdoor that exists in many (but not all) groups of sea snails and freshwater snails, and also in a few groups of land snails; the structure is found in some marine and freshwater gastropods, and in a minority of terrestrial gastropods…”

Translation: The operculum is a cover, like a trapdoor, for the shells of some snails. It can be fingernail material or seashell material (flexible or rock-hard).

“The operculum is attached to the upper surface of the foot and in its most complete state, it serves as a sort of "trapdoor" to close the aperture of the shell when the soft parts of the animal are retracted.”

Translation: When the snail wants to stay home alone, it pulls its one foot all the way inside its shell, using the operculum as a closed door.

“The shape of the operculum varies greatly from one family of gastropods to another. It is fairly often circular, or more or less oval in shape. In species where the operculum fits snugly, its outline corresponds exactly to the shape of the aperture of the shell and it serves to seal the entrance of the shell.”

Translation: The operculum is usually round or oval, whatever shape it needs to be to close off the shell. Some snails can completely seal the doorway with it.

“Many families have opercula that are reduced in size, and which are not capable of closing the shell aperture. Opercula have sometimes been modified: in the Strombidae the operculum is claw-shaped and is used to push into the substrate in a leaping form of locomotion.”

Translation: Some snails don’t bother with a complete seal or even closing the door; some stick it in the dirt like a pole to vault away.

This pole vaulting makes more sense when you discover that Strombidae live in the ocean. They’re pitching themselves through the water, not out of a tree.

Wikipedia goes on to say, and show: snails that have opercula can rest their shells on them while creeping along. That way the edge of the shell won’t cut into the snail. Pretty convenient.

Some snails breathe air through lungs. I didn’t know that. They’re called pulmonate snails, same as your lungs are part of your pulmonary system.

Wikipedia again: “Virtually all pulmonate snails are inoperculate, i.e. they do not have an operculum, with the exception of the Amphiboloidea.”

Translation: Pulmonate snails have lungs and don’t have opercula, except this one exception which apparently has lungs and grows a fingernail on its back.

“However, some terrestrial pulmonate species are capable of secreting an epiphragm, a temporary structure that can in some cases serve some of the same functions as an operculum.”

Translation: Some land snails with lungs can produce an epiphragm, that can function as a door to close their shells.

If you look up epiphragm, it’s dried snot. Some species even coat their epiphragm with a layer of calcium carbonate, to make it stronger; in other words, they add a layer of pearl to their snot.

Some societies use opercula as gemstones.

—Wikipedia: Operculum: https://en.wikipedia.org/wiki/Operculum_(gastropod), retrieved July 28, 2024. I also looked up epiphragm: https://en.wikipedia.org/wiki/Epiphragm, retrieved July 28, 2024.