What is an operculum?

Operculum means ‘little lid.’ What animal has a little lid?

A gastropod mollusc – a snail – has an operculum. It is like a trapdoor at the mouth of many sea snails and freshwater snails, and also in some land snails.

The snail shell has a rounded or circular opening. The operculum is the lid that seals the opening. It stops the snail from drying out, because snails like to keep damp and moist. It is also protection from other animals trying to get the snail out of the shell. 

The operculum completely seals the opening of sea snails, but the operculum usually only partially seals the opening of land snails – and most land snails don’t have an operculum. 

The operculum is made of protein and is usually yellow, brown, or translucent (see through). 

A snail with an operculum is called an operculate snail. 

The plural of operculum is operculums or opercula.

Photographer: Martina Nicolls

Martina Nicolls: SIMILAR BUT DIFFERENT IN THE ANIMAL KINGDOM