Pneumostome

Air enters through the pneumostome into the animal's single lung, the air-filled mantle cavity.

[1] Inside the mantle cavity the animal has a highly vascularized area of tissue that functions as a lung.

The pneumostome is often much easier to see in slugs than in snails, because of the absence of a shell which can often block the view of this area.

The frequency of pneumostome closing and opening is typically less than 0.5 closures per minute in fully hydrated slugs and snails.

[2] The images in the gallery below show the position of the pneumostome in three different families of slugs: This gastropod-related article is a stub.