The pneumostome or breathing pore is a respiratory opening of the external body anatomy of an air-breathing land

slug Slug, or land slug, is a common name for any apparently shell-less terrestrial gastropod mollusc. The word ''slug'' is also often used as part of the common name of any gastropod mollusc that has no shell, a very reduced shell, or only a smal ...

land snail A land snail is any of the numerous species of snail that live on land, as opposed to the sea snails and freshwater snails. ''Land snail'' is the common name for terrestrial gastropod mollusks that have shells (those without shells are known as ...

. It is a part of the

respiratory system of gastropods The respiratory system of gastropods varies greatly in form. These variations were once used as a basis for dividing the group into subclasses. The majority of marine gastropods breathe through a single gill, supplied with oxygen by a current of wat ...

. It is an opening in the right side of the mantle of a

stylommatophora Stylommatophora is an orderPhilippe Bouchet, Jean-Pierre Rocroi, Bernhard Hausdorf, Andrzej Kaim, Yasunori Kano, Alexander Nützel, Pavel Parkhaev, Michael Schrödl and Ellen E. Strong. 2017. Revised Classification, Nomenclator and Typification ...

n snail or slug. Air enters through the pneumostome into the animal's single

lung The lungs are the primary organs of the respiratory system in humans and most other animals, including some snails and a small number of fish. In mammals and most other vertebrates, two lungs are located near the backbone on either side of t ...

, the air-filled mantle cavity. Inside the mantle cavity the animal has a highly

vascular The blood vessels are the components of the circulatory system that transport blood throughout the human body. These vessels transport blood cells, nutrients, and oxygen to the tissues of the body. They also take waste and carbon dioxide away f ...

ized 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 Shell may refer to: Architecture and design * Shell (structure), a thin structure ** Concrete shell, a thin shell of concrete, usually with no interior columns or exterior buttresses ** Thin-shell structure Science Biology * Seashell, a hard ou ...

which can often block the view of this area. In a land slug, when the pneumostome is wide open, it is usually very clearly visible on the right side of the animal. However, the position of the pneumostome is often not at all easy to discern when this orifice is completely closed. The pneumostome opens and closes in a cyclical manner. The frequency of pneumostome closing and opening is typically less than 0.5 closures per minute in fully hydrated slugs and snails. The rate of closures per minute increases the more dehydrated the slug is.Pneumostome's response to dehydration
The pneumostome rhythm in slugs: a response to dehydration controlled by hemolymph osmolality and peptide hormones. Dickinson PS, Prior DJ, Avery C. Source Department of Biology, Bowdoin College, Brunswick, ME 04011.

Position of pneumostome as a diagnostic feature

The images in the gallery below show the position of the pneumostome in three different families of slugs: Image:Black slug.jpg, Arionidae, (''

Arion ater Arion (; grc-gre, Ἀρίων; fl. c. 700 BC) was a kitharode in ancient Greece, a Dionysiac poet credited with inventing the dithyramb. The islanders of Lesbos claimed him as their native son, but Arion found a patron in Periander, tyrant ...

''), the pneumostome is just anterior to the midpoint of the mantle Image:Bielzia coerulans-1.jpg,

Limacidae Limacidae, also known by their common name the keelback slugs, are a taxonomic family of medium-sized to very large, air-breathing land slugs, terrestrial pulmonate gastropod molluscs in the superfamily Limacoidea. Distribution The distr ...

, (''

Bielzia coerulans ''Bielzia coerulans'', commonly known as the Carpathian blue slug or simply the blue slug, is a species of very large land slug, a terrestrial pulmonate gastropod in the family Limacidae, the keelback slugs. Taxonomy ''Bielzia coerulans'' wa ...

''), the pneumostome is just posterior to the midpoint of the mantle Image:Tandonia budapestensis 2.jpg,

Milacidae Milacidae is a family of air-breathing, keeled, land slugs. These are shell-less terrestrial gastropod mollusks in the superfamily Parmacelloidea. This family has no subfamilies (according to the taxonomy of the Gastropoda by Bouchet & Rocro ...

, (''

Tandonia budapestensis ''Tandonia budapestensis'' is a species of air-breathing, keeled, land slug, a shell-less terrestrial gastropod mollusks in the family Milacidae.Marshall, B. (2014). Tandonia budapestensis (Hazay, 1880). Accessed through: World Register of Marin ...

''), the pneumostome is just posterior to the midpoint of the mantle

References

External links

Short clip of ''Ariolimax columbianus'' displaying its pneumostome
YouTube, Feb 17, 2008 Gastropod anatomy Invertebrate respiratory system Articles containing video clips {{respiratory-stub