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Stylommatophora is the most diverse group of land snails and slugs. Pallial cavity forms a spacious, air-filled lung. Anus is located on the right side close to the pneumostome. Operculum is missing. Two pairs of tentacle are retractable and the posterior pair bears eyes on the tips. Radula typically has many small, quite uniform teeth per row.
Pulmonata or pulmonates is an informal group (previously an order, and before that, a subclass) of snails and slugs characterized by the ability to breathe air, by virtue of having a pallial lung instead of a gill, or gills. The group includes many land and freshwater families, and several marine families.
Planorbidae, common name the ramshorn snails or ram's horn snails, is a family of air-breathing freshwater snails, aquatic pulmonate gastropod molluscs. Unlike most molluscs, the blood of ram's horn snails contains iron-based hemoglobin instead of copper-based hemocyanin . [ 3 ]
An operculum is a somewhat similar but permanent anatomical feature that is found in other clades of gastropods. The operculum serves some of the same functions as an epiphragm. Sometimes it protects the snail against predation. It protects certain species of snail if they are eaten by birds (such as Japanese white-eye). The snail can remain ...
In some prosobranch gastropods, the aperture of the shell can be closed, and even completely sealed, with a sort of door or operculum. The aperture of many snail shells is more or less round, rounded, elliptical or oval. This shape usually corresponds roughly to the cross-section of the body whorl of the shell.
Shell of marine snail Lunella torquata with the calcareous operculum in place Gastropod shell of the freshwater snail Viviparus contectus with corneous operculum in place. The operculum (Latin for '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 ...
Stylommatophora is an order [3] of air-breathing land snails and slugs, terrestrial pulmonate gastropod molluscs. This taxon includes most land snails and slugs . Stylommatophorans lack an operculum , but some close their shell apertures with temporary "operculum" ( epiphragm ) made of calcified mucus.
The Pulmonata includes the majority of land snails and slugs, many freshwater snails, and a small number of marine species. The mantle cavity of the Pulmonata is modified into an air-breathing organ. They are also characterized by detorsion and a symmetrically-arranged nervous system.