Sacoglossa
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 Oxynoe olivacea, a Mediterranean sacoglossan in the family Oxynoidae
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Boselliidae |
Sacoglossa, commonly known as the sacoglossans, are a taxonomic order of small bubble snails, sea snails and sea slugs, marine opisthobranch gastropod mollusks in the superorder Heterobranchia.
In the taxonomy of Bouchet & Rocroi (2005), the clade Sacoglossa is arranged as follows:
- Subclade Oxynoacea
- Superfamily Oxynooidea : family Oxynoidae, family Juliidae, family Volvatellidae
- Subclade Placobranchacea
- Superfamily Placobranchoidea : family Placobranchidae : family Boselliidae, family Platyhedylidae,
- Superfamily Limapontioidea : family Limapontiidae, family Caliphyllidae, family Hermaeidae
In this new taxonomy the family Elysiidae Forbes & Hanley, 1851 is considered a synonym of the family Placobranchidae Gray, 1840 and the families Oleidae O'Donoghue, 1926 and Stiligeridae Iredale & O'Donoghue, 1923 synonyms of the family Limapontiidae Gray, 1847
The sacoglossan families Volvatellidae and Oxynoidae are shelled, and the shells somewhat resemble those of the small bubble snails of the order Cephalaspidea.
The sacoglossan family Juliidae are extraordinary in that they are shelled, bivalved, gastropods. They have a shell in two pieces which superficially resemble the valves of a minute clam. The living members of this family had never been noticed until recent years, and had previously only been known to science as fossil shells. The fossil shells were thought to be remains of a somewhat unusual bivalve mollusk, not a gastropod at all.
All the sacoglossans other than the Volvatellidae, Oxynoidae and Juliidae are shell-less, and as a result are called sea slugs. Even though some of them are highly colored and attractive, such as some species within the family Elysiidae, these are not nudibranchs, which belong to a different order.
Many sacoglossans are green in color, and this is because they sequester, and utilize within their own tissues, living chloroplasts from the algae they eat, a very unusual phenomenon known as kleptoplasty. This earns them the title of the "solar-powered sea slugs", and makes them unique among animals.
[edit] References
- Bouchet, P. & Rocroi, J.-P. (2005). "Classification and Nomenclator of Gastropod Families". Malacologia 47 (1-2): 1-397.
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