Nudibranchs are a group of soft-bodied marine gastropod molluscs which shed their shells after their larval stage. They are noted for their often extraordinary colours and striking forms, and they have been given colourful nicknames. Nudibranchs are often casually called sea slugs, as they are a family of opistobranchs within the phylum Mollusca, but many sea slugs belong to several taxonomic groups which are not closely related to nudibranchs. A number of these other sea slugs such as the photosynthetic Sacoglossa and the colourful Aglajidae, are often confused with nudibranchs. Nudibranchs are commonly divided into two main kinds, dorid and aeolid.
Dorids are recognised by the branchial plume, which forms a cluster on the posterior part of the body, around the anus. Fringes on the mantle do not contain any intestines.
Aeolids have cerata spread across the back instead of the branchial plume. They lack a mantle. Some are hosts to zooxanthellae.
Scientific classification;
Kingdom: Animalia
Phylum: Mollusca
Class: Gastropoda
Subclass: Heterobranchia
Infraclass: Euthyneura
Subterclass: Ringipleura
Superorder: Nudipleura
Order: Nudibranchia
