A nudibranch (pronounced /ˈnjuːdɨbræŋk/)[1] is a member of what is now a taxonomic clade, and what was previously a suborder, of soft-bodied, marine opisthobranch gastropod mollusks which shed their shell after their larval stage[2]. They are noted for their often extraordinary colors and striking forms. The clade Nudibranchia is the largest clade within the heterobranchs, with more than 3,000 described species.
The word "nudibranch" comes from the Latin nudus, naked, and the Greek brankhia, gills.
Nudibranchs are often casually called "sea slugs", a non-scientific term. This has led some people to assume that every sea slug must be a nudibranch. Nudibranchs are very numerous in terms of species, and are often very attractive and noticeable, but there are a wide variety of other kinds of sea slugs, and these belong to several taxonomic groups that are not very closely related to nudibranchs. A fair number of these other sea slugs are colorful, and can be confused with nudibranchs.
These other marine shell-less gastropods or "sea slug" groups include additional heterobranch shell-less gastropod groups such as the Cephalaspidea sea slugs including the colorful Aglajidae, and other heterobranchs such as the Sacoglossa, the sea butterflies, the sea angels, and the often rather large sea hares. The term sea slug is also sometimes loosely applied to the only very distantly related pelagic caenogastropods within the superfamily Carinarioidea, and may also be casually used for the even more distantly related pulmonate sea slugs, the Onchidiidae.
Aeolidiella stephanieae. Typical body of a nudibranch with cerata consist of:
ot = oral tentacles,
ft = foot tentacles,
e = eye,
r = rhinophores,
c = cerata. This species has cnidosacs at the cerata tips.
The body forms of nudibranchs vary enormously, but because they are opisthobranchs, unlike most other gastropods they are bilaterally symmetrical because they have undergone secondary detorsion. Some species have venomous appendages on their sides. These are used to deter predators. Many also have a simple gut and a mouth with a radula.
They lack a mantle cavity.
They vary in adult size from 20 to 600 millimetres (0.79 to 24 in).
Their eyes are simple and able to discern little more than light and dark.[3] The eyes are set into the body, are about a quarter of a millimeter in diameter, and consist of a lens and five photoreceptors.[4]
They vary in adult size from 20 to 600 millimetres (0.79 to 24 in).
The adult form is without a shell or operculum (a bony or horny plate covering the opening of the shell, when the body is withdrawn).
The name nudibranch is appropriate, since the dorids (infraclass Anthobranchia) breathe through a "naked gill shaped" like branchial plumes of bushy extremities on their back, near their tail rather than using gills.[5] By contrast, on the back of the aeolids in the clade Cladobranchia there are brightly colored sets of protruding organs called cerata.
Nudibranchs have cephalic (head) tentacles, which are sensitive to touch, taste, and smell. Club-shaped rhinophores detect odors.
Nembrotha chamberlaini
Chromodoris leopardus
Chromodoris magnifica
Durvilledoris pusilla
Hypselodoris bullockii
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