Editing Nudibranch (section)

==Anatomical description==
[[File:Aeolidiella stephanieae.png|thumb|alt=Resembling a strip of damp sheepskin is a slug-like body with its back covered in cigar-shaped tentacles (most of which are called cerata)|''[[Berghia stephanieae]]'' nudibranch body: Note the oral tentacles (ot), foot tentacles (ft), eye (e), [[rhinophore]]s (r), and [[cerata]] (c). This species has [[cnidosac]]s (cn) at the cerata tips. Scale bar is 100 μm.]]

The body forms of nudibranchs vary greatly. Because they are opisthobranchs, unlike most other gastropods, they are apparently [[bilateral symmetry|bilaterally symmetrical]] externally (but not internally) because they have undergone secondary [[torsion (gastropod)|detorsion]]. In all nudibranchs, the male and female sexual openings are on the right side of the body, reflecting their asymmetrical origins. They lack a [[mantle (mollusc)|mantle]] cavity. Some species have venomous appendages ([[cerata]]) on their sides, which deter predators. Many also have a simple gut and a mouth with a [[radula]].<ref name=thompson/>

The eyes in nudibranchs are simple and able to discern little more than light and dark.<ref>{{cite web |url=http://ngm.nationalgeographic.com/2008/06/nudibranchs/holland-text/2 |archive-url=https://web.archive.org/web/20080617030023/http://ngm.nationalgeographic.com/2008/06/nudibranchs/holland-text/2 |url-status=dead |archive-date=June 17, 2008 |title=Nudibranchs – National Geographic Magazine |publisher=Ngm.nationalgeographic.com |date=2013-04-25 |access-date=2013-07-04}}</ref> The eyes are set into the body, are about a quarter of a millimeter in diameter, and consist of a lens and five photoreceptors.<ref>{{cite journal
 | journal = Journal of Experimental Biology
 | url = http://jeb.biologists.org/cgi/content/abstract/60/3/707
 | pmid = 4847278
 | title = The Electrophysiology of Photoreceptors in the Nudibranch Mollusc, Tritonia Diomedia
 | volume = 60
 | issue = 3
 | pages = 707–19
 | author = Chase, Ronald
 | date = June 1, 1974 | doi = 10.1242/jeb.60.3.707
 | url-access = subscription
 }}</ref>

Nudibranchs vary in adult size from {{convert|4|to|600|mm|in|abbr=on}}.<ref>{{Cite web |title=Hexabranchus sanguineus {{!}} DORIS |url=https://doris.ffessm.fr/Especes/Hexabranchus-sanguineus-Danseuse-espagnole-411 |access-date=2023-04-17 |website=doris.ffessm.fr}}</ref>

The adult form is without a shell or [[operculum (gastropod)|operculum]] (in shelled gastropods, the operculum is a bony or horny plate that can cover the opening of the shell when the body is withdrawn). In most species, there is a swimming [[veliger]] larva with a coiled shell, but the shell is shed at [[metamorphosis]] when the larva transforms into the adult form. Some species have [[direct development]], and the shell is shed before the animal emerges from the egg mass.<ref name="thompson">Thompson, T. E. (1976). ''Biology of opisthobranch molluscs'', '''1''', 207 pp., 21 pls. Ray Society, no. 151.</ref>
[[File:Blue dragon-glaucus atlanticus (8599051974).jpg|left|thumb|''[[Glaucus atlanticus]]'' is an example of a nudibranch that has its cerata positioned like wings instead of on its back.]]
The name ''nudibranch'' is appropriate, since the dorids (infraclass [[Anthobranchia]]) breathe through a "naked gill" shaped into branchial plumes in a rosette on their backs.<ref>{{cite journal |last=Dayrat |first=B. |year=2005 |title=Advantages of naming species under the PhyloCode: An example of how a new species of Discodorididae (Mollusca, Gastropoda, Euthyneura, Nudibranchia, Doridina) may be named |journal=Marine Biology Research |volume=1 |pages=216–232 |url=https://campillos.ucmerced.edu/~bdayrat/PDF%20of%20Papers/Dayrat-MBR-2005.pdf |access-date=2009-06-14 |doi=10.1080/17451000510019141 |issue=3 |bibcode=2005MBioR...1..216D |s2cid=53557429 }}</ref> By contrast, on the back of the aeolids in the clade [[Cladobranchia]], brightly coloured sets of protruding organs called [[cerata]] are present.

Nudibranchs have cephalic (head) tentacles, which are sensitive to touch, taste, and smell. Club-shaped [[rhinophore]]s detect odors.

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