Onchidoris neapolitana

Onchidoris neapolitana (delle Chiaje, 1841)

Onchidoris neapolitana @ Costa Brava (Spain) by Miquel Pontes

Class: Gastropoda  Cuvier, 1797
Subclass: Heterobranchia  Gray, J.E., 1840
Clade: Euthyneura  Spengel, 1881
Clade: Nudipleura  Wägele & Willan, 2000
Order: Nudibranchia  Cuvier, 1817
Suborder: Euctenidiacea  Tardy, 1970
Infraorder: Doridacea  Thiele, 1931
Superfamily: Onchidoridoidea  Gray, 1827
Family: Onchidorididae  Gray, J.E., 1827
Genus: Onchidoris  de Blainville, 1816
Species: Onchidoris neapolitana (delle Chiaje, 1841) [Idalia]


  • Idalia neapolitana Delle Chiaje, 1841

This species can reach a size of 10 mm. The body is very flat and coloured red-orange with many brown spots in the center of the back. Some individuals may have a yellowish hue. The most characteristic feature of this species are the numerous digitiform papillae on the back, of the same colour as the dorsum, smaller in the center and longer on the margins, which may extend past the edges of the mantle. These papillae provide a “villous” aspect to the specimens. The rhinophores are semitransparent with an orange hue, can be fully retracted and have about 6-7 lamellae; the rhinophoric orifice is smooth. The gill consists of 12 unipinnate gill leaves arranged in an incomplete oval open in the back. The gill leaves are semitransparent orange. The interbranchial area holds the anus and it also has 6-7 elongated papillae. The mantle is very broad and, on its ventral side, radial spicules of the margin of the body can be seen by transparency. The foot is red-orange, like the oral veil. The foot features a dark brown spot corresponding to the digestive gland of the animal.

This species, like others of the same genus is often found under stones, on encrusting bryozoans. It is often located on Schizobrachiella sanguinea, of the same red color as the nudibranch, so it is possibly eating the pigment that gives its color while it mimics on the bryozoan. It is easy to tell when predation of O.neapolitana occurs, since predated areas of the colony appear white. This nudibranch can also be found on red algae like Sphaerococcus coronopifolius. The spawn is a transparent cord laid forming an spiral of 2 to 5 turns with large (225 micron) orange eggs, aligned in two rows along the cord. The diameter of the spawn is about 6 mm.


  • Onchidoris, Doris with tubercles.
  • Doris, a sea Nymph in Greek mythology.
  • Neapolitana, related to Naples (Italy) where there is an important oceanographic station.

This is a mediterranean species that, in the Iberian Peninsula, it has only been cited in the Strait of Gibraltar and in Catalonia (Cadaqués, Tossa de Mar, Colera). Outside the Iberian coasts it has been observed in the French Mediterranean coast (Banyuls, Villefranche), the Gulf of Naples and the Adriatic Sea.

Known georeferenced records of the species: Onchidoris neapolitana
: GROC 2010-2011
: Enric Madrenas
: João Pedro Silva
: Bernard Picton
: Manuel Ballesteros.
: M@re Nostrum
: Altres fonts
: Marine Regions


    Western Mediterranean:
    Eastern Mediterranean:
    Atlantic Ocean:
This chart displays the observation probability for Onchidoris neapolitana based on our own records.

More pictures


Further reading

Cite this article as:

Ballesteros, Manuel, Enric Madrenas, Miquel Pontes (2012-2018) "Onchidoris neapolitana" in OPK-Opistobranquis, Published: 17/05/2012, Accessed: 18/01/2018 at (https://opistobranquis.info/en/z7wAz)

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