Knoutsodonta neapolitana

Knoutsodonta neapolitana (delle Chiaje, 1841)

Knoutsodonta neapolitana @ Costa Brava by Enric Madrenas













































Knoutsodonta neapolitana  (Delle Chiaje, 1841)

 Classification according to Bouchet et al. (2017)
Taxonomic source: World Register of Marine Species (AphiaID: 1259491).

  • Idalia neapolitana Delle Chiaje, 1841
  • Onchidoris 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 K.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.


  • Knoutsodonta, from the Greek meaning “lame tooth”, to represent
    nudibranch species that lack a rachidian or middle tooth.
  • 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: Knoutsodonta neapolitana
: GROC 2010-2011
: Enric Madrenas
: João Pedro Silva
: Bernard Picton
: Manuel Ballesteros.
: M@re Nostrum
: Altres fonts
: Marine Regions


    Western Mediterranean:2 out of 5 stars
    Eastern Mediterranean:1 out of 5 stars
    Atlantic Ocean:0 out of 5 stars

This chart displays the monthly observation probability for Knoutsodonta neapolitana based on our own records.

More pictures


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Further reading

Cite this article as:

Ballesteros, Manuel, Enric Madrenas, Miquel Pontes (2012-2020) "Knoutsodonta neapolitana" in OPK-Opistobranquis, Published: 17/05/2012, Accessed: 06/07/2020 at (

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