Knoutsodonta pusilla

Knoutsodonta pusilla (Alder & Hancock, 1845)

Knoutsodonta pusilla by Bernard Picton













































Knoutsodonta pusilla  (Alder & Hancock, 1845)

 Classification according to Bouchet et al. (2017)
Taxonomic source: World Register of Marine Species (AphiaID: 1259492).

  • Doris pusilla Alder & Hancock, 1845
  • Onchidoris pusilla (Alder & Hancock, 1845)

This species of doridacean can reach a size of 9-10 mm in length. The body is oval shaped and very flattened, nearly circular when the animal is at rest. The body color is dark brown because of numerous densely packed colour patches covering it. Near the edge of the mantle there are usually whitish stains. All the dorsal mantle is covered with small conical brown tubercles, although frequently their base is whitish; tubercles located near the margin of the mantle are smaller. As in other species of Knoutsodonta, the mantle is very espiculous with elongated transversally laid spicules in the center, and diagonally laid near the edges, but this spiculation is not apparent due to the pigmentation of the body. The rhinophores are white, short, with up to nine lamellae and do not have a high rhinophoric sheath; the rhinophoric orifice has two tubercles in an anterior-internal position and in lateral-external position. The gill consists of up to nine small simply pinnate leaves arranged in a circle on the back of the dorsum, almost completely surrounding the anus; The gill crown is also tuberculate, with two tubers in anterior position and another one closing the gill circle. The gill leaves colour is white, like rhinophores, but Mediterranean specimens are pigmented dark brown with scores, like the mantle, although the spine is coloured cream. The cephalic region under the mantle does not differentiate oral palps; the cephalic veil border is usually pigmented brown. The foot is whitish with tiny brown spots; internal viscera can be glimpsed through the center of the foot as a reddish-brown stain.

The specimens of this species tend to live both in the intertidal and subtidal stratum, often under stones and on the bryozoan colonies from which they feed. There have been cited, as food or substrate,  the following species of bryozoans: Callopora spp., Escharella immersa, Microporella ciliata, Escharoides coccineus, Porella concinna and Schizomavella linearis (McDonald & Nybakken, 1999). The spawn consists of a semitransparent narrow cord with white eggs, wound in a tight flat spiral with up to 9 turns; sometimes there are two egg spirals surrounded by a unique exterior cord. The spawns have been observed in the month of May.


  • Knoutsodonta, from the Greek meaning “lame tooth”, to represent nudibranch species that lack a rachidian or middle tooth.
  • Pusilla, from Latin “pusillus”, petty, trifling, insignificant, very small.

There are few known references of this species. It has been observed in the Norwegian coast, in the British Isles, and in the Atlantic Iberian Peninsula shores. In the Iberian Coast it has been cited in the Cantabrian Sea and the Strait of Gibraltar.

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

References for the species: Knoutsodonta pusilla

    Galicia: Ortea (1979b), Urgorri and Besteiro (1983, 1984). Gibraltar: Sánchez Santos (pers. comm.).

    General: Brown & Picton, 1979:13; Picton & Morrow, 1994:66[P]; Thompson, 1988:190; Thompson & Brown, 1976:104; 1984:60[P]

    Sources: Cervera et al., 2004, Ballesteros, 2007 & 2016, McDonald, 2006 and other sources.


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

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

More pictures


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Further reading

Cite this article as:

Ballesteros, Manuel, Enric Madrenas, Miquel Pontes (2021) "Knoutsodonta pusilla" in OPK-Opistobranquis. Published: 17/05/2012. Accessed: 06/03/2021. Available at (

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