Knoutsodonta pictoni

Knoutsodonta pictoni  Furfaro & Trainito, 2017

Knoutsodonta pictoni by Enric Madrenas
Taxonomy
Class: Gastropoda  Cuvier, 1797
Subclass: Heterobranchia  J.E. Gray, 1840
Clade: Euthyneura  Spengel, 1881
Clade: Nudipleura  Wägele & Willan, 2000
Order: Nudibranchia  Cuvier, 1817
Suborder: Euctenidiacea  Tardy, 1970
Infraorder: Doridacea  Thiele, 1931
Superfamily: Onchidoridoidea  J.E. Gray, 1827
Family: Onchidorididae  J.E. Gray, 1827
Genus: Knoutsodonta Hallas & Gosliner, 2015
Species: Knoutsodonta pictoni  Furfaro & Trainito, 2017

Taxonomic Note: This recently described species has been identified repeatedly as Onchidoris pusilla (Alder & Hancock, 1845) because of its similar morphology: dark brown body due to scores of the same color and completely white rhinophores. However, the gill leaves in K. pictoni are of the same color as the body, in contrast to the white gill of the original description and the other reports of true O. pusilla. Hallas & Gosliner (2015) in their study on the phylogeny of the Onchidoridae establish the new genus Knoutsodonta Hallas & Gosliner, 2015 where they include several Onchidoris species (brasiliensis, depressa, jannae and oblonga) lacking a medial tooth in their radula. In the article describing K. pictoni, Furfaro & Trainito (2017) extend to 16 the number of known species of the genus Knoutsodonta, of which 6 are species living in the Mediterranean (K. pictoni, K. albonigra, K. bouvieri , K. depressa, K. neapolitana and K. sparsa).

Description
Animals of this species may reach up to 13 mm in length, but they do not usually exceed a size of 9-10 mm. The body shape is almost circular and it has a very dark brown color, formed by almost continuous spots of the same color. There are whitish spots near the edge of the mantle. Under the mantle the typical spiculation of the genus Onchidoris can be seen by transparency. The dorsum has slightly conical elevated and well spaced tubercles. The tubercles at the edge of the mantle are smaller. The tubercles have whitish the base and brown the apex. The rhinophores are completely white and retractile; have rudimentary lamellae, up to 10 in the largest specimens. The rhinophoral sheath is not high and has two large tubercles, one antero-internal and one lateral. The gill is formed by up to 9-10 bipinnate leaves in the largest specimens; the gill leaves are arranged in a circle around the anus, they are not retractile, they are semitransparent but they have numerous brown spots that give them a dark color. The intrabranchial circle has three tubercles, two anterior and one posterior, which closes the circle of gill leaves. The foot is whitish but has tiny brownish-red spots, visible with a binocular microscope, and a reddish-brown stain corresponding to the internal viscera. There are also brown spots on the flanks of the body and on the back of the foot. The mouth is located at the center of a sort of oral veil that extends laterally.

Biology
Specimens of this species were known in different points of the Catalan Costa Brava (Spain) since 1992 but were erroneously assigned to the species Onchidoris pusilla. It lives under rocks and almost always on colonies of encrusting bryozoans such as Reptadeonella violacea (see Furfaro & Trainito, 2017) on which it is usually unnoticed due to its color similarity. The predated areas of the bryozoan colony appear whitish, making it easier to tell if the nudibranch is around or not. The spawn, which is usually laid on top of the bryozoan briozoo, is formed by a semitransparent cord wrapped in a tight circular spiral of up to 7 turns, with numerous white eggs. It has been reported how two animals can lay a complex pattern in which one egg spiral is completely enclosed within another. Eggs are usually laid from April to May.

Etymology

  • Knoutsodonta, from the Greek meaning “lame tooth”, to represent
    nudibranch species that lack a rachidian or middle tooth.
  • Pictoni. After Bernard Picton, eminent British specialist in opistobranchs of the North Atlantic.

Distribution
K. pictoni has an Atlantic-Mediterranean distribution and has only been found so far on the Scottish and Irish coasts and in the central and western Mediterranean (see Furfaro & Trainito, 2017). In the Iberian Peninsula there are only reliable reports from the Costa Brava (Port Lligat to Lloret de Mar), and from the Maresme, where it has been reported in Llavaneres (Ballesteros et al., 2016), in all cases cited as O. pusilla or Knoutsodonta sp.

Known georeferenced records of the species: Knoutsodonta pictoni (z-200).
Sources:
: OBIS : OPK
: GROC 2010-2011 : VIMAR
: Enric Madrenas : Manuel Ballesteros.
: João Pedro Silva : M@re Nostrum
: Bernard Picton : Other sources
: GBIF.ORG : Marine Regions

Abundance

        Western Mediterranean:1 Stars
        Eastern Mediterranean:0 Stars
        Atlantic Ocean:1 Stars
This chart displays the observation probability for Knoutsodonta pictoni
based on our own records.

More pictures

Bibliography

Bibliography based on the works by Steve Long, 2006. Bibliography of Opisthobranchia 1554-2000 and Gary McDonald, 2009. Bibliographia Nudibranchia, with later updates from other resources.

Further reading

Cite this article as:

Ballesteros, Manuel, Enric Madrenas, Miquel Pontes et al. (2012-2017) "Knoutsodonta pictoni" in OPK-Opistobranquis, Published: 15/09/2015, Accessed: 24/09/2017 at (http://opistobranquis.info/en/Zv9eN)

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