Dendronotaceans have a long and narrow body and have a row of branched or tuberculate processes on each side of the body, in dorsolateral position. The rhinophores can be smooth or have lamellae but their base is always surrounded by a high sheath, into which they can be retracted. Head may differentiate either rounded lateral expansions or a face veil with several digitations. The anus and the genital openings are located to the right of the body.

by Enric Madrenas

They feed primarily on cnidarians, such as hydroid colonies, soft corals and gorgonians. Species of the family Tethydidae, however, tend to eat small crustaceans such as amphipods, copepods, isopods and ostracods. Within this family, a big sizes species, Tethys fimbria, has a wider food spectrum as it has been cited feeding on small echinoderms, gastropods, polychaetes and small fish. Most dendronotacean are benthic but some species can swim by undulating movements of the body; species of the family Phylliroidae are pelagic and prey on jellyfish and siphonophores.

Members of the Dotidae family, characterized by having tuberculate dorsal processes, have been until recently considered within the Dendronotaceans. However, this group does no longer appear in the updated classification of nudibranchs accepted in WoRMS. The Dotidae, along with other traditional arminacean families are now grouped into the provisional clade “unassigned Cladobranchia” until new molecular phylogeny analysis clarify their relations with the other groups of nudibranchs.

  • Parvorder Dendronotida
    • Superfamily Tritonioidea Lamarck, 1809
      • Bornellidae Family Bergh, 1874: family with a single genus Bornella  Gray, 1850 that includes a dozen species distributed in tropical and subtropical waters.
      • Family Dendronotidae Allman, 1845: includes a single genus Dendronotus  Alder & Hancock, 1845 with about 17 accepted species. Only Dendronotus frondosus (Ascanius, 1774) is found in Iberian waters.
      • Family Hancockiidae MacFarland, 1923: includes as well a single genus Hancockia  Gosse, 1877 and six species. Just one species H.uncinata (Hesse, 1872) is known in Iberian waters.
      • Lomanotidae Family Bergh, 1890: with a single genus as well, Lomanotus  Verany, 1844 and six species, two of which L. marmoratus (Alder & Hancock, 1845) and L. Barlettai Garcia-Gomez, López-González & Garcia, 1990 have been cited in the Iberian Peninsula.
      • Family Phylliroidae Menke, 1830: species of this family are fully pelagic. Includes the genus Cephalopyge Hanel, 1905 with a single species C. trematoides (Chun, 1889) and the genus Phylliroe Péron & Lesueur, 1810 with only two species P. bucephala Lamarck, 1816 and P. lichtensteinii Eschscholtz, 1824. All three species have been found in the waters of the Canary Islands.
      • Family Scyllaeidae Alder & Hancock, 1835. This family includes the gesnus Crosslandia Eliot, 1902, Notobryon Odhner, 1936 and Scyllaea Linnaeus, 1758. Only S. pelagica Linnaeus, 1758 has been cited in Iberian waters and is called “Sargassum nudibranch” because it lives on the phaeophycean alga of the genus Sargassum, commonly found floating on the sea surface.
      • Family Tethydidae Rafinesque, 1815, this family includes two genus, Melibe Rang, 1829 with 17 known species and Tethys Linnaeus, 1767 with three species, of which only one T. fimbria Linnaeus, 1767 lives in european and Iberian waters.
      • Family Tritoniidae Lamarck, 1809: this is the largest family in genus and species, including the genus Marianina Pruvot-Fol, 1931, Marionopsis Odhner, 1934, Paratritonia Baba, 1949, Tochuina Odhner, 1963, Tritoniella Eliot, 1907, Tritonidoxa Bergh, 1907 , Tritonia Cuvier, 1797, Marionia Vayssière, 1877 and Tritoniopsis Eliot, 1905. Species of only the last three genus are known in the Iberian Peninsula.

Dendronotacean species recorded in the Mediterranean Sea or around the Iberian Peninsula:

Hancockia uncinata by Enric Madrenas

Hancockia uncinata

Lomanotus barlettai by José Carlos García Gómez

Lomanotus barlettai

Dendronotus frondosus by Klas Malmberg (Sweden)

Dendronotus frondosus

Lomanotus genei Adult with parasitic copepod eggs protruding from back. Mulroy Bay, Co Donegal, Ireland. - Photograph ©Bernard Picton

Lomanotus genei

Lomanotus marmoratus by Klas Malmberg (Sweden)

Lomanotus marmoratus

Marionia blainvillea @ Port de la Selva 26/10/2013 by Miquel Pontes

Marionia blainvillea

Melibe viridis @ Punta Japlenicka-island Ugljan, Croatia, length 45cm, depth 6m by Đani Iglic

Melibe viridis

Phylliroe lichtensteinii 3-01-2017 by Linda Ianello

Phylliroe lichtensteinii

Scyllaea pelagica by Enrico Ricchitelli

Scyllaea pelagica

Tethys fimbria by Gilles Cavignaux

Tethys fimbria

Tritonia coralliumrubri by Egidio Trainito

Tritonia coralliumrubri

Tritonia hombergii 85mm @ West Hurker, St. Abbs Head, Scotland, 4-08-2007 13m by Jim Anderson

Tritonia hombergii

Tritonia lineata by Enric Madrenas

Tritonia lineata

Tritonia manicata by Enric Madrenas

Tritonia manicata

Tritonia nilsodhneri per Enric Madrenas

Tritonia nilsodhneri

Tritonia plebeia - Photograph ©Bernard Picton

Tritonia plebeia

Tritonia striata by Enric Madrenas

Tritonia striata

Tritoniopsis cincta @ Argentario, Italy 25-05-2012 by Riccardo Delle Fratte

Tritoniopsis cincta