D. frondosus can be found all around the British Isles. The species range extends southwards to the Atlantic coast as far south as France; eastwards to Canada and the United States as south as new Jersey, and the Pacific coast of Canada and United States as far south as Los Angeles; and northwards into the Arctic circle.

Biogeographic Regions: arctic ocean (Native ); atlantic ocean (Native ); pacific ocean (Native )

This species of nudibranch is highly variable in colour and has been thought to be a collection of several species. They may have white or mottled coloring with yellow, red or brown pigment. There may be up to nine pairs of gills along the pallial rim, which is the mantle. They have gills, oral veil and rhinophore sheaths, antenna-like organs, that are extended to form branched processes. Adults of this species may grow to 100 mm in length. The key distinguishing characteristics of this species are the large arborescent gills arising from the mantle edge and the arborescent processes on the edge of the rhinophore sheaths. The head is blunt with six branched projections extending forward. A striking feature is the two rows of 5-8 bushy projections along the back. (Amos and Amos 1985)

D. frondosus are part of the bottom creepers that live in cold northern seas.

Aquatic Biomes: benthic

D. frondosus feeds on a variety of hydroids. The younger juvenille members of the species typically feed on calyptoblastic hydroids of Obelia, Halecium and Sertularia cupressina & Dynamena pumila . The adults usually feed on the gymnoblastic hydroids of the genus Tubularia.

Dendronotus frondosus is hermaphroditic. The larval stage of the development is asymmetrical, although the adults show bilateral symmetry.

US Federal List: no special status

CITES: no special status

There are no known negative effects of this soecies to humans.

There are no known positive benefits of this species to humans.