Dendronotus robustus
Verrill, 1870

Family: Dendronotidae


Known from nth Atlantic and Arctic Oceans  [Svalbard (Spitzbergen), Greenland, nthn Norway] and Atlantic coast of Nth America [Cape Cod to Nova Scotia]  (Robilliard, 1970).         


Locality: Svalbard  (Spitzbergen), 15 metres, Norway, Arctic Ocean, 2002, Very silty bottom out of a glacier. Length: 15 cm.  Photographer: Erling Svensen.

Body translucent with fine reddish brown specks giving the body a reddish tinge and a pattern of reticulate reddish wrinkles. Scattered over dorsum are quite large white spots. Verrill described the white spots as yellow and also describe yellow tips to the gills and oral veil papillae. In the specimen illustrated here the spots and tips are white not yellow.

The body is relatively flattened and short and the large oral veil has four or five papillae on each side. They are usually thick and short with small simple branches. There are 6 - 7 pairs of gills down each side of the body. They are short and relatively unbranched. Often, each 'gill' consists of two or three separate trunks inserting separately into the body wall.

Little is known of the ecology of this species. Robilliard (1972) notes reports of it living from the intertidal to 230 m deep. He also reports frinding hydroid remains in the stomachs of Nth American animals and sabellid worms in animals from Norway.

Erling Svensen's animals at 15 cm long, are much longer than any previous record of the species.

  • Bergh, L. S. R. (1894) Reports on the dredging operations off the west coast of Central America to the Galapagos, to the west coast of Mexico, and in the Gulf of California, in charge of Alexander Agassiz, carried on by the U. S. Fish Commission steamer "Albatross", during 1891, Lieut. Commander Z. L. Tanner, U.S.N. commanding. Part 13. Die Opisthobranchien. Bulletin of the Museum of Comparative Zoology, Harvard, 32: 125-233, Pls.1-12.
  • Robilliard, G. A. (1970) The systematics and some aspects of the ecology of the genus Dendronotus. The Veliger, 12: 433-479, pls. 63-64.
  • Robilliard, G. A. (1972) A new species of Dendronotus from the northeastern Pacific with notes on Dendronotus nanus and Dendronotus robustus (Mollusca: Opisthobranchia).  Canadian Journal of Zoology, 50(4): 421-432.
  • Verrill, A.E. (1870) Contributions to zoology from the Museum of Yale College. No 8 - Descriptions of some New England Nudibranchiata. American Journal of Science & Arts, 50: 405-406.
Authorship details
Rudman, W.B., 2007 (March 6) Dendronotus robustus Verrill, 1870. [In] Sea Slug Forum. Australian Museum, Sydney. Available from

Related messages

Dendronotus robustus from Massachusetts, USA

March 8, 2007
From: Alan Shepard

Bill -
I saw Erling Svensen's wonderful photos of Dendronotus robustus [#19087 ] and figured I might as well send you my rather poor shot of the species. I have encountered this species only once and unfortunately it was at the end of a dive with only one frame left in the camera and a framer a bit too small for the species. The result was a shot which does not show the entire nudibranch and a rather poor shot at that. The coloration was a yellowish gold with numerous spots.

Locality: Folly Cove, Gloucester, 4 metres, Massachusetts, USA, Atlantic Ocean, summer 2003, Sandy bottom edged by rocks and boulders. Length: 5 centimetres. Photographer: Alan Shepard

Anyway I encountered it in the summer of 2003 in only 4 metres of water in a very sandy area. It was fairly large compared to other local species at just over 5 centimetres. I know of only one other local underwater photographer that has been able to take a photograph of D. robustus locally and he encountered it twice in the same cove at a depth of about 20 metres. His specimens were red with the typical spots.

This is one species that I really wish I would encounter again.

Alan Shepard

Shepard, A., 2007 (Mar 8) Dendronotus robustus from Massachusetts, USA. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from

Dear Alan,
Thanks very much for this photo of an animal from the other side of the Atlantic than Erling's. Don't worry that it isn't perfect - imperfections add reality to the Forum. Your photo shows an almost identically coloured animal, and if I look carefully I am pretty sure that the gills, instead of having a single trunk, are a cluster of two or three stalks, as in Sven's animal.

Best wishes,
Bill Rudman

Rudman, W.B., 2007 (Mar 8). Comment on Dendronotus robustus from Massachusetts, USA by Alan Shepard. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from

Dendronotus robustus from Spitzbergen, Nth Atlantic

March 7, 2007
From: Erling Svensen

Dear Bill,
I have been diving at Svalbard (Spitzbergen) in the Arctic Ocean, quite far to the north of Norway (aprox. 80 degrees) while on voyages on the research vessel Jan Mayen. In Kongsfjord with Ny Aalesund, just out from the glacier, I came across this Dendronotus robustus. At that time, in 2002 - I was using film, so I show only two pictures. One of an adult, more than 15 cm long, and one juvenile. I enclose the pictures. The water temperature was minus 1 degree Celsius and the depth aprox. 15 meters on a very silty bottom.

Locality: Svalbard  (Spitzbergen), 15 metres, Norway, Arctic Ocean, 2002, Very silty bottom out of a glacier. Length: 15 cm.. Photographer: Erling Svensen.

Thanks for very nice and helpful WEB-pages. Here is a new one for the Forum.

Best regards
Erling Svensen

Svensen, E., 2007 (Mar 7) Dendronotus robustus from Spitzbergen, Nth Atlantic. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from

Dear Erling,
I felt very cold just reading your message. Thanks very much for these photos of Dendronotus robustus. It is indeed a new one for the Forum and I don't recall ever seeing a photo of this species alive before.

Although Gordon Robilliard listed a number of differences between D. robustus and his new species D. albopunctatus, from the NE Pacific, they certainly look very similar externally. Do you know much about the biology of Dendronotus robustus? My first thought when seeing your upper photo was just how similar in body shape it is to a number of other unrelated opisthobranchs which live on soft sediments such as Euselenops luniceps and Kalinga ornata [see Fact Sheet], with a relatively wide foot, wide oral veil with tentacles along the edge, and flattened body. It would be interesting to know if D. robustus is also a burrower.

We know little about this species, which was first described by Verrill (1870) from Massachusetts, on the Atlantic coast of Nth America, and a few years later from Norwegian waters by Sars, (1878) as Dendronotus velifer. Thanks for this very interesting addition to the Forum.

Best wishes,
Bill Rudman

Rudman, W.B., 2007 (Mar 7). Comment on Dendronotus robustus from Spitzbergen, Nth Atlantic by Erling Svensen. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from