Is this the largest nudibranch?

November 30, 1999
From: Yoshi Hirano

Dear Bill,

A technician of our laboratory found a very large dorid nudibranch in nearby port this week. It measures more than 350 mm long! I am not familar with the species. I took these pictures in the aquarium. By the way, do you know what is the biggest record of body size for nudibranchs?

The colour of our specimen is dorsally quite dark brown overall. It weighs 2 kg! The tubercle patterns of the present species seem to consist of large tubercles, each of which is surrounded by several small ones. The secondary gills remind me of those of Dendrodoris. Can this species be Dendrodoris tuberculosa? I hope to hear your suggestions.

I measured the animal in the relaxed condition in a tide pool. It was 35 cm long. Out of water, flattened on the laboratory sink it was 40 cm in length

Data: Amatsu-Kominato, Boso Peninsula, central Japan. 35 07N, 140 11E. Found near the surface on the concrete wall of a fishing port. 23rd November, 1999. Still alive at Kominato Marine Laboratory Aquarium. The maximum length is 40 cm. The wet weight is 2 kg. Photo: Yoshi J. Hirano.

I hope all is well with you and am hoping to hear from you.

Best wishes,

Hirano, Y., 1999 (Nov 30) Is this the largest nudibranch?. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from

Dear Yoshi,
Your animal is Dendrodoris carbunculosa Kelaart, 1858 which has usually been confused with Dendrodoris tuberculosa. I have prepared new pages on both these species to show the differences.

I knew this species grew quite large but I don't know of one reaching your 350 - 400mm range.

Concerning the largest sea-slug, nudibranch etc. By coincidence, I have just received a message from Amelia Campbell asking the very question, so I have started a page for the largest, smallest, fastest etc sea slug. Any contributions are welcome. Have a look at my answer to her question.

Best wishes,
Bill Rudman.

Rudman, W.B., 1999 (Nov 30). Comment on Is this the largest nudibranch? by Yoshi Hirano. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from

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