Melibe leonina loses cerata [1]

October 1, 2005
From: Jan Kocian

Hello Bill,
I had an interesting encounter with Melibe leonina. Carried by the current, it was swimming by , its body flip-flopping back and forth. I decided to follow it on its journey through the pilings beneath the the old wharf. In spite of the strong current, it managed to land on leeward side of one of the pilings and start to explore area where a piece of kelp stuck on some of the Green Sea Urchins. The eddies dislodged the slug and it landed on one of sea anemones also thriving on the piling. By wriggling around and detaching some of its cerata the slug got away only to land on second anemone. Again, after some maneuvering it got free, but only two cerata left on its body. From here it continued to swim away, this time avoiding the rest of pilings. I wonder if it can survive with this many cerata missing..

Locality: Whidbey Island, Puget Sound, Washington, USA. Pacific Ocean.
Depth: 15 feet. Length: 2 inches. 24 September 2005. old wharf. Photographer: Jan Kocian


Dear Jan,
Firstly, thanks for the wonderful cartoon! I'll have to make you the Forum's 'official cartoonist' - no salary unfortunately. Thanks also for the interesting observation and photos. I've include some in a second message [#14889 ] as we have to restrict the number of images per message.

Species of Melibe, and some other opisthobranchs are able to drop some of their cerata, and other body parts as a defensive measure - a bit like some lizards drop their tails. It is called autotomy. Not much is known about regrowth of body parts. There is a big paper by Bickell-Page (1989) on ceratal autotomy, which investigates the complex processes in both the nervous system and the muscles, which is needed for autotomy to occur. But from memory I am pretty sure no mention is made of regrowth. However there is a paper on ceratal loss in our old friend Hermissenda crassicornis (see Miller & Byrne, 2000) which did study regrowth, and they showed that Hermissenda can fully regrow its cerata in about 40 days. An earlier study by Kress (1968) on a number of species of Doto, showed it took between 30 and 60 days for full regrowth depending on the species. When you think this means regrowing the internal digestive gland as well as the cerata, with all the skin glands etc, it is quite a complex process. Most nudibranchs can survive periods of starvation, often by absorbing their gonads so I suspect no great harm will come to the Melibe as it regrows its cerata. As you can see in your photo,  Melibe leonina also has branches of the digestive galnd in its body wall as well as the cerata, so its not totally bereft of a gut even when it loses its cerata.

  • Bickell-Page, L. R. (1989) Autotomy of cerata by the nudibranch Melibe leonina (Mollusca): ultrastructure of the autotomy plane and neural plane and neural correlate of the behaviour. Philosophical Transactions of the Royal Society of London, B 324: 149-172.
  • Kress, A. (1968) Untersuchungen zur histologie, autotomie und regeneration dreier Doto-Arten Doto coronata, D. pinnatifida, D. fragilis (Gastropoda, Opisthobranchia). Revue Suisse de Zoologie 75: 235-303.
  • Miller, J. A. and Byrne, M. (2000) Ceratal autotomy and regeneration in the aeolid nudibranch Phidiana crassicornis and the role of predators. Invertebrate Biology 119: 167-176.

Best wishes,
Bill Rudman

Rudman, W.B., 2005 (Oct 1). Comment on Melibe leonina loses cerata [1] by Jan Kocian. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from


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