Cuthona sp.

Photo courtesy of Francis and Pirjo Pellet
Seraya Beach,Tulamben, Bali, Indonesia
Apr. 2006

Cuthona sp.? Hummmmmm…..

As our Brancher buddies look closer and closer, they are finding the most incredible tiny aeolids. Here is another, or maybe the same species of a hydroid mimicking aeolid. Some time back Webmaster Mike ran John Greenameyer’s amazing species from PNG. Francis and Pirjo’s specimen here is very similar except for the lack of red and white in the swollen, hydroid polyp-like ceratal tips. This might me simple variation between localities, however. The latter also has a very clear body with no pigmentation.

A similar species can be found on the Sea Slug Forum , referred to as Cuthona kuiteri. In fact, our Cuthona sp. can be seen feeding on a solidary hydroid in a picture taken by Pirjo with her Olympus 770.

This feeding behavior corresponds very well with that set out by Rudman in his description of Cuthona kuiteri :

"...Cuthona kuiteri has only been found associated with Zyzzyzus spongicola , which is a solitary tubularian hydroid which lives partially buried in sponge colonies. In a unique type of mimicry the aeolid has evolved cerata which mimic the polyps of the hydroids, ..."

All three have long smooth rhinophores and cerata swollen into the shape of the polyp of a tubularian hydroid. The only difference is the degree to which the ceratal tips are developed. The cerata of C. kuiteri have developed rings of both oral and aboral tentacles of the hydroid.

It would be fascinating if these turned out to be three separate and distinguishable species.


Rudman, W.B. 1981. Polyp mimicry in a new species of aeolid nudibranch mollusc. Journal of Zoology, London, 193: 421-427.

Behrens, D.W. 2005. Nudibranch Behavior. New World Publications. 176 pp.

Dave Behrens
Gig Harbor, Washington
May 2006

Francis and Pirjo Pellet in laboratory, Cerbere, July, 2005

Francis and Pirjo Pellet live in Les Vans in the Rhone Valley, France. I met Francis and Pirjo at the July, 2005 Opisthobranch Course held at Cerbere, France hosted by Robert Oms .

I believe this was their third time in attending the course so that gives you an idea how enthusiastic they are about branching! They are well traveled and enjoy diving as a team to find and photograph sea slugs!

Am looking forward to seeing more of their images as they certainly excel in the art of taking branch photographs!

To quote Francis:

"...I was born in Paris 1954. Since 1954 I have my practice as a doctor in the South of France.I started diving at the age of 15 years and I am instructor since 2004. I am interested in sea slugs since 5 years and taking pictures with Nikon Coolpix 5000 in Subal housing and 2 Inon strobes since 3 years. I am diving in France and Spain (Mediterranean Sea) and every holiday in South East Asia to discover its fabulous biodiversity.

My wife Pirjo was born in Finland and in everyday life we work as a team as we do underwater. She is Padi Dive Master and has studied marine biology with the french diving school. She is just starting taking underwater pictures with her olympus UZ 770 with Inon strobe. Our ambition is to take good pictures but above all, we want to bring a little bit happiness if possible to those who share our passion..."

Send Francis and Pirjo mail at

What more can be said!

San Diego, Calif

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