Re: 'Aeolidia' helicochorda

June 23, 2001
From: Richard Willan

Dear Bill,
Noticing your couple of recent messages on the Forum relating to "Aeolidia" helicochorda, I realised you had not caught up with Michael Miller's recent review of the New Zealand Aeolidiidae. A new genus, Burnaia, is created in that article for this species and there are other major changes to the taxonomy and nomenclature of the whole family.

In my opinion, the aeolid from Malaysia you have included on the Forum is not Burnaia helicochorda. Three characters are too disparate to call it that name. Firstly, the rhinophores of the Malaysian animal are much longer in proportion to the cerata and they have many lamellae. Secondly, the cerata are larger and not cylindrical; they actually seem to be inflated and/or compressed like those of Cyerce. Thirdly, the digestive diverticulum is much narrower. In addition, this species seems to lack the dark red horseshoe-shaped marking on its head that is very characteristic of B. helicochorda. Though it it impossible to be certain on this last point because the photo of the Malaysian animal does not show the head clearly.

Miller, M.C. (2001) Aeolid nudibranchs (Gastropoda: Opisthobranchia) of the family Aeolidiidae from New Zealand waters. Journal of Natural History, 35(5): 629-663.


Willan, R.C., 2001 (Jun 23) Re: 'Aeolidia' helicochorda. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from

Note added 13 Jan 2003: This is almost certainly Facelina rhodopos. See Nishina Masayoshi's message.

Dear Richard,
Thanks for alerting me to Michael Miller's review. Michael pronised this review when he first described A. helicochorda so I wondered when it was to be published.

Concerning the identity of the animal from Malaysia, I find it a bit difficult to be quite as definite in my views as you apparently feel. The rhinophores do seem more slender but they are certainly do not appear to be any more lamellate than new South Wales animals. Concerning the shape of the cerata - they certainly seem cylindrical to me. As you say they are inflated, which is certainly different from in Michael's description where they are described as long and slender, much like in the photos at the top of the page from New South Wales. However the very animals in the photos were able to transform the shape of their cerata into much shorter inflated structures. Unfortunately I have been unable to photograph them in this state but I have drawings of them doing this, and as I say at the top of the page, when they are inflated like this there are distinctive concentric rings just below the tip, a bit like an earthworms annuli. The thickness of the digestive gland is also a function of feeding, starved animals having very narrow digestive gland ducts. Concerning the H marking on the head, it's just not possible to see in Nishina's photos, and for that matter you can't see it on my photos either.

I don't know whether Nishina's animal is Burnaia helicochorda or not, we would need to know more about its anatomy before we could say anything sensible, but I think it is worth making the suggestion at this stage.
Best wishes,
Bill Rudman

Rudman, W.B., 2001 (Jun 23). Comment on Re: 'Aeolidia' helicochorda by Richard Willan. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from


Facelina rhodopos

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