Chelidonura flavolobata & C. inornata

May 31, 2003
From: Bill Rudman

PHOTOS: Upper: 'Spotted' form of C. flavolobata. Red Sea ca. 20 km south of "Quseir", May 2003. Photo: Nils Anthes. Lower: C. inornata. Christmas Island, Line Islands, eastern Kiribati, 35mm long. May 2003. Photo: Don Barclay.

Nils Anthes recent messages [message 1, message 2, message 3] raise the question of just what is the relationship between C. flavolobata from the Indian Ocean and C. inornata from the Western Pacific. Also, is Chelidonura sp. 4 from Fiji a colour variant of C. inornata?

C. flavolobata, known previously from only 2 specimens, was originally characterised by the solid yellow lobes on either side of the head and the lack of white spots anywhere. Nils's observations suggest that C. flavolobata can vary quite significantly in colour from animals which are pure black with yellow head lobes, to animals in which the yellow is restricted to a marginal band on white head lobes and with 'dense white spots around the eyes, at the edges of the parapodia and the rear end of the head shield'. In the upper photo which shows one of these 'spotted' animals, there also appears to be a white band across the front of the head. A similar band is found in C. inornata.

Looking at the messages of other animals identified as C. flavolobata, I am sure that Marina Poddubetskaia's March 2003 photo has the same colour pattern, but I can't see the head clearly enough in her earlier messages [photo 1, photo 2] to be sure.

How can we interpret this? From Nils' mating observations it would seem that C. flavolobata is much more variable in colour than earlier reports would suggest. If we compare the colour of this 'spotted' form to the colour of Chelidonura inornata then the only differences are that C. inornata has white spots on the parapodia and foot and usually the white band across the head is more prominent. The similarities though, including the orange band on the head lobes and the position of the white pigmentation on the parapodial borders is quite remarkable.

I would agree that it is probably best to consider the Pacific species and the Indian Ocean species to be separate, but we will need to enlarge the definition of C. flavolobata. However I don't know what to do with Chelidonura sp. 4, from Fiji, which seems to be a C. inornata without white specks on the parapodia, which would make it identical to the white spotted C. flavolobata from the Red Sea.
Bill Rudman

Rudman, W.B., 2003 (May 31) Chelidonura flavolobata & C. inornata. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/10121

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