Syphonata geographica feeding on Halophila

November 27, 2007
From: Leanne & David Atkinson

Hi Bill,
We've been finding a few Syphonota geographica in the same area as the Petalifera ramosa and some Aplysia sydneyensis so we have been watching closely to try to see what they eat and hoping to catch them laying eggs or mating. We found this Syphonata geographica grazing on the leaf shaped seaweed that we've been finding the Petalifera ramosa on. The Petaliferas seem to glide over as if they are grazing on something on the surface since there are no sign of damage. This Syphonata geographica just munches its way through the entire leaf. Here is an action sequence. Hope it is of interest. We haven't seen the burrowing under the sand as mentioned in other postings but there does seem to be a root system under the sand maybe they can camouflage and eat at the same time.

Locality: Fly Point, Marine Park, Port Stephens, 8 metres, New South Wales, Australia, Pacific, 10 November 2007, Sandy bottom scattered sponges, ascidians and seaweed. Length: approximately 130 mm. Photographer: Leanne & David Atkinson.

Hope this finds you well.
Leanne & David Atkinson

Atkinson, L. & D., 2007 (Nov 27) Syphonata geographica feeding on Halophila. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from

Dear Leanne & David,

This is a very interesting observation as I know of no direct observations of Syphonota feeding.  The plant they are eating in your photos is a flowering plant rather than an algae. It is the sea grass Halophila, probably Halophila ovata, but I am no expert on sea grasses. There is an earlier message from Singapore [#9109] showing a Syphonota burrowing right by a clump of same sea grass which may be more than a coincidence.

Even more interesting is scientifc paper published earlier this year (Gavagnin et al, 2007) which reports on the secondary metabolites found in Syphonota, including one molecule that suggested that Syphonota geographica feeds on the sea grass Halophila stipulacea. As I said to Margherita Gavagnin at the time [message #20811] this type of research is proving to be a powerful tool in linking particular species to their food items.

Your observation certainly confirms this.

  • M. Gavagnin, M. Carbone, P. Amodeo, E. Mollo, R. M. Vitale, V. Roussis and G. Cimino. (2007) Structure and absolute stereochemistry of syphonoside: a unique macrocyclic glycoterpenoid from marine organisms.  J. Org. Chem., 72: 5625-5630.

Best wishes,
Bill Rudman

Rudman, W.B., 2007 (Nov 27). Comment on Syphonata geographica feeding on Halophila by Leanne & David Atkinson. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from

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