Camouflaged sea slug from Sydney

April 9, 2000
From: Robyn Stevens

Dear Bill,
I have found some tiny (2cm long) sea slugs in about 3m water off Sydney and I would love to know what they are.

They are dark green, with white antennae, 2 flaps of mantle that almost meet along the top (like a sea hare),and 3 white dots along the top margin of the flaps. They are eating the large dark green algae (Codium duthiae / galeatum?) which is in my fish tank. They are perfectly matched colourwise and tend to sit in the U-shaped bends in the algae making them difficult to find.

Also, I'd love some hints on how to photograph them. Are the amazing photos on your site taken with underwater cameras?
Thanks for your time,

Stevens, R., 2000 (Apr 9) Camouflaged sea slug from Sydney. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from

Dear Robyn,
I am pretty sure your animal is Elysia maoria. It belongs to a group of sea-slugs called sacoglossans which are all herbivores, different species feeding on different species of algae. Another species found on the same species of Codium as Elysia maoria is Placida dendritica. Have a look at the page on that species to find out about the amazing ability of some sacoglossans to keep plant organelles alive and photosynthesising in their own bodies.

For a further idea of diversity in the sacoglossans go to the Species List and look at any of the species listed in the Order Sacoglossa.

The short answer to your question about photographs is that most are taken in special dishes and aquaria I have made so I can control the lighting and background etc. It requires very clean glass and very clean water, but for microscopic and intertidal animals there are no easy alternatives. I have had quite a few inquiries about photography, and I have been meaning to prepare a page on the subject. With luck I will get around to it soon.

Best wishes,
Bill Rudman.

Rudman, W.B., 2000 (Apr 9). Comment on Camouflaged sea slug from Sydney by Robyn Stevens. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from


Elysia maoria

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