Berthella stellata found sthrn Queensland

November 21, 2008
From: Gary Cobb

Concerning message #10544:

Hi Bill and everyone!
May I present a record for Berthella stellata, which is quite common here in the sthn Queensland intertidal areas. In regards to it's spawning ... I have never witnessed any 'Slug' that produces an egg mass so large in proportion to its body! The mass is round in diameter and even though it's body is near transparent you can't see eggs within the body.

Locality: Alexandra Headland, Mooloolaba, 100mm, Queensland, Australia, Pacific Ocean, 19 November 2008, Intertidal. Length: 15-20mm. Photographer: Gary Cobb.

I have included a photo of the shell.

Cobb, G.C., 2008 (Nov 21) Berthella stellata found sthrn Queensland. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from

Thanks Gary,

The egg mass is certainly very large in proportion to the animal. Some of the mucus molecules, which make up the jelly surrounding the egg string, have amzing powers of expansion when they come into contact with water. One of the great problems in dissecting the reproductive systems of opisthobranchs preserved in alcohol is to accidently cut into the mucus glands. I usually immerse specimens in water when I dissect and as soon as the mucus makes contact with the water it begins to expand quickly obscuring the rest of the anatomy and making further dissection impossible until all the mucus gland has been cut away.

It's good to get a photo of the fragile internal shell. Like so many 'primitive' sea slugs, the shell is - in evolutionary terms - in the process of disappearing. One character separating the genera Berthella and Berthellina is that in Berthella, the shell is relatively large covering much of the viscera, while in Berthellina it is reduced to a small plate, perhaps a tenth of the width of the mantle. I am pretty sure I can see the outline of the shell in your upper photo.

Best wishes,
Bill Rudman

Rudman, W.B., 2008 (Nov 21). Comment on Berthella stellata found sthrn Queensland by Gary Cobb. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from


Berthella stellata

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