Sacoglossa - general anatomy, natural history

• See messages below.
• See Cynthia Trowbridge's message discussing predation on sacoglossans.
• See Sacoglossan feeding.

Authorship details
Rudman, W.B., 1999 (October 18) Sacoglossa - general anatomy, natural history. [In] Sea Slug Forum. Australian Museum, Sydney. Available from

Related messages

How many Sacoglossan species?

June 7, 2002
From: Paola Gianguzza

Dearest all,
How many sacoglossan species have been descibed up until now? I've read that they should be around 250? Do you agree? Have you some recent references to mention for this?
Thank you in advance

Gianguzza, P., 2002 (Jun 7) How many Sacoglossan species?. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from

Dear Paola,
Perhaps someone is keeping a list and can give us a 'guesstimate'
Bill Rudman

Oxynoe viridis life cycle

May 31, 2002
From: Amanda Edwards

Hi Dr Rudman,
My name is Amanda Edwards and I am currently doing an Honours project at Wollongong University with Andy Davis and Jeff Wright. My project involves looking at fauna associated with a number of Caulerpa species. It also involves a set of feeding trials on Caulerpa taxifolia and C. filiformis with Oxynoe viridis . At the moment I have not been able to obtain much useful information on the Oxynoe viridis life cycle or how to raise and culture them in a lab. Could you please give me an idea of how to do this and the names of some web sites or books that could help me? Also, do you know what species of opisthobranchs are associated with different Caulerpa species. Your help would be much appreciated.
Thanks heaps!

Edwards, A., 2002 (May 31) Oxynoe viridis life cycle. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from

Dear Amanda,
Your project sounds very interesting and I look forward to hearing of your results. I don't know of any life history / life cycle studies on Oxynoe viridis but I am pretty sure it has planktotrophic eggs so will be difficult to breed in aquarium conditions unless you have facilities to culture phytoplankton-feeding veliger larvae. Concerning feeding, have a look at the Sacoglossan Feeding and Sacoglossan Biology pages for some background information. There are references and messages there discussing the food of Australian species.

There is also a lot of information on feeding scattered through various messages so it would pay to use the search facility on the Forum to search for food and feeding. Another way would be to look through the sacoglossan species in the Species List. There are many photos of species on their probable food algae.
Best wishes,
Bill Rudman

Rudman, W.B., 2002 (May 31). Comment on Oxynoe viridis life cycle by Amanda Edwards. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from

Function of the sacoglossan ascus

October 19, 1999
From: Victor Chow

Dr. Rudman

I have been doing some reading about sacoglossans and am curious as to the function of the blind pouch "ascus" where old teeth are stored. Is there a known reason for the collection of worn out radular teeth?
Thank you

Victor Chow

Chow, V., 1999 (Oct 19) Function of the sacoglossan ascus. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from

Dear Victor,
The short answer is I know of no reason why they should store old teeth. Perhaps its to do with the way they feed. Certainly in molluscs which treat their teeth relatively roughly - grazers and scrapers for example, the worn teeth are broken off just through the nature of the feeding behaviour of the animal. However sacoglossans feed by piercing the cell wall of their algal food. Perhaps the way they feed means the functional teeth need to be strongly attached to the underlying ribbon, so strongly attached in fact that once the tooth is blunt and of no further it can't be easily broken off during the feeding movements of the sacoglossan. A sac would be a place for the useless teeth to accumulate out of 'harm's way'.

Just a flight of fancy on my behalf. Hopefully one of our sacoglossan experts can give us a better explanation.
Bill Rudman.

Rudman, W.B., 1999 (Oct 19). Comment on Function of the sacoglossan ascus by Victor Chow. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from