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

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