Siphon Withdrawal Reflex in Sea Hares

December 15, 2000
From: Steve Potts

Dear Dr. Rudman,

I am in a chemical ecology course and have chosen to study Aplysia. A paper written by Stopfer, Chen, and Carew: "Evoked Ink Release in Aplysia Produces Inhibition of the Siphon Withdrawal Reflex in Neighboring Conspecifics" suggests that the ink may serve an alarm function. I cannot ascertain from the article, however, what is meant by the "ink rapidly inducing inhibition of the tail-elicited siphon withdrawal reflex" in neighboring Aplysia.

Can you please help me understand what this means?

Thank you very much,
Steve Potts

Potts, S., 2000 (Dec 15) Siphon Withdrawal Reflex in Sea Hares. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from

Dear Steve,
I am not sure I can help that much if they haven't defined the terms they are using in the paper. When Eric Kandel and others began studying Aplysia behaviour many years ago they needed to qualify, describe and name every part of the Sea Hare's behaviour so that they could describe all the reactions they would observe when studying the effect of stimulating individual nerve cells. The 'siphon withdrawal reflex' is just a name for the withdrawal of the siphon into the mantle cavity when the animal is stimulated some way. I can only assume that a 'tail-elicited siphon withdrawal reflex' is a withdrawal caused by poking the Sea Hare's 'tail' or posterior end of the foot.

It seems they are suggesting that the ink of one Sea Hare makes neighbouring Sea Hares less likely to withdraw their siphons - which doesn't fit with your suggestion that the ink may have some alarm function.

Basically I am not sure. I guess you are aware of Eric Kandel's important books on Sea Hare behaviour. I read recently that he has been awarded a Nobel Prize, so there is still hope for us slug workers.

I would like a full reference to the Stopfer et al paper please.

Best wishes,
Bill Rudman.


Ink glands

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