Coral - feeding ? aeolid

July 29, 2006
From: Charles Raabe

This specimen was found at the base of an Acropora sp. and is my only real suspect as to the coral losing tissue.

Locality: Coral Reef, 15 feet, Philippines, Indo-pacific, 14 July 2006, reef . Length: less than 1 mm. Photographer: Charles Raabe.

This specimen is so small it took the aid of a microscope to get these images. Thank you.

Charles Raabe

Raabe, C., 2006 (Jul 29) Coral - feeding ? aeolid. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from

Dear Charles,
I don't know of any aeolid whichs feeds on Acropora but I guess its certainly a likely candidate for a hungry aeolid. I have summarised most of what we know about coral feeding nudibranchs on a separate page. One way coral-feeding aeolids differ from other aeolids, which usually feed on hydroids and sea anemones, is that they have lost the cnidosac at the tip of the cerata. Instead the tips of their cerata are swollen with large gland cells, which I presume produce defensive secretions [see Coral-feeding - defensive adaptations ].

If you look at your animal, the tips of the cerata are a bit swollen and do seem to have glands at the tip, so it is possible that you have an aeolid feeding on Acropora.  I am afraid the only way to be sure would be to leave the aeolid where it is and see if it grows and the Acropora continues to decline. I would suspect if it is small and you have noticed damage to the coral then there may be a group of these aeolids present. Probably not what you wish to hear, but very interesting to me.

Best wishes,
Bill Rudman

Rudman, W.B., 2006 (Jul 29). Comment on Coral - feeding ? aeolid by Charles Raabe. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from

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