September 17, 2002
From: Baki Yokes
Here is a series of photos of a Dondice banyulensis eating another slug. When I first saw them, I thought that the D. banyulensis was eating the last portion of the hydroid colony, on which it was standing. Then I realized that the victim was not a hydroid but a Facelina rubrovittata. The big slug was swallowing the little one, millimeter by milimeter. All of a sudden, D. banyulensis squeezed the F. rubrovittata and half of the animal fell down. After chewing the last portion for a few seconds, D. banyulensis started to search for the rest of the meal. I didn't know if the F. rubrovittata could survive, but at that moment, with its halved foot, it was moving much faster than its predator.
Up to now, I only knew that D. banyulensis feeds on hydroid colonies. In Gary McDonald & James Nybakken's List of the Worldwide Food Habits of Nudibranchs, Flabellina pedata and Flabellina affinis are also listed on the menu for D. banyulensis. All these Aeolids (D. banyulensis, F. affinis, F. pedata, F. rubrovittata) feed on hydroids of the genus Eudendrium. As these slugs store the nematocysts of the cnidarians they eat, on their cerata, is it possible that, D. banyulensis misidentifies these slugs as a delicious hydroid colony? Or is it just a competetion for the same kind of foodstuff, since the food is scarce?
Upper Right: Dondice eating Facelina. Lower Left: Half eaten Facelina escaping. Lower Right: Facelina caught again. Antalya, Turkey, Dive site: Uc Adalar. Depth: 18m, Sept.1, 2002. Photos: Baki Yokes.
Yokes, B., 2002 (Sep 17) Slug eating slug - Dondice banyulensis. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/7965
Thanks for this interesting observation and wonderful photos. I've included a closeup alongside. While I guess it is possible Dondice mistakes its aeolid prey as hydroids, I suspect its much more likely that it is just a voracious carnivore which feeds on these aeolids because they feed on the same hydroid colonies and so are 'available'. There are a number of glaucid aeolids with a reputation for feeding on things other than their standard hydroid food. It's never a good idea when collecting to put glaucids together in collecting jars as 'tragedies' often occur.
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