Favorinus japonicus Baba, 1949

At least 25 specimens have been found at Enewetak and Kwajalein Atolls on lagoon reefs, pinnacles, and on the seaward reef. They are often found in small groups eating the eggs of other opisthobranch mollusks, and their highly variable colors generally reflect the colors of the eggs they have been eating. We have found them eating the eggs of Hexabranchus sanguineus, Dendrodoris nigra, and Dolabella auricularia, among others.

These three from Kwajalein are finishing up an unidentified egg mass.

This specimen is on the egg mass of Dendrodoris nigra. The Dendrodoris was still under the same rock.

That's quite a long tail.

Favorinus japonicus may deposit its own eggs, the small white tight spiral below, on the opisthobranch egg mass it is eating.

The photo below was shot on 5 October 2008 of an egg mass being eaten by both Favorinus japonicus and F. mirabilis. There were initially two of each species on the mass, but one of the F. mirabilis had crawled away by the time this photo was taken. Many of the eggs appear to have already been eaten. There is a pink F. japonicus crawling away just below the egg mass, and a white one curled up in the center. A small egg mass, possibly from one of the Favorinus, can be seen just above the larger mass being eaten.

The white specimen from the center of the egg mass above is seen in the closer shot below. This specimen helped us confirm that what we previously considered an unknown eolid is indeed a color form of Favorinus japonicus. The previously specimen is shown in the bottom photo.

Created 8 January 2007
Updated 5 January 2009