Hallaxa indecora (Bergh, 1905)

About a dozen specimens of this species have been shaken out of clumps of Halimeda algae on the atoll's eastern lagoon slope at depths of about 8 to 15m. The nudibranchs measured 7 to 23mm in length. They appeared to come off a very soft, dark brown sponge colored very much like the nudibranchs. They are probably fairly common, but their small size and close resemblance to the sponge makes them hard to find.

There is some variation in color from orange-brown to dark brown.

Most specimens have a hump on their backs just in front of the gills.

The two shots below are of the largest specimen found, which measured 23mm in length.

Note added August 2008: Indeed this species is not rare in the Halimeda patches. Probably several dozen have been shaken from the algae, where they seem to be feeding on a soft sponge that is the same color as the nudibranchs.

Created 19 February 2008
Updated 16 August 2008