Asteronotus cespitosus (van Hasselt, 1824)

The unmistakable species Asteronotus cespitosus is known from the Marshalls from about a dozen specimens so far. Most of them, including four clustered together with egg masses, were found at a depth of about 3 meters in Kwajalein Harbor under sheets of aluminum siding blown into the water by a storm. This and other aluminum debris that rest on the sand and Halimeda algae bottom under our moored boat have proven very fruitful as "nudibranch collectors." A number of other species are known from the Marshalls solely from specimens found under these few sheets of aluminum. Two more specimens were found together at low tide on an intertidal reef southeast of Roi-Namur Island in Kwajalein Atoll.

The shot below shows the anterior end with the rhinophores.

Here is a close-up of the branching gills.

When found, the two animals had just deposited an egg mass on the sponge-encrusted undersurface of the aluminum sheet. This image is captured from video and is therefore not very clear.

The specimen below appeared to be a young one of these. It measured 50mm, about half the length of most of our specimens. It was found in a patch of Halimeda and other algae at a depth of 8m on 22 December 2008.

The two below were observed in the harbor on 1 July 2012.

Another large pair found in Kwajalein Harbor in May, 2016.

We have also seen A. cespitosus in Hawaii and in the Solomon Islands.

Created 15 December 2006
Updated 16 July 2016

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