Berthella martensi (Pilsbry, 1896)

As can be seen from the photos below, Berthella martensi is a variable species. Many other color forms can be seen on the Sea Slug Forum. All are characterized by having the mantle split into three lobes, one on each side and one posterior. These lobes can autotomize, or break off, if the animal is disturbed. This species is found in the Marshalls under rocks on lagoon reefs, pinnacles, and seaward reefs at depths of two to at least 20 meters. We have seen specimens at Kwajalein, Enewetak, and Utirik Atolls, as well as one color form from Hawaii. Note the two black eyes on the right side just out from under the anterior dorsal lobe in the first photo below.

The one below has lost the rear lobe of its mantle.

The specimen below has lost the rear lobe of its mantle.

This one was found on 7 March 2010 under a rock on the Kwajalein Atoll seaward reef in about 7m of water.

This small 10mm individual was in a Kwajalein Halimeda patch on 4 September 2011.

A very small specimen found on 16 October 2016 had the shell slightly visible through the dorsum.

Created 27 January 2007
Updated 19 March 2017

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