Pleurobranchus forskalii (Rüppell & Leuckart, 1828)

Pleurobranchus forskalii was unknown in the Marshalls until 16 February 1998. One day when the trade winds were blowing the water across the reef, we decided to hide behind a sand bar to do some shallow reef diving in a place we had seen a particular species of surgeonfish we wanted to photograph. In shallow water at this spot, at a depth of 3 meters or less, were lots of large loose rocks. We had looked under some of these on previous dives and found a few nudibranchs and other interesting creatures, so part way through the dive, we moved shallow and turned over a few more. What we found on that day were lots--several dozen at least--Pleurobranchus forskalii plus a bunch of Pleurobranchus albiguttatus, another rare species in the Marshalls. There were a number of color forms of the former species and many were spawning. We stopped by the reef the next day to take another look, and they were still present in large numbers. However, when we next returned a couple of months later, not a single pleurobranch could be found. No more were seen until 17 June 2007, when four specimens were found hidden among Halimeda algae at a depth of about 15m on a lagoon slope several kilometers north of the previous sightings. Since then, a fair number have been sighted in similar Halimeda patches along the same reef, but we haven't yet seen all the color forms we saw that first day. Two of the shots below were captured from video, so are not very sharp. However, the captures illustrate the large variation in color of the species. The first shot below was the only still photo taken during the 1998 sighting.

The next three photos are of specimens found in 2007 and 2008.

They often bury in the sand by day. A thin layer of sand was just swept from the individual on the left, and another still partly covered sits just to the right.

The specimen below is next to its egg mass.

The one immediately below is putting an egg mass on a blade of algae.

More eggs from a lagoon algae patch on 3 October 2011.

Three differently colored specimens from the large group found in 1998 are in the capture below.

The next video capture show another color form.

The large specimen in the next two photos below was found in alagoon Halimeda patch at night on 3 July 2008. It measured approximately 175mm.

The specimen below was a tiny juvenile.

Here are some more recent color forms.

The next one was in a Kwajalein Atoll lagoon reef Halimeda patch at a depth of about 8m on 5 July 2009.

We have also seen one specimen in the Solomon Islands.

Created 5 February 2007
Updated 11 December 2011

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