Thorunna purpuropedis was originally described from the Marshalls. It is known here from three specimens found at Enewetak Atoll and as of this writing 12 more from Kwajalein. All were found on lagoon reefs and pinnacles under chunks of dead coral at depths of 6 to 10m and measured 5 to 11mm in length. Dorsal color ranges from purple to blue to white, as seen in the photos below. The first specimen was found under a rock on 20 August 2007. Thorunna purpuropedis was first reported in the Marshalls from Enewetak Atoll by Rudman (1985).
The next two shots show a Kwajalein Atoll specimen found on 7 September 2008. It measured 8mm in length. Unlike the previous specimen, purple patches extended through the orange and red marginal bands just anterior and lateral to the rhinophores.
On 24 December 2007, we found two specimens that looked like the one below and thought they were quite similar to Thorunna montrouzieri from New Caledonia, except in that species, the wide orange marginal band is interrupted twice in the front and once in the rear by patches of purple not present in the Marshall Islands specimens. The larger of the pair measured 11mm in length, and neither had any trace of the anterior or posterior purple except for a light tinge of the color at the tip of the tail. The two nudibranchs were under a chunk of dead coral resting on a rubble bottom on a Kwajalein Atoll lagoon pinnacle at a depth of about 8m. They were eating a thinly encrusting light tan colored sponge, and there was a white egg mass nearby. Since it appeared that this could be something different, one specimen was collected for closer examination; the other crawled into a hole in the rock out of reach. The next two shots show one of the specimens found at that time and the egg mass.
On 20 January 2008, we returned to the same site and under the very same rock were again two specimens, so at least one of them had to be different from the previous observation. Notice from the photos below that the smaller one, which measured 9mm in length, has purple patches replacing the orange marginal coloration just forward of the rhinophores, similar to the blue specimen above. These two were munching on the same encrusting sponge colony as last time, and there was a new egg mass, seen at the left side in the bottom photograph. At this point, we still assumed the white and blue ones were different species.
On 17 February 2009, enlightenment was attained with the three specimens in the photo below were found together under a rock on a Kwajalein lagoon pinnacle at a depth of about 8m. Here a purple specimen, shown close in the following photo, with anterolateral purple patches, was with two of the white ones, one with the purple patches (although hard to see on the middle specimen) and one without. Then we noticed that if you ignore the middorsal coloration, these animals are identical. These two pictures were taken with a video camera, so are not as clear as the rest.
Here is a closeup of the head of the larger white form found on 17 February 2009. The oral tentacles and tail show a bit of purple.
A few more pictures of this species can be found on Thorunna purpuropedis, page 2.
Created 3 January 2006
Updated 23 February 2009