This is a striking looking species. The body is black with dramatic orange ridges, the crest of each which are capped with a white line. The species was named "halgerda" because it had often been mistaken for members of the cryptobranch dorid genus, Halgerda (H. willeyi, for example). R. halgerda lacks the circle of gills around the anus. Its gills, like that of all phyllidids, are located below the mantle along the hyponotum.
While this species is known from throughout the Indo-Pacific (Australia; Tonga; Fiji; New Guinea; Solomon Islands; Indonesia; Taiwan; Philippines; Okinawa; Marshall Islands) it is recorded as rare on Heron Island in the newly released Nudibranchs of Heron Island, Great Barrier Reef, by Julie Marshall and Richard Willan.
This large species, which reaches 65 mm in length, is found is found on
exposed walls in moderate depths 3-65 meters deep. It has been observed to
feed on the siliceous sponge of the genus Aplysina.
David W. Behrens
Pacific Coast Nudibranchs
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