Although this nudibranch is fairly common it is usually overlooked due to its diminutive size and the fact that it is often found on a similarly coloured food sponge. All animals photographed here were under 15 mm (5/8″) and found in wave washed lagoons or fishponds from La Perouse Bay to North Kihei, Maui.  The only other blue dorid found in Hawaii is the Doris nucleola, but it has a full branchial plume (whereas the pecten has a half-moon shaped branchia)  and two pronounce Y-shaped marks on its mantle. For more photos and information please see Sea Slugs of Hawaii.