It seems that not much is really known about Hawaii’s flatworms, perhaps because they are rarely seen and few scientists seem to specialize in this phylum. With Cory Pittman’s help, John Hoover has compiled the most comprehensive Hawaii Flatworm site and it is definitely worth visiting. Over the past few years, our snorkelling group have seen approximately 42 different species (all during the day and at snorkeling depths) and I will be adding to the list as I have time. These animals can be absolutely stunning in colour and markings and many seem to mimic one another. A close study of their lines, spots, blotches, margins, papillae and pseudotentacles is needed for an identification. Even that effort may not be rewarded — or you may be rewarded with a new “find” entirely. They have a simple structure (though they have eyes, they are lacking in a nervous system and are basically only a few cells thick) Unlike nudibranchs (which they are sometimes mistaken for), they breath oxygen through their skin and eat and pass waste through the same orifice. For more photos, check out Keoki Stender’s Marine Photography and the Sea Slugs of Hawaii’s site (where even more links can be found).
Pseudobiceros Sp. 5, Pseudobiceros kikokiko 
