At first glance this flatworm could easily be mistaken for a nudibranch. Flatworms also have a very flattened body and dazzling colors. However they don't have tentacles (rhinophores) nor gills.
Some flatworms are toxic and most are distasteful. Those flatworms are usually very colorful. The colors are used as a warning display for defense and better survival. Predators might bite once, but then they learn, that flatworms taste extremely unpleasant and these animals are left alone. This phenomenon where a species evolves to resemble another species (the model) for gaining some biological benefit is called mimicry.
Click here for another species of flatworms mating. All photos were taken on the Japanese cargo wreck. Actually that wreck was packed with flatworms of many kind. Look at the blue flatworm or the leopard flatworm.
Japanese cargo wreck, Malapascua island, Cebu, Philippines, March 2001
Taken with a Sea and Sea Motomarine II EX , 1:2, F 22
. Copyright Teresa Zubi