Fun facts about this Roboi Nudibranch/underwater sea slug: Its rhinophores (on its head) are used for smell and are retractable as a defense mechanism. It can perform autotomy, or self-amputation, of body parts like its rhinophores or mantle if threatened, and these parts will regenerate. It prefers deeper water than many other species, found at depths of about 30-50 meters in Okinawa.