The sea slugs are a very diverse and successful group of animals. Over 3,000 species have been identified. Many species are grazers, while others are active predators.
The Blue Glaucus (Glaucus Atlanticus ), also known as Blue Dragon, is a very odd looking animal. It spends all its time upside down and the camouflage patterns are found on its front. The mollusc is boldly colored with a blue and blue-and-white back (which helps camouflage it from sea birds) and a silvery underside (which may disguise it from predatory fish beneath). The animal sucks air into its stomach to keep it at the surface.
The body is elongate measuring up to 3 cm and is flattened. The head is small and blunt with a pair of small oral tentacles near the mouth. It can grow to 3 cm in length and has dozens of so-called "cerata," outgrowths that give the creature a nasty sting.
Using its very sensitive organs, this sea slug can detect the presence of the Portuguese man-of-war (Physalia utriculus) or one of its close relatives. It recycles their venomous cells and deploys them to the tips of its cerata for
its own defense. If the prey is small Glaucus will swallow it in one mouthful.
The beautiful appearance of this animal is attractive to marine aquarium keepers, but a single slug can kill all the fish inhabitants.
References: File # 112