Underwater, nudibranchs are the undisputed fashion designers. No other animal species has such a colorful, bright, imaginative outfit. They captivate divers and photographers just as much as haute couture does during Fashion Week in Paris, Rome, London or New York.

Pyjama star snail/Chromodoris quadricolor                Twin star snail/Chromodoris geminus

In contrast to Fashion Week, the realm of slugs has existed for over 400 million years. Nudibranchs belong to the phylum of invertebrates, of which the class of snails is the most extensive with 110,000 species. The snails that we encounter again and again as divers in tropical waters belong to the order Oposthobranchia. These include the suborder of the cephalaspidea (Cephalaspidea) with 7000 species and the nudibranchia (Nudibranchia) with 3000 species.

Blue spotted head shield snail/ Chelidonura livida          Ringed star snail/Chromodoris annulata

Sea snails are hermaphrodites. This means that one animal produces sperm and eggs. Reproduction takes place in several stages. After fertilization, the snails lay the eggs on the seabed. There they develop into larvae, from which the snail emerges after metamorphosis. The process from fertilization to the developed snail takes 4 to 8 weeks. The size varies from a few millimeters to half a meter.

Depending on size and species, the lifespan is between a few months and a year. The relatively short lifespan is explained by the fact that the animals are naked and therefore unprotected. Their predators are fish, crabs and other snail species. However, sea snails are not completely defenceless. First of all, there is their brightly colored dress, which is perceived by their enemies as "could be poisonous". Many nudibranchs secrete toxins or produce poisonous secretions that adhere to the surface of their bodies.

Depending on the species, the snails themselves feed on plants such as algae, seaweed and sponges and animals such as corals, sea squirts and fish eggs.

Photos: Johann Vifian

Sources: geo.de/ meerwasser-lexikon.de