Nudibranch

Nudibranchs are a large and diverse group of soft-bodied marine gastropod mollusks found in oceans worldwide, from tropical reefs to polar waters, prized among divers and underwater photographers for their vivid colors and elaborate body shapes. Having lost the protective shell of their ancestors as adults, many species instead rely on bright warning coloration to advertise that they are toxic or distasteful, often having taken stinging cells or chemical defenses directly from the sponges, corals or anemones they eat. Their name, meaning naked gill, refers to the exposed, feathery or finger-like gill structures many species carry on their backs, used for respiration in place of an internal gill cavity. Nudibranchs are entirely carnivorous and often highly specialized, with many species feeding on only one or a few prey species throughout their lives, and most are simultaneous hermaphrodites capable of mating with any other adult of their species. With several thousand described species and new ones still regularly discovered, nudibranchs remain one of the most actively studied groups in marine biodiversity research.