Nudibranchs are an order within the subclass Opisthobranchia, which belongs to the class Gastropoda in the Phylum Mullusca. In plain english, that means they are a type of mollusc -- related to snails and slugs. Also known as "sea slugs" or "branchs" (pronounced "branks"), nudibranchs are one of the most beautiful, colorful groups of animals anywhere. Most are small -- from less than 1/8" to 3", but a few grow as large as 12" long.

Because they have no shell, nudibranchs often have other protective devices. Most exhibit bright colors which serve as a warning to potential predators that they don't taste good. Others, however, resemble the backround you generally find them on and are, therefore, very difficult to see. Some secrete toxic chemicals like sulfuric acid. Others fire stinging cells (nematocysts) which they acquire from other animals which they have eaten, such as hydroids and anemones. These pass through the digestive system and migrate into their cerata (the finger-like projections along their back).

Nudibranchs are hermaphroditic, possessing both male and female sex organs. After mating, they lay beautiful strings or ribbons containing anywhere from a few eggs up to a million.

Here are some found along the Southern California coast.