Top 10 Nudibranch Facts!

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The word “nudibranch” comes from the Latin word “nudus,” meaning “naked,” and the Greek word “brankhia,” meaning “gills.” The nudibranch, in essence, is a beautiful, vibrantly colored type of sea slug. There are more than 3,000 known species of nudibranchs and each has its own body shape and coloring. Here follow 10 interesting facts about nudibranchs.

Number 10: They are mollusks

Nudibranchs are gastropod mollusks. They belong to the phylum Mollusca, which consist of a large group of soft–bodied animals, usually with a shell. Nudibranchs, however, belong to a group of soft-bodied marine gastropods that shed their shells after their larval stage. To date, more than 3,000 species of nudibranchs have been discovered and more are identified every day. There are two main group types, namely the dorid nudibranchs, which breathe through gills on their backs, and eolid nudibranchs, which have finger-like appendages called cerata on their backs. The cerata come in a variety of shapes and have multiple functions, including breathing, digestion, and defense. Nudibranchs vary in size from being very small — only a few millimeters — up to almost 23 inches, or 60 centimeters, long for the biggest species. They also vary in body shape and color, with most of them sporting bright and beautiful markings.

Number 9: They live in every ocean

Nudibranchs live in all the oceans of the world, even in the Arctic and Antarctic. They live on or near the seafloor and have been identified at depths between 30 and 6,500 feet, or 10 and 2,000 meters. They are almost entirely restricted to salt water, although a few species do inhabit brackish water with lower salinity. The greatest diversity of nudibranchs lives in warm, tropical waters where they make their home on shallow reefs, although some have been found in deeper waters. Nudibranchs are benthic animals and can be found crawling on the ocean floor. The only exceptions to this are the glaucus atlanticus nudibranchs, which float upside down near the ocean surface; pelagic nudibranchs that swim in the water column; and the Phylliroe bucephalum.

Number 8: Nudibranchs are hermaphrodites

Nudibranchs are simultaneous hermaphrodites, meaning they possess both male and female organs. Copulation is usually reciprocal, with both individuals donating and storing sperm. The reproductive organs open on the right side of the body and individuals copulate facing in opposite directions with their right sides together. Hermaphrodism has a distinct advantage, in that any mature individual of the same species is a potential mate, thereby increasing the chances of fertilization. Each individual can lay eggs, thereby maximizing reproductive effort. Nudibranchs will lay their eggs on the organism on which they feed or on a prominent object nearby. The size, color, and shape of nudibranch eggs varies from species to species and goes through various developmental stages. The first stage is the larval stage. As the larva hatches, it will drift with plankton and will slowly undergo a metamorphosis into an adult. In a few species, development takes place inside the egg and the larva is not released. This is known as direct development and a miniature form of the adult will emerge from the egg.