The Blue Sea Slug - Glaucus atlanticus

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The Blue Sea Slug (Glaucus atlanticus) is a nudibranch, class Gastropoda, phylum Mollusca. This conspicuous group of molluscs are usually very brightly coloured and can range in size from less than one eigth of an inch to over a foot in length. They lack a shell and their bodies are always bilaterally symmetrical. The head sports a pair of antennae-like rhinopores. Most have gills on the posterior part of the body and some can retract their gills into a branchial pocket. The dorsal surface of the nudibranch often has cerata, digitate or club-like projections of tissue that can often be extremely colourful. These cerata are used in respiration, defense and digestion. Glaucus is a voracious predator of the Portuguese Man-O-War (Physalia physalis), the By-The-Wind-Sailor (Velella velella) and the Blue Sea Star (Porpita porpita). When feeding upon these cnidarians it transfers its prey's stinging cells, nematocysts, into its own cerata and then utilizes them for its own defence. Glaucus is found floating on the sea surface where it maintains bouyancy by swallowing air.


Origin and meaning of the name 'Glaucus'

Glaucus was a character in Greek mythology and it means the "colour of the sea".

Glaucus was a fisherman. One day he had drawn his nets to land, and had taken a great many fishes of various kinds. So he emptied his net, and proceeded to sort the fishes on the grass. All of sudden, the fishes, which had been laid out on the grass, began to revive and move their fins as if they were in water; and while he looked on astonished, they one and all moved off to the water, plunged in, and swam away. He did not know what to make of it, whether some god had done it or some secret power in the herbage. "What herb has such power?" he exclaimed; and gathering some of it, he tasted it. Scarce had the juices of the plant reached his palate when he found himself agitated with a longing desire for water. He could no longer restrain himself, but bidding farewell to the earth, he plunged into the stream. The gods of the water received him graciously, and admitted him to the honor of their society. He lost all sense of his former nature and consciousness. When he recovered, he found himself changed in form and mind. His hair was sea-green, and trailed behind on the water. He was endowed with the gift of prophecy and instructed Apollo in the art of soothsaying.

This story is from


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