Symsagittifera roscoffensis

Species of flatworm-like animal

Symsagittifera roscoffensis, also called the Roscoff worm, the mint-sauce worm, or the shilly-shally worm, is a marine worm belonging to the phylum Xenacoelomorpha. The origin and nature of the green color of this worm stimulated the intrigued zoologists in the 1870's. It was discovered that the coloring resulted from the symbiosis between the animal and a green micro-algae, the species Tetraselmis convolutae, hosted under its epidermis. It is the photosynthetic activity of the micro-algae in hospite that provides the essential nutrients for the worm. This partnership is called photosymbiosis, from "photo", "light", and symbiosis "who lives with". These photosynthetic marine animals live in colonies on the tidal zone.

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