A new marine gastrotrich species, Desmodasys abyssalis sp. nov. (Gastrotricha: Macrodasyida), is described from deep-sea hydrothermal vents of the East Pacific Rise based on light microscopy and scanning electron microscope observations. Desmodasys abyssalis was collected from artificial tubeworm aggregations exposed to the intermediate flow zone (medium productivity) and occurred in low abundance. Desmodasys abyssalis is the first record of a gastrotrich inhabiting a deep-sea hydrothermal vent habitat and is the first description of a deep-sea gastrotrich.
