aschelminth

Any of various, mostly microscopic wormlike invertebrates of the group Aschelminthes, including the nematodes, rotifers, and gastrotrichs. Aschelminths typically inhabit water or moist soil, are often parasitic, and have complex internal structures. The status of the Aschelminthes as a single taxonomic group is controversial, and many researchers consider its members to be separate phyla.