Gastrotricha
Gastrotricha is a
phylum of tiny, free-living,
freshwater and marine-dwelling
animals. They are
bilaterally symmetrical and
acoelomate. They have a
mouth and an
anus, as well as
circulatory and nervous systems with some poorly understood sensors. The
skeleton is hydrostatic. The body surface has
cilia,
scales, and
adhesive tubes. About 450
species are known, with no
fossils.
