Author: Jan Scholten
Name: Myxozoa from Greek myxa slime or mucus and zoon animal.
Genera: 2180 species, some estimates of at least 30,000 undiscovered species.
Habitat: freshwater and marine.
Myxozoa are aquatic, obligately parasitic cnidarian animals; small, 10 to 20 μm, up to 2 mm. Many have a two-host lifecycle, involving a fish and an annelid worm or a bryozoan.
Myxozoans are highly derived cnidarians that have undergone dramatic evolution from a free swimming, self-sufficient jellyfish-like creature into their current form of obligate parasites composed of a mere handful of cells. As myxozoans evolved into microscopic parasites, they lost many genes responsible for multicellular development, coordination, cell-cell communication, and even, in some cases, aerobic respiration. The genomes of some myxozoans are now among the smallest genomes of any known animal species.