Oodinium

''Oodinium'' is a genus of

parasitic Parasitism is a close relationship between species, where one organism, the parasite, lives on or inside another organism, the host, causing it some harm, and is adapted structurally to this way of life. The entomologist E. O. Wilson ha ...

dinoflagellate The dinoflagellates ( Greek δῖνος ''dinos'' "whirling" and Latin ''flagellum'' "whip, scourge") are a monophyletic group of single-celled eukaryotes constituting the phylum Dinoflagellata and are usually considered algae. Dinoflagellates are ...

s. Their hosts are

salt Salt is a mineral composed primarily of sodium chloride (NaCl), a chemical compound belonging to the larger class of salts; salt in the form of a natural crystalline mineral is known as rock salt or halite. Salt is present in vast quant ...

- and fresh-water

fish Fish are Aquatic animal, aquatic, craniate, gill-bearing animals that lack Limb (anatomy), limbs with Digit (anatomy), digits. Included in this definition are the living hagfish, lampreys, and Chondrichthyes, cartilaginous and bony fish as we ...

, causing a type of fish

velvet disease Velvet disease (also called gold-dust, rust and coral disease) is a fish disease caused by dinoflagellate parasites of the genera '' Amyloodinium'' in marine fish, and '' Oodinium'' in freshwater fish. The disease gives infected organisms a dusty ...

(also called gold dust disease). One species has also been recorded on various

cnidaria Cnidaria () is a phylum under kingdom Animalia containing over 11,000 species of aquatic animals found both in freshwater and marine environments, predominantly the latter. Their distinguishing feature is cnidocytes, specialized cells that ...

ns. The host typically develops a yellow or gold "dust" scattered on its head, fins and body. At this stage, the infestation is already severe. The attack usually starts at the gills, at which stage it is difficult to observe. The host fish is irritated, and often sporadically darts about or rubs itself against rocks. The yellowish spots are more vivid under a strong light source. It is very similar to '' Ichthyophthirius'', though the oodinium spots are yellowish and smaller. The life cycle of oodinium starts as a

dinospore {{Short pages monitor