Apodinium floodi is an ectoparasitic dinoflagellate found in the vicinity of northwest Washington, USA.

Its host is the sea squirt Oikopleura labradoriensis.

Divisions occur perpendicular to this axis, and eventually the spores are produced.

A. floodi attaches to its host with a peduncle, which it penetrates into the larvacean tunicate's musculature, reaching the notochord.

Two principle rhizoids penetrate the outer region of the notochord, presumably to absorb nutrients from O. labradoriensis blood.