Tetramyxa parasitica is a species of parasitic cercozoan, member of the plasmodiophorids, that causes gall formation on multiple genera of aquatic plants.
[3][4] It was first discovered on roots of Ruppia and described by Karl von Goebel in 1884 in his work Flora, where it became the type species of the genus Tetramyxa.
It is an obligate endoparasite of several species of the aquatic plants Ruppia (rastellata, maritima, spiralis, brachypus), Zannichellia (palustris, repens) and Potamogeton (pusillus, panormitanus, striatus, berteroanus).
[5] When attacking a plant stem, the species generates galls that are roughly spherical in shape, with a diameter of 1-5 mm, and with color ranging from light cream and green (during the phase of sporogenic development where small plasmodia become mature resting spores) to dark brown (after the resting spores reach maturity).
The surrounding cells accumulate big quantities of starch granules of up to 12 μm.