Acanthocystis: Carter (1863)

Freshwater plankton, occasionally marine plankton.

Unicellular heliozoans with multiple external bifurcate or pointed siliceous bristles anchored in and extending from flat siliceous scales (plates) lining the periplast. Two or three species of Acanthocystis, including A. aculeata and A. turfacea (most common), contain multiple endobiotic photosynthetic cells of Zoochlorella.