Choanocystis aculeata with zoochlorellae
Choanocystis (Penard, 1904) used to be part of Acanthocysts (Carter, 1863). The difference is the form of the base plate of the radial spicula. In Choanocystis the base plate has the form of a Water Lily where in Acanthocystis the base plate is more or less round. For the exact identification of species a SEM (Scanning Electron Microscope) is required.