C - centroplast, N - nucleolus, Ax - axoneme, FV - food vacuole, CV - contractile vacuole, Ki - kinetosome, Ts - tangential scale, Rs - radial spicula
Acanthocystis penardi, binary fission
All Centrohelidas have a single nucleus that is situated eccentrically. In the center of the Centrohelida is a single MTOC (MicroTubule-Organzing Center), the centroplast from where all axonemes originate. The axonemes are bundles of microtubules that form the core of the axopodia. The axopodia are coated with plasma in which extrusomes (kinetocyts and/or mucocysts) travel up and down.
The genus Acanthocystis (Carter, 1863) is part of the order Centrohelida. Acanthocystis is mostly around 25 µm in diameter and possesses radial spicules and tangential scales. The tangential scales form a tight body armor. The radial spicules are formed like spikes with a root plate. The form of the spicules and the root plate determines the species. Correct identification most often requires the aid of a SEM (Scanning Electron Microscope).