English: The flagellar apparatus of Cafileria marina, reconstructed in 3D based on TEM pictures. The whole FA comprised of the anterior and posterior basal body (AB and PB.; respectively), the connection between basal bodies (BC), four microtubular roots (R1–R4), and the multi-microtubular structure “abc”. The cell orientation is shown in the left corner of the drawing: A: anterior, P: posterior, L: left, and R: right. Microtubular roots R1–R4 are the main structures forming the FA and supporting the feeding basket of C. marina; the R3 root is the defining morphological structure for Bicosoecida and consists of eight microtubules; the R2 root consists of three microtubules; and the remaining roots R1, R4, and ‘x’ consist of one microtubule. The number and angle of microtubules of the each root and their presence/absence are species-specific, so these structures are utilized as species-determining features.