The flagellar apparatus and canal structure in Prorocentrum micans (Dinophyceae)

Abstract

We have determined the three-dimensional structure of the flagellar apparatus in Prorocentrum micans Ehrenberg (Dinophyceae). The flagellar apparatus consists of two basal bodies that lie at approximately a 35° angle to one another. Each basal body bears a typical dinophycean complement of microtubular and fibrous components. Unlike the majority of Dinophyceae, the longitudinal microtubular root lies adjacent to the longitudinal basal body and abuts the transverse basal body. The transverse microtubular root is associated with an extension of microtubules that is directed posteriorly (dorsal, using proposed terminology) into the cell to a region adjacent to the nucleus. On the opposite side of the flagellar apparatus, the microtubules of the peduncle extend posteriorly (dorsal, using proposed terminology) from the flagellar canal region. The microtubules extend for several micrometers and the peduncle is closely associated with a complex striated collar that circumscribes the flagellar canal and its components. We report on the three-dimensional nature of the flagellar canal and accessory pore canal region. We conclude that the flagellar canal and accessory pore canal are not attached to each other and that the ‘Prorocentrum’ type of flagellar apparatus and cell architecture is most likely the result of episome/hyposome compression.