Ultrastructure of the flagellar apparatus of Noctiluca miliaris Suriray swarmers (Dinophyceae)

The swarmers of Noctiluca miliaris Suriray are not uniflagellate, as was assumed for more than a century, but are biflagellate cells. Their flagellar apparatus displays two distinctly heteromorphic flagella: a long flagellum extending posteriorly (=longitudinal flagellum) and a very short flagellum oriented to the cells left side (=transverse flagellum). The transverse flagellum is situated in a groove and is therefore not visible in the light microscope. A serial section analysis of the basal apparatus of the swarmers reveals structures which are typical for dinoflagellates including a posteriorly directed microtubular root (pmr) and a ventral ridge with microtubular and fibrous components (vrm and vrf). Striated fibrous roots are, however, lacking. The structurally relatively simple flagellar apparatus of N. miliaris swarmers may reflect their functional specialization as (micro-)gametes.