Direct observations on flagellar transformation in Mallomonas splendens (Synurophyceae)

Interphase cells of Mallomonas splendens (G. S. West) Playfair have two basal bodies: BB1 bears no flagellum, and BB2 produces a mastigoneme‐bearing, anteriorly directed flagellum (F2). Light microscopy of live cells undergoing mitosis and cytokinesis showed that two small flagella arise adjacent to F2 at preprophase. These new flagella commenced beating soon after their emergence and elongated as F2 shortened. By metaphase the new flagella were en. 12 μm long, and their bases had moved to either side of the metaphase plate. The shortening F2 segregated with one of the new flagella. At early cytokinesis the new flagella were ca. 15 μm long and the parental F2 had completely retracted so that its basal body (BB2) was transformed into a BB1. A similar pattern of events is described for Mallomonas papillosa Harris & Bradley. We conclude that the mastigoneme‐bearing flagellum in Mallomonas spp. is produced from first generation basal bodies. This flagellum entirely retracts during the next mitosis so that its basal body becomes a BB1. BB1 remains as such for subsequent generations.