HIGH-SPEED VIDEO ANALYSIS OF THE FLAGELLAR BEAT AND SWIMMING PATTERNS OF ALGAE - POSSIBLE EVOLUTIONARY TRENDS IN GREEN-ALGAE

The flagellar beat and swimming patterns of flagellated cells of 22 green plants, including 17 green flagellates (volvocalean and prasinophyte algae), motile cells of three seaweeds, Bryopsis, Caulerpa, and Ulva, sperms of a liverwort, Marchantia, and a fern, Athyrium, were examined using a high-speed video system. So-called breast-stroke is widely distributed in green plants, and occurs rarely in prasinophyte flagellates and ulvophycean algae; in these algal groups flagellar beat similar to that found in animal sperm is common, both during forward and backward swimming. Different types of swimming patterns were observed in prasinophytes. The results indicate evolutionary trends of flagellar beat and swimming patterns in green plants such as change from backward to forward swimming, from flagellar to ciliary beating and from uni-directional (parallel) to radial-directional (cruciate) beating. Such trends are shown in two prasinophyte groups, the Pyramimonas-lineage and Tetraselmis-lineage.