| Research Abstract |
Flagellar beat pattern in green monads is generally believed to be the same as cilia, i.e. green monads Dull the cell by forward swimming, beating their flagella ahead of them with breastroke. However, it is known that some marine taxa push the cell by backwards swimming, beating their flagella behind. The flagellar beat pattern of three species of three genera, Pterosperma, Pyramimonas and Prasinovapilla (nom. nud.) were examined with a high speed Video (Nac HMS 200, 200 frames per second) and their flagellar apparatus ultrastructure examined by transmission electron microscopy. These genera can be assigned, based on morphological examinations, into a monophyletic taxon, the Halosphaeraceae. However, in these genera, there are many differences in flagellar movement, such as the following: Pterosperma swims vy backwards swimming. Characteristics of the flagellar movement in this species are; 1) the movement is similar to that of flagellar movement showing a repetition of the same patte
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rn, i.e. there is no sign of effective and recovery strokes, 2) the flagell beat in the same direction, 3) the beat is synchronous; Pyramimonas swims by forward swimming. Characteristics of its flagellar movement are, 1) ciliary movement comprising of effective and recovery strokes, 2) the beat occurs in four radial directions, 3)the beat cycle of opposed flagella is synchronous; Prasinopapilla can be assigned as an intermediate of Pterosperma and Pyramimonas. It swims by forward swimming, with flagella beating in radial directions; the flagella beat is synchronous and their movement is of the flagellum, not cilium. The cell structure is also intermediate between Pterosperma and Pyramimonas.
These observations show that in the evolution of these green monads, the following evolutionary changes may have occurred: 1)from backward swimming to forward swimming, 2) from flagellar to ciliary beat pattern, 3) from synchronized to unsynchronized movement, 4) from uni- to radial-directional beating. Less
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