Spermatogenesis Incoleochaete Pulvinata(charophyceae): Sperm Maturation1

Ultrastructural study showed that the sequence of developmental events occurring during spermatozoid maturation inColeochaete pulvinataBraun was similar in a number of respects to sperm development in the Charales and lower land plants. Elaboration of cytoskeletal components and associated flagellar basal bodies occurs early, and is followed by an extensive decrease in cytoplasmic volume and increases in densities of cytoplasm and nucleoplasm. Volume decrease and density increases appear to result from exocytosis involving dictyosome vesicles and perhaps endoplasmic reticulum. Elongation of flagella is accompanied by deposition of flagellar and body scales as in the Charales. During final stages of sperm maturation, the MLS undergoes changes in organization of the lamellar strip, which may also occur in archegoniates. In mature sperm ofC. pulvinatathe MLS and basal bodies are so occluded by dense material that determination of absolute orientation (configuration) is difficult. Thus, absolute orientation of the flagellar apparatus was determined by study of mid‐stage spermatids, and found to be the same as previously described by Sluiman for zoospores ofC. pulvinata.Finally, it is proposed that the large complex, striated fiber which connects basal bodies inC. pulvinatahas been evolutionarily reduced in the Charales andPhaeocerossp., ultimately disappearing from most embryophytic lines of descent.