Synaptonemal Complexes and Meiosis in Didymium Iridis: A Reinvestigation

SUMMARY

The ultrastructure of meiotic events has been studied in three isolates of Didymiutn iridis, including the one used by Carroll and Dykstra in an earlier study. In all three isolates a precleavage mitotic division occurs. About 9–12 hr after spore cleavage, synaptonemal complexes appear in virtually all spore nuclei, indicating the onset of meiotic prophase. Subsequent division stages have also been observed. Attempts to change the time of meiosis by manipulation of the time of onset of illumination were unsuccessful. Re-examination of the original blocks used by Carroll and Dykstra revealed that the sporangium containing the synaptonemal complexes studied by them represented an incompletely cleaved, aberrant development and was in reality a stage about 12–18 hr after an abnormal cleavage.