Meiosis in Coprinus. IV. Morphology and behaviour of spindle pole bodies.

Meiotic synchrony in the genus Coprinus has permitted the sequential study of spindle pole body (SPB) behaviour through the meiotic process. The SPBs are monoglobular in the young basidia immediately after the last premeiotic mitosis. From 10 to 15 h before karyogamy until pachytene, spindle pole bodies are not found. They become conspicuous in diplotene and persist until the completion of meiosis. During diplotene, metaphase, anaphase and telophase stages the spindle pole bodies are monoglobular but at late diplotene they duplicate and become diglobular with an isthmus connecting the 2 globular elements. The spindle pole bodies remain in a diglobular state until diakinesis when the isthmus breaks separating the 2 daughter spindle pole bodies. The diglobular SPBs in late diplotene and prophase II are believed to represent the duplicated form of the monoglobular state. The spindle pole bodies in Coprinus contain no centrioles. In thin sections the SPBs appear to be fibrillar amorphous structures with a dense inner core surrounded by a less-dense outer zone.