FINE-STRUCTURE OF DWARF MALES IN OEDOGONIUM-PLUVIALE (CHLOROPHYCEAE)

Oedogonium pluviale Nordstedt is nannandrous, described as possessing single-celled dwarf males. In some studies the dwarf males appear to h ave a reduced, lens-shaped pedicular portion whose nature and structur e remain unclear. The present study aims to: 1) establish whether dwar f males of O. pluviale are single- or two-celled, 2) describe the diff erent developmental stages of dwarf males, and 3) understand the natur e of the pedicular portion. Mitotic division of the dwarf male was obs erved, but neither upwards phycoplast migration nor synthesis of a gam tangial cell wall occurred. Instead, the phycoplast and the cell plate migrated downwards, producing a small pedicular portion whose content then degenerated. The antheridium occupied most of the dwarf male wal l. Gametogenesis thus took place inside the wall of the young dwarf ma le (internal gametangium). Because of the pedicular cell degenerated, we define this type of dwarf male as pseudo-single-celled to different iate if from a true single-celled dwarf male. The antheridial nucleus underwent one mitotic division to give rise to two gametes. Instead of a true wall between gametes, mucilage condensed and was observed as a discrete layer that disappeared during a gamete release.