GAMETOGENESIS IN NITZSCHIA PUNGENS F. MULTISERIES

Rosowski et al. (1992) have written a well-documented and instructive comment on our 1991 paper (Vol. 27:21-6) in this journal. Based on the current literature on diatom life cycles, they argue that the flagellated and nonflagellated cells that we repeatedly observed in our monoclonal cultures of Nitzschia pungens were probably not gametes but, rather, could have been parasitic chytrids. It is true that the schematic life cycle that we tried to reconstruct from light microscopical observations and flow cytometric data, rather than the conventional single hanging drop isolation studies or electron microscopic studies, differs significantly from that of the pennate diatoms studied so far, including Nitzschia species. It is noteworthy, however, that this diatom is unique in several respects other than in its life cycle, including a physiological capacity to form monospecific blooms during winter (perhaps by induction of the sexual cycle), the novel formation of a neurotoxin an exceptional photosynthesis-photon density flux response (Pan et al. 1991), and the existence of morphological variants.