Appearance and developmental kinetics of a unique cell type in Dictyostelium discoideum: Is it the gamete phase of sexual development?

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Abstract
A unique cell type appears during sexual development in Dictyostelium discoideum. These tiny ameboid cells migrate actively making both short‐lived and stable contacts with other cells. When fixed and stained with Hoechst 33258, each of these small amebae is seen to possess a condensed fluorescent nucleus. The cell type demonstrates a transient appearance in mated cultures appearing prior to 8 h and increasing to a peak of about 16% of the cell population by 10 h before decreasing in number. The decrease is correlated with the formation of pre‐zygotic, binucleate cells. In single strain cultures, the small cells are present at 8 h and rise to a plateau by 10–12 h but do not decrease in number, and pre‐zygotic binucleate cells do not form. The events of cell fusion were observed directly using time‐lapse video microscopy. The unique structure, developmental kinetics, and behavior of the cell type suggest that it may be the gametic phase of D. discoideum.
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