Author: Liu Zhi-li and Zhang Shu-qun
J Integr Plant Biol 1987, 29 (3): -.
Sexual reproduction of the dinoflagellate Peridinium bipes Stein was observed. At the late growth season (from late March to early April), the small, unarmored motile cells i.e. gametes are produced by division of the cate cell. Isogamy occurs in this species. Two gametes in fusion are morphologically indistinguishable, but their behavior are different. Before fusion, two gametes are connected by a transparent granular structure and move quickly for about ten minutes. When the plasmogamy almost completes, the fusing cells stop moving for a while and the transverse flagellum of one gamete is cast off. By staining with modified carbol fuchsin, it was proved that the karyogamy takes place soon after plasmogamy and the change of chromosomes in this period was also observed. The zygote keeps motile for about 14 days before casts off its two flagella and becomes aplanozygote. During this period i.e. planozygote stage, the zygote enlarges from 55 × 50 μm to 75 ×70 μm, intercolary bands connecting thecai plates widen, lots of oil droplets are produced as storage granules. After sinking to the bottom of flask, aplano- zygote continues changing: exospore wall is cast off, mesospore wall and endospore wall are thickened, oil droplets turn to starch grains, protoplast contracts and becomes spherical, a large red lipid granule, perhaps eye-spot, appears. Afterward, aplanozygote has become hypnozygote i.e. resting cyst. The type of sexual reproduction, the amphiesma of the zygote, the resistance of hypnozygotic wall to acid and alkali, the relationship between fossil dinoflagellate remain and the wall of hypnozygote were discussed. It was also considered that the three formas of P. bipes named by Huber-Pestalozzi were the different stages of zygote development.