Encystment and excystment in the life cycle of a dinoflagellate Peridinium sp. B3, which was isolated from Lake Begnas in the Pokhara Valley, Nepal, were investigated by use of a clonal population. The maximum cell concentration was 3103 vegetative cellsml-1 in BL medium after about 4 weeks at 30C. Sexual reproduction of the cells was induced after the cells in late logarithmic phase were inoculated into nitrogen and phosphorous deficient medium, and also was spontaneously induced in BL medium.

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... Sexual reproduction was isogamous and homothallic. The cycle was initiated by gamete formation, rn which gametes were produced by binary asexual divisions of the vegetative cells. Fusing pairs were formed by the mid-ventral union of gametes. The planozygote retained two red bodies and remained motile for about 2 weeks. Two weeks after the planozygote lost motility, the zygotes enlarged and became dark in color. The theca of the planozygote split around the girdle region and the hypnozygote (cyst) was produced. The matured cysts were dormant and remained viable for at least 1 month at 10C in darkness following maturation for 3 months at 30C. The dark-cold treated cysts excysted synchronously when the incubation temperature was raised to 30C. The protoplast emerged from the cyst wall by amoeboid movement. The excysted cell had two red bodies. This cell divided within 24-48h into 2 daughter cells each with a red body.