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PHYCOLOGICAL SOCIETY OF AMERICA

Gonyaulax Life History

Asexual reproduction is the most common way of making more dinoflagellates.

In asexual reproduction the haploid parent cell undergoes mitosis, producing two identical daughter cells. During this process the theca may be discarded or retained, with each daughter cell keeping one half and regrowing the other half.

Sexual reproduction is also observed in dinoflagellates.

Because the adult, motile cells are haploid (1N), they form their gametes via mitosis, resulting in either a naked or armored, free swimming, miniature version of the parent cell. When the flagella of the male and female gametes become entangled, they fuse to form a diploid (2N) planozygote, an actively swimming zygote. The planozygote then enlarges, developing into a diploid hypnozygote, or resting cyst that is provisioned with food reserves and sometimes toxins. The resting cyst sinks to the ocean floor where they remain dormant during the winter for at least four months. The hypnozygote finally undergoes meiosis, restoring the haploid motile cell.

Temporary cysts are not involved in reproduction.

They form when dinoflagellates experience stressful conditions, such as cold temperature. However, when reintroduced to favorable conditions they reconvert to the motile stage within hours.

(Left) G. polyedra cyst stage. (Right) G. polyedra motile stage

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© 1999  Allison Arnold and Monica Draghici.     All rights reserved.