Some Insights into the Inventiveness of Dinoflagellates: Coming Back to the Cell Biology of These Protists.

In this review dedicated to the great protistologist Edouard Chatton (1883-1947), I wanted to highlight the originality and remarkable diversity of some dinoflagellate protists through the lens of cell biology. Their fossilized traces date back to more than 538 million years (Phanerozoic eon). However, they may be much older because acritarchs from the (Meso) Proterozoic era (1500 million years ago) could be their most primitive ancestors. Here, I described several representative examples of the various lifestyles of free-living (the autotrophic thecate Ehrenberg and the heterotrophic athecate McCartney and other "pseudo-noctilucidae", as well as the thecate Biecheler) and of parasitic dinoflagellates (the mixotroph Chatton). Then, I compared the different dinoflagellate mitotic systems and reported observations on the eyespot (ocelloid), an organelle that is present in the binucleated Stein and in some Warnowiidae dinoflagellates and can be considered an evolutionary marker. The diversity and innovations observed in mitosis, meiosis, reproduction, sexuality, cell cycle, locomotion, and nutrition allow us to affirm that dinoflagellates are among the most innovative unicells in the Kingdom Protista.