Combining cytogenetics and flow cytometry to the study of the marine dinoflagellate life cycle

Very few studies have focused on the chromosomal characterization of the different life cycle stages of the dinoflagellates, unicellular algae best known for being causative agents of the popularly known as “red tides”. These algae, some able to cause human health problems through the accumulation of their toxins in bivalve mollusks, grow very fast asexually, causing the bloom. However, their high environmental resilience is acquired by their ability to encyst as zygotes (sexually). The main difficulty in the study of these organisms life cycle lies in the difficulty to take apart the different stages of the cellular cycle (mitotic and meiotic nuclei), and of the life cycle (sexual and asexual phases), which are very similar when traditional technics of optical microscopy are used. Since it is not possible to obtain a total (100%) sexual induction, cultures in which sexuality is induced are a mixture of sexual and asexual stages, which adds difficulty to their study. With the objective of analyzing the growth strategies of dinoflagellates and characterizing the cellular cycle phases, we designed an experiment in which we monitored with image flow cytometry the cellular cycle during mitotic proliferation and during sexual induction every 2 h during 3 days. We selected populations according to ploidy, separated them with sorting, and stained them with DAPI and with a marker of telomeric sequences. The comparative study of these cultures indicates that the life cycle of dinoflagellates could be much more complex than the depicted to dat