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dinoflagellata(dī'nōflăj'əlät`ə, –lā`tə), phylum (division) of unicellular, mostly marine algaealgae
[plural of Lat. alga=seaweed], a large and diverse group of primarily aquatic plantlike organisms. These organisms were previously classified as a primitive subkingdom of the plant kingdom, the thallophytes (plants that lack true roots, stems, leaves, and flowers).
..... Click the link for more information. , called dinoflagellates. In some classification systems this division is called Pyrrhophyta. There are approximately 2,000 species of dinoflagellates. Most have two flagella that lie perpendicular to one another and cause them to spin as they move through the water. Most have walls, or thecae, that are rigid and armorlike and sometimes take on fantastic shapes. The plates that make up these walls are actually located inside the plasma membrane rather than outside, as cell walls are. Some species are heterotrophic, but many are photosynthetic organisms containing chlorophyll a and chlorophyll c. The green of these chlorophylls may be masked by various other pigments. Still other species are symbionts, living inside such organisms as jellyfish and corals. Food reserves are largely starch.
Reproduction for most dinoflagellates is asexual, through simple division of cells following mitosis. They are unusual in that in each cell, the chromosomes remain compact between divisions, instead of stretching out into slender threads, as in most other organisms. The chromosomes are constricted at regular intervals and do not have centromeres, or fiber-attachment centers. There is no spindle, yet the very numerous chromosomes are divided equally at the time of mitosismitosis
, process of nuclear division in a living cell by which the carriers of hereditary information, or the chromosomes, are exactly replicated and the two copies distributed to identical daughter nuclei.
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The dinoflagellates are important constituents of plankton, and as such are primary food sources in warmer oceans. Many forms are phosphorescent; they are largely responsible for the phosphorescence visible at night in tropical seas. The phenomenon known as red tide occurs when the rapid reproduction of certain dinoflagellate species results in large brownish red algal blooms. Some of these organisms are highly toxic and can kill fish and shellfish and kill or weaken the animals (including humans) that eat them in their turn or, in some cases, are merely exposed to water containing the organisms.
(also Peridinea), an order of protozoans of the class Flagellata. Botanists classify dinoflagellates as pyrrophytes. Dinoflagellates are widespread in brackish waters, fresh-waters, and seas; they are also found in bogs and snow. The diversity among species is greater in the tropics, but the biomass of the dinoflagellates is 100 times higher in northern than in southern seas. Some species are responsible for water bloom, luminescence in the sea, and red tide.
Fossil dinoflagellates have been preserved since the end of the Paleozoic, and some scientists consider dinoflagellates precursors of radiolarians. The four main subgroups of dinoflagellates are the Gymnodiniinea, the Dinophysinea, the Peridinea, and the Blastodiniina. Members of the Gymnodiniinea, which comprise six families, one of which includes the genus Noctiluca, may or may not have a pellicle. Algae in the single family of the Dinophysinea have a full, conical shell, while those constituting the 22 families of the Peridinea have shells that consist of numerous perforated plates. Finally, all the organisms of the Blastodiniina, which consist of one family, are endoparasites.