Peridinium is a genus of motile, marine and freshwater dinoflagellates. Their morphology is considered typical of the armoured dinoflagellates, and their form is commonly used in diagrams of a dinoflagellate's structure. Peridinium can range from 30 to 70 μm in diameter, and has very thick thecal plates.
Morphology Peridinium is enclosed by cellulose theca and with two flagellates. The composition of the theca is laminaribiose and laminaritriose linking by β – 1, 4 and β – 1, 3 linkages. The cell body of Peridinium is highly polarized and is distinguishable from apical and antapical sides or dorsal and ventral sides. Their theca is divided into epicone and hypocone by the middle region (also called girdle or cingulum). The flagellates have two different directions, one is surrounding the middle region while the other are in the longitudinal groove of hypocone. The chloroplast in Peridinium is triple membrane, and some plastid-derived organelles like pyrenoid or eyespot also. This provides the evidence that these organelles originated from secondary endosymbiosis. The inner membrane of mitochondrion is tubular. Trichocyst is a specialized organelle in dinoflagellate which help them defense to predators.
Life cycle Peridinium is a haplontic algae. Most time of Peridinium are haploid vegetative cells and undergoing asexual or sexual cycle. They only form zygote before dormancy. In asexual cycle, the haploid vegetative cell throws the theca before mitosis and produces two daughter cells by mitosis. During mitosis, the chromosome in their nucleus condenses but the nucleus of endosymbiont doesn’t. After the cleavage furrow starts to separate their nucleus, the nucleus of endosymbiont then passes through the gaps between cleavage furrow and their nucleus. Then the nucleus of endosymbiont was divided by cleavage furrow together. In sexual cycle, they produce gametes as isogamete and the gametes fuse to form planozygotes to get dormancy. After dormancy, the zygote starts to undergo meiosis. The first meiosis produces a two diploid nuclei cell without cytokinesis. An asynchronized nucleus division then occurs in one of the two nuclei. One nucleus undergoing second meiosis before cytokinesis in first meiosis and turns into a trinucleate stage. After it, the cytokinesis of first meiosis is completed, and the trinucleate cell is divided into a diploid nucleus cell and a double haploid nuclei cell. When the cytokinesis of second meiosis is completed, finally, it produces four haploid daughter cells. Overall, Peridinium dominants in mobile haploid generation. Between spring and summer, the haploid venerative cells produce gametes by mitosis and fuse gametes into a diploid planozygote. The diploid planozygotes then transform into immobile hypnozygotes and deposit to get dormancy in winter. After a year, the hypnozygotes germinate in spring and release haploid vegetative cells.
Ecology Peridinium gatunense blooms in the Lake Kinneret in Israel which changing the color of the lake is discovered in 1960. The blooming event occurs because the organic mineral is flushed into the sea every year in spring. Organic mineral nourishes the diatom and increases their population. Thus, the planozygotes of Peridinium break dormancy and release thousands of vegetative cells into the sea by feeding on diatom. From 1960 to 1996, the annual pattern was regularly peaked at spring in each year. But starting from 1996, the blooming was broken. The break of blooming is related to high temperature, other phytoplanktonic competitor (Chytrid or Microcystis), and human activities in the aquatic system by managing the water flow of the river.
Species Species include:
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