Dinoflagellates are a diverse group of flagellate eukaryotic microorganisms. Most of the species are marine planktons. However, they are commonly seen in fresh water habitats. Dinoflagellates are unicellular, free-swimming, biflagellate organisms. All organelles and life sustaining components are present within the cell. Many dinoflagellates are known to be photosynthetic in nature. Moreover, a large fraction have mixotrophic mode of nutrition. There are a number of non-motile forms such as amoeboid, palmelloid, coccoid, and filamentous types. Dinoflagellates have approximately 150 genera and 1500 species.
Superphylum : Alveolata
Phylum : Dinoflagellata
All Dinoflagellates contain flagella. This slender threadlike structure (locomotory organelles) gives them hydrodynamic advantages. It helps them to move or glide from place to place. Dinoflagellates have transverse as well as perpendicular flagella. These flagella are situated in the grooves of the cellulose plates around the cell. Moreover, the dinoflagellate nucleus is very distinctive. It displays an unusual combination of prokaryotic and eukaryotic characteristics.
The modes of nutrition vary according to individual species. Some Dinoflagellate can have a parasitic mode of nutrition. They thrive on other organisms to meet their nutritional requirements. Typically, Dinoflagellates kill their host organisms after feeding on their bodily fluids and non-vital organs. Many Dinoflagellates are autotrophic in nature. They are capable of producing their own food. They contain chlorophyll a & c, beta-carotene, neoperidinin, xanthophyll, fucoxanthin, dinoxanthin, peridinin, neodinoxanthin, and diatoxanthin. Histones are absent. Foods are reserved as starch and oil. These Dinoflagellates are known as "primary producers" since they are not dependent on any other organism for their food supply. Heterotrophic Dinoflagellates are potentially harmful organisms. They are usually carnivorous by nature. They release deadly toxins in the water bodies to harm other marine organisms. They obtain chloroplasts by ingesting autotrophic organisms. Symbiotic dinoflagellates consume the unused food of the host organism. These Dinoflagellates are also known as "zooxanthellae". They are found to be living amicably with corals, jellyfish, sponges and many other marine invertebrates. Cnidarians feed on autotrophic Dinoflagellates.
Dinoflagellates are asexual organisms. They do not require an opposite strain for creating new progeny. Identical daughter cells are simply produced by mitosis. Sexual reproduction among Dinoflagellates is very uncommon. In this form of reproduction, two different gametes fuse together to form a zygote.
When colony of Dinoflagellates blooms in ponds or other water bodies, they release some nasty harmful toxins. These pigments change the color of water. It assumes a red color. This phenomenon is colloquially known as red tide. Marine lives are heavily affected as a result of this toxin. Red Tide can pose serious threats to the ecosystems and human society. If red tide fish contaminated fishes are consumed by the local population, they may suffer from early puberty, obesity, reproductive problems, and neurological problems. Phosphate and Nitrate pollution encourage the growth of Dinoflagellates.