What Are Dinoflagellates of Kingdom Protista?

Dinoflagellates are marine photosynthetic protists. They occur in large number and cause water to look red. Some of the emit light and this property is referred as bioluminescence. They have photosynthetic mode of nutrition. They are unicellular, motile, golden brown colored organisms. Their color is not static. It keeps on changing with change in pigment proportion. Cells are generally covered by plates of cellulose. These are sculptured and are referred as armoured dinoflagellates. They have outer covering which is rigid and is referred as theca. Theca has two grooves sulcus (longitudinal) and cingulum (circular). Flagella are two in number which are longitudinal and transverse. They beat in different a direction which leads to spinning. Nucleus is large and referred as Mesokaryon. Chlorophyll a and c are present in plastids. Mucin occurs beneath the cell membrane. They have no contractile vacuoles but they have a non contractile vacuole referred as Pusule. Trichocysts and Nematocysts have also been reported. Their food is reserved in the form of starch. Both sexual and asexual reproduction occurs in this species. Asexual reproduction is mainly done by cell division. Sexual reproduction is isogamous and anisogamous. Zygotic meiosis also occurs. A few of dinoflagellates produce a toxin which kills aquatic animals except shell fishes. These toxins also affect human beings and cause a condition referred as paralytic shell fish poisoning. Noctiluca is also known as Night Light. It is colorless dinoflagellate with holozoic mode of nutrition. It has isogametes and has bioluminescence property.