prey through the sulcus. in several protoperidinium spp., e.g. p. conicum, a large feeding veil—a pseudopod called the pallium—is extruded to capture prey which is subsequently digested extracellularly (= pallium-feeding). oblea, zygabikodinium, and diplopsalis are the only other dinoflagellate genera known to use this particular feeding mechanism. katodinium (gymnodinium) fungiforme, commonly found as a contaminant in algal or ciliate cultures, feeds by attaching to its prey and ingesting prey cytoplasm through an extensible peduncle. two related species, polykrikos kofoidii and neatodinium, shoots out a harpoon-like organelle to capture prey. some mixotrophic dinoflagellates are able to produce neurotoxins that have anti-grazing effects on larger copepods and enhance the ability of the dinoflagellate to prey upon larger copepods. toxic strains of k. veneficum produce karlotoxin that kills predators who ingest them, thus reducing predatory populations and allowing blooms of both toxic and non-toxic strains of k. veneficum. further, the production of karlotoxin enhances the predatory ability of k. veneficum by immobilizing its larger prey. k. arminger are more inclined to prey upon copepods by releasing a potent neurotoxin that immobilizes its prey upon contact. when k. arminger are present in large enough, they are able to cull whole populations of its copepods prey. the feeding mechanisms of the oceanic dinoflagellates remain unknown, although pseudopodial extensions were observed in podolampas bipes. introduction dinoflagellate blooms are generally unpredictable, short, with low species diversity, and with little species succession. the low species diversity can be due to multiple factors. one way a lack of diversity may occur in a bloom is through a reduction in predation and a decreased competition. the first may be achieved by having predators reject the dinoflagellate, by, for example, decreasing the amount of food it can eat. this additionally helps prevent a future increase in predation pressure by cause predators that reject it to lack the energy to breed. a species can then inhibit the growth of its competitors, thus achieving dominance. harmful algal blooms dinoflagellates sometimes bloom in concentrations of more than a million cells per millilitre. under such circumstances, they can produce toxins (generally called dinotoxins) in quantities capable of killing fish and accumulating in filter feeders such as shellfish, which in turn may be passed on to people who eat them. this phenomenon is called a red tide, from the color the bloom imparts to the water. some colorless dinoflagellates may also form toxic blooms, such as pfiesteria. some dinoflagellate blooms are not dangerous. bluish flickers visible in ocean water at night often come from blooms of bioluminescent dinoflagellates, which emit short flashes of light when disturbed. algal bloom (akasio) by noctiluca spp. in nagasaki a red tide occurs because dinoflagellates are able to reproduce rapidly and copiously as a result of the abundant nutrients in the water. although the resulting red waves are an interesting visual phenomenon, they contain toxins that not only affect all marine life in the ocean, but the people who consume them, as well. a specific carrier is shellfish. this can introduce both nonfatal and fatal illnesses. one such poison is saxitoxin, a powerful paralytic neurotoxin. human inputs of phosphate further encourage these red tides, so strong interest exists in learning more about dinoflagellates, from both medical and economic perspectives. dinoflagellates are known to be particularly capable of scavenging dissolved organic phosphorus for p-nutrient, several has species have been found to be highly versatile and mechanistically diversified in utilizing different types of dops. the ecology of harmful algal blooms is extensively studied. bioluminescence long exposure image of bioluminescence of n. scintillans in the yacht port of zeebrugge, belgium at night, water can have an appearance of sparkling light due to the bioluminescence of dinoflagellates. more than 18 genera of dinoflagellates are bioluminescent, and the majority of them emit a blue-green light. these species contain scintillons, individual cytoplasmic bodies (about 0.5 µm in diameter) distributed mainly in the cortical region of the cell, outpockets of the main cell vacuole. they contain dinoflagellate luciferase, the main enzyme involved in dinoflagellate bioluminescence, and luciferin, a chlorophyll-derived tetrapyrrole ring that acts as the substrate to the light-producing reaction. the luminescence occurs as a brief (0.1 sec) blue flash (max 476 nm) when stimulated, usually by mechanical disturbance. therefore, when mechanically stimulated—by boat, swimming, or waves, for example—a blue sparkling light can be seen emanating from the sea surface. dinoflagellate bioluminescence is controlled by a circadian clock and only occurs at night. luminescent and nonluminescent strains can occur in the same species. the number of scintillons is higher during night than during day, and breaks down during the end of the night, at the time of maximal bioluminescence. the luciferin-luciferase reaction responsible for the bioluminescence is ph sensitive. when the ph drops, luciferase changes its shape, allowing luciferin, more specifically tetrapyrrole, to bind. dinoflagellates can use bioluminescence as a defense mechanism. they can startle their predators by their flashing light or they can ward off potential predators by an indirect effect such as the "burglar alarm". the bioluminescence attracts attention to the dinoflagellate and its attacker, making the predator more vulnerable to predation from higher trophic levels. bioluminescent dinoflagellate ecosystem bays are among the rarest and most fragile, with the most famous ones being the bioluminescent bay in la parguera, lajas, puerto rico; mosquito bay in vieques, puerto rico; and las cabezas de san juan reserva natural fajardo, puerto rico. also, a bioluminescent lagoon is near montego bay, jamaica, and bioluminescent harbors surround castine, maine. within the united states, central florida is home to the indian river lagoon which is abundant with dinoflagellates in the summer and bioluminescent ctenophore in the winter. lipid and sterol production dinoflagellates produce characteristic lipids and sterols. one of these sterols is typical of dinoflagellates and is called dinosterol. transport dinoflagellate theca can sink rapidly to the seafloor in marine snow. life cycle introduction dinoflagellates have a haplontic life cycle, with the possible exception of noctiluca and its relatives. the life cycle usually involves asexual reproduction by means of mitosis, either through desmoschisis or eleuteroschisis. more complex life cycles occur, more particularly with parasitic dinoflagellates. sexual reproduction also occurs, though this mode of reproduction is only known in a small percentage of dinoflagellates. this takes place by fusion of two individuals to form a zygote, which may remain mobile in typical dinoflagellate fashion and is then called a planozygote. this zygote may later form a resting stage or hypnozygote, which is called a dinoflagellate cyst or dinocyst. after (or before) germination of the cyst, the hatchling undergoes meiosis to produce new haploid cells. dinoflagellates appear to be capable of carrying out several dna repair processes that can deal with different types of dna damage. dinoflagellata life cycle: 1-mitosis, 2-sexual reproduction, 3-planozygote, 4-hypnozygote, 5-planomeiocyte the life cycle of dinoflagellates, including possible described transitions dinoflagellate cysts