Ecology and physiology Dinoflagellate

1 ecology , physiology

1.1 habitats
1.2 endosymbionts
1.3 nutritional strategies
1.4 harmful algal blooms
1.5 bioluminescence
1.6 lipid , sterol production
1.7 transport
1.8 life cycle

ecology , physiology
habitats

dinoflagellates can occur in aquatic environments: marine, brackish, , fresh water, including in snow or ice. common in benthic environments , sea ice.

endosymbionts

all zooxanthellae dinoflagellates , of them members within genus symbiodinium. association between symbiodinium , reef-building corals known. however, endosymbiontic zooxanthellae inhabit great number of other invertebrates , protists, example many sea anemones, jellyfish, nudibranchs, giant clam tridacna, , several species of radiolarians , foraminiferans. many extant dinoflagellates parasites (here defined organisms eat prey inside, i.e. endoparasites, or remain attached prey longer periods of time, i.e. ectoparasites). can parasitize animal or protist hosts. protoodinium, crepidoodinium, piscinoodinium, , blastodinium retain plastids while feeding on zooplanktonic or fish hosts. in parasitic dinoflagellates, infective stage resembles typical motile dinoflagellate cell.

nutritional strategies

three nutritional strategies seen in dinoflagellates: phototrophy, mixotrophy, , heterotrophy. phototrophs can photoautotrophs or auxotrophs. mixotrophic dinoflagellates photosynthetically active, heterotrophic. facultative mixotrophs, in autotrophy or heterotrophy sufficient nutrition, classified amphitrophic. if both forms required, organisms mixotrophic sensu stricto. free-living dinoflagellates not have chloroplasts, host phototrophic endosymbiont. few dinoflagellates may use alien chloroplasts (cleptochloroplasts), obtained food (kleptoplasty). dinoflagellates may feed on other organisms predators or parasites.

food inclusions contain bacteria, bluegreen algae, small dinoflagellates, diatoms, ciliates, , other dinoflagellates.

mechanisms of capture , ingestion in dinoflagellates quite diverse. several dinoflagellates, both thecate (e.g. ceratium hirundinella, peridinium globulus) , nonthecate (e.g. oxyrrhis marina, gymnodinium sp. , kofoidinium spp.), draw prey sulcal region of cell (either via water currents set flagella or via pseudopodial extensions) , ingest prey through sulcus. in several protoperidinium spp., e.g. p. conicum, large feeding veil — pseudopod called pallium — extruded capture prey subsequently digested extracellularly (= pallium-feeding). oblea, zygabikodinium, , diplopsalis other dinoflagellate genera known use particular feeding mechanism). katodinium (gymnodinium) fungiforme, commonly found contaminant in algal or ciliate cultures, feeds attaching prey , ingesting prey cytoplasm through extensible peduncle. feeding mechanisms of oceanic dinoflagellates remain unknown, although pseudopodial extensions observed in podolampas bipes.

harmful algal blooms

dinoflagellates bloom in concentrations of more million cells per millilitre. under such circumstances, can produce toxins (generally called dinotoxins) in quantities capable of killing fish , accumulating in filter feeders such shellfish, in turn may passed on people eat them. phenomenon called red tide, color bloom imparts water. colorless dinoflagellates may form toxic blooms, such pfiesteria. dinoflagellate blooms not dangerous. bluish flickers visible in ocean water @ night come blooms of bioluminescent dinoflagellates, emit short flashes of light when disturbed.

algal bloom (akasio) noctiluca spp. in nagasaki

the same red tide mentioned above more produced when dinoflagellates able reproduce rapidly , copiously on account of abundant nutrients in water. although resulting red waves unusual sight, contain toxins not affect marine life in ocean, people consume them, well. specific carrier shellfish. can introduce both nonfatal , fatal illnesses. 1 such poison saxitoxin, powerful paralytic neurotoxin. human inputs of phosphate further encourage these red tides, strong interest exists in learning more dinoflagellates, both medical , economic perspectives. ecology of harmful algal blooms extensively studied.

bioluminescence

long exposure image of bioluminescence of n. scintillans in yacht port of zeebrugge, belgium




kayaking in bioluminescent bay, vieques, puerto rico

at night, water can have appearance of sparkling light due bioluminescence of dinoflagellates. more 18 genera of dinoflagellates bioluminescent, , majority of them emit blue-green light. these species contain scintillons, individual cytoplasmic bodies (about 0.5 µm in diameter) distributed in cortical region of cell, outpockets of main cell vacuole. contain dinoflagellate luciferase, main enzyme involved in dinoflagellate bioluminescence, , luciferin, chlorophyll-derived tetrapyrrole ring acts substrate light-producing reaction. luminescence occurs brief (0.1 sec) blue flash (max 476 nm) when stimulated, mechanical disturbance. therefore, when mechanically stimulated—by boat, swimming, or waves, example—a blue sparkling light can seen emanating sea surface.

dinoflagellate bioluminescence controlled circadian clock , occurs @ night. luminescent , nonluminescent strains can occur in same species. number of scintillons higher during night during day, , breaks down during end of night, @ time of maximal bioluminescence.

the luciferin-luciferase reaction responsible bioluminescence ph sensitive. when ph drops, luciferase changes shape, allowing luciferin, more tetrapyrrole, bind. dinoflagellates can use bioluminescence defense mechanism. can startle predators flashing light or can ward off potential predators indirect effect such burglar alarm . bioluminescence attracts attention dinoflagellate , attacker, making predator more vulnerable predation higher trophic levels.

bioluminescent dinoflagellate ecosystem bays among rarest , fragile, famous ones being bioluminescent bay in la parguera, lajas, puerto rico; mosquito bay in vieques, puerto rico; , las cabezas de san juan reserva natural fajardo, puerto rico. also, bioluminescent lagoon near montego bay, jamaica, , bioluminescent harbors surround castine, maine.

lipid , sterol production

dinoflagellates produce characteristic lipids , sterols. 1 of these sterols typical of dinoflagellates , called dinosterol.

transport

dinoflagellate theca can sink rapidly seafloor in marine snow.

life cycle

dinoflagellata life cycle: 1-binary fission, 2-sexual reproduction, 3-planozygote, 4-hypnozygote, 5-planomeiocyte

dinoflagellates have haplontic life cycle, possible exception of noctiluca , relatives.

the life cycle involves asexual reproduction means of binary fission, either through desmoschisis or eleuteroschisis. more complex life cycles occur, more particularly parasitic dinoflagellates. sexual reproduction occurs, though mode of reproduction known in small percentage of dinoflagellates. takes place fusion of 2 individuals form zygote, may remain mobile in typical dinoflagellate fashion , called planozygote. zygote may later form resting stage or hypnozygote, called dinoflagellate cyst or dinocyst. after (or before) germination of cyst, hatchling undergoes meiosis produce new haploid cells.