Protists are usually one-celled microorganisms. They include algae (autotrophs which make their own food) and protozoans (heterotrophs which eat the algae for food). In recent years, researchers have discovered many protists are mixotrophs, which can function in both modes.
Marine protists are defined by their habitat as protists that live in marine environments, that is, in the saltwater of seas or oceans or the brackish water of coastal estuaries. Life originated as marine single-celled prokaryotes (bacteria and archaea) and later evolved into more complex eukaryotes. Eukaryotes are the more developed life forms known as plants, animals, fungi and protists. Protists are the eukaryotes that cannot be classified as plants, fungi or animals. They are mostly single-celled and microscopic. The term protist came into use historically as a term of convenience for eukaryotes that cannot be strictly classified as plants, animals or fungi. They are not a part of modern cladistics because they are paraphyletic (lacking a common ancestor for all descendants).
Most protists are too small to be seen with the naked eye. They are highly diverse organisms currently organised into 18 phyla, but not easy to classify.[1][2] Studies have shown high protist diversity exists in oceans, deep sea-vents and river sediments, suggesting large numbers of eukaryotic microbial communities have yet to be discovered.[3][4] There has been little research on mixotrophic protists, but recent studies in marine environments found mixotrophic protists contribute a significant part of the protist biomass.[5] Since protists are eukaryotes (and not prokaryotes) they possess within their cell at least one nucleus, as well as organelles such as mitochondria and Golgi bodies. Many protist species can switch between asexual reproduction and sexual reproduction involving meiosis and fertilization.[6]
In contrast to the cells of prokaryotes, the cells of eukaryotes are highly organised. Plants, animals and fungi are usually multi-celled and are typically macroscopic. Most protists are single-celled and microscopic. But there are exceptions. Some single-celled marine protists are macroscopic. Some marine slime molds have unique life cycles that involve switching between unicellular, colonial, and multicellular forms.[7] Other marine protist are neither single-celled nor microscopic, such as seaweed.
Protists have been described as a taxonomic grab bag of misfits where anything that doesn't fit into one of the main biological kingdoms can be placed.[8] Some modern authors prefer to exclude multicellular organisms from the traditional definition of a protist, restricting protists to unicellular organisms.[9][10] This more constrained definition excludes all brown, the multicellular red and green algae, and, sometimes, slime molds (slime molds excluded when multicellularity is defined as "complex").[11]
Part of a series of overviews on
Marine life
Habitats
Microorganisms
Microbiomes
Viruses
Prokaryotes
Protists
Fungi
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^Cavalier-Smith T (December 1993). "Kingdom protozoa and its 18 phyla". Microbiological Reviews. 57 (4): 953–94. doi:10.1128/mmbr.57.4.953-994.1993. PMC 372943. PMID 8302218.
^Corliss JO (1992). "Should there be a separate code of nomenclature for the protists?". BioSystems. 28 (1–3): 1–14. doi:10.1016/0303-2647(92)90003-H. PMID 1292654.
^Slapeta J, Moreira D, López-García P (2005). "The extent of protist diversity: insights from molecular ecology of freshwater eukaryotes". Proceedings of the Royal Society B: Biological Sciences. 272 (1576): 2073–81. doi:10.1098/rspb.2005.3195. PMC 1559898. PMID 16191619.
^Moreira D, López-García P (2002). "The molecular ecology of microbial eukaryotes unveils a hidden world" (PDF). Trends in Microbiology. 10 (1): 31–8. doi:10.1016/S0966-842X(01)02257-0. PMID 11755083.
^Leles, S.G.; Mitra, A.; Flynn, K.J.; Stoecker, D.K.; Hansen, P.J.; Calbet, A.; McManus, G.B.; Sanders, R.W.; Caron, D.A.; Not, F.; Hallegraeff, G.M. (2017). "Oceanic protists with different forms of acquired phototrophy display contrasting biogeographies and abundance". Proceedings of the Royal Society B: Biological Sciences. 284 (1860): 20170664. doi:10.1098/rspb.2017.0664. PMC 5563798. PMID 28768886.
^Characteristics of Protists In: Rye, Connie; Avissar, Yael; Choi, Jung Ho; DeSaix, Jean; Jurukovski, Vladimir; Wise, Robert R. (2013). Biology. Houston, Texas. ISBN 978-1-938168-09-3. OCLC 896421272.{{cite book}}: CS1 maint: location missing publisher (link) Modified text was copied from this source, which is available under a Creative Commons Attribution 4.0 International License.
^Devreotes P (1989). "Dictyostelium discoideum: a model system for cell-cell interactions in development". Science. 245 (4922): 1054–8. Bibcode:1989Sci...245.1054D. doi:10.1126/science.2672337. PMID 2672337.
^Neil A C, Reece J B, Simon E J (2004) Essential biology with physiology Pearson/Benjamin Cummings, Page 291. ISBN 9780805375039
^O'Malley MA, Simpson AG, Roger AJ (2012). "The other eukaryotes in light of evolutionary protistology". Biology & Philosophy. 28 (2): 299–330. doi:10.1007/s10539-012-9354-y. S2CID 85406712.
^Adl SM, Simpson AG, Farmer MA, Andersen RA, Anderson OR, Barta JR, Bowser SS, Brugerolle G, Fensome RA, Fredericq S, James TY, Karpov S, Kugrens P, Krug J, Lane CE, Lewis LA, Lodge J, Lynn DH, Mann DG, McCourt RM, Mendoza L, Moestrup O, Mozley-Standridge SE, Nerad TA, Shearer CA, Smirnov AV, Spiegel FW, Taylor MF (2005). "The new higher level classification of eukaryotes with emphasis on the taxonomy of protists". The Journal of Eukaryotic Microbiology. 52 (5): 399–451. doi:10.1111/j.1550-7408.2005.00053.x. PMID 16248873. S2CID 8060916.
^Margulis L, Chapman MJ (19 March 2009). Kingdoms and Domains: An Illustrated Guide to the Phyla of Life on Earth. Academic Press. ISBN 9780080920146.
A protist (/ˈproʊtɪst/ PROH-tist) or protoctist is any eukaryotic organism that is not an animal, land plant, or fungus. Protists do not form a natural...
protists, but recent studies in marine environments found mixotrophic protests contribute a significant part of the protist biomass. Since protists are...
mixotrophic protists, but recent studies in marine environments found mixotrophic protests contribute a significant part of the protist biomass. Single-celled...
bacteria and pathogenic protists, and engulf them by phagocytosis. Amoeboid stages also occur in the multicellular fungus-like protists, the so-called slime...
viruses affecting marineprotists had been isolated and examined, most of them viruses of microalgae. The genomes of these marineprotist viruses are highly...
water column. Marine snow is made up of a variety of mostly organic matter, including dead or dying animals and phytoplankton, protists, fecal matter...
multicellular organisms as well as many unicellular protists and protozoans that are microbes. Some protists are related to animals and some to green plants...
Coccolithophore shells Many protists have protective shells or tests, usually made from silica (glass) or calcium carbonate (chalk). Protists are a diverse group...
Picozoa, Picobiliphyta, Picobiliphytes, or Biliphytes are protists of a phylum of marine unicellular heterotrophic eukaryotes with a size of less than...
the naked eye. They are phytoplankton typically found in freshwater and marine systems, living in both the water column and sediment. They are unicellular...
(seaweeds) are technically marineprotists since they are not true plants. Macroalgae Giant kelp is technically a protist since it is not a true plant...
International License. Tarangkoon, Woraporn (29 April 2010). "Mixtrophic Protists among Marine Ciliates and Dinoflagellates: Distribution, Physiology and Ecology"...
microbiome researchers agree bacteria, archaea, fungi, algae, and small protists should be considered as members of the microbiome. The integration of phages...
Decelle J, Colin S, Foster RA (2015). "Photosymbiosis in Marine Planktonic Protists". MarineProtists. pp. 465–500. doi:10.1007/978-4-431-55130-0_19. ISBN 978-4-431-55129-4...
bacteria, around 40,000 varieties of fungi, and hundreds of species of protists, algae, mosses and liverworts that live some part of their life cycle as...
Code of Zoological Nomenclature for zoology (covering animals, zoological protists, and trace fossils attributable to the activities of animals), the International...
study of protists, a highly diverse group of eukaryotic organisms. All eukaryotes apart from animals, plants and fungi are considered protists. Its field...
animals, fungus, protists, bacteria and archaea. Terrestrial microfossils include pollen and spores. Marine microfossils found in marine sediments are the...
multicellular organisms, including plants. Microbiota include bacteria, archaea, protists, fungi, and viruses, and have been found to be crucial for immunologic...
has been proposed as the explanation for magnetoreception in some marineprotists. Research is underway on whether a similar relationship may underlie...
amoeba or amoeboids. Other protists are not motile, and consequently have no built-in movement mechanism. Unicellular protists comprise a vast, diverse...
The International Census of Marine Microbes is a field project of the Census of Marine Life that inventories microbial diversity by cataloging all known...
of marine biogeochemical cycling. In all ocean ecosystems, grazing by heterotrophic protists constitutes the single largest loss factor of marine primary...
Marine biology is the scientific study of the biology of marine life, organisms in the sea. Given that in biology many phyla, families and genera have...
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