Editing Algae (section)

==Classifications==
[[File:Gephyrocapsa oceanica color.jpg|thumb|False-color [[scanning electron micrograph]] of the unicellular [[coccolithophore]] ''[[Gephyrocapsa]] oceanica'']]
One definition of algae is that they "have [[chlorophyll]] as their primary [[photosynthetic pigment]] and lack a sterile covering of cells around their [[Gamete|reproductive cells]]".<ref>{{cite book |last=Lee |first=R. E. |date=2008 |title=Phycology |url=https://archive.org/details/phycology00leer_0 |url-access=registration |publisher=Cambridge University Press |isbn=9780521367448 }}</ref> On the other hand, the colorless ''Prototheca'' under ''[[Chlorophyta]]'' are all devoid of any chlorophyll. [[Cyanobacteria]] are often referred to as "blue-green algae" and are included as algae by the [[International Code of Nomenclature for algae, fungi, and plants]], although some authorities exclude all [[prokaryote]]s, including cyanobacteria, from the definition of algae.<ref name="Nabors-2004">{{cite book |last=Nabors |first=Murray W. |title=Introduction to Botany |date=2004 |publisher=Pearson Education, Inc |location=San Francisco |isbn=978-0-8053-4416-5 |url=https://archive.org/details/introductiontobo0000nabo/page/386/mode/2up |url-access=registration}}</ref><ref>{{cite dictionary |editor-last=Allaby |editor-first=M. |date=1992 |title=The Concise Dictionary of Botany |publisher=Oxford University Press |entry=Alga |url=https://archive.org/details/conciseoxforddic00mich/page/14/mode/2up |url-access=registration}}</ref>

Eukaryotic algae contain [[chloroplast]]s that are similar in structure to cyanobacteria. Chloroplasts contain circular [[DNA]] like that in cyanobacteria and are interpreted as representing reduced endosymbiotic [[cyanobacteria]]. However, the exact origin of the chloroplasts is different among separate lineages of algae, reflecting their acquisition during different endosymbiotic events. The table below describes the composition of the three major groups of algae. Their lineage relationships are shown in the figure in the upper right. Many of these groups contain some members that are no longer photosynthetic. Some retain plastids, but not chloroplasts, while others have lost plastids entirely.<ref>{{cite journal |last1=Sato |first1=Naoki |title=Are Cyanobacteria an Ancestor of Chloroplasts or Just One of the Gene Donors for Plants and Algae? |journal=Genes |date=27 May 2021 |volume=12 |issue=6 |pages=823 |doi=10.3390/genes12060823 |doi-access=free |pmid=34071987 |pmc=8227023 |issn=2073-4425}}</ref>

[[Phylogeny]] based on [[plastid]]<ref>{{cite journal |last1=Bhattacharya |first1=D. |last2=Medlin |first2=L.|author-link2=Linda Medlin |year=1998 |journal=Plant Physiology |volume=116 |issue=1 |pages=9–15 |url= http://www.plantphysiol.org/cgi/reprint/116/1/9.pdf |doi=10.1104/pp.116.1.9 |title=Algal Phylogeny and the Origin of Land Plants |url-status=live |archive-url= https://web.archive.org/web/20090207051438/http://www.plantphysiol.org/cgi/reprint/116/1/9.pdf |archive-date=7 February 2009 |pmc=1539170}}</ref> not nucleocytoplasmic genealogy:

{{clade
|1=[[Cyanobacteria]] (blue-green algae)
|2={{clade
   |1=[[Glaucophyte]]s
   |2={{clade
      |sublabel1=''with rhodoplasts''
      |1={{clade
         |1=[[Rhodophytes]] (red algae)
         |2=[[Stramenopile]]s (including [[golden algae|golden]] and [[brown algae]])
         |3={{clade
            |1=[[Cryptomonad|Cryptophytes]]
            |2=[[Haptophytes]]
            }}
         }}
      |sublabel2=''with chloroplasts''
      |2={{clade
         |1=[[Euglenophyte]]s
         |2={{clade
            |1=[[Chlorarachniophytes]]
            |2={{clade
               |1=[[Chlorophyte]]s (green algae)
               |2={{clade
                  |1=[[Charophyte]]s
                  |2=[[Embryophytes|Land plants (Embryophyta)]]
                  }}
               }}
            }}
         }}
      }}
   }}
}}

{|class="wikitable"
|-
! Supergroup affiliation !! Members !! [[Endosymbiont]] !! Summary
|-
|[[Primoplantae]]/<br />[[Archaeplastida]]
|
* [[Chlorophyta]]
* [[Rhodophyta]]{{efn|name=Rhodaria|Algae also include representatives of the minor groups [[Rhodelphidia]] and [[Picozoa]], assuming they lost the ability of oxygenic photosynthesis only secondarily.<ref name="Guiry-2024"/>}}
* [[Glaucophyta]]
|[[Cyanobacteria]]
|These algae have "primary" [[chloroplast]]s, i.e. the chloroplasts are surrounded by two membranes and probably developed through a single endosymbiotic event. The chloroplasts of red algae have [[chlorophyll]]s ''a'' and ''c'' (often), and [[phycobilin]]s, while those of green algae have chloroplasts with chlorophyll ''a'' and ''b'' without phycobilins. Land plants are pigmented similarly to green algae and probably developed from them, thus the [[Chlorophyta]] is a sister taxon to the plants; sometimes the Chlorophyta, the [[Charophyta]], and land plants are grouped together as the [[Viridiplantae]].
|-
|[[Excavata]] and [[Rhizaria]]
|
*[[Chlorarachniophyte]]s
*[[Euglenid]]s
|[[Green algae]]
|
These groups have green chloroplasts containing chlorophylls ''a'' and ''b''.<ref>{{cite book |title=Biology |edition=8 |last1=Losos |first1=Jonathan B. |last2=Mason |first2=Kenneth A. |last3=Singer |first3=Susan R. |publisher=McGraw-Hill |date=2007 |isbn=978-0-07-304110-0}}</ref> Their chloroplasts are surrounded by four and three membranes, respectively, and were probably retained from ingested green algae.

'''Chlorarachniophytes''', which belong to the [[phylum]] [[Cercozoa]], contain a small [[nucleomorph]], which is a [[relict]] of the algae's [[cell nucleus|nucleus]].

'''Euglenids''', which belong to the phylum [[Euglenozoa]], live primarily in fresh water and have chloroplasts with only three membranes. The endosymbiotic green algae may have been acquired through [[myzocytosis]] rather than [[phagocytosis]].<ref>{{cite journal |last1=Archibald |first1=J. M. |last2=Keeling |first2=P. J. |title=Recycled plastids: A 'green movement' in eukaryotic evolution |journal=Trends in Genetics |volume=18 |issue=11 |date=November 2002 |pages=577–584 |doi=10.1016/S0168-9525(02)02777-4 |pmid=12414188}}</ref>

(Another group with green algae endosymbionts is the dinoflagellate genus '''[[Lepidodinium]]''', which has replaced its original endosymbiont of red algal origin with one of green algal origin. A nucleomorph is present, and the host genome still have several red algal genes acquired through endosymbiotic gene transfer. Also, the euglenid and chlorarachniophyte genome contain genes of apparent red algal ancestry)<ref>{{cite journal|doi=10.1016/j.pisc.2015.07.002 | volume=6 | title=Euglena in time: Evolution, control of central metabolic processes and multi-domain proteins in carbohydrate and natural product biochemistry|year=2015|journal=Perspectives in Science|pages=84–93 | last1 = O'Neill | first1 = Ellis C. | last2 = Trick | first2 = Martin | last3 = Henrissat | first3 = Bernard | last4 = Field | first4 = Robert A.| bibcode=2015PerSc...6...84O | doi-access = free }}</ref><ref>{{Cite journal |last1=Ponce-Toledo |first1=Rafael I. |last2=López-García |first2=Purificación |last3=Moreira |first3=David |date=October 2019 |title=Horizontal and endosymbiotic gene transfer in early plastid evolution |journal=New Phytologist |language=en |volume=224 |issue=2 |pages=618–624 |doi=10.1111/nph.15965 |issn=0028-646X |pmc=6759420 |pmid=31135958|bibcode=2019NewPh.224..618P }}</ref><ref>{{Cite journal |last1=Ponce-Toledo |first1=Rafael I |last2=Moreira |first2=David |last3=López-García |first3=Purificación |last4=Deschamps |first4=Philippe |date=2018-06-19 |title=Secondary Plastids of Euglenids and Chlorarachniophytes Function with a Mix of Genes of Red and Green Algal Ancestry |url=https://doi.org/10.1093/molbev/msy121 |journal=Molecular Biology and Evolution |volume=35 |issue=9 |pages=2198–2204 |doi=10.1093/molbev/msy121 |issn=0737-4038 |pmc=6949139 |pmid=29924337}}</ref>
|-
|[[Halvaria]] and [[Hacrobia]]
|
* [[Heterokont]]s
* [[Chromerid]]s
* [[Dinoflagellate]]s
* [[Haptophyta]]
* [[Cryptomonad]]s
|[[Red algae]]
|
These groups have chloroplasts containing chlorophylls ''a'' and ''c'', and phycobilins. The shape can vary; they may be of discoid, plate-like, reticulate, cup-shaped, spiral, or ribbon shaped. They have one or more pyrenoids to preserve protein and starch. The latter chlorophyll type is not known from any prokaryotes or primary chloroplasts, but genetic similarities with red algae suggest a relationship there.<ref>{{cite journal |last1=Janson |first1=Sven |last2=Graneli |first2=Edna |title=Genetic analysis of the psbA gene from single cells indicates a cryptomonad origin of the plastid in Dinophysis (Dinophyceae) |journal=Phycologia |date=September 2003 |volume=42 |issue=5 |pages=473–477 |issn=0031-8884 |doi=10.2216/i0031-8884-42-5-473.1|bibcode=2003Phyco..42..473J |s2cid=86730888 }}</ref>

In the first three of these groups, ([[Chromista]]), the chloroplast has four membranes, retaining a [[nucleomorph]] in [[cryptomonad]]s, and they likely share a common pigmented ancestor, although other evidence casts doubt on whether the [[heterokont]]s, [[Haptophyta]], and [[cryptomonad]]s are in fact more closely related to each other than to other groups.<ref>{{cite journal |title=Evaluating Support for the Current Classification of Eukaryotic Diversity |first1=Laura |last1=Wegener Parfrey|author-link1=Laura Wegener Parfrey |first2=Erika |last2=Barbero |first3=Elyse |last3=Lasser |first4=Micah |last4=Dunthorn |first5=Debashish |last5=Bhattacharya|author-link6=David J. Patterson |first6=David J. |last6=Patterson|author-link7=Laura A. Katz |first7=Laura A |last7=Katz |doi=10.1371/journal.pgen.0020220 |journal=PLOS Genetics |date=December 2006 |volume=2 |issue=12 |pages=e220 |pmid=17194223 |pmc=1713255 |doi-access=free }}</ref><ref>{{cite journal |last1=Burki |first1=F. |last2=Shalchian-Tabrizi |first2=K. |last3=Minge |first3=M. |last4=Skjæveland |first4=Å. |last5=Nikolaev |first5=S. I. |year=2007 |title=Phylogenomics Reshuffles the Eukaryotic Supergroups |journal=PLOS ONE |volume=2 |issue=8 |page=e790 |doi=10.1371/journal.pone.0000790 |pmid=17726520 |pmc=1949142 |editor-last=Butler |editor-first=Geraldine |bibcode=2007PLoSO...2..790B |display-authors=etal|doi-access=free }}</ref>

The typical dinoflagellate chloroplast has three membranes, but considerable diversity exists in chloroplasts within the group, and a number of endosymbiotic events apparently occurred.<ref name="Keeling-2004" /> The [[Apicomplexa]], a group of closely related parasites, also have plastids called [[apicoplast]]s, which are not photosynthetic.<ref name="Keeling-2004" /> The [[Chromerida]] are the closest relatives of apicomplexans, and some have retained their chloroplasts.<ref name="Moore 2008">{{cite journal |title=A photosynthetic alveolate closely related to apicomplexan parasites |journal=Nature |volume=451 |issue=7181 |pages=959–963 |date=February 2008 |pmid=18288187 |doi=10.1038/nature06635 |author1=Moore RB |author2=Oborník M  |author3=Janouskovec J |author4=Chrudimský T |author5=Vancová M |author6=Green DH |author7=Wright SW |author8=Davies NW |author9=Bolch CJ|display-authors=8 |last10=Heimann |first10=Kirsten |last11=Šlapeta |first11=Jan |last12=Hoegh-Guldberg |first12=Ove |last13=Logsdon |first13=John M. |last14=Carter |first14=Dee A. |bibcode=2008Natur.451..959M |s2cid=28005870 }}</ref> The three [[alveolate]] groups evolved from a common [[myzozoa]]n ancestor that obtained chloroplasts.<ref>{{cite journal|first1=J.|last1=Janouškovec|first2=D.V.|last2=Tikhonenkov|first3=F.|last3=Burki|first4=A.T.|last4=Howe|first5=M.|last5=Kolísko|first6=A.P.|last6=Mylnikov|first7=P.J.|last7=Keeling|title=Factors mediating plastid dependency and the origins of parasitism in apicomplexans and their close relatives|journal=PNAS|volume=112|issue=33|pages=10200–10207|doi=10.1073/pnas.1423790112|date=2015|pmc=4547307}}</ref> 
|}

[[File:Gmelin - Historia Fucorum (Titelblatt).png|thumb|upright |Title page of [[Samuel Gottlieb Gmelin|Gmelin]]'s ''Historia Fucorum'', dated 1768]]

[[Carl Linnaeus|Linnaeus]], in ''[[Species Plantarum]]'' (1753),<ref>{{cite book |last=Linnæus |first=Caroli |date=1753 |title=Species Plantarum |volume=2 |page=1131 |url= https://www.biodiversitylibrary.org/item/13830#page/573/mode/1up |publisher=Impensis Laurentii Salvii}}</ref> the starting point for modern [[botanical nomenclature]], recognized 14 genera of algae, of which only four are currently considered among algae.<ref>{{Cite book |url= https://books.google.com/books?id=hOa74Hm4zDIC&pg=PA22 |title=Textbook of Algae |isbn=9780074519288 |last1=Sharma |first1=O. P. |date=1 January 1986 |page=22|publisher=Tata McGraw-Hill }}</ref> In ''[[10th edition of Systema Naturae|Systema Naturae]]'', Linnaeus described the genera ''[[Volvox]]'' and ''[[Corallina]]'', and a species of ''[[Acetabularia]]'' (as ''[[Madrepora]]''), among the animals.

In 1768, [[Samuel Gottlieb Gmelin]] (1744–1774) published the ''Historia Fucorum'', the first work dedicated to marine algae and the first book on [[marine biology]] to use the then new binomial nomenclature of Linnaeus. It included elaborate illustrations of seaweed and marine algae on folded leaves.<ref>{{cite book |last=Gmelin |first=S. G. |date=1768 |url= https://books.google.com/books?id=YUAAAAAAQAAJ&q=%22Historia+Fucorum%22 |via=Google Books |title=Historia Fucorum |publisher=Ex typographia Academiae scientiarum |location=St. Petersburg}}</ref><ref>{{cite book |last1=Silva |first1=P. C. |last2=Basson |first2=P. W. |last3=Moe |first3=R. L. |date=1996 |url= https://books.google.com/books?id=vuWEemVY8WEC&q=%22Historia+Fucorum%22+binomial+nomenclature&pg=PA2 |via=Google Books |title=Catalogue of the Benthic Marine Algae of the Indian Ocean|publisher=University of California Press |isbn=9780520915817 }}</ref>

[[William Henry Harvey|W. H. Harvey]] (1811–1866) and [[Lamouroux]] (1813)<ref name="Medlin-1997">{{cite journal |first1=Linda K. |last1=Medlin |first2=Wiebe H. C. F. |last2=Kooistra |first3=Daniel |last3=Potter |first4=Gary W. |last4=Saunders |first5=Robert A. |last5=Anderson |year=1997 |url=http://epic.awi.de/2100/1/Med1997c.pdf |title=Phylogenetic relationships of the 'golden algae' (haptophytes, heterokont chromophytes) and their plastids |url-status=live |archive-url= https://web.archive.org/web/20131005084158/http://epic.awi.de/2100/1/Med1997c.pdf |archive-date=5 October 2013 |journal=Plant Systematics and Evolution |page=188}}</ref> were the first to divide macroscopic algae into four divisions based on their pigmentation. This is the first use of a biochemical criterion in plant systematics. Harvey's four divisions are: red algae (Rhodospermae), brown algae (Melanospermae), green algae (Chlorospermae), and Diatomaceae.<ref>{{cite book |last=Dixon |first=P. S. |title=Biology of the Rhodophyta |date=1973 |publisher=Oliver & Boyd |location=Edinburgh |isbn=978-0-05-002485-0 |page=232}}</ref><ref>{{cite book |last=Harvey |first=D. |date=1836 |chapter-url= http://img.algaebase.org/pdf/562E38EB0a0fc2A17Eukv24B7E9F/18893.pdf |archive-url=https://ghostarchive.org/archive/20221009/http://img.algaebase.org/pdf/562E38EB0a0fc2A17Eukv24B7E9F/18893.pdf |archive-date=2022-10-09 |url-status=live |access-date=31 December 2017 |title=''Flora hibernica'' comprising the Flowering Plants Ferns Characeae Musci Hepaticae Lichenes and Algae of Ireland arranged according to the natural system with a synopsis of the genera according to the Linnaean system |chapter=Algae |editor-last=Mackay |editor-first=J. T. |pages=157–254}}.</ref>

At this time, microscopic algae were discovered and reported by a different group of workers (e.g., [[Otto Friedrich Müller|O. F. Müller]] and [[Christian Gottfried Ehrenberg|Ehrenberg]]) studying the [[Infusoria]] (microscopic organisms). Unlike [[macroalgae]], which were clearly viewed as plants, [[microalgae]] were frequently considered animals because they are often motile.<ref name="Medlin-1997" /> Even the nonmotile (coccoid) microalgae were sometimes merely seen as stages of the lifecycle of plants, macroalgae, or animals.<ref>Braun, A. ''[https://www.biodiversitylibrary.org/bibliography/2057#/summary Algarum unicellularium genera nova et minus cognita, praemissis observationibus de algis unicellularibus in genere (New and less known genera of unicellular algae, preceded by observations respecting unicellular algae in general)] {{webarchive |url= https://web.archive.org/web/20160420033958/http://www.biodiversitylibrary.org/bibliography/2057 |date=20 April 2016}}.'' Lipsiae, Apud W. Engelmann, 1855. Translation at: Lankester, E. & Busk, G. (eds.). ''Quarterly Journal of Microscopical Science'', 1857, vol. 5, [http://jcs.biologists.org/content/s1-5/17/13.full.pdf+html (17), 13–16] {{webarchive |url= https://web.archive.org/web/20160304130906/http://jcs.biologists.org/content/s1-5/17/13.full.pdf+html |date=4 March 2016}}; [http://jcs.biologists.org/content/s1-5/18/90.full.pdf+html (18), 90–96] {{webarchive |url= https://web.archive.org/web/20160305133158/http://jcs.biologists.org/content/s1-5/18/90.full.pdf+html |date=5 March 2016}}; [http://jcs.biologists.org/content/s1-5/19/143.full.pdf+html (19), 143–149] {{webarchive |url= https://web.archive.org/web/20160304113651/http://jcs.biologists.org/content/s1-5/19/143.full.pdf+html |date=4 March 2016}}.</ref><ref>Siebold, C. Th. v. "[https://www.biodiversitylibrary.org/item/49155#page/5/mode/1up Ueber einzellige Pflanzen und Thiere (On unicellular plants and animals)] {{webarchive |url= https://web.archive.org/web/20141126005532/http://www.biodiversitylibrary.org/item/49155 |date=26 November 2014}}". In: Siebold, C. Th. v. & Kölliker, A. (1849). ''Zeitschrift für wissenschaftliche Zoologie'', Bd. 1, p. 270. Translation at: Lankester, E. & Busk, G. (eds.). ''Quarterly Journal of Microscopical Science'', 1853, vol. 1, [http://jcs.biologists.org/content/s1-1/2/111.full.pdf+html (2), 111–121] {{webarchive |url= https://web.archive.org/web/20160304114623/http://jcs.biologists.org/content/s1-1/2/111.full.pdf+html |date=4 March 2016}}; [http://jcs.biologists.org/content/s1-1/3/195.full.pdf+html (3), 195–206] {{webarchive |url= https://web.archive.org/web/20160304115243/http://jcs.biologists.org/content/s1-1/3/195.full.pdf+html |date=4 March 2016}}.</ref>

Although used as a taxonomic category in some pre-Darwinian classifications, e.g., Linnaeus (1753),<ref name="Ragan-2010">{{cite journal |last1=Ragan |first1= Mark |date=2010-06-03 |title=On the delineation and higher-level classification of algae |url= https://www.tandfonline.com/doi/abs/10.1080/09670269810001736483 |journal=European Journal of Phycology |volume=33 |issue=1 |pages=1–15 |doi=10.1080/09670269810001736483 |access-date=2024-02-16}}</ref> de Jussieu (1789),<ref name="de Jussieu-1789">{{cite book |last=de Jussieu |first=Antoine Laurent |date= 1789 |title=Genera plantarum secundum ordines naturales disposita |url= https://archive.org/details/generaplantarums00juss/page/n3/mode/2up  |publisher= Parisiis, Apud Viduam Herissant et Theophilum Barrois |page=6}}</ref> Lamouroux (1813), Harvey (1836), Horaninow (1843), Agassiz (1859), Wilson & Cassin (1864),<ref name="Ragan-2010" /> in further classifications, the "algae" are seen as an artificial, polyphyletic group.<ref name="Khan-2020b">{{cite journal |last1=Khan |first1=Amna Komal |last2=Kausar |first2=Humera |last3=Jaferi |first3=Syyada Samra |last4=Drouet |first4=Samantha |last5=Hano |first5=Christophe |last6=Abbasi |first6=Bilal Haider |last7=Anjum |first7= Sumaira |display-authors=3 |date=2020-11-06 |title="An Insight into the Algal Evolution and Genomics |journal=Biomolecules |volume=10 |issue=11 |pages=1524  |doi=10.3390/biom10111524 |doi-access=free |pmid=33172219 |pmc=7694994 }}</ref>

Throughout the 20th century, most classifications treated the following groups as divisions or classes of algae: [[cyanophyte]]s, [[rhodophyte]]s, [[chrysophyte]]s, [[xanthophyte]]s, [[diatom|bacillariophytes]], [[phaeophyte]]s, [[Dinoflagellate#History|pyrrhophytes]] ([[Cryptomonad|cryptophytes]] and [[dinophyte]]s), [[euglenophyte]]s, and [[chlorophyte]]s. Later, many new groups were discovered (e.g., [[Bolidophyceae]]), and others were splintered from older groups: [[charophyte]]s and [[glaucophyte]]s (from chlorophytes), many [[heterokontophyte]]s (e.g., [[Synurophyceae|synurophytes]] from chrysophytes, or [[eustigmatophyte]]s from xanthophytes), [[haptophyte]]s (from chrysophytes), and [[chlorarachniophyte]]s (from xanthophytes).<ref>{{Cite journal |date=1980 |title=Compte rendu du premier colloque de l'association des Diatomistes de Langue Française. Paris, 25 janvier 1980 |url=https://doi.org/10.5962/p.308988 |journal=Cryptogamie. Algologie |volume=1 |issue=1 |pages=67–74 |doi=10.5962/p.308988 |bibcode=1980CrypA...1...67. |issn=0181-1568}}</ref>

With the abandonment of plant-animal dichotomous classification, most groups of algae (sometimes all) were included in [[Protist]]a, later also abandoned in favour of [[Eukaryota]]. However, as a legacy of the older plant life scheme, some groups that were also treated as [[protozoa]]ns in the past still have duplicated classifications (see [[ambiregnal protist]]s).<ref>{{Cite journal |last=Corliss |first=J O |date=1995 |title=The ambiregnal protists and the codes of nomenclature: a brief review of the problem and of proposed solutions |url=http://www.biodiversitylibrary.org/part/6717 |journal=The Bulletin of Zoological Nomenclature |volume=52 |pages=11–17 |doi=10.5962/bhl.part.6717 |issn=0007-5167|doi-access=free }}</ref>

Some parasitic algae (e.g., the green algae ''[[Prototheca]]'' and ''[[Helicosporidium]]'', parasites of metazoans, or ''[[Cephaleuros]]'', parasites of plants) were originally classified as [[fungi]], [[sporozoan]]s, or [[protist]]ans of ''[[incertae sedis]]'',<ref>{{cite book |last1=Williams |first1=B. A. |last2=Keeling |first2=P. J. |date=2003 |chapter=Cryptic organelles in parasitic protists and fungi |editor-last=Littlewood |editor-first=D. T. J. |title=The Evolution of Parasitism |publisher=Elsevier Academic Press |location=London |page=46 |isbn=978-0-12-031754-7 |chapter-url= https://books.google.com/books?id=_fAQGEJobT0C&pg=PA46}}</ref> while others (e.g., the green algae ''[[Phyllosiphon]]'' and ''[[Rhodochytrium]]'', parasites of plants, or the red algae ''[[Pterocladiophila]]'' and ''Gelidiocolax mammillatus'', parasites of other red algae, or the dinoflagellates ''[[Oodinium]]'', parasites of fish) had their relationship with algae conjectured early. In other cases, some groups were originally characterized as parasitic algae (e.g., ''[[Chlorochytrium]]''), but later were seen as [[endophytic]] algae.<ref>Round (1981). pp.&nbsp;398–400, {{Cite book |url= https://books.google.com/books?id=Rm08AAAAIAAJ&pg=PA398 |title=The Ecology of Algae |access-date=6 February 2015 |isbn=9780521269063 |last1=Round |first1=F. E. |date=8 March 1984|publisher=CUP Archive }}.</ref> Some filamentous bacteria (e.g., ''[[Beggiatoa]]'') were originally seen as algae. Furthermore, groups like the [[apicomplexan]]s are also parasites derived from ancestors that possessed plastids, but are not included in any group traditionally seen as algae.<ref>{{Cite book |last1=Grabda |first1=Jadwiga |title=Marine fish parasitology: an outline |last2=Grabda |first2=Jadwiga |date=1991 |publisher=VCH-Verl.-Ges |isbn=978-0-89573-823-3 |location=Weinheim}}</ref><ref>{{Cite journal |last1=Smith |first1=David Roy |last2=Keeling |first2=Patrick J. |date=2016-09-08 |title=Protists and the Wild, Wild West of Gene Expression: New Frontiers, Lawlessness, and Misfits |url=https://www.annualreviews.org/doi/10.1146/annurev-micro-102215-095448 |journal=Annual Review of Microbiology |language=en |volume=70 |issue=1 |pages=161–178 |doi=10.1146/annurev-micro-102215-095448 |pmid=27359218 |issn=0066-4227}}</ref>