Oocystis
{{Short description|Genus of algae}}
{{Automatic taxobox
| image = Oocystis borgei.JPG
| image_caption = Oocystis borgei
| taxon = Oocystis
| authority = Nägeli ex A. Braun, 1855
| type_species = Oocystis naegelii
| type_species_authority = A.Braun{{AlgaeBase genus|id=43441|name=Oocystis|access-date=2025-02-03}}
| subdivision_ranks = Species
| subdivision =
- O. heteromucosa
- O. marssonii
- O. solitaria
- O. nephrocytioides
- O. sp. AN 2/29-4
- O. sp. Tow 6/3 P-10w
- O. lacustris
- O. sp. WH
- O. apiculata
}}
Oocystis is a planktonic genus of mostly freshwater green algae of the family Oocystaceae.See the NCBI [https://www.ncbi.nlm.nih.gov/Taxonomy/Browser/wwwtax.cgi?mode=Info&id=120746 webpage on Oocystis]. Data extracted from the {{cite web | url=http://ftp.ncbi.nih.gov/pub/taxonomy/ | title=NCBI taxonomy resources | publisher=National Center for Biotechnology Information | accessdate=2007-03-19}} It is the type genus of its family. Oocystis is mostly found in freshwater habitats and has a cosmopolitan distribution. A few species are found in terrestrial, such as wet rocks, or in marine waters.
Description
Oocystis is solitary or borne in colonies of two, four or eight surrounded in a thin mucilaginous envelope or mother cell wall. The colony is up to 77 μm in diameter and oval to ellipsoid. Individual cells may be fusiform, ellipsoidal, oval or nearly spherical, 7–46 μm long. The cell wall is smooth but may be thickened at the poles. Cells contain one to many parietal chloroplasts.
Asexual reproduction occurs by the formation of two, four or eight autospores which are released by the rupture of the parental cell wall. Sexual reproduction and flagellated stages have not been observed in this genus.
Taxonomy
The taxonomy of Oocystis is difficult and in need of revision. Species of Oocystis are distinguished based on morphological features, such as the size and shape of cells, number of chloroplasts, presence or absence of pyrenoids, and the morphology of the mucilaginous envelope.{{cite book | title= Chlorophyceae (Grünalgen), Ordnung Chlorococcales | last1=Komárek | first1=J. | last2=Fott | first2=B. | date=1983 | publisher= E. Schweizerbart'sche Verlagsbuchhandlung | series=Das Phytoplankton des Süßwassers | language=German | pages=1044 }} Some species exhibit considerable phenotypic plasticity.{{cite journal|title=Oocystis lacustris Chod. (Chlorophyta, Trebouxiophyceae) in Lake Tanganyika (Africa)|last1=Stoyneva|first1=M.P.|last2=Cocquyt|first2=C.|last3=Gärtner|first3=G.|last4=Vyverman|first4=W.|journal=Linzer biologische Beiträge|date=2007|volume=39|issue=1|pages=571–632}}
In particular, the presence and absence of pyrenoids is controversial. The type species, Oocystis naegelii, has chloroplasts without pyrenoids. Some authors, such as František Hindák, separated the pyrenoid-bearing species into a separate genus, Oocystella. However, other authors have stated that pyrenoids may be indistinct and difficult to observe,{{cite journal|title=Freshwater Algae in Northwest Washington, Volume II, Chlorophyta and Rhodophyta|year=2016 |doi=10.25710/fctx-n773|last1=Matthews |first1=Robin |journal=A Collection of Open Access Books and Monographs |publisher=Western Washington University }} and consider the two genera synonymous.{{cite journal|doi=10.1007/s40415-014-0118-6 |title=Oocystis apicurvata sp. nov. (Oocystaceae, Trebouxiophyceae), a new species of green algae from Chapada Diamantina, northeast Brazil |date=2015 |last1=Ramos |first1=Geraldo J. P. |last2=De m. Bicudo |first2=Carlos E. |last3=Do n. Moura |first3=Carlos Wallace |journal=Brazilian Journal of Botany |volume=38 |pages=171–173 }}
In its current circumscription, Oocystis is paraphyletic.{{cite journal|doi= 10.1111/jpy.12581|title= Molecular and morphological delimitation and generic classification of the family Oocystaceae (Trebouxiophyceae, Chlorophyta)|date= 2017|last1= Štenclová|first1= Lenka|last2= Fučíková|first2= Karolina|last3= Kaštovský|first3= Jan|last4= Pažoutová|first4= Marie|journal= Journal of Phycology|volume= 53|issue= 6|pages= 1263–1282|pmid= 28833138|bibcode= 2017JPcgy..53.1263S}}
Ecology
Oocystis species are an important component of the biomass in freshwater habitats. As primary producers, Oocystis species are often preyed on by zooplankton,{{cite journal|title=Ecology of Oocystis spp. in Lake Biwa: abundance, colony composition, viability, and food relations with Eodiaptomus japonicus and Daphnia longispina|last1=Kawabata|first1=Keiichi|date=1988|journal=Memoirs of the Faculty of Science, Kyoto University. Series of Biology|volume=13|pages=41–47}} or parasitized by Chytridium fungi.{{cite journal|doi=10.1139/b71-016 |title=The ecology of Chytridium deltanum and other fungus parasites on Oocystis spp. |date=1971 |last1=Masters |first1=Margaret J. |journal=Canadian Journal of Botany |volume=49 |pages=75–87 }} On the other hand, species like Oocystis borgei have significant allelopathic effects on Microcystis aeruginosa, a species which forms harmful algal blooms.{{cite journal|doi=10.1080/09593330.2020.1847202 |title=Allelopathic effect of Oocystis borgei culture on Microcystis aeruginosa |date=2022 |last1=Wang |first1=Xiaoqian |last2=Zhang |first2=Yulei |last3=Li |first3=Changling |last4=Huang |first4=Xianghu |last5=Li |first5=Feng |last6=Wang |first6=Xinyu |last7=Li |first7=Guanbao |journal=Environmental Technology |volume=43 |issue=11 |pages=1662–1671 |pmid=33151809 }}