{{Short description|Genus of algae}} {{Automatic taxobox | image = | taxon = Asterochloris | authority = [[Tscherm.-Woess]], 1980 | type_species = ''[[Asterochloris phycobiontica]]'' | type_species_authority = Tscherm.-Woess, 1980 | subdivision_ranks = Species | subdivision = }}
'''''Asterochloris''''' is a [[genus]] of [[green algae]] in the family [[Trebouxiophyceae]]. It is a common {{lichengloss|photobiont}} in [[lichen]], occurring in the [[thallus|thalli]] of more than 20 lichen genera worldwide. ''Asterochloris'' is distinguishable from the [[morphology (biology)|morphologically]] similar genus ''[[Trebouxia]]'', primarily due to its deeply lobed [[chloroplast]], the placement of the chloroplast along the cell's periphery before the initiation of [[zoospore]] or [[aplanospore]] formation, and its tendency to primarily [[asexual reproduction|reproduce asexually]] through the production of aplanospores.
==Taxonomy== The genus was [[circumscription (taxonomy)|circumscribed]] in 1980 by [[Elisabeth Tschermak-Woess]], with ''[[Asterochloris phycobiontica]]'' assigned as the [[type species]]. She differentiated it from the related genus ''[[Trebouxia]]'' by differences in [[chloroplast]] morphology.<ref name="Tschermak-Woess 1980"/> Later [[molecular phylogenetics|molecular]] research showed that ''Trebouxia'' was [[paraphyletic]],<ref name="Friedl & Zeltner 1994"/><ref name="Friedl & Rokitta 1997"/> and that some ''Trebouxia'' species were closely related to genus ''Asterochloris''.<ref name="Helms et al. 2001"/><ref name="Piercey-Normore & DePriest 2001"/><ref name="Škaloud & Peksa 2008"/> In 2010, Škaloud and Peksa proposed to split the genus ''Trebouxia'' and formally delineate genus ''Asterochloris''.<ref name="Skaloud & Peksa 2010"/>
Within the broader classification of green algae, ''Asterochloris'' belongs to the order [[Trebouxiales]] within the class [[Trebouxiophyceae]]. Current research suggests that several cryptic species within the genus still await formal description.<ref name="Veselá et al. 2024"/>
==Description== ''Asterochloris'' is characterised by its unique cellular structure and reproduction methods. Each ''Asterochloris'' cell is spherical and exists in isolation, containing a single [[cell nucleus|nucleus]]. The cell wall is thin and firm, lacking the gelatinous texture often found in similar organisms. Inside, there is a single [[chloroplast]]—the component responsible for [[photosynthesis]]—shaped like a thick cup with edges that resemble the rays of a star, and it may contain one or multiple [[pyrenoid]]s. Pyrenoids are specialised structures within the chloroplast that play a crucial role in the synthesis of [[starch]]. These pyrenoids are encircled by grains of starch, suggesting an active photosynthetic machinery.<ref name="Tschermak-Woess 1980"/>
Additionally, the cells of ''Asterochloris'' frequently contain clear, oily droplets, which are likely used as energy storage. Unlike some algae that reproduce through the production of autosporous (self-generating) spores, ''Asterochloris'' propagates through the release of [[zoospore]]s or [[aplanospore]]s. These spores are produced through successive [[cell division]]s.<ref name="Tschermak-Woess 1980"/>
In 2015, Skaloud and Peksa updated the description of ''Asterochloris'', providing more detailed insights into its cellular features and reproductive behaviours. They observed that, in addition to being spherical, cells of ''Asterochloris'' can also be oval or pear-shaped, and the cell wall, while generally thin, may have localized areas of thickening. The nucleus of each cell is positioned along the side within a large fold of the chloroplast, a green structure critical for photosynthesis that has a star-like shape with lobes extending to the cell's edge. Central to the chloroplast are one to several pyrenoids, structures essential for starch production, surrounded by a noticeable layer of starch, indicating the cell's active energy production.<ref name="Škaloud et al. 2015"/>
Skaloud and Peksa further detailed that before the algae reproduce asexually—either through the release of swimming spores (zoospores) or non-swimming spores (aplanospores)—the chloroplast changes shape, flattening against the cell wall. The reproduction process typically results in a large number of spores, ranging from 64 to 128, and in rare cases, the algae can produce 2 to 8 self-replicating spores (autospores). They also noted that zoospores are unique in their appearance, lacking a protective covering, being flattened from back to front, and equipped with two forward-facing flagella for movement. These zoospores carry their green chloroplast at the back, the nucleus in the middle or toward the back, and lack a clear visual receptor ([[Eyespot apparatus|stigma]]). When zoospores are released, they initially swim together as a group, connected at the back, before dispersing. Skaloud and Peksa also mentioned that sexual reproduction occurs but is rare, involving the merging of two similar ([[isogamy|isogamous]]) [[gamete]]s.<ref name="Škaloud et al. 2015"/>
==Habitat and distribution==
''Asterochloris'' is a widely distributed and [[cosmopolitan distribution|cosmopolitan]] genus. It is a common {{lichengloss|photobiont}} in [[lichen]], occurring in the [[thallus|thalli]] of more than 20 lichen genera worldwide.<ref name="Škaloud et al. 2015"/> The genus associates primarily with mycobionts from the families [[Cladoniaceae]] and [[Stereocaulaceae]].<ref name="Veselá et al. 2024"/>
While primarily known as a lichen symbiont, free-living populations of ''Asterochloris'' have been documented in various environments. These include soil communities, mountain [[tundra]] regions, and on tree bark in sub-[[Mediterranean Basin|Mediterranean]] regions of Slovenia and Italy. In an unusual habitat, the genus has also been detected on the hair of [[sloth]]s in South and Central America.<ref name="Veselá et al. 2024"/>
==Species== * ''[[Asterochloris antarctica]]'' {{au|Y.J.Kim, J.I.Kim & W.Shin}}, 2020<ref name="Kim et al. 2020"/> – Antarctica * ''[[Asterochloris echinata]]'' {{au|Skaloud & Peksa}}<ref name="Škaloud et al. 2015"/> * ''[[Asterochloris erici]]'' {{au|(Ahmadjian) Skaloud & Peksa}} * ''[[Asterochloris excentrica]]'' {{au|(Archibald) Skaloud & Peksa}} * ''[[Asterochloris friedlii]]'' {{au|Skaloud & Peksa}}<ref name="Škaloud et al. 2015"/> * ''[[Asterochloris gaertneri]]'' {{au|Skaloud & Peksa}}<ref name="Škaloud et al. 2015"/> * ''[[Asterochloris glomerata]]'' {{au|(Warén) Skaloud & Peksa}} * ''[[Asterochloris irregularis]]'' {{au|(Hildreth & Ahmadjian) Skaloud & Peksa}} * ''[[Asterochloris italiana]]'' {{au|(Archibald) Skaloud & Peksa}} * ''[[Asterochloris leprarii]]'' {{au|Skaloud & Peksa}}<ref name="Škaloud et al. 2015"/> * ''[[Asterochloris lobophora]]'' {{au|Skaloud & Peksa}}<ref name="Škaloud et al. 2015"/> * ''[[Asterochloris magnus]]'' {{au|(Archibald) Skaloud & Peksa}} * ''[[Asterochloris mediterranea]]'' {{au|E.Barreno, S.Chiva, P.Moya & P.Škaloud}}, 2015<ref name="Moya et al. 2015"/> – Iberian Peninsula; Canary Islands * ''[[Asterochloris phycobiontica]]'' {{au|E.Tschermak-Woess}} * ''[[Asterochloris pseudoirregularis]]'' {{au|Y.J.Kim, J.I.Kim & W.Shin}}, 2020<ref name="Kim et al. 2020"/> – Antarctica * ''[[Asterochloris pyriformis]]'' {{au|Thüs et al.}} * ''[[Asterochloris sejongensis]]'' {{au|Kim & Shin}}, 2017<ref name="Kim et al. 2017"/> – Antarctica; ''[[Cladonia pyxidata]]'', ''[[Sphaerophorus globosus]]'' * ''[[Asterochloris stereocaulonicola]]'' {{au|Y.J.Kim, J.I.Kim & W.Shin}}, 2020<ref name="Kim et al. 2020"/> – Antarctica * ''[[Asterochloris woessiae]]'' {{au|Skaloud & Peksa}}<ref name="Škaloud et al. 2015"/>
==References== {{Reflist|colwidth=30em|refs=
<ref name="Friedl & Zeltner 1994">{{cite journal |last1=Friedl |first1=Thomas |last2=Zeltner |first2=Cornelia |title=Assessing the relationships of some coccoid green lichen algae and the Microthamniales (Chlorophyta) with 18s ribosomal RNA gene sequence comparisons 1 |journal=Journal of Phycology |volume=30 |issue=3 |year=1994 |doi=10.1111/j.0022-3646.1994.00500.x |pages=500–506 |bibcode=1994JPcgy..30..500F}}</ref>
<ref name="Friedl & Rokitta 1997">{{cite journal |last1=Friedl |first1=T. |last2=Rokitta |first2=C. |year=1997 |title=Species relationships in the lichen alga ''Trebouxia'' (Chlorophyta, Trebouxiophyceae): molecular phylogenetic analyses of nuclear-encoded large subunit rRNA gene sequences |journal=Symbiosis |volume=23 |pages=125–148}}</ref>
<ref name="Helms et al. 2001">{{cite journal |last1=Helms |first1=Gert |last2=Friedl |first2=Thomas |last3=Rambold |first3=Gerhard |last4=Mayrhofer |first4=Helmut |title=Identification of photobionts from the lichen family Physciaceae using algal-specific ITS rDNA sequencing |journal=The Lichenologist |volume=33 |issue=1 |year=2001 |doi=10.1006/lich.2000.0298 |pages=73–86}}</ref>
<ref name="Kim et al. 2017">{{cite journal |last1=Kim |first1=Jong Im |last2=Nam |first2=Seung Won |last3=So |first3=Jae Eun |last4=Hong |first4=Soon Gyu |last5=Choi |first5=Han-Gu |last6=Shin |first6=Woongghi |title=Asterochloris sejongensis sp. nov. (Trebouxiophyceae, Chlorophyta) from King George Island, Antarctica |journal=Phytotaxa |volume=295 |issue=1 |year=2017 |doi=10.11646/phytotaxa.295.1.5 |pages=60–70 |url=https://repository.kopri.re.kr/bitstream/201206/5850/1/349151.pdf}}</ref>
<ref name="Kim et al. 2020">{{cite journal |last1=Kim |first1=Jong Im |last2=Kim |first2=Yong Jun | last3=Nam |first3=Seung Won |last4=So |first4=Jae Eun |last5=Hong |first5=Soon Gyu |last6=Choi |first6=Han-Gu |last7=Shin |first7=Woongghi |title=Taxonomic study of three new Antarctic ''Asterochloris'' (Trebouxiophyceae) based on morphological and molecular data |journal=Algae |volume=35 |issue=1 |year=2020 |doi=10.4490/algae.2020.35.2.23 |pages=17–32|doi-access=free }}</ref>
<ref name="Moya et al. 2015">{{cite journal |last1=Moya |first1=Patricia |last2=Škaloud |first2=Pavel |last3=Chiva |first3=Salvador |last4=García-Breijo |first4=Francisco J. |last5=Reig-Armiñana |first5=José |last6=Vančurová |first6=Lucie |last7=Barreno |first7=Eva |title=Molecular phylogeny and ultrastructure of the lichen microalga ''Asterochloris mediterranea'' sp. nov. from Mediterranean and Canary Islands ecosystems |journal=International Journal of Systematic and Evolutionary Microbiology |volume=65 |issue=Pt_6 |year=2015 |doi=10.1099/ijs.0.000185 |pages=1838–1854 |pmid=25757706|hdl=10251/68891 |hdl-access=free }}</ref>
<ref name="Piercey-Normore & DePriest 2001">{{cite journal |last1=Piercey-Normore |first1=Michele D. |last2=DePriest |first2=Paula T. |title=Algal switching among lichen symbioses |journal=American Journal of Botany |volume=88 |issue=8 |year=2001 |doi=10.2307/3558457 |pages=1490–1498 |jstor=3558457 |pmid=21669682}}</ref>
<ref name="Škaloud & Peksa 2008">{{cite journal |last1=Škaloud |first1=Pavel |last2=Peksa |first2=Ondřej |title=Comparative study of chloroplast morphology and ontogeny in ''Asterochloris'' (Trebouxiophyceae, Chlorophyta) |journal=Biologia |volume=63 |issue=6 |year=2008 |doi=10.2478/s11756-008-0115-y |pages=873–880 |bibcode=2008Biolg..63..873S |url=https://botany.natur.cuni.cz/skaloud/soubory/publikace/2008_Skaloud_Peksa.pdf}}</ref>
<ref name="Skaloud & Peksa 2010">{{cite journal |last1=Skaloud |first1=Pavel |last2=Peksa |first2=Ondrej |title=Evolutionary inferences based on ITS rDNA and actin sequences reveal extensive diversity of the common lichen alga ''Asterochloris'' (Trebouxiophyceae, Chlorophyta) |journal=Molecular Phylogenetics and Evolution |volume=54 |issue=1 |year=2010 |doi=10.1016/j.ympev.2009.09.035 |pages=36–46 |pmid=19853051 |url=https://botany.natur.cuni.cz/algo/soubory/publikace/2010-Skaloud-Peksa.pdf}}</ref>
<ref name="Škaloud et al. 2015">{{cite journal |last1=Škaloud |first1=Pavel |last2=Steinová |first2=Jana |last3=Řídká |first3=Tereza |last4=Vančurová |first4=Lucie |last5=Peksa |first5=Ondřej |title=Assembling the challenging puzzle of algal biodiversity: species delimitation within the genus ''Asterochloris'' (Trebouxiophyceae, Chlorophyta) |journal=Journal of Phycology |volume=51 |issue=3 |year=2015 |doi=10.1111/jpy.12295 |pages=507–527|pmid=26986666 |bibcode=2015JPcgy..51..507S}}</ref>
<ref name="Tschermak-Woess 1980">{{cite journal |last=Tschermak-Woess |first=Elisabeth |title=''Asterochloris phycobiontica'', gen. et spec., nov., der Phycobiont der Flechte ''Varicellaria carneonivea'' |journal=Plant Systematics and Evolution |volume=135 |issue=3–4 |year=1980 |doi=10.1007/BF00983192 |pages=279–294 |language=de}}</ref>
<ref name="Veselá et al. 2024">{{cite journal |last1=Veselá |first1=Veronika |last2=Malavasi |first2=Veronica |last3=Škaloud |first3=Pavel |title=A synopsis of green-algal lichen symbionts with an emphasis on their free-living lifestyle |journal=Phycologia |volume=63 |issue=3 |year=2024 |doi=10.1080/00318884.2024.2325329 |doi-access=free |pages=317–338|hdl=11577/3511125 |hdl-access=free }}</ref>
}}
{{Taxonbar|from=Q84403360}}
[[Category:Trebouxiales]] [[Category:Trebouxiophyceae genera]] [[Category:Lichen photobionts]] [[Category:Taxa described in 1980]] [[Category:Taxa named by Elisabeth Tschermak-Woess]] [[Category:Terrestrial algae]]