Micrasterias

Micrasterias is a unicellular green alga of the order Desmidiales. Its species vary in size reaching up to hundreds of microns.

Micrasterias
Micrasterias furcata
Scientific classification
Kingdom:	Plantae
Division:	Charophyta
Class:	Zygnematophyceae
Order:	Desmidiales
Family:	Desmidiaceae
Genus:	Micrasterias C.Agardh ex Ralfs
Type species
Micrasterias furcata C.Agardh ex Ralfs
Species
See text.

Micrasterias displays a bilateral symmetry, with two mirror image semi-cells joined by a narrow isthmus containing the nucleus of the organism. This dual semi-cell structure is unique to the group of green algae to which Micrasterias belongs. Each semi-cell contains a single large chloroplast, the site of photosynthesis for Micrasterias. Chloroplasts within Micrasterias contain chlorophyll a and chlorophyll b and the enzymes required for photosynthesis. The sugar created is used to provide energy for the organism or, if not used, taken up by many small round pyrenoids which are embedded in the chloroplast. They convert the sugar to a starch for storage.

Micrasterias can produce both asexually and sexually. Asexual reproduction occurs via mitosis. When this occurs the genetic material of Micrasterias is duplicated and two small semi-cells grow between the original semi-cells, gradually increasing in size. Sexual reproduction occurs through a process called conjugation whereby two organisms come together and fuse their haploid cells to form a diploid zygote. This zygote typically forms a thick protective wall which can allow the organism to remain dormant for many months to survive cold winters and long droughts. When adequate conditions resume, the zygospore will germinate, undergo meiosis, and produce new haploid algal cells.

Morphology

Micrasterias species consist of two semicells that are almost entirely filled with chloroplasts, with a nucleus that lies at the center where the two semicells are joined together. The gaps between the two semicells are joined by an isthmus. Each semicell is further divided into a polar lobe and two lateral lobes. These lobes can be further subdivided up to the fourth order.[1] As is common in the green algae, the chloroplasts of Micrasterias contain pyrenoids.

Species

Accepted species

Micrasterias rotata

Micrasterias comprises the following species:[2]

• Micrasterias abrupta West & G.S.West
• Micrasterias adscendens Nordstedt
• Micrasterias africana (F.E.Fritsch & F.Rich) Coesel & Van Geest
• Micrasterias alata Wallich
• Micrasterias americana Ehrenberg ex Ralfs
• Micrasterias anomala W.B.Turner
• Micrasterias apiculata Meneghini ex Ralfs
• Micrasterias archeri Coesel & M.Dingley
• Micrasterias arcuata Bailey
• Micrasterias bangladeshensis A.K.M.N.Islam & Haroon
• Micrasterias borgei Willi Krieger
• Micrasterias bourrellyana J.A.Rino
• Micrasterias brachyptera P.Lundell
• Micrasterias ceratofera Joshua
• Micrasterias compereana J.Neustupa, J.St'astný & P.Skaloud
• Micrasterias conferta P.Lundell
• Micrasterias cruciata Kützing
• Micrasterias crux-africana F.J.Cohn
• Micrasterias crux-melitensis Ralfs
• Micrasterias decemdentata (Nägeli) W.Archer
• Micrasterias denboeri Coesel & Van Geest
• Micrasterias denticulata Brébisson ex Ralfs
• Micrasterias dickiei (Ralfs) Skaloud et al.[1]
• Micrasterias doveri Biswas
• Micrasterias echinata P.E.Brandham
• Micrasterias elegans (W.West & G.S.West) Coesel & Van Geest
• Micrasterias elongata (Schmidle) Coesel & Van Geest
• Micrasterias euastriellopsis S.G.Bharati
• Micrasterias excavata (Nordstedt) C.E.M.Bicudo & L.Sormus
• Micrasterias fimbriata Ralfs
• Micrasterias foersteri Thomasson
• Micrasterias foliacea Bailey ex Ralfs
• Micrasterias furcata C.Agardh ex Ralfs
• Micrasterias hardyi G.S.West
• Micrasterias hieronymusii Schmidle
• Micrasterias incisa Ralfs
• Micrasterias integra Nordstedt
• Micrasterias jenneri Ralfs
• Micrasterias johnsonii West & G.S.West
• Micrasterias khasiae W.B.Turner
• Micrasterias laticeps Nordstedt
• Micrasterias lebrunii Oye
• Micrasterias lux Joshua
• Micrasterias mahabaleshwarensis J.P.Brühl & K.P.Biswas
• Micrasterias mahabuleshwarensis J.Hobson
• Micrasterias moebii (Borge) West & G.S.West
• Micrasterias muricata Bailey ex Ralfs
• Micrasterias nordstedtiana Wolle
• Micrasterias nordstedtii Thomasson
• Micrasterias oscitans Ralfs
• Micrasterias papillifera Brébisson ex Ralfs
• Micrasterias pinnatifida Ralfs
• Micrasterias pseudotorreyi Wolle
• Micrasterias radians W.B.Turner
• Micrasterias radiosa Ralfs
• Micrasterias ralfsii (Brébisson ex Ralfs) Skaloud et al.[1]
• Micrasterias rotata Ralfs
• Micrasterias schmidleana Coesel & Van Geest
• Micrasterias schweickerdtii M.I.Claassen
• Micrasterias schweinfurthii Cohn
• Micrasterias sexpinata (Irénée-Marie & Hilliard) H.Croasdale & G.W.Prescott
• Micrasterias simplex Børgesen
• Micrasterias stauromorpha W.B.Turner
• Micrasterias subdenticulata (Nordstedt) Willi Krieger
• Micrasterias suboblonga Nordstedt
• Micrasterias subtruncata A.I.Lobik
• Micrasterias thomasiana W.Archer
• Micrasterias torreyi Bailey
• Micrasterias triangularis Wolle
• Micrasterias tropica Nordstedt
• Micrasterias truncata Brébisson ex Ralfs
• Micrasterias verrucosa Bisset
• Micrasterias zeylanica F.E.Fritsch

Species names with uncertain taxonomic status

The status of the following species is unresolved:[2]

• Micrasterias aculeata M.Rostock
• Micrasterias aequilobata Borge
• Micrasterias ambadiensis (Grönblad & A.M.Scott) Thomasson
• Micrasterias anomale W.B.Turner
• Micrasterias articulata (C.Agardh) Kützing
• Micrasterias berganii H.V.Hauge
• Micrasterias bewsii F.E.Fritsch & M.F.Rich
• Micrasterias bicaudata (A.K.H.Braun ex Kützing) Kuntze
• Micrasterias bioctonaria G.Rabenhorst
• Micrasterias boryana (P.J.F.Turpin) Ehrenberg
• Micrasterias boryi Kützing
• Micrasterias braunii (C.W.Nägeli ex Kützing) Kuntze
• Micrasterias ceratophora Joshua
• Micrasterias comperei R.S.Ganem & P.A.C.Senna
• Micrasterias complecta C.G.T.Preuss
• Micrasterias convoluta (A.K.J.Corda) Kuntze
• Micrasterias cordae A.Braun
• Micrasterias cornuta A.W.Bennett
• Micrasterias coronula Ehrenberg
• Micrasterias croasdaleana C.E.M.Bicudo & L.Sormus
• Micrasterias crucigenia Kützing
• Micrasterias cunningtonii G.S.West
• Micrasterias decemdentatum (C.W.Nägeli) W.Archer
• Micrasterias denticula Istvanfy
• Micrasterias depauperata Nordstedt
• Micrasterias disputata H.C.Wood
• Micrasterias divisa Willi Krieger
• Micrasterias doverii K.P.Biswas
• Micrasterias duplex (Meyen) Kützing
• Micrasterias ecornis
• Micrasterias eichleri Schmidle
• Micrasterias enneactis Ehrenberg
• Micrasterias expansa Bailey
• Micrasterias extendens W.B.Turner
• Micrasterias falcata Corda
• Micrasterias floridensis R.K.Salisbury
• Micrasterias galeata Borge
• Micrasterias ghibellina Meneghini
• Micrasterias granulata H.C.Wood
• Micrasterias groenewaldii M.I.Claassen
• Micrasterias halis Raciborski
• Micrasterias hamata (Wolle) F.C.E.Børgesen
• Micrasterias hardeyii
• Micrasterias heliactis Kützing
• Micrasterias heptactis Ehrenberg
• Micrasterias hermanniana Reinsch
• Micrasterias hexactis Ehrenberg
• Micrasterias hexagona G.W.Grant
• Micrasterias hexagonalis F.Steinecke
• Micrasterias horrida C.E.Taft
• Micrasterias inflata C.Bernard
• Micrasterias kangofurinensis N.Woodhead & R.D.Tweed
• Micrasterias kitchellii Wolle
• Micrasterias lacerata Kützing
• Micrasterias ledouxii A.M.Scott & Croasdale
• Micrasterias lundii P.Bourrelly
• Micrasterias margaritifera (P.J.F.Turpin) L.A.Brébisson & P.Godet
• Micrasterias mbugensis E.M.Lind
• Micrasterias melitensis G.G.A.Meneghini
• Micrasterias mohii (Borge) ?
• Micrasterias multifida Wolle
• Micrasterias napoleonis (P.J.F.Turpin) Kützing
• Micrasterias nordstetiana Wolle
• Micrasterias notata (Nordstedt) Y.Okada
• Micrasterias novae-terrae (J.A.Cushman) Willi Krieger
• Micrasterias nylstromica M.I.Claassen
• Micrasterias oblonga Ehrenberg
• Micrasterias ornamentalis Borge
• Micrasterias paradoxa Kützing
• Micrasterias piquata R.K.Salisbury
• Micrasterias platyptera W.B.Turner
• Micrasterias polonica (B.Eichler & R.Gutwinski) West & G.S.West
• Micrasterias polycyclia G.Rabenhorst
• Micrasterias prescottiana C.E.M.Bicudo & L.Sormus
• Micrasterias pseudofurcata Wolle
• Micrasterias quadragies-cuspidata (Corda) Ralfs
• Micrasterias quadridentata (Nordstedt) Grönblad
• Micrasterias quadriverrucosa (Thomasson) C.E.M.Bicudo & L.Sormus
• Micrasterias ranoides R.K.Salisbury
• Micrasterias renicarpa (P.J.F.Turpin) Kützing
• Micrasterias ricciaeformis C.Agardh
• Micrasterias ringens Bailey
• Micrasterias robusta West & G.S.West
• Micrasterias rosula Kützing
• Micrasterias rotula Ehrenberg
• Micrasterias sanctipaulensis C.E.M.Bicudo & L.Sormus
• Micrasterias selenaea Kützing
• Micrasterias semiradiata L.A.Brébisson ex Kützing
• Micrasterias senaria Ehrenberg
• Micrasterias simplex (F.J.F.Meyen) Kützing
• Micrasterias simplex Wolle
• Micrasterias sinuata L.A.Brébisson
• Micrasterias siolii A.M.Scott & Croasdale
• Micrasterias sphaerastrum Kützing
• Micrasterias staurastrum Kützing
• Micrasterias stuhlmannii G.H.E.W.Hieronymus
• Micrasterias subaequalis Grönblad
• Micrasterias subfimbriata Wolle
• Micrasterias subincisa Willi Krieger
• Micrasterias sublagoensis Kurt Förster & F.Eckert
• Micrasterias tetracera Kützing
• Micrasterias tetraptera West & G.S.West
• Micrasterias tricera Kützing
• Micrasterias tricyclia Ehrenberg
• Micrasterias trigemina E.H.P.A.Haeckel
• Micrasterias upsaliensis (Cleve) W.Archer

Phylogenetics

Modern molecular phylogenetics suggest the following relationships (not all accepted species are included):[1]

Micrasterias         Clade A         A1     Micrasterias truncata     Micrasterias ralfsii       Micrasterias semiradiata     A2   Micrasterias decemdentata     Micrasterias laticeps       A3   Micrasterias zeylanica     Micrasterias truncata var. pusilla       A4   Micrasterias furcata       Micrasterias pinnatifida     Micrasterias dickiei         A5   Micrasterias ceratofera       Micrasterias crux-melitensis pro parte     Micrasterias radians var. bogoriensis         A6   Micrasterias crux-melitensis pro parte     Micrasterias radians var. evoluta         Clade B   Micrasterias anomala     Micrasterias apiculata     Clade C     Micrasterias brachyptera     Micrasterias fimbriata         Micrasterias rotata     Micrasterias doveri           Clade D   Micrasterias thomasiana       Micrasterias denticulata     Micrasterias jenneri         Clade E Triploceras       Clade F Micrasterias tropica   Clade G   Micrasterias foliacea       Micrasterias radiosa var. swainei       Micrasterias tetraptera       Micrasterias conferta       Micrasterias radiosa var. radiosa       Micrasterias novae-terrae     Micrasterias papillifera                   Clade G   Micrasterias hardyi       Micrasterias americana       Micrasterias mahabuleshwarensis     Micrasterias muricata             Staurastrum (outgroup)

Even though Triploceras was recovered as embedded within Micrasterias, there was low statistical support for this placement, so it remains a separate genus.[1][3][4][5][6]

References

1. Škaloud P, Nemjová K, Veselá J, Černá K, Neustupa J. (2011). "A multilocus phylogeny of the desmid genus Micrasterias (Streptophyta): Evidence for the accelerated rate of morphological evolution in protists". Molecular Phylogenetics and Evolution. 61 (3): 933–943. doi:10.1016/j.ympev.2011.08.018.CS1 maint: uses authors parameter (link)
2. Guiry MD. (12 September 2013). "Micrasterias C.Agardh ex Ralfs, 1848". Algaebase. National University of Ireland, Galway. Retrieved 1 November 2017.
3. Gontcharov AA, Melkonian M. (2008). "In search of monophyletic taxa in the family Desmidiaceae (Zygnematophyceae, Viridiplantae): The genus Cosmarium". Am J Bot. 95 (9): 1079–1095. doi:10.3732/ajb.0800046. PMID 21632428.CS1 maint: uses authors parameter (link)
4. Hall JD, Karol KG, McCourt RM, Delwiche CF. (2008). "Phylogeny of the conjugating green algae based on chloroplast and mitochondrial nucleotide sequence data". Journal of Phycology. 44 (2): 467–477. doi:10.1111/j.1529-8817.2008.00485.x. PMID 27041201.CS1 maint: uses authors parameter (link)
5. Gontcharov AA, Melkonian M. (2011). "A Study of Conflict between Molecular Phylogeny and Taxonomy in the Desmidiaceae (Streptophyta, Viridiplantae): Analyses of 291 rbcL Sequences". Protist. 162 (2): 253–267. doi:10.1016/j.protis.2010.08.003. PMID 20971037.CS1 maint: uses authors parameter (link)
6. Neustupa J, Škaloud P, Šťastný J. (2010). "The molecular phylogenetic and geometric morphometric evaluation of Micrasterias crux-melitensis/M. radians species complex". Journal of Phycology. 46 (4): 703–714. doi:10.1111/j.1529-8817.2010.00863.x.CS1 maint: uses authors parameter (link)

External links

• Micrasterias Pictures Page