Open main menu

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

Micrasterias
Micrasterias radiata.jpg
Micrasterias furcata
Scientific classification
Kingdom:
Division:
Class:
Order:
Family:
Genus:
Micrasterias

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.

MorphologyEdit

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.

SpeciesEdit

Accepted speciesEdit

 
Micrasterias rotata

Micrasterias comprises the following species:[2]

Species names with uncertain taxonomic statusEdit

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

PhylogeneticsEdit

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]

ReferencesEdit

  1. ^ a b c d e 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. ^ a b 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 linksEdit