Actinastrum

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Actinastrum
Actinastrumhantzii EPA.jpg
Actinastrum hantzschii
Scientific classification OOjs UI icon edit-ltr.svg
Clade: Viridiplantae
Division: Chlorophyta
Class: Trebouxiophyceae
Order: Chlorellales
Family: Chlorellaceae
Genus: Actinastrum
Lagerheim, 1882
Type species
Actinastrum hantzschii
Lagerheim [1]
Species

See below

Actinastrum is a genus of freshwater green algae. [1] It was first described by Gustaf Lagerheim in 1882. [2] Members of the genus are commonly found in eutrophic freshwater ponds and lakes, and have a cosmopolitan distribution. [1]

Contents

Traditionally, Actinastrum was placed within the family Coelastraceae based on morphology (spherical, three-dimensional colonies and reproduction by autospores). However, molecular phylogenetic studies have shown that the type species Actinastrum hantzschii is closely related to Chlorella , another autospore-forming genus in the family Chlorellaceae. [3] [4]

Description

Actinastrum consists of eight (sometimes two, four or 16) cells, which are attached together at a common point to form a star-shaped colony, termed a coenobium. The colonies are often aggregated to form compound coenobia. Cells are 7–40 μm long and 1–8 μ wide, much longer than broad, and are cylindrical, cigar-shaped, or pointed. The cell wall is smooth, thin, and not thickened. Cells are uninucleate (with a single nucleus) and a contain a single chloroplast, which is elongated, parietal and contains a single pyrenoid. [5] [1] [6]

Actinastrum reproduces asexually, by forming 4-16 autospores usually arranged into a coenobium. The first protoplast division occurs transversely, the second perpendicular to it, and the third occurs along the long axis of the cell. [6] Spores are released by the dissolution of the parental cell wall. Sexual reproduction has not been observed in this genus. [1]

Species

As of 2025, AlgaeBase accepts ten species, including one fossil species: [1]

Species in Actinastrum are distinguished based on the overall shape of the cells. However, the genus is very morphologically, and the cell shape changes considerably during its life cycle and in response to external conditions. [6]

Related Research Articles

<span class="mw-page-title-main">Chlorophyceae</span> Class of green algae

The Chlorophyceae are one of the classes of green algae, distinguished mainly on the basis of ultrastructural morphology. They are usually green due to the dominance of pigments chlorophyll a and chlorophyll b. The chloroplast may be discoid, plate-like, reticulate, cup-shaped, spiral- or ribbon-shaped in different species. Most of the members have one or more storage bodies called pyrenoids located in the chloroplast. Pyrenoids contain protein besides starch. Some green algae may store food in the form of oil droplets. They usually have a cell wall made up of an inner layer of cellulose and outer layer of pectose.

<span class="mw-page-title-main">Chlorophyta</span> Phylum of green algae

Chlorophyta is a division of green algae informally called chlorophytes.

<span class="mw-page-title-main">Prasiolales</span> Order of algae

Prasiolales is an order of green algae in the class Trebouxiophyceae. Members of this order are ecologically widespread and are found in freshwater, marine, and terrestrial habitats from the Arctic to the Antarctic.

<span class="mw-page-title-main">Selenastraceae</span> Family of algae

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<i>Botryococcus</i> Genus of algae

Botryococcus is a genus of green algae. It is a microscopic or semi-microscopic alga that is found in freshwater habitats worldwide. It consists of colonies of cells in an irregular, gelatinous matrix.

Dictyochloropsis is a genus of unicellular green alga of the phylum Chlorophyta. This genus consists of free-living algae which have a reticulate (net-like) chloroplast that varies slightly in morphology between species, and that when mature always lacks a pyrenoid. Dictyochloropsis is asexual and reproduces using autospores.

<i>Dictyosphaerium</i> Genus of algae

Dictyosphaerium is a genus of green algae, in the family Chlorellaceae. It occurs in freshwater habitats around the world and is planktonic. The name comes from the Greek roots diktyon, meaning "net", and sphaira, meaning "ball", referring to its morphology.

<i>Didymogenes</i> Genus of algae

Didymogenes is a genus of microscopic green algae in the class Trebouxiophyceae. It is a planktonic species found in freshwater habitats worldwide. Formerly placed in the family Scenedesmaceae, molecular studies have placed it in the family Chlorellaceae.

<i>Elliptochloris</i> Genus of algae

Elliptochloris is a genus of green algae in the order Prasiolales. Species of this genus are common and found in a variety of terrestrial habitats such as soils. Some species in the genus are photobiont partners in lichens. One species, E. marina, is a symbiont within two species of sea anemone, Anthopleura elegantissima and A. xanthogrammica. It seems to have a worldwide distribution.

<i>Koliella</i> Genus of algae

Koliella is a genus of green algae in the order Prasiolales. Members of this genus are found in freshwater plankton, but some are also found on snow and ice.

<i>Lagerheimia</i> Genus of algae

Lagerheimia is a genus of green algae in the family Oocystaceae. It is commonly found in freshwater habitats all over the world, although some species are rare and have only been recorded from Europe or the United States.

<i>Micractinium</i> Genus of algae

Micractinium is a genus of green algae in the family Chlorellaceae. Species of the genus Micractinium are common in freshwater habitats. A few species are found as endosymbionts of protozoa, such as Micractinium conductrix and Micractinium tetrahymenae.

<i>Paradoxia</i> Genus of algae

Paradoxia is a genus of microscopic green algae, in the family Coccomyxaceae. It is found in freshwater habitats as phytoplankton worldwide, but species are rare.

<i>Trebouxia</i> Genus of algae

Trebouxia is a unicellular green alga. It is a photosynthetic organism that can exist in almost all habitats found in polar, tropical, and temperate regions. It can either exist in a symbiotic relationship with fungi in the form of lichen or it can survive independently as a free-living organism alone or in colonies. Trebouxia is the most common photobiont in extant lichens. It is a primary producer of marine, freshwater and terrestrial ecosystems. It uses carotenoids and chlorophyll a and b to harvest energy from the sun and provide nutrients to various animals and insects.

<i>Watanabea</i> Genus of algae

Watanabea is a genus of microscopic green algae in the family Watanabeaceae. It is widespread in terrestrial and freshwater habitats, including as a photobiont within lichens, but is apparently rare.

<i>Crucigenia</i> Genus of algae

Crucigenia is a genus of green algae in the class Trebouxiophyceae. It is widespread, but not often abundant, in freshwater habitats around the world.

<i>Tetrastrum</i> Genus of algae

Tetrastrum is a genus of green algae (Chlorophyta). It is a common component of the phytoplankton of freshwater habitats, particularly eutrophic and alkaline waters.

Symbiochloris reticulata is a species of green alga in the Trebouxiales. It is a known as a photobiont with several lichen species, like Lobaria pulmonaria, but also as a free-living soil alga as well. Phylogenetic analysis of rRNA sequence data revealed that the species shares a sister group relationship with two other green algae that lack motile stages, Chlorella saccharophila and C. luteoviridis.

<i>Raphidonema</i> (alga) Genus of algae

Raphidonema is a genus of filamentous green alga comprising five species. It is a member of the Trebouxiophyceae.

<span class="mw-page-title-main">Koliellaceae</span> Family of algae

Koliellaceae is a family of green algae in the order Prasiolales.

References

  1. 1 2 3 4 5 6 Guiry, M.D.; Guiry, G.M. "Actinastrum Lagerheim, 1882". AlgaeBase . World-wide electronic publication, National University of Ireland, Galway. Retrieved 2025-01-09.
  2. ↑ Gustaf Lagerheim (February 1882). "Bidrag till kännedomen om Stockholmstraktens Pediastréer, Protococcacéer och Palmellacéer". Öfversigt af Kongl. Vetenskaps-Akademiens Förhandlingar. 39 (2): 47–81.
  3. ↑ Wolf M, Kreinitz L, Hepperle D (April 2002). "Phylogenetic position of Actinastrum hantzschii LAGERHEIM 1882 (Chlorophyta, Trebouxiophyceae)". Algological Studies. 104: 59–67. doi:10.1127/algol_stud/104/2002/59.
  4. ↑ Luo W, Pröschold T, Bock C, Krienitz L (April 2010). "Generic concept in Chlorella‐related coccoid green algae (Chlorophyta, Trebouxiophyceae)". Plant Biology. 12 (3): 545–553. doi:10.1111/j.1438-8677.2009.00221.x. PMID   20522192.
  5. ↑ Shubert, Elliot; Gärtner, Georg (2014). "Chapter 7. Nonmotile Coccoid and Colonial Green Algae". In Wehr, John D.; Sheath, Robert G.; Kociolek, J. Patrick (eds.). Freshwater Algae of North America: Ecology and Classification (2 ed.). Elsevier Inc. ISBN   978-0-12-385876-4.
  6. 1 2 3 Komárek, J.; Fott, B. (1983). Chlorophyceae (Grünalgen), Ordnung Chlorococcales. Das Phytoplankton des Süßwassers (in German). E. Schweizerbart'sche Verlagsbuchhandlung. p. 1044.
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