''Astrephomene'' is a

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of living and fossil organisms as well as viruses. In the hierarchy of biological classification, genus comes above species and below family. In binomial n ...

green algae The green algae (singular: green alga) are a group consisting of the Prasinodermophyta and its unnamed sister which contains the Chlorophyta and Charophyta/ Streptophyta. The land plants ( Embryophytes) have emerged deep in the Charophyte alg ...

in the family Goniaceae, order

Chlamydomonadales Chlamydomonadales, also known as Volvocales, are an order of flagellated or pseudociliated green algae, specifically of the Chlorophyceae.See the NCBIbr>webpage on Chlamydomonadales Data extracted from the Chlamydomonadales can form planar or ...

. The genus was first described in 1937 by Pocock and named by Pockock in 1953 (Stein 1958).

Taxonomy

It was formerly placed in the monotypic family Astrephomenaceae. Astrephomenaceae is now considered obsolete, and ''Astrephomene'' is now classified within the Goniaceae.

Description

''Astrephomene gubernaculifera'' is a colonial, flagellated volvocine green algae. It consists of 16, 32, 64 or 128 cells, 2 to 7 of which are small and oriented such that their flagella form a rudder (Stein 1958). Each cell is surrounded by a gelatinous matrix and contains an eyespot, two flagella and 1-3 contractile vacuoles at the anterior end. ''Astrephomene gubernaculifera'' can reproduce sexually or asexually. During asexual reproduction of Astrephomene, rotation of daughter protoplasts occurs in conjunction with the movement of basal bodies during successive cell divisions, ending with the anterior end of all cells of the daughter colony outside after the first nuclear and cytoplasmic division. This type of asexual reproduction is unique among the colonial volvocine green algae (Pocock 1953). By contrast, in Eudorina, protoplast rotation is lacking during successive divisions; a spheroidal colony is formed by means of inversion after successive divisions. ''Astrephomene gubernaculifera'' has two mating types that reproduce to form zygotes. Doi 10

Evolution

Colony inversion is believed to have arisen twice in the order

. Spheroidal colony formation differs between the two lineages: rotation of daughter protoplasts during successive cell divisions in Astrephomene, and inversion after cell divisions in Eudorina. Doi 10

Habitats

''Astrephomene gubernaculifera'' is often found in organically rich temporary pools, often in pasture ponds. It typically persists for 1–3 weeks after ponds are formed in beginning of the wet season (Pocock 1953). It has been collected from South Africa, Australia and the United States (Pocock 1953).

References

External links

Chlamydomonadales genera Chlamydomonadales {{Chlorophyceae-stub