Green algae

Unravelling the algae: the past, present …, 2007

Phycologia, 2006

Two new species of Volvocalean green snow algae are described from Upstate New York, Chloromonas chenangoensis and Chloromonas tughillensis. According to rbcL sequence analysis, these species belong to a subclade of five snow species of Chloromonas that includes Cr. brevispina, Cr. nivalis and Cr. pichinchae. These species have zoosporangia/gametangia (cell packs) that are propelled by flagella. The life cycles of Cr. chenangoensis and Cr. tughillensis include a change in cell shape from oblong to spherical before the loss of the cell wall. Using 8-h laboratory experiments, a peak in the change of cell shape occurred at 4 h for Cr. chenangoensis and between 2 and 4 h for Cr. tughillensis after the onset of light, and this was followed by a decline in change of cell shape for both species. Spherical cells peaked between 6 and 8 h for Cr. chenangoensis and at 8 h for Cr. tughillensis. Maximum total matings occurred at 4 h for Cr. chenangoensis and 6 h for Cr. tughillensis, which was followed by a peak in quadriflagellate zygotes at 8 h for both species. Mature zygotes (zygospores) were observed only in Cr. tughillensis.

The Algae World, 2015

The Classification of the Algae. 85 much stretch of imagination be considered reconstructed stemforms, which inhabited Greater New Zealand or elsewhere during the earlier Pliocene or earlier still. As to whether, the normal spiny form of the Discaria ana the artificial spineless form, i.e. the prolonged seedless-form, are really two distinct species, or merely the two extremes of one variable species, opens up far too wide a question for consideration here. It is obvious however, that the presence of either or both in a region would be entirely a matter of climate, station and competition with other plants and animals. In conclusion, I must express my thanks to Professor Charles Chilton, D Sc. for his kmdness in allowing me to use the moist chamber of the Biological School, Canterbury College, Christchurch, New Zealand, for the completion of the above mentioned experiment. Wellington, New Zealand, >«. 23rd, 1905.

Freshwater Algae of North America, 2003

Golden-brown algae Chlorophyta Green algae 15 May be in the form of single cells, colonial or filamentous. Organisms mostly blue-green or olive-green or brown in colour, but very seldom bright green. Organisms motile or perform gliding movements. Mostly single cells or colonies that are yellow or golden-brown in colour. Cells motile by means of two unequal flagella. Mostly unicellular organisms or adjacent cells may be attached to each other to form of chains. Colour of chloroplasts varies from yellow to yellow-brown. Cells immotile or perform gliding movements. The cell wall is hard and resistant and comprise of two halves fitting into each other. Organisms are always unicellular. Cells may vary in colour from red, blue-green, olive-green to olive-brown. Cells swim by means of two slightly unequal flagella. Unicellular organisms that are usually brown to yellow-brown in colour. Cells are motile by means of two flagella located inside grooves on the cell surface. In some species, the cell covering consists of conspicuous plates. Cells are single and mostly bright green in colour, sometimes with a bright red eyespot. Cells swim by means of one emergent flagellum and some species are able of changing their shape. Cells may occur single, in the form of colonies or in the form of filaments (branched or unbranched). They are usually grass green in colour, hence the name "green algae". Cells may be immotile, motile by means of two to four flagella, or gliding movements are performed. 17 Cyanophyta Blue-green algae Cyano is derived from Greek, meaning "blue" and phyta meaning "plant". Cyanophyta are often referred to as cyanobacteria, bluegreen algae or blue-green bacteria. Because they are prokaryotic (no membrane-bounded organelles), blue-green algae are considered to be more closely related to bacteria than to other algae. Representatives may be in the form of single cells, colonies or filaments and are usually blue-green (most common), grey, brownish, blackish or even purple in colour, but never bright green. The blue-green colour is the result of photosynthetic pigments such as chlorophyll-a (green pigment) and phycocyanin (blue pigment). Some also contain phycoerythrin (a red pigment). When all three pigments are present, the cells may appear purplish. No flagellated stages are present, but some filaments can perform gliding movements. A characteristic feature of many blue-green algae is the presence of gas vacuoles in the cells, which provide buoyancy to the organism. Cells are covered with a thick, layered cell wall that is often surrounded by mucous. Sexual reproduction is absent. The group include marine as well as freshwater, brackish water and terrestrial species. Under conditions of excessive nutrient (primarily phosphorus) availability, slow moving or stagnant water, and warmth, cyanobacteria may proliferate, producing a variety of problems such as surface scums, tastes and odour problems, skin irritations and the release of toxic substances. When these blooms decompose, severe oxygen depletion may occur, resulting in fish kills. Anabaena Bory ex Bornet et Flahault Origin: From Greek anabaino, "to rise" or "to go up". Characteristics: Anabaena has unbranched filaments (trichomes) that can be straight, curved, or coiled. Filaments may be solitary or clustered, forming a gelatinous mass. The filaments are uniformly broad and consist of spherical, ellipsoidal or cylindrical cells, often giving the filaments the appearance of a string of beads. Although the filaments lack a distinct sheath (hence the term trichomes is used to describe them), some species have soft and colourless mucilage enveloping them. Heterocysts (used for nitrogen fixation) are rounded or spherical, solitary and generally intercalary. Within the trichome there are akinetes that are larger than vegetative cells, spherical, ellipsoidal, cylindrical, or curved in shape, solitary or in groups of 2 to 5, intercalary and they can be found distant or adjacent to heterocysts. Gas vacuoles in the cells provide buoyancy for planktonic species. Dimensions: Cells are 7-12 µm in diameter. Ecology: Anabaena is common, widespread and seasonally abundant (highest concentrations usually occur during the summer months) and it often grows in association with Microcystis Kützing ex Lemmermann. It occurs in freshwater and marine habitats. Some species are planktonic (common in lakes and ponds, but also occur in slow-flowing waters), others are epiphytic, living in damp soil, or forming gelatinous masses on submersed substrates. Certain species are symbionts in higher plants, e.g. Anabaena azollae Strasburger in species of the water fern (Azolla Lam.). When nutrients are abundant, some planktonic species are responsible for blooms (visible as surface scums) that result in odours, smells and tastes associated with the water. Anabaena is also capable of producing lethal toxins (anatoxin-a), which is a neuromuscular blocking agent causing respiratory arrest, liver and gastro-intestinal damage, and is possibly carcinogenic. Animals and birds may die soon after drinking the infested water. Blooms of Anabaena can also cause contact irritations, leading to severe dermatitis. Notes: Anabaena is comparable in morphology with Nostoc Vaucher ex Bornet et Flahault. When clumped, or colonial in soft mucilage, the colony is, however, soft and formless, whereas Nostoc colonies are firm and keep a definite shape. Anabaena also has less constricted trichomes, akinetes are in different locations, it has more motile hormogonia, and a different habitat.

Journal of Phycology, 2008

Phycologia, 1999

European Journal of Phycology, 2011

Plant Biology, 2010

Using a combined set of sequences of SSU and ITS regions of nuclear-encoded ribosomal DNA, the concept of the experimental algal genus Chlorella was evaluated. Conventionally in the genus Chlorella, only coccoid, solitary algae with spherical morphology that do not possess any mucilaginous envelope were included. All Chlorella species reproduce asexually by autospores. However, phylogenetic analyses showed that within the clade of 'true' Chlorella species (Chlorella vulgaris, C. lobophora, and C. sorokiniana), taxa with a mucilaginous envelope and colonial lifeform have also evolved. These algae, formerly designated as Dictyosphaerium, are considered as members of the genus Chlorella. In close relationship to Chlorella, five different genera were supported by the phylogenetic analyses: Micractinium (spherical cells, colonial, with bristles), Didymogenes (ellipsoidal cells, two-celled coenobia, with or without two spines per cell), Actinastrum (ellipsoidal cells within starshaped coenobia), Meyerella (spherical cells, solitary, without pyrenoids), and Hegewaldia (spherical cells, colonial, with or without bristles, oogamous propagation). Based on the secondary structures of SSU and ITS rDNA sequences, molecular signatures are provided for each genus of the Chlorella clade.