Trebouxiophyceae

Portrait of the trebouxiophyte,Microthamnion strictissimum (Rabenhorst). The thalli of this filamentous alga are uniseriate (cells in a single row) and have a more distinguishable main axis than the similar M. kuetzingianum. Branches originate as lateral outgrowths from cells. Thalli are attached to the substrate by a basal cell with a small bulbous holdfast. Cells are cylindrical and of the same diameter. Terminal cells taper to a blunt tip. The single parietal plate-like chloroplast lacks a pyrenoid. Reproduction is by biflagellate zoospores which escape from the parent cell through a lateral rupture of the cell wall. One of the distinguishing features of trebouxiophytes is metacentric mitosis in which centrioles are located near the metaphase plate of the chromosomes rather than at the spindle poles. Other characteristics include formation of microtubules parallel to the dividing cell wall during cytokinesis (phycoplast)and a cruciate arrangement of flagellar roots with the basal bodies offset in a counterclockwise fashion on electron microscopy. Collected from a freshwater dredge pond near Idaho City, Idaho. June 2005.Phase contrast.

Portrait of the trebouxiophyte,Microthamnion strictissimum (Rabenhorst). The thalli of this filamentous alga are uniseriate (cells in a single row) and have a more distinguishable main axis than the similar M. kuetzingianum. Branches originate as lateral outgrowths from cells. Thalli are attached to the substrate by a basal cell with a small bulbous holdfast. Cells are cylindrical and of the same diameter. Terminal cells taper to a blunt tip. The single parietal plate-like chloroplast lacks a pyrenoid. Reproduction is by biflagellate zoospores which escape from the parent cell through a lateral rupture of the cell wall. One of the distinguishing features of trebouxiophytes is metacentric mitosis in which centrioles are located near the metaphase plate of the chromosomes rather than at the spindle poles. Other characteristics include formation of microtubules parallel to the dividing cell wall during cytokinesis (phycoplast)and a cruciate arrangement of flagellar roots with the basal bodies offset in a counterclockwise fashion on electron microscopy. Collected from a freshwater dredge pond near Idaho City, Idaho. June 2005.DIC.

Micractinium pusillum (Fresenius,1858). Usually found in four-celled colonies (only three of the four cells of this colony are seen here). Each cell has two to seven long, delicate setae. Each cell has one cup-shaped plastid with a pyrenoid. 18S ribosomal RNA gene studies place this genus in the Trebouxiophyceae. One of the distinguishing features of trebouxiophytes is metacentric mitosis in which centrioles are located near the metaphase plate of the chromosomes rather than at the spindle poles. Other characteristics include formation of microtubules parallel to the dividing cell wall during cytokinesis (phycoplast). The similar genus, Errerella, has only one spine per cell.Collected from a freshwater pond near Boise, Idaho. July 2005. Phase contrast.

Portrait of the planktonic trebouxiophyte alga, Tetrastrum staurogeniaeforme (Schröder) Lemmermann.The colonies consist of four ellipsoid cells with four to six short spinous projections from the each cell surface. several four-celled colonies may join together to form compound colonie (compound coenobia). Each cell has one plastid and one pyrenoid.Collected from a freshwater pond near Boise,Idaho. July 2005.DIC.

Green algae live in a mucus ball. Phase contrast microscopy.

Chlorella (clo-rell-a), tentatively identified as such. The genus contains solitary green algal cells without flagella. Phase contrast.

Chlorella ( Beijerinck, 1890) from the cytoplasm of a burst Frontonia cell in which they had been living as symbionts.DIC.

Microthamnion (mike-row-tham-knee-on), is a branching filamentous green alga. With cellulosic cell wall, plastids with chlorophylls a and b giving the plastids a green colour. Phase contrast.

Portrait of Dictyosphaerium pulchellum (Nägeli,1849), a colonial green alga. The small cells are ovoid to reniform and are borne at the ends of colorless branching threads in groups of four. The threads are remnants of parental cell walls. Each cell has a cup-shaped chloroplast and solitary pyrenoid.The entire colony is embedded in a nearly invisible spherical gelatinous matrix. Collected from a freshwater pond near Boise, Idaho June 2004. DIC optics.

Portrait of Dictyosphaerium pulchellum (Nägeli,1849), a colonial green alga. The small cells are ovoid to reniform and are borne at the ends of colorless branching threads in groups of four. The threads are remnants of parental cell walls. Each cell has a cup-shaped chloroplast and solitary pyrenoid.The entire colony is embedded in a nearly invisible spherical gelatinous matrix. Collected from a freshwater pond near Boise, Idaho June 2004. DIC optics.

Dictyosphaerium pulchellum is a common chlorophyte of Lake Kinneret, relatively more abundant in winter, but never dominant. This specimen was sampled at the shore of the lake in March 2006.

Dictyosphaerium pulchellum is a common chlorophyte (Chlorococcales) of Lake Kinneret, relatively more abundant in winter, never abundant or dominant. Note that the sphaerical cells are in clusters of 4, attached by parental cell wall fragments radiating from a common center. The chloroplasts are parietal and cup shaped with a single pyrenoid. This specimen was sampled at the shore of the lake in March 2006.

Portrait of the nonmotile green alga, Franceia droescheri (Lemmermann, 1898). The cell is ovoid with a thin inflexible cell wall. Usually solitary but may be found in small colonies embedded in a gelatinous matrix.Long fine slightly tapered spinous projections are randomly distributed over the entire cell surface. The otherwise identical Chodatella ciliata has spines lacalized to the poles of the cell. F. droescheri has one to three parietal chloroplasts eache with a pyrenoid.The nucleus is not well seen in this image. Collected from freshwater pond near Boise, Idaho December 2003. DIC optics.

Chodatella citriformis containing 8 autospores, sampled from shore water of Lake Kinneret in March 2006. This Chlorophyte (Chlorococcales) can be found in the plankton of the lake at most times of the year, particularly in May-June, but is never dominant.

Botryococcus braunii (Chlorophyta, Chlorococcales) is a colonial chlorophyte, made of ovoid cells that are closely packed to form golden brown mucilaginous lumps. Older cells usually have large amounts of reserve food material (oil) such that the cell contents are obscured, and the colonies float. The species is abundant at times, forming surface scums at lee shores. On a single occasion in January 2000 a bloom of this species covered the entire lake for several days, giving it a golden color, then disappeared abruptly. This photo shows Botryococcus braunii colonies at x200 mag, with their typical mucilaginous strands connecting colonies and enveloping them.

A young colony of Botryococcus braunii (Chlorophyta, chlorococcales) budding out of an old colony, photographed at x1000 mag. Note cup-shape of the mucilage in which each cell is embedded.

Botryococcus braunii (Chlorophyta, Chlorococcales) is a colonial chlorophyte, made of ovoid cells that are closely packed to form golden brown mucilagenous lumps. Older cells usually have large amounts of reserve food material (oil) such that the cell contents are aboscured, and the colonies float. The species is abundant at times, forming surface scums at lee shores. On a single occassion in January 2000 a bloom of this species covered the entire lake for several days, giving it a golden color, then disappeared abruptly. This photo shows Botryococcus braunii colonies at x200 mag, with their typical mucilagenous strands connecting colonies and enveloping them.

Colorful colonies of Botryococcus braunii (Chlorophyta, Chlorococcales) photographed at dark-field

Portrait of the planktonic trebouxiophyte alga,Chodatella wratislaviensis (Schröder) Ley,1948.The ellipsoid cells are solitary.There are four slightly curved tapering spines each with a button-like base. two are polar and two equatorial.There is a single parietal chloroplast and a pyrenoid.Collected from a freshwater pond near Boise,Idaho(43°37'03.94"N 116°11'07.62"W elev. 2754 ft.)  November 2005.DIC