The Charophyceae

Largely on the basis of ultrastructural information, Mattox and Stewart constructed an enlarged Class Charophyceae, in which they recognized five orders: Chlorokybales, Klebsormidiales, Coleochaetales, Charales, and Zygnematales.

The Class Charophyceae
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Chlorokybus atmosphyticus is a 'sarcinoid', or packet forming soil alga. It has only rarely been found, always in alpine areas. The structure of its zoospores and molecular data place it in the Charophyceae


Klebsormidium sp. is an unbranched filamentous alga with biflagellate zoospores.


Spirogyra sp. is an unbranched filamentous alga. Like all of the Zygnematales, it has no flagellate stages, and reproduces by conjugation. This is an 'optical cross section'. The nucleus is visible in the center of the cell. Several ribbon-like chloroplasts spiral around the cell, but are in focus only at the margin of the cell.


Zygnema sp. is an unbranched filamentous alga. Unlike spirogyra, it has axile chloroplasts.


Sorry, waiting for a better picture...


Vegetative Coleochaete "orbicularis". This is the isolate 'pondspride'. Although often called "C. orbicularis", this species has not been named. The Coleochaetales are branched, filamentous algae with sheathed hairs. All are oogamous, and many have very complex thalli and life histories. The Charales and Coleochaetales are the closest algal relatives of embryophytes (land plants).

The Order Coleochaetales

The Coleochaetales are tiny but structurally complex freshwater algae that live attached to surfaces in ponds and slow moving streams.

A Rogues Gallery

To the right is Coleochaete soluta ---> [Picture of Coleochaete soluta]

Links to larger size images:

Charophyceae: the Order Coleochaetales
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Chaetosphaeridium sp. Like Coleochaete, Chaetosphaeridium is a branched, filamentous alga with sheathed hairs. Sexual reproduction has been reported to be oogamous, but this has never been photographed, and zygotes are not retained on the thallus.


Coleochaete irregularis, growing in culture. Despite its name, Coleochaete irregularis grows in very orderly filaments tightly appressed to the substrate.


The arrangement of cells in the center of the thallus is important when distinguishing Coleochaete circularis from similar species.


Coleochaete 'orbicularis', fluorescing under violet light. The chloroplasts fluoresce red because of the presence of chlorophyll. The cell walls fluoresce white because of the presence of a phenolic polymer that is deposited in the cell walls close to zygotes.


This high magnification fluorescence image shows the granal stacks in the zygote plastids of Coleochaete scutata.


KR Mattox and KD Stewart. 1984. Classification of the green algae: a concept based on comparative cytology. Pp. 29-72 in DEG Irvine and DM John, "Systematics of the Green Algae", Systematics Association Special Volume #27, Academic Press, London and Orlando.