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Filamentous Chlorophyceae

 Common Characteristic-
All of the following examples are haploid members in the division Chlorophyta. While they each belong to a separate Class, they all chare a common characteristic. All of these green algal species have a filament at some point in their life cycle. View each and note the similarities, but remember that they are not classified under the same Class or Order.
 

 

Oedogonium

Oedogonium (right) is the most advanced of the filamentous Chlorophyceae. Its cell division is unique with cellulose rings at the anterior end of vegetative cells. These rings are remnants of broken parietal cell walls.

They reproduce sexually and asexually through a process of fragmentation. Asexual vegetative cells are able to generate zoospores from the protoplasm while motile reproductive cells produce gametes and reproduce in the typical sexual manner.

Oedogonium are found in freshwater and arranged in filaments. In the specimen to the right, notice the motile reproductive cell in the center and its surrounding vegetative cells.

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Spirogyra

Spirogyra (right), commonly known as ubiquitous pond scum, is a unicellular freshwater algae that occurs in large free floating submerged mats, ponds, ditches, and slow moving streams. It has internally a helical structure (seen to the right) which are actually spiral bands of chloroplasts. Spirogyra do not produce swimming gametes. However, during reproduction, filaments form from the opposite mating organisms (+ or -) as they lie adjacent to one another. The connection is called a conjugation pilus. Nuclei may take as many as 30 days to fuse. The pilus many be seen in the reproductive progression below.

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Spirogyra Sexual Reproduction

Notice the various stages of reproduction. By tracing the darker green matter, the transfer of genetic information can be seen in a progression from right to left. One organisms becomes an empty shell. Immediate division in the third row to the right keeps the cell haplod instead of doploid. Now, sexual reproduction is complete.

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Ulothrix

Ulothrix is found mainly in freshwater . It may occasionally live in marine environments.

The life cylce is called monbiontic since it only has one free living cellular generation and it haploid. The cells are identical with symmetrical motile cells and apical tinsel flagella.

Each cell has the ability to reproduce by sexual or asexual means, typically by its flagellated zoospores.

Asexual zoospores have four filaments while sexual gametes only have two.

The only specialized cell is the basal cell which is modified into a holdfast. The basal holdfast is responsible for adhering the Ulothrix to a rocky subtrate, but may not always be present.

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