A common fresh water alga.

by Steve Durr, UK

Zygnema belongs to the Chlorophyceae and is a conjugate alga.

Zygnema is a very common alga and is usually found along side Spirogyra in quite still waters. Zygnema can be instantly recognised by the two stellate chloroplasts that are embedded in each filament. The very dark regions in the above photograph are probably where the pyrenoids are located. There are many species of Zygnema and it is very difficult to establish which species that you have, G.W.Prescott in his book (How to know the freshwater algae) states that species can be identified by the zygospores that they produce, being round, oval etc. When viewed in the water the filaments look a yellow - green colour, and like Spirogyra are slimy to the touch. I have been unable to observe the reproduction of this alga because it does not appear to occur quite has frequently as in Spirogyra. I am hoping to get further samples so I can make more observations this spring.

Reproduction can occur in three ways: - Asexual, sexual and vegetative.

The large bridge that traverses from one chloroplast to the other is where the nucleus resides.

The above photograph was taken with T-Max 100, using a X50 water immersion lens.

Any comments to steve@durr.demon.co.uk.

If you have time, please visit my Web Site.

Editor's note: Steve's web site has some fine photomicrographs and practical advice on many aspects of photomicrography.


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