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How to tell filamentous gree from fillamentous blue-green algae? - (Dec/26/2008 )

How do you tell filamentous green algae and filamentous blue-green algae apart? On line I can find only that others have asked that question. The only answer I found is with a DNA test. Very funny. Like, I am equipped to look through a microscope and see how many loops or whatever in the DNA. If I understand correctly commercial food grade spirogyra jumped from green to blue-green algae, and the decision does not appear to ahve been based on a DNA test, whatever it was based on.

I've seen a number of authoritative claims that spirogyra is green algae adn blue-green algae. Conceivably it depends on whether one is talking about spirogyra or teh food product called spirogyra. Apparently those two species were originally considered spirogyra but now have their own clade, Arthrospira, and are now considered blue-green algae, even by those who consider spirogyra to be green algae.

How did Arthospira jump to a new phylum and leave its parent clade behind?

How are blue-green filamentious algae and green filamentious algae distinguished? None in my diagrams and none that I'm seeing under the microscope ahve nucleii, if that's how I'm supposed to be able to tell blue-green algae and green algae apart. They look pretty similar under the microscope.

Dora Smith


Bluegreen algae (more correctly called cyanbacteria) are prokaryotic whereas green algae are eukaryotic. You're on the right track in looking for organelles - if you can't distinguish these, they're prob not there and you should know what you have.