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Freshwater Hydra

Phylum Cnidaria, Class Hydrozoa


Barely macroscopic, about .5mm long, white. Photo taken at 10x magnification w/ compound light microscope, image being projected onto classroom SMARTboard.


Hydra are common in freshwater ponds and slow-moving streams. Some hydra possess zooxanthellae (symbiotic algae). This species does not appear to.


This specimen was found in one of my Corydoras catfish breeding tanks, attached to a piece of gravel. Upon closer inspection, there were several dozen, spread out on the gravel & one side of the tank glass. The tank does have a healthy population of Ulothrix algae - I assume that the hydra originated with the algae culture. It is unusual to spot one w/ the naked eye in a tank.

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1 Comment

BlueFerns 10 years ago

Wonderful documentation. thanks for all the information!

Spotted by

Hartford, Connecticut, USA

Spotted on Mar 4, 2011
Submitted on Mar 6, 2011

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