Hydra amp Bryozoa

>> YOUR LINK HERE: ___ http://youtube.com/watch?v=-a9irUZAzT8

A movie of Hydra and Bryozoa. Hydra are primitive animals related to sea anemones and jellyfish. The arms have specialised cells (cnidocysts) containing tiny, stinging harpoons (nematicysts) which they use to capture prey. Hydra have an amazing ability to regenerate: you can see one arm is just a stump in the process of regrowing (0:07-0:10). Medical scientists study Hydra looking for clues to improve wound-healing or organ regeneration in humans. Sometimes Hydra have small protozoans living on them (0:15 0:29), it is not clear whether these are harmful. • The second half of the movie is of a Bryozoa (0:38). These are much more complex animals. They feed with a retractable, U-shaped array of tentacles (the lophophore 1:03) each of which is covered in cilia (e.g. 1:42). You can see peristaltic movements in the U-shaped gut (2:02) which vents close to the mouth but below the lophophore. This is a freshwater example which was living on the back of a pond snail.

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