How do crayfish breathe?
We are teachers teaching a unit on crayfish. Our students would like to
know how crayfish breath? Are there any experiments or demonstrations that
would help demonstrate how they breath?
They breathe by extracting oxygen from water using their gills. Gills simply
provide a large surface area for contact between blood and the water, so that oxygen
can diffuse from water into the blood efficiently. To make the process more efficient,
blood and water flow in opposite directions in structures like gills. It would take a
lot of space and diagrams to explain this, but one good picture in a textbook will make
it very clear. Just look in a general biology text under "countercurrent distribution".
This may be a bit too much for young students, however. The main point is that an animal
can extract oxygen from water just like air-breathing animals extract it from air.
Unfortunately, I can't think of a good experiment to demonstrate this in a student lab.
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Update: June 2012