MadSci Network: General Biology |
Hello Jenny, Your question is a very interesting one. You are correct in saying that you can't tell if an earthworm is alive by feeling its pulse. However, if you can observe your earthworm under a dissecting microscope, you might be able to see blood moving anteriorly (tail --> head) through its dorsal blood vessel. Then again, it will be difficult to see any blood flow at all when the worm's metabolic processes slow down due to the cold - a cold, barely-alive earthworm will look an awful lot like a cold, dead earthworm. And an earthworm's blood flow isn't the most dynamic thing even under the best of circumstances, so maybe we should find another measure of the worm's "liveliness." You could try measuring some more visible response to the cold, such as lethargy or decreased burrowing activity. Earthworms will burrow into soil if you shine light on them, so you could put the worms in the freezer for various amounts of time, then remove them and shine a light on them, and time how long it takes them to start burrowing. Alternately, you could measure how reactive the worms are to poking after their stays in the freezer. Of course, by shining a light on the worm you'll also be heating it up, which would be a confounding factor for your study. If you could devise a way of giving them light without heat, that would be ideal. One thing you should know about earthworms before you get started, however. Earthworms are extremely sensitive to desiccation, and the inside of a refrigerator or freezer is a very dryinc place. Your worms will dry up after only a few minutes if you don't give them any protection. If you're going to do this experiment, put the worms in small cups, covered, and buried in damp soil. This will protect them from desiccation, and they'll still be subject to your cold treatments. And one last thing. Please be kind to the worms. They may be only worms, but no living creature should suffer any more than is absolutely necessary. Thank you! Allison J. Gong Mad Scientist
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