A short little paper of mine just got published in Triton No. 13 (pdf). It is about the diet of Oxyloma retusa, one of my favorite land snails. In the spring and summer I find them abundantly crawling on the mud and on cattails along the shores of a small local lake.
About 4 years ago I decided to figure out what these snails were eating. At different times of the year, I collected a bunch of snails and kept them in clean wet containers without food for several hours. Then I collected the feces they had deposited inside the containers and examined them under a microscope. It was a very simple study, but it told me a lot about their diet.
Here is a bunch of samples of Oxyloma feces preserved in glycerol.
Once broken apart and magnified, even crap can become interesting, believe it or not. For example, this snail ate some pollen (cattail?) and some other dead plant material, whose stomata are easily recognized.
The picture on the left below shows the feces of a snail that ate zucchini in the lab. The green particles are probably chloroplasts. Similar green particles are visible in the picture of the feces of a snail that had eaten green plants in the wild (right).
The results indicated that the snails were eating both dead and live plants.