A survey of the green algae epiphytic on the shells of some freshwater molluscs

6. Summary

• 1. The green algae epiphytic on a number of freshwater mollusc shells have been investigated.

• 2. The algae exist in a very reduced state in nature, but about one hundred and twenty fairly distinct forms were found and cultured.

• 3. All species of gastropods from a single habitat tend to have similar algal populations.

• 4. Lamellibranchs tend to have similar floras to gastropods except that a few species may be absent, these have been shown to be adversely affected by silting up.

• 5. No correlation appears to exist between the algae and the roughness or smoothness of the shell, its size and shape.

• 6. Some variation occurs with the age of a snail, it is suggested that the periodicity of the algae concerned and the movement of the animal are responsible. After death providing the shell stays in the same habitat, the flora remains fairly constant.

• 7. Inter-relationships between molluscs and algae are discussed.