TURNOVER OF CO-60 BY EARTHWORMS (EISENIA-FOETIDA) (LUMBRICIDAE, OLIGOCHAETA)

In laboratory experiments, earthworms (Eisenia foetida) exhibited no assimilation of radioactive Co-60 from mineral soil, but did assimilate small quantities (about 7% of ingestion) of Co-60 from manure. This study supports earlier work suggesting that earthworms assimilate only small amounts of inorganic elements from mineral soil, and that any assimilation of metals must be from the organic fraction of soils. Thus, assimilation rates are a function of substrate quality. When fed to earthworms, gamma-emitting radioactive elements can provide measurement of assimilation efficiency, gut passage time and feeding rate.