Fate of ciliates in the earthworm gut: An in vitro study.

The behavior of the ciliateColpidium campylum was unaffected by exposure in vitro to high concentrations of pharyngeal and hindgut fluids from the earthwormLumbricus terrestris, but movement became abnormal and ceased in concentrations of midgut fluid as low as 1.5%. On mixingC. campylum culture with an equal volume of midgut fluid, which often contained resident astomatous ciliates, the.C. campylum cells were immediately immobilized and frequently disintegrated, while the astomatous ciliates continued to behave normally. Possible causes of the hostility of the midgut environment, and implications for earthworm nutrition, are discussed.