Ref ID : 4773
Tom Fenchel, Bland J. Finlay, and Alessandro Gianni; Microaerophily in Ciliates: Responses of an Euplotes species (Hypotrichida) to Oxygen Tension. Arch.Protistenk 137:317-330, 1989
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We have studied the responses to oxygen by a marine species of Euplotes (Ciliophora, Hypotrichida). The ciliate prefers an oxygen tension of about 5% atm sat. and it displays chemosensory behaviour, so cells tend to accumulate at this level in oxygen gradients. The respiratory rate is almost maximal at the preferred oxygen tension. The ciliate can grow at higher oxygen tensions, but it then has a longer generation time and a lower growth efficiency. Under strict anaerobic conditions the ciliates survive and remain viable for many weeks, but division rate declines and they do not seem to be able to sustain a constant rate of division. Neither mitochondria nor their cristae degenerate during prolonged anoxia, but they do show some characteristic changes. This suggests that mitochondria play a role in anaerobic power generation. A few other studied species of Euplotes show a similar behaviour, but their preferred pO2 is around 20% atm sat. Microaerophily is probably a widely distributed phenomenon among ciliates and its ecological, physiological and evolutionary implications are discussed.