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The World of Protozoa, Rotifera, Nematoda and Oligochaeta

Ref ID : 4686

Klaus-Peter Ferber and Klaus Hausmann; [Untersuchungen an den kontraktilen Vakuolen von Homalozoon vermiculare und Dileptus anser] (Studies on the Contractile Vacuoles of Homalozoon vermiculare and Dileptus anser). Arch.Protistenk 129:45-53, 1985

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Homalozoon vermiculare and Dileptus anser are elongate predatory ciliates which contain many (5-21 in Homalozoon, 6-15 in Dileptus) contractile vacuoles. In both cases the total number was greater in longer animals. The behaviour of these structures was investigated by analysis of video recordings. The vacuoles appear simple, there are no collecting canals. No ampullae are visible after expulsion of vacuolar fluid has taken place. Vesicles are not involved in vacuolar filling. The average diastolic diameter attained by contractile vacuoles of H. vermiculare was 9.5 µm (range 4-15 µm) and in D. anser 4.0 µm (range 2-5 µm). The frequency of contractions in H. vermiculare varied greatly averaging 1 contraction per 45 sec, and individual vacuoles had a wide range of cycle period, e.g., 38-53 sec. The vacuoles of D. anser, in contrast, have cycle periods varying within quite a narrow range and had a mean cycle duration of 25 sec. The frequency of contractions in H. vermiculare show gradual, sinusoidal fluctuation in the duration of the cycle. In both organisms the vacuoles towards the front and back ends of the cell contract less frequently than those towards the centre of the cell. There is a direct correlation between vacuolar contraction frequency and the width of the body. However, there is no direct correlation between vacuolar output and the volume of the intervacuolar cytoplasm, or the intervacuolar cell surface area. There is an apparent gradient in the functional activity (output per vacuole per volume of cytoplasm) of the contractile vacuoles of these organisms, with a maximum encountered immediately behind the cytopharynx.