It should be emphasized that the 24-h LC50 value
(0.03 mg l1) registered for this hypotrichous ciliate for nickel
is lower than those reported for the heterotrich Spirostomum
teres (0.17 mg l1) which is considered an excellent and
convenient bioindicator for evaluating the toxicity of waters
polluted by nickel (Madoni, 2000).