Adaptive toe morphology of Euchlanis cf. mikropous Koch-Althaus, 1962 (Rotifera: Euchlanidae) exposed directly and indirectly to invertebrate predators

摘要

We have been culturing a species of Euchlanis cf. milcropous isolated from a river in Mexico. This species frequently loses its toes, which then reappear in successive generations. We studied the population dynamics of this species at different food levels of Chlorella vulgaris (0.25 x 10(6), 0.5 x 10(6) and 1.0 x 10(6) cells ml(-1)) and in the direct and indirect presence of the invertebrate predators Stenostomum leucops (Turbellaria) and Asplanchna brightwellii (Rotifera). Experiments were conducted in 50 ml containers with 25 ml of moderately hard water and the desired food level or predator treatment. We initiated the experiments with exclusively females with and without toes. We observed that at high densities, in the test jars containing females with toes, toeless individuals developed. We also found that the females produced more mictic and amictic eggs in the controls than in the presence of the predators. The lifespan of this species was < 10 days and its population growth rate ranged from 0.10 to 0.60 d(-1), depending on the treatment. To our knowledge this is the first laboratory study on Euchlanis cf. mikropous.