Ref ID : 4814
Henry Tamar; Four Marine Species of Mesodinium (Ciliophora: Mesodiniidae) II. Mesodinium pulex Clap. & Lachm., 1858. Arch.Protistenk 141:284-303, 1992
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Seven populations of Mesodinium pulex, some sampled from widely-separated coasts of the U.S.A., were examined morphometrically (5 in some detail). Body shape and dimensions, and the external appendages, were studied and measured by dark phase-contrast microscopy and photomicrography. Some inclusions, behaviour and movement, and cell division were also observed. Large differences often yielding high significance were found between morphometric means of some populations, and some typical cirri numbers differed greatly. However, the ranges of variation formed a continuum, supporting the author's belief that all the investigated populations belonged to the same species, M. pulex. Populations were best differentiated by width of cone base, and differed qualitatively in cone shape, cirrus structure and the cytostome's rim. Surprisingly, the populations at the lowest ambient temperatures did not have larger body dimensions or more cirri. The endings of the 8-10 tentacular processes were cone-shaped or globose. Cells vertically attached to the substrate in lakes of seawater rose upward at intervals. The extreme cone forms often observed in one population (M72) may have been called forth by the presence of sewage. The identifying characteristics of M. pulex, Mesodinium acarus and Species III are given.