Locomotion as a criterion to read the adaptive biology of protozoa and their evolution toward metazoa

Abstract

The locomotory patterns of Protozoa have been compared, in an attempt to draw a general picture of how these protists solved the problem of relating properly with their environment. Locomotion seems to have evolved according to a progressive complexification not only of the engines (from prokaryotes to eukaryotes) but also of the systems that control how they work (different beating patterns of the eukaryotic flagella and cilia under a sophisticated control of the electrophysiological potentials of the cell). Among ci‐liates, the Hypotrichida with their ciliary engines (cirri) and electric control (cell membrane more complex and sophisticated), have reached the highest peak of specialization. The evolutionary leap to a multicellular organization typical of Metazoa did not play any relevant role in locomotion: it was only with the appearance of the most complex phyla (Mollusca, Annelida) that a new locomotory asset was gained (muscular layers or bundles) and perfected by the coupling of muscles and levers (art), especially by Arthropoda and Chordata. © 1989 Taylor & Francis Group, LLC.