Mechanisms of Movement in Taxonomy of Sarcodina. I. As a Basis for a New Major Dichotomy into Two Classes, Autotractea and Hydraulea

Abstract

Members of the Sarcodina seem to possess either of two basic mechanisms for protoplasmic movement: 1) a contraction-hydraulic system in which protoplasmic flow is caused by contraction of a tube of gel; and 2) an active shearing or active sliding mechanism in which two surfaces, usually both of gel, but possibly one of sol and one of gel, move in relation to one another. Our observations and those of other recorded in the literature indicate that an organism which has and employs one of these basic mechanisms either does not have or does not ordinarily employ the other. If these two mechanisms are distinct, possession and locomotive employment of one or the other must be of great phylogenetic importance to the organisms and, therefore, are also important, or should be, in taxonomy. If so, the Sarcodina logically might be divided into two major groups on the basis of the functional presence of either of these two mechanisms. Current and past taxonomic class levels for the Sarcodina are discussed and shown to be illogical. They require revision, particularly in view of the upsurge in the use of logical computer systems in taxonomy. The logical employment of a dichotomy of Sarcodina based on these two fundamental mechanisms of movement is an initial step in this direction. We suggest abolishment of all previously proposed classes of Sarcodina and the establishment of: 1) the class AUTOTRACTEA for organisms employing the active shearing mechanism; and 2) the class HYDRAULEA for those organisms employing the contraction-hydraulic mechanism.