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The Changing World of Ciliate Systematics: Historical Analysis of Past Efforts and a Newly Proposed Phylogenetic Scheme of Classification for the Protistan Phylum Ciliophora

John O. Corliss
Systematic Zoology
Vol. 23, No. 1 (Mar., 1974), pp. 91-138
DOI: 10.2307/2412242
Stable URL: http://www.jstor.org/stable/2412242
Page Count: 48
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The Changing World of Ciliate Systematics: Historical Analysis of Past Efforts and a Newly Proposed Phylogenetic Scheme of Classification for the Protistan Phylum Ciliophora
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Abstract

New information of value in phylogenetic and systematic considerations of the ciliate Protozoa is rapidly accumulating; to give this the attention it merits, a revised scheme of classification for the CILIOPHORA, now believed to represent a separate protistan phylum in its own right, needs to be developed. First, the history of past attempts at erecting phylogenetically-based classifications for the group is reviewed, with emphasis on changes which have evolved in response to technical advances in the field, growth in interest of biologists in these protozoa, and promulgation of new ideas and hypotheses by qualified leaders. Such a critical look at the past lends perspective to the overall problem and has provided a basis for the new revision proposed here. The First Period (1880-1930), the Age of Discovery, is noted for the simplicity of the classification scheme, credited principally to Otto Butschli. But there were only 500 species of ciliates known at the beginning of the period and they were separated into several groups primarily on the basis of easily visible differences in the location and composition of the external ciliature. The long life of the Butschlian system is credited to its adequacy, under the conditions which existed, and to the weight of the authority of the men backing it. The Second Period (1930-1950), the Age of Exploitation, was marked by the tremendous growth both in numbers of species and in interest in these protozoa by biologists who were not exclusively taxonomists or parasitologists. The diversity of the 3,000 species recognized by the early 1930's required considerable expansion in the number of higher-level taxa within the subphylum, as it was then called. The leadership fell to Alfred Kahl, an able and hard-working ciliatologist from Hamburg who described many new species and published monumental monographs, still indispensable in many ways today, on nearly all groups. But the classical scheme was essentially retained in the Kahlian classification. The Third Period (1950-1970), the Age of the Infraciliature, gave birth to what appeared to be a very conservative scheme of classification; but, in fact, it represented a revolutionary change over the preceding systems. Brilliantly conceived by E. Faure-Fremiet of Paris and supported almost entirely by the insightful works of other French protozoologists of the time (and of men like E. Chatton even earlier), the combination of a most appropriate and effective cytological technique (silver impregnation) and of phylogenetic and evolutionary hypotheses based on a full appreciation of the heretofore unknown infraciliature of ciliates made possible a fundamental revision of the Kahlian classification. Supposed evolutionary interrelationships were reflected in significant and often iconoclastic regroupings of major taxa within the subphylum. The number of species involved reached about 6,000 by 1960, and many new ecological niches (e.g., sands of intertidal zones) were beginning to be explored. The Fourth Period (1970-), the Age of Ultrastructure, can be identified primarily by its focus on the exciting data made available through electron microscopy. Fine structure studies of the parts of the infraciliature and of other organelles have supplied information bearing directly on the degrees of difference and similarity among ciliate species (now nearly 7,500 in number). A greater diversity than expected has demanded a splitting up of many of the groups established in the Faurean scheme, description of entirely new groups, and important evolutionary realignment of a number of groups. Even recognition of the ciliates as comprising an independent phylum is based on appreciation of the tremendous diversity within the overall assemblage. Leadership has become diffuse; E. Faure-Fremiet himself foresaw a number of the changes; critical ideas have emanated from various sources; but many of the ultrastructural facts so crucial to the revision have been produced by members of the de Puytorac school in Clermont-Ferrand. Most active in publishing new overall schemes for the ciliates has been Anatol Jankowski of Leningrad. The new classification of the CILIOPHORA proposed in the present paper incorporates some of Jankowski's ideas but reflects many other changes over the Faurean scheme as well, including a sizable multiplication in number of high-level taxa and postulation of quite different affinities among some of the key groups, the latter based in large measure on interpretation of pertinent morphogenetic data available from studies (including, but far from exclusively, ultrastructural research) on cortical, infraciliary, organellar, and macronuclear material in species representative of many ciliate taxa.

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