The Significance of Cytological Characteristics as Revealed by Protargol Silver Staining in Evaluating the Systematics of the Ciliate Suborder Tintinnina

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The present systematics of the tintinnid ciliates is based on the shape, size, and composition of the lorica as established by Kofoid and Campbell. Construction of a classification based on a restricted set of characteristics, such as those pertaining only to the lorica in the tintinnid ciliates, may lead to an artificial or unnatural scheme. This lorica based classification also prohibits phylogenetic comparisons of the tintinnids to other ciliate groups whose taxonomy is based on cytological characteristics. In an attempt to demonstrate the value and necessity of employing cytological characteristics in constructing the taxonomy of the tintinnid ciliates, the cytology of representative species was examined using the protargol silver-impregnation technique. Specimens were collected from a wide range of environments, including marine, brackish, and fresh water habitats which ranged from tropical to temperate latitudes. Eleven species comprising ten genera and representing seven families were chosen to represent the suborder in this preliminary analysis. The examination of the stained species provided the first precise description of somatic ciliation patterns, a more complete understanding of the buccal organization, and insight into the biological processes of these ciliates. Using these observations,comparisons are made to other ciliate groups and a preliminary analysis of evolutionary trends in the tintinnid ciliates is supported. It is suggested that a revision of the placement of certain genera within the families of tintinnids is necessary and that such changes should be based on both cytology and morphology of the lorica.