Paraurostyla Weissei Research Articles

Cortical Pattern in Non‐dividers, Dividers and Reorganizers of an Austrian Population of Paraurostyla weissei (Ciliophora, Hypotrichida): A Comparative Morphological and Biometrical Study

The morphology and the regulation of cortical pattern associated with the cell size, division, and reorganization of Paraurostyla weissei (Stein, 1859) were investigated. The ranges of variation of the Austrian, Polish, and American strains were compared by biometrical analyses. The Austrian population most frequently shows 4 frontal cirri in the anteriormost and 2 in the posterior row, 4 ventral rows, 8 transverse cirri, and 7 dorsal kineties. The oral primordium originates next to the postoral ventral row. The undulating membrane field and 3 frontal‐ventral‐transverse(FVT)‐streaks for the opisthe develop as a result of the dispersion of the basal bodies of 1 or 2 cirri of the 1st ventral row. The farthest‐right ventral row is of composite origin from 2 FVT‐streaks. Three short dorsal bristle rows originating beside the right marginal row are a constant feature. In reorganizers the oral primordium characteristically possesses a group of kinetosomes extending toward the anterior right, fusing with the undulating membrane field. The development of dorsal primordia always starts in the 3rd dorsal kinety. These results provide important criteria for future species discrimination, if the examination of non‐morphological characters supplies evidence that P. weissei is a complex of sibling species.

Ultrastructural aspect of size dependent regulation of surface pattern of complex ciliary organelle in a protozoan ciliate

A regulation is shown for size and number of the elements of complex ciliary structures forming the oral apparatus (OA) of a ciliate Paraurostyla weissei. Morphometric investigations were performed on oral ciliature of normal and size-reduced cells. Those constituents of the OA which exist as single structures, such as the inner and outer preoral membranelles, are not eliminated. Both shorten and the outer membranelle becomes narrower. Within the adornal zone of membranelles in size-reduced cells some frontal and ventral membranelles become eliminated, whereas the respective ratio of these types remain size invariant. In each individual adoral zone of membranelles there are membranelles of different length specifically located along the ventral part. Membranelles from small cells are significantly smaller than those of normal cells. The number of kinetosomes is reduced in all four rows constructing an adoral membranelle. The analysis showed that regardless of cell size, the number of kinetosomes in the two inner rows of a membranelle is linearly and proportionately related. Regulation of the size of all components of the oral ciliature in P. weissei occurs at the time when the primordia of oral ciliature are formed. The results are discussed in relation to recent ideas about pattern formation and size dependent regulation of the number and size of pattern elements.

Temporal coordination and spatial autonomy in regulation of ciliary pattern in double forms of a hypotrich ciliate Paraurostyla weissei

AbstractRegulation of cortical pattern was analyzed in homopolar back‐to‐back doublets of Paraurostyla weissei. After surgical removal of the anterior quarter of one component, both components form primordia of the ciliature, each one positioning the primordia according to its own boundaries. Both regenerated components were measured several hours after the operation, and the number of cortical elements was counted in each component. On the average, the operated component is smaller by about 17% and possesses about 25% fewer AZM membranelles and about 14% fewer left marginal cirri than the unoperated component. The analysis shows that in spite of the endoplasmic and membrane continuity and the morphogenetic signals passing from one component to the other, the two halves of a doublet show remarkable autonomy both in positioning of the primordia and in regulation of the number of cortical elements, which remain proportionate to the size of each component of the double form.

The proportional regulation of cortical structures in a hypotrich ciliate Paraurostyla weissei

AbstractThe relationships between the size of a cell and the number of some compound cortical structures (cirri and membranelles) were studied using cells of a hypotrich ciliate Paraurostyla weissei stained with protargol. The length of cells was measured, the number of AZM membranelles, frontal, transverse and left marginal cirri were counted in cells from growing populations and in miniaturized cells obtained by starvation or repetitive regeneration.Changes in the number of cortical elements occur mainly through replacement of the whole ciliature during a morphogenetic process (division, reorganization, regeneration). In growing populations small postdividers and large predividers do not differ with respect to the number of membranelles and cirri despite the differences in size. In miniaturized cells the number of cortical elements formed decreases and is directly correlated with the length of the cell showing a proportional regulation in accordance to the cell size. Different modes of pattern regulation are discussed.

Conjugation in the Hypotrich Ciliate, Paraurostyla weissei (Stein): A Scanning Electron Microscope Study*

SYNOPSIS. Conjugation in Paraurostyla weissei has been investigated by scanning electron microscopy. In the course of conjugation, one member of each conjugating pair is resorbed. An organism that is being resorbed always lies to its partner's left and is always fused to its partner's oral region. A mechanism for the development of this asymmetry is proposed, based on the asymmetry of individual Paraurostyla. After resorption is complete, exconjugants enter a rounded, nonmotile stage which lasts several days. Exconjugants at this stage have been compared with cysts and have been found to be dissimilar.