S. M. Gittleson’s research while affiliated with Fairleigh Dickinson University and other places

A review of the Genus Polytomella, initially described by Aragao in 1910, is presented. Polytomella spp. are colorless eukaryotic quadriflagellates. They are typically oval or elliptical to pyriform in shape and may range in size from 9 × 8 to 30 × 20 μm. The four flagella are approximately body length and originate from an anterior cruciform papilla. The objective was to compile all the information in the literature in order to update the first and only review of Polytomella published by Pringsheim in 1955. The following areas are discussed: classification, morphology, life cycle, metabolism, and motilitv.

In this note are shown what may well be the first pictures of encysted Polytomella by SEM. There are major differences in surface topography of the vegetative and encysted forms of this flagellate. The cysts are spherical in shape with either a smooth or wrinkled surface.

SYNOPSIS The response of vertical aggregates of Polytomella agilis to increased viscosity of the medium indicates that viscous resistance of the medium is a critical factor controlling the formation and sedimentation of protozoan aggregates. Aggregate formation time increased from 20 sec to 6.5 min as viscosity was increased 1.72 times. Sedimentation rate decreased about 140 μm/sec for each 10% increment in viscosity. Although there was a 60% decrease in speed of falling aggregates when relative viscosity was increased from 1.0 to 1.6, individually swimming P. agilis decreased less than 22% in speed even at a relative viscosity of 1.84 where aggregates did not form. Cells continued to accumulate near the surface by negative geotactic swimming after vertical aggregation ceased. Vertical aggregation is a cyclic process composed of 4 phases: a) accumulation‐aggregation; b) aggregate sedimentation; c) ablation and dispersal; and d) negative geotaxis. Phase d is unique to motile microorganisms and only in such populations is vertical aggregation continuously selfperpetuating. Phases a‐c occur with both motile and nonmotile bodies and are dependent upon viscous forces of the medium.

Populations of protozoa in limestone waters of Kentucky vary with extremes of seasonal temperatures. Of the total 47 species of protozoa identified, 21 % were found only in the 2 to 3C samples, 59% were found only in the 15 to 17C samples and 20% were common to both samples.Protozoen-Populationen der Kalkstein-Gewsser von Kentucky, U.S.A., zeigen ein anderes Bild whrend der jahreszeitlichen Temperaturschwankung. Unter den insgesamt 47 identifizierten Protozoen-Arten fanden sich nur 21 % in 2 Bis 3C warmen Proben, nur 59% wurden in 15Bis 17C warmen Proben gefunden und 20% waren in beiden Proben anteilmig gleich vertreten.

Cellular organization of Polytomella agilis changes when the trophic form undergoes encystment: 1) initially a thin capsule is secreted about the organism which in the mature cyst develops into a thick 3-layered wall; 2) starch bodies increase in number and volume; and 3) mitochondria, ribosomes and other organelles disappear. These data point to the need for metabolic studies on homogeneous populations and suggest that Polytomella agilis may serve as a useful tool for investigation of mitochondrial biogenesis.

Analysis of high speed 16 mm cinephotomicrographs of the quadriflagellate Polytomella agilis and of polystyrene spheres in the medium shows that: 1) Usually the two flagella on each side of the anterior end of P. agilis beat synchronously in a latero-posterior cilia-type beat; 2) Unlike typical cilia which have an effective stroke duration shorter than the return stroke, P. agilis flagella have a slower effective stroke occupying 70-90% of the total cycle; 3) By applying Stokes' law to the action of the flagella on polystyrene spheres in the medium, the beating forces are estimated to be about 1.2 x 10-8 dynes; 4) Data on forward movement of P. agilis along straight, curved, and helical paths is discussed in terms of flagellar beating forces; 5) The effect of flagellar-produced currents on polystyrene spheres in the medium out to a distance of 45 μ from the cell surface suggests that hydrodynamic associations are involved in the formation of cell aggregations.

The commonly occurring phenomenon of vertical aggregation is described and analyzed using Stokes' law for the flagellate protozoan Polytomella agilis. Vertical aggregations are generated by the following cycle of events: (1) The cells, more dense (1.018 g/cc) than the medium (0.998 g/cc), swim as individuals and collect near the upper surface of the medium. (2) The crowding of organisms interferes with normal motility. (3) The number of P. agilis per unit volume of medium increases until a critical point is reached where the effective density of the fluid plus its contained organisms becomes greater than that of the medium alone. According to Stokes' law the increased downward force produced by the increased density of the massing cells plus medium compared to an equal volume of water alone overcomes the opposing frictional forces and the aggregates fall. (4) Although the aggregates become smaller in diameter they fall at a relatively constant rate of 860 μ/sec which is about 780 times that which is attained by an individual cell falling under the influence of gravity. (5) Aggregates break up when they reach the bottom and the cells again swim to the surface.

SYNOPSIS. Xenon applied at sufficient pressures ranging from 30 pounds per square inch to 225 p.s.i. caused reduction in contractile vacuole activity, increase in cellular volume, expansion of the surface region, cessation of forward movement, and cytolysis of paramecia. Krypton at 915 p.s.i. prevented contractile vacuole activity, but forward movement continued for at least 30 min. When subjected to 115 p.s.i. of N2O, paramecia moved in slow oscillations, and contractile vacuoles failed to empty. At 265 p.s.i. of N2O movement ceased and cytolysis resulted. The pressure required to terminate movement in the same time interval following application of the pressure was less for N2O than for xenon. The expansion of the surface of the cells suggests that inert gases produce narcosis by dissolving into this region.