world of amoeboid organisms

Phryganella laurentiana
Phryganella laurentiana, after Nicholls, 2007

Phryganella laurentiana Nicholls, 2007 incertae sedis

Diagnosis: Cell with a centrally located nucleus about 6 μm in diameter and a single nucleolus 2 μm in diameter; pseudopodia single to many, slowly metabolic and of varied shapes including those with sharp-pointed apices and lobate rounded apices, rarely extending longer than 1.5 x the test diameter. Test bowl-shaped with a rounded dorsal surface, covered with agglutinated siliceous particles. Ventral pseudostomal aperture extends to the full internal diameter of the test (no discernable ventral surface).

Dimensions: Test height, 17–22 μm; exterior diameter, 24–27 μm.

Ecology: Freshwater, Canada.

Remarks: It is highly questionable if this is a Phryganella species.
Nicholls (2007): “In all specimens measured, test diameter was always greater than test height, but still resulted in noticeable differences in test shape revealed by light microscopy. Some tests in lateral view with a relatively low profile (a low H/D) were in contrast with those having a relatively high H/D ratio. In addition to its small size (median test height and diameter = 20 μm and 26 μm, respectively, the lack of any ventral margin or border surrounding the pseudostomal aperture are among the most distinctive features of this species. The rim of the pseudostomal aperture was constructed of very small particles and thick organic cement that imparted a uniformly smooth outline to this region of the test. Relatively large siliceous particles were often observed in dorsal regions of the test and on the lateral wall of the test, sometimes even as low as the outer margin of the ventral apertural rim. In their ability to change form continuously, pseudopodia were highly distinctive in living specimens; these included lobose and sharp-pointed forms, and specimens with both forms, as well as transitional pseudopodial forms.”

Nicholls; K.H., 2007. Descriptions of Phryganella laurentiana n. sp. and Difflugia yorkui n. sp. two new species of testate amoebae from boreal forest wetlands in Ontario, Canada. Acta Protozool. 46: 65–72

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