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Acanthocystis dürrschmidtidae

P. mikrjukovii – after Wujek, 2003

Pterocystis mikrjukovii  Wujek, 2003
  
Diagnosis: Cells 35-40 µm (based on a whole mount). Periplast comprising scales of two types, plate- and spine-scales. Details of protoplast unknown. Plate-scales are ovoid or elliptical, ca. 1.5-2 x 0.8-1.5 µm. They are patternless except for an axial thickening and lack a peripheral rim. The spine-scales are almost spade-form, 4-4.5 µm long, with a flared or winged base, ca. 1-1.2 µm 1-1.2 wide; the tapered shaft is straight, ca. 2 µm long, terminating with a slightly bent pointed apex. The winged base-plate has 3-4 ribs extending from the base of the shaft to the basal wing’s margin. Two-five ribs are also present that do not extend completely across the basal wing. Lateral wings narrow abruptly and taper briefly terminating about two-thirds from the shaft’s apex.

Type location: Freshwater; Lake Tyler, southeast side of Farm Road 848, Smith County, Texas.

Remarks: The spine-scales of Pterocystis mikrjukovii most closely resemble those of Pterocystis paliformis (Dürrschmidt) Page & Siemensma. The major differences being P. mikrjukovii spine-scale basal wings possess ribs which are lacking in the patternless A. paliformis, and the lateral wings are not parallel and taper toward the shaft and do not narrow abruptly and terminate subapically.

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