Paraphysomonas vestita

Paraphysomonas vestita (Stokes, 1885) De Saedeleer, 1929. Ovoid to elongate cells, from 6 to 15 microns long. Two flagella insert in an apical depression. One flagellum is very short and held laterally while the other, two to three times the length of the cell, is held anteriorly and beats with short wavelength and high amplitude wave pattern. Cells often contain granules. Scales are visible in light microscopy as delicate spines. In electron microscopy, the scales have a plain circular base (1-2 microns) with a well-marked rim and a tapering spine 3 to 5 microns long.

Detail of spine scales of Paraphysomonas vestita a colourless stramenopile flagellate. This is the type species for the genus. About 50 species are recognized. . Radiating endogenous siliceous spine scales (seen here) cover the cell surface. Scale morphology (by EM) is species specific. Most Paraphysomonas species have spine scales of a single morphology but some species have 2 or 3 different types. These pushpin-shaped spine scales of P. vestita have imperforate circular base-plates by EM. The scales persist in sediments for months, providing a tool for population studies. From standing freshwater near Boise, Idaho. DIC optics.

Portrait of Paraphysomonas vestita, a colourless stramenopile flagellate. This is the type species for the genus. About 50 species are recognized. Swims freely but may attach to substrate by thin posterior stalk. The body is spherical, pyriform or ovoid. There are two flagella (visible but slightly out of focal plane here), one longer with tripartite hairs and a short less active one, which is smooth. The slightly eccentric nucleus is seen here. A single contractile vacuole is seen here. Stigma absent. Radiating endogenous siliceous spine scales (seen here) cover the cell surface. Scale morphology (by EM) is species specific. Most Paraphysomonas species have spine scales of one morphology but some species have 2 or 3 different types. Cells consume bacteria, diatoms and algae. From standing freshwater near Boise, Idaho. DIC optics.