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Velamentofex
V. tyrolensis (photomicrograph Steffen Clauß)

Velamentofex tyrolensis Völcker and Clauß, 2020

Diagnosis: Trophozoites ovoid, 98-125 μm, with reticulopodia up to 300 μm long, with a hyaline, extremely flexible, membranous test sheathed with a broad layer of mucus-like material, that is covered with food particles and digestion residues. Cytoplasm yellowish, with 5-12 contractile vacuoles in the periphery of the cell, and numerous refractive rod-shaped crystalline inclusions attached to a spherical body, ca. 2 µm in diameter. Nuclei numerous, ovular, with 7-15 spherical nucleoli mostly located close to the nuclear membrane. Peduncle narrow; radiating network with 3-5 thickened strings of pseudopodia. Cells multiplying inside the layer of mucus-like material. Resting stages about 50 μm in diameter, surrounded by multilayered mucus-like material.

Type locality: Submerged Sphagnum, Sima Moor near Sankt Ulrich, Austria (47°35’3.20″N 12°37’1.55″E), June 2017.

Description: Cells are ovoid with a hyaline membranous test which is very thin and extremely flexible, often with attached bacteria. The test is surrounded by a thick layer of mucus-like material, that is obscured by a cover of food particles and digestion residues, which makes it often difficult to recognize the cell. The nuclei vary in size between specimens. One specimen had nuclei between 9.8-10.7 µm (n=20), while another contained smaller nuclei, 5.1-6.1 µm (n=20). The peduncle is narrow and barely V-shaped. Cells move slowly along a polar extended relatively thick pseudopodium. Stationary cells build an envelope of algae and digestion residues.

Cells multiply inside the layer of mucus-like material, and daughter cells commonly stay inside this layer. Daughter cells can also leave the layer along the peduncle and migrate as small elongate bulges along the pseudopodial network. Resting stages are surrounded by a thin layer of mucus-like material, which becomes distinctly thicker and multilayered after some days. Feeds on coccale algae, cyanobacteria, diatoms, rotifers and yeast.

Remarks: This species differs from V. berolinensis in the size of the nuclei (5.1-10.7 µm vs. 11.6-11.2 µm) and their structure (some nucleoli scattered through the nucleus vs. a completely fine-grained nucleus). It differs from V. saxonensis in the structure of the nuclei (some nucleoli scattered through the nucleus vs. one central nucleolus and some smaller peripheral nucleoli).

Velamentofex
V. tyrolensis (photomicrograph Steffen Clauß)
Velamentofex
V. tyrolensis (photomicrograph Steffen Clauß)
Velamentofex
V. tyrolensis nuclei (photomicrograph Steffen Clauß)
Velamentofex
V. tyrolensis, pressed cell (photomicrograph Steffen Clauß)
Velamentofex
V. tyrolensis (photomicrograph Steffen Clauß)
Velamentofex
V. tyrolensis (drawing: Steffen Clauß)
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