Quadrulella longicollis, 147 um long, stacked

Quadrulella longicollis Taranek, 1882

Diagnosis: Much larger than Q. symmetrica and with straight sides, usually without pronounced lips.

Dimensions: c. 150 µm.

Ecology: mosses, fresh water.

Remarks: The specimens below were collected from the Heelsumse Beek, a clear stream near the city of Arnhem. These shells were the only Arcellinida which were found in a thin layer of sediment in this oligotrophic stream, fed by pure groundwater. The shell length ranges from 69-147 µm. The two smaller ones are Q. symmetrica, the largest three are Q. longicollis. Kosakyan et al (2012) found genetic distances, up to 11%, between Q. symmetrica and Q. longicollis.

These records from one location suggest rather a species complex than distinct intraspecific diversity.
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