The very long furca is characteristic for Eurytemora lacustris which is recorded from a few lakes in the east/southeast part of county Østfold.
The last pair of legs (p5) and the very long furca is characteristic for this genus. Eurytemora lacustris is smaller than E. velox and separated from this species by the appearance of the last thorax segment which in E. lacustris is only scarcely expanded. In E. velox the same segment is greatly expanded. The furca of E. lacustris is slightly longer than it is in E. velox. Its body is highly pellucid, and more or less colourless.
Female: Length 1.0–1.5 mm
Male: Length 1.0–1.4 mm
Ecology and distribution
A few specimens of E. lacustris were found by G.O. Sars in the beginning of the 1860's in Lake Femsjø, southeast of Oslo. Since then it has been recorded from additionally a few more lakes, respectively in the catchment Haldensvassdraget, Lake Stora Le and Lake Kirkevatn (Enningdalsvassdraget). pH is close to neutral (6.3–6.9), while conductivity is about 6.0 mS/m in the waterbodies where E. lacustris is found.
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