Limnocalanus macrurus can habitually be distinguished from other calanoids by its comparatively longer furca. It is a so called glacial relict and found in a restricted number in quite deep lakes located in marine sediments.

Key characteristics

Limnocalanus macrurus is a large planktonic species with a slender and elongated body. Habitually this species can be distinguished from other calanoids by its comparatively longer furca. Seen from the side this species has a small depression just behind the eye. The appearance of the last pair of legs can also be used to separate this species from other species. The body of both sexes are highly pellucid and nearly hyaline, and more or less colourless.

Female: Length 2.0–3.0 mm

Male: Length 2.0–2.5 mm

Ecology and distribution

L. macrurus was found by G.O. Sars in five of the great lowland lakes in the southeast of Norway. Today the species is recorded from about 20 lakes. All lakes are located in marine sediments and L. macrurus was one of the first immigrants to Norwegian lakes, being a so called glacial relict. The lakes are neutral (pH: 6.0–7.0) and medium electrolyte rich (4–9 mS/m).