Gammarus (Martynov, 1935) J. C. Fabricius, 1775

Sidorov, Dmitry, Yalysheva, Elena & Sharyi-Ool, Mariana, 2021, Morphology and zoogeography of the burrower-like gammarid Gammarus koshovi (Bazikalova, 1946) (Crustacea, Amphipoda, Gammaridae) - An overlooked and poorly known species in the Siberian fauna, European Journal of Taxonomy 774, pp. 178-199 : 190

Key to the Siberian species of Gammarus (based on adults of both sexes)

Gammarus barnaulensis Schellenberg, 1937 is not included in the key as the original description does not provide appropriate morphological features.

1. Body and appendages ordinary, length more than 8.0 mm ............................................................... 2

– Body compact, appendages shortened, length up to 8.0 mm (burrowing group *) .......................... 9

2. Species with dense setation on pereopods III–IV and uropod III ( pulex group) .............................. 3

– Species with poorly setose pereopods III–IV and uropod III (balcanicus group) ............................ 8

3. Pereopod dactyli long, slender .......................................................................................................... 4

– Pereopod dactyli short, stout ............................................................................................................. 5

4. Urosomal segments moderately armed .................................................. G. lacustris G.O. Sars, 1863

– Urosomal segments richly armed ............................................................... G. hanhi Safronov, 2006

5. Uropod III endopodite inner face with setae .................................................................................... 6

– Uropod III endopodite inner face naked ........................................... G. teletzkensis Martynov, 1930

6. Epimeral plates II–III, ventral margins without setae, with spines .................................................. 7

– Epimeral plates II–III, ventral margins with a row of long setae ........ G. angulatus Martynov, 1930

7. Antenna I slightly more than half of body length .............................. G. korbuensis Martynov, 1930

– Antenna I distinctly less than half of body length ....... G. dabanus Tachteev & Mekhanikova, 2000

8. Antenna I, main flagellum up to 28 articles ....................................... G. angustatus Martynov, 1930

– Antenna I, main flagellum with 34–35 articles .................................. G. pellucidus Gurjanova, 1930

9. Telson, lobes apically with 4 spines ................................................... G. koshovi ( Bazikalova, 1946)

– Telson, lobes apically with 1 or 2 spines ................................... Gammarus sp. in Gurjanova (1930)

* Conventionally proposed group to which we additionally assign Gammarus sp. in Gurjanova (1930).