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 Author Sidorov, Dmitry 55C1264F-67C0-4C3F-8E6B-ECE1E821457B Federal Scientific Center of the East Asia Terrestrial Biodiversity, Russian Academy of Sciences, Vladivostok 690022, RF. biospeorossica@gmail.com Author Yalysheva, Elena 88AB67D2-1F97-4A2C-8121-362132FCF07C Municipal State Educational Institution “ Osinovskaya shkola ”, Osinovyy Mys 663457, RF. ona_vita@rambler.ru Author Sharyi-Ool, Mariana 9DE31FF0-0660-4980-B819-63305D609CAC Federal Scientific Center of the East Asia Terrestrial Biodiversity, Russian Academy of Sciences, Vladivostok 690022, RF. sharyiool@biosoil.ru text European Journal of Taxonomy 2021 2021-10-13 774 178 199 http://dx.doi.org/10.5852/ejt.2021.774.1541 journal article 4025 10.5852/ejt.2021.774.1541 bc28e8d7-56ea-4318-86bc-834a0fdb87c8 2118-9773 5567144 F8F78338-FF22-4E48-91FA-6EB1A9EC76EB 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) .