A widespread Ponto-Caspian invader with a mistaken identity: integrative taxonomy elucidates the confusing taxonomy of Trichogammarus trichiatus (= Echinogammarus) (Crustacea: Amphipoda) Author Copilaș-Ciocianu, Denis Author Palatov, Dmitry Author Rewicz, Tomasz Author Sands, Arthur F. Author Arbačiauskas, Kęstutis Author Haaren, Ton Van Author Hebert, Paul D. N. Author Grabowski, Michał Author Marin, Ivan text Zoological Journal of the Linnean Society 2023 2023-07-31 198 821 846 journal article 10.1093/zoolinnean/zlad010 0024-4082 9B8367A2-727A-451E-A922-AD88CDEA5E66 GENUS CHAETOGAMMARUS MARTYNOV , 1924 Type species: Gammarus ischnus Stebbing, 1899 . I n c l u d e d s p e c i e s: C h a e t o g a m m a r u s h y r c a n u s Pjatakova 1962 , C. pauxillus ( Sars, 1896 ) , C. placidus ( Sars, 1896 ) , C. aearpachoaeskyi (Sars, 1894) and C. trichiatus Martynov, 1932 . Non-included species: Echinogammarus karadagiensis Grintsov, 2009 and E. mazestiensis Marin & Palatov, 2020 will be transferred to a new genus (I. Marin, D. Palatov, and D. CopilaȘ- Ciocianu, unpub. obs.). Amended diagnosis: Small- to large-sized species (≤ 15 mm ); females smaller than males. Head with oblique anteroventral lobe, sometimes distally produced. Eyes large, reniform, well pigmented. Body non-carinate. Antenna 1 feebly setose, accessory flagellum two- to eight-segmented; antenna 2 usually shorter that antenna 1, without calceoli, deeply setose in males and less setose in females. Lower lip (labium) with mostly reduced inner lobes. Gnathopod 1 smaller than gnathopod 2, sexually dimorphic, stronger in males, propodus generally teardrop shaped; gnathopod 2 sexually dimorphic, stronger in males, propodus trapezoidal with oblique palmar margin. Basis of pereopods 5–7 without or with weak posteroventral lobes, dominated by spines. Uropod 3 with exopod about four to six times as long as wide, generally dominated by spines. Urosomites 1 and 2 without elevations, armed with clusters of spines; urosomite 3 with a pair of submedian spines. Telson deeply cleft into suboval lobes, bearing clusters of spines distally and submedially. Figure 7. Scanning electron micrographs. A, antenna 1. B, antenna 2. C, basis of pereopod 7. D, pereopod 3. Scale bars: 0.2 mm. Synonymized genera: Trichogammarus Hou & Sket, 2016 . Distribution: The native range of the genus is restricted to the Ponto-Caspian basin. Its species occur in the Caspian Sea at up to 500 m depth, and in lagoons, estuaries and lower stretches of rivers that drain into the Black, Azov and Caspian seas.