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CHAETOGAMMARUS TRICHIATUS MARTYNOV, 1932 (FIGS 8–11) Brief redescription: Based on specimen ZMMU Mb-1227, ♂, Russia, Krasnodar Krai, Sochi Urban Okrug, Lazarevsky District, mouth of the Ashe River, in the stream under stones (43°57.376ʹN, 39°15.954ʹE), 13 May 2019, coll. D. Palatov & I. Marin. Relatively large species (≤ 15 mm); females smaller than males. Head with oblique anteroventral lobe with distally produced anterior margin (Fig. 6B), eyes large, reniform, well pigmented. Body unpigmented, moderately elongated, generally smooth, non-carinate. Urosomites 1–3 smooth, without elevations; urosomites 1 and 2 with solitary strong median and submedian spines; urosomite 3 with two submedian spines and a pair of median simple setae (Fig. 6A). Antenna 1 feebly setose, with small aesthetascs; accessory flagellum eight-segmented (Figs 7A, 8A). Antenna 2 is about one-third shorter than antenna 1, massive and deeply setose in males and less setose in females, without calceoli and aesthetascs (Figs 7B, 8C, D). Upper lip (labrum) with convex distal part (Fig. 9A). Lower lip (labium) usually with mostly reduced inner lobes (Fig. 9B). Mandible with well-developed palp and setose basal segment (Fig. 9C–F). Maxilla 1 with outer lobe bearing hairbrush-like distal setae, subequal to inner lobe; inner lobe distally expanding with a row of marginal setae (Fig. 9G). Maxilla 2 with outer lobe wider than inner lobe, bluntly expanding distally (Fig. 9I). Maxilliped with outer and inner plates wide (Fig. 9J). Gnathopod 1 is smaller than gnathopod 2, with weak sexual dimorphism, stronger in males; propodus (palm) teardrop shaped, with oblique palmar margin in males and females (Fig. 8E, F). Gnathopod 2 is significantly larger in males, rectangularly elongated, with straight palmar margin in both males and females (Fig. 8H, I). Basis (article 2) of pereopods 5–7 with feebly marked ventral lobes (Fig. 10D, F, G); pereopod 3 with highly developed coiled setation along posterior margin (Figs 7D, 10A); basis of pereopod 7 elongated, ~2.5 times as long as wide, without ventral lobe (Figs 7C, 10G). Pleopods with two elongated hooks and one or two thick bristles in retinacules (Fig. 11F, G). Uropod 3 exopod broad, furnished with clusters of long, distally coiled setae, about four to six times as long as wide, with reduced distal article furnished with numerous long, simple distal setae (Figs 6D, 11K, J). Epimeral plates 1–3 with sharply produced inferoposterior corners (Fig. 11A–C). Telson deeply cleft into suboval lobes, abruptly tapering distally, bearing clusters of strong, stout setae distally and submedially (Figs 6A, 11D, E). Remarks: Males of C. trichiatus can be distinguished from males of other species of Chaetogammarus by the highly developed coiled setation on pereopod 3 posterior margin and uropod 3 exopod, acutely produced anterolateral head lobes, and telson lobes abruptly tapering distally. Chaetogammarus trichiatus is most similar to C. ischnus, but differs from that species in the following traits: significantly more elongate appendages (Fig. 5C); epimeres 2 and 3 with more produced posterodistal corners; presence of coiled setae along the outer margin of uropod 3 exopod (Fig. 6D); longer basis of pereopod 7 (length = 3 × width vs. length = 2 × width; Fig. 7C). Distribution: Chaetogammarus trichiatus is endemic to lakes, lower (slow current) river stretches and river mouths along the north-eastern Black Sea coast, from Abrau to the Shahe River, and a separate population is known from New Athos (Fig. 4). Found only on substrates with pebbles or large stones and boulders, apparently avoiding sandy and silty substrates. Type locality: Estuarine part of Khosta River, Sochi area, Russia. Presently absent at its original type locality owing to anthropogenic influence and the urban reconstruction of the lower part of the river., Published as part of Copilaș-Ciocianu, Denis, Palatov, Dmitry, Rewicz, Tomasz, Sands, Arthur F., Arbačiauskas, Kęstutis, Haaren, Ton Van, Hebert, Paul D. N., Grabowski, Michał & Marin, Ivan, 2023, A widespread Ponto-Caspian invader with a mistaken identity: integrative taxonomy elucidates the confusing taxonomy of Trichogammarus trichiatus (= Echinogammarus) (Crustacea: Amphipoda), pp. 821-846 in Zoological Journal of the Linnean Society 198 on page 834, DOI: 10.1093/zoolinnean/zlad010, http://zenodo.org/record/8152446, {"references":["Martynov AB. 1932. Contribution to the knowledge of the freshwater fauna of the Black Sea coast of Caucasus. I. Amphipoda. TraVaux de l'Institut Zoologique de l'Academie des Sciences de l'URSS 1: 73 - 98."]}

GENUS SPIROGAMMARUS COPILAȘ-CIOCIANU, PALATOV, MARIN & GRABOWSKI GEN.NOV. PALATOV, MARIN & GRABOWSKI GEN.NOV. Z o o B a n k r e g i s t r a t i o n: u r n: l s i d: z o o b a n k. o r g: a c t: D 5 2 6 9 6 B 2 - A E B A - 4 0 D B - A 7 C C - BF712AAD3780 Type and only species: Chaetogammarus tenellus major CărăuȘu, 1943. Diagnosis: Large Echinogammarus -like gammarid amphipods (≤ 16 mm). Body smooth and non-carinate. Head anterolateral lobe straight. Antenna 1 poorly setose, accessory flagellum well developed (up to nine articles). Antenna 2 flagellum and peduncle segments densely set with tufts of setae twice as long as the width of underlying segment (distally coiled in males), calceoli absent. Gnathopod 1 propodus subequal to gnathopod 2 propodus. Posterior margin of carpal and meral (sometimes ischial) articles of pereopod 3 set with dense and distally coiled setae as long as/longer than the width of underlying segment; pereopods 4–7 with sparse and short setae, dominated by spines. Uropod 3 exopod with dense setae as long as/longer than the width of underlying segment (coiled in males); endopod short and rudimentary; pleonites unarmed dorsally; epimeral plates with spines only (second straight; third with produced inferoposterior corner); urosomites 1–2 without elevations, armed with four dorsolateral clusters of two to four spines. Telson fully cleft, as long as broad, armed with distal and lateral spines, with lobes abruptly tapering distally. Etymology: From the Latin spira, meaning coil/ spiral, with reference to the coiled setae found on the antennae, gnathopods, pereopods and uropod 3 in males. The gender is masculine. Remarks: Spirogammarus can be distinguished readily from any species of Chaetogammarus and Echinogammarus s.l. by the presence of dense, distally coiled setae on the carpus and merus of pereopod 3 that are as long as/longer than the width of the underlying segment in both sexes. To our knowledge, no Echinogammarus -like taxa have females with coiled setae on the carpus and the merus of pereopod 3 (Pinkster, 1993). Spirogammarus is similar to Echinogammarus tibaldii Pinkster & Stock, 1970 with respect to the highly developed setosity of antenna 2, pereopod 3 and weakly setose pereopods 5–7 (Pinkster, 1993). However, Spirogammarus is distinguished by the weak setation of antenna 1 (highly developed), higher number of articles in the accessory flagellum (nine vs. five), coiled setae on gnathopod propodi and uropod 3 (non-coiled), and absence of long setae along the distal margin of epimeres. For further comparisons, see Supporting Information, Table S4., Published as part of Copilaș-Ciocianu, Denis, Palatov, Dmitry, Rewicz, Tomasz, Sands, Arthur F., Arbačiauskas, Kęstutis, Haaren, Ton Van, Hebert, Paul D. N., Grabowski, Michał & Marin, Ivan, 2023, A widespread Ponto-Caspian invader with a mistaken identity: integrative taxonomy elucidates the confusing taxonomy of Trichogammarus trichiatus (= Echinogammarus) (Crustacea: Amphipoda), pp. 821-846 in Zoological Journal of the Linnean Society 198 on pages 831-832, DOI: 10.1093/zoolinnean/zlad010, http://zenodo.org/record/8152446, {"references":["Carausu S. 1943. Amphipodes de Roumanie I. Gammarides de type Caspian. Bucharest: Institutul de Cercetari Piscicole al Romaniei.","Pinkster S. 1993. A revision of the genus Echinogammarus (Stebbing, 1899) with some notes on related genera. Memorie del Museo CiVico di Storia Naturale, (lia serie), (Sezione scienze della Vita. A, Biologia) 10: 1 - 183."]}

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. 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., Published as part of Copilaș-Ciocianu, Denis, Palatov, Dmitry, Rewicz, Tomasz, Sands, Arthur F., Arbačiauskas, Kęstutis, Haaren, Ton Van, Hebert, Paul D. N., Grabowski, Michał & Marin, Ivan, 2023, A widespread Ponto-Caspian invader with a mistaken identity: integrative taxonomy elucidates the confusing taxonomy of Trichogammarus trichiatus (= Echinogammarus) (Crustacea: Amphipoda), pp. 821-846 in Zoological Journal of the Linnean Society 198 on pages 833-834, DOI: 10.1093/zoolinnean/zlad010, http://zenodo.org/record/8152446, {"references":["Martynov AB. 1924. Etudes sur les Crustaces de Mer du Bassin du bas Don et leur distribution ethologique. Annuaire du Musee Zoologique de l'Academie des Sciences de Russie 25: 1 - 115.","Pjatakova GM. 1962. Novye formy gammarid Kaspiiskogo Morya. Doklady Akademii Nauk Azerbaidzhanskoi SSR 18: 47 - 51.","Sars GO. 1896. Les Crustacees caspiennes. Contributions pour server a la connaissance de la faune carcinologique de la mer Caspienne. Bulletin de I'Academie Imperiale des Sciences de St. - Petersbourg 4: 421 - 489.","Martynov AB. 1932. Contribution to the knowledge of the freshwater fauna of the Black Sea coast of Caucasus. I. Amphipoda. TraVaux de l'Institut Zoologique de l'Academie des Sciences de l'URSS 1: 73 - 98.","Grintsov V. 2009. A new amphipod species Echinogammarus karadagiensis sp. n. (Amphipoda, Gammaridae) from Crimean coasts (Black Sea). Vestnik Zoologii 43: e 23.","Hou Z, Sket B. 2016. A review of Gammaridae (Crustacea: Amphipoda): the family extent, its evolutionary history, and taxonomic redefinition of genera. Zoological Journal of the Linnean Society 176: 323 - 348."]}

SPIROGAMMARUS MAJOR (CĂRĂUȘU, 1943) COMB. & STAT. NOV. Chaetogammarus tenellus major CărăuȘu, 1943. Diagnosis: Same as for genus (see above). Remarks: Spirogammarus major can be distinguished from C. trichiatus (in parentheses) by: its larger size (16 vs. 12 mm; Fig. 5C), absence of setae on the basal segment of mandibular palp, subequal gnathopod propodi (propodus 2 longer than propodus 1), straight anterolateral head lobes (acutely produced; Fig. 6B), denser setation along the inner side of the gnathopod palm (Fig. 6C), urosomites armed with clusters of two to four spines (solitary spines; Fig. 6A), uropod 3 exopod with dense setation in both sexes (only males have dense setation; Fig. 6D), and uropod 3 endopod in males is armed with spines and long setae (setae absent in both sexes; Fig. 6D). Both taxa are similar with respect to the setosity of antennae (Fig. 7A, B) and pereopod 3 (Fig. 7D). Distribution: Lagoons, estuaries and lower stretches of rivers that drain along the north-western to western shore of the Black Sea. Our morphomolecular analyses confirm that S. major is a widespread invasive species in European inland waters, being widely distributed along the Danube, lower Rhine, Oder and Dnieper rivers (Fig. 4). Type locality: Lake Shabla (Shablensko Ezero), Bulgaria., Published as part of Copilaș-Ciocianu, Denis, Palatov, Dmitry, Rewicz, Tomasz, Sands, Arthur F., Arbačiauskas, Kęstutis, Haaren, Ton Van, Hebert, Paul D. N., Grabowski, Michał & Marin, Ivan, 2023, A widespread Ponto-Caspian invader with a mistaken identity: integrative taxonomy elucidates the confusing taxonomy of Trichogammarus trichiatus (= Echinogammarus) (Crustacea: Amphipoda), pp. 821-846 in Zoological Journal of the Linnean Society 198 on page 833, DOI: 10.1093/zoolinnean/zlad010, http://zenodo.org/record/8152446, {"references":["Carausu S. 1943. Amphipodes de Roumanie I. Gammarides de type Caspian. Bucharest: Institutul de Cercetari Piscicole al Romaniei."]}