Descrição de três novas espécies de Hyalella (Crustacea, Amphipoda, Hyalellidae) da região noroeste do estado do Rio Grande do Sul, Brasil

Abstract

Currently there are 68 species of Hyalella gender described, whereas in South America, the largest diversity of species is observed, 52 record species. The State of Rio Grande do Sul has nine species of this gender recorded. Through an extensive sampling period, the current study objectives to described three new species of Hyalella observed at the Northwest Region of Rio Grande do Sul State, South region of Brazil. The specimens were sampled at a small spring, an artificial pond and a natural pond, in the municipality of Palmeira das Missões. The three species have a curved seta on the inner ramus of uropod 1 and an accessory seta for the males. Hyalella sp. nov. 1 has dactylus of gnathopod 2 shorter than the propodus palm, showing simple apical setae on outer ramus of uropod 3, in addition of having 9 serrate setae inner face of propodus of gnathopod 1 and a peculiar pattern of setae on peduncle of uropod 3 ramus. This species differs from H. montenegrinae and H. carstica by showing sternal gills on segments 2 to 7 and more than two apical setae on telson. The Hyalella sp. nov. 2 resembles the species H. bonariensis, H. castroi, H. curvispina, H. kaigang, H. pampeana e H. pleoacuta by having gills on sternum of segments 2 to 7. This specie differs from H. pleoacuta, H. kaingang and H. pseudoazteca by lacking dorsal flanges on pereions and pleonites. Finally, Hyalella sp. nov. 3 differs from others species found in the State of Rio Grande do Sul (H. bonariensis, H. castroi, H. kaigang, H. imbya, H. montenegrinae and H. pampeana) in type and number of setae on uropods, telson and inner face of gnathopod 1. Despite the resemblance with H. curvispina, Hyalella sp. nov. 3 has only two simple setae on telson, inner face of gnathopod 1 with five serrate setae and denticles in comb-scales only at the posterior distal margin, and also has sternal gills on segments 3 to 7. After this study, the number of Hyalella species found in Brazil raises to 26 and to 71 worldwide for the gender.