Freshwater Amphipod Crustaceans of Patagonia, Argentina: Two New Species of Hyalella Smith, 1874 with an Identification Key for the Genus

Abstract

The genus Hyalella (Amphipoda, Hyalellidae) includes over 100 species, exclusively inhabiting freshwater ecosystemsacross South, Central, and North America. In southern South America, pristine natural environments are rapidly decliningdue to the exploitation of natural resources and changes in land use. These activities exert significant pressure on aquaticecosystems, degrading water quality. Within these ecosystems, the macroinvertebrate fauna, particularly the diversity ofHyalella, remains understudied and highly vulnerable. This paper describes two new species from hydrographic basinsnear glaciers in western Patagonia, Argentina, specifically in the provinces of Santa Cruz and Neuquén, south of 36º Slatitude. Both species belong to the ‘patagonica complex’, named after Hyalella patagonica. They share key characteristicssuch as a long palp on maxilla 1, a hatchet-shaped propodus on male gnathopod 1, a male inner ramus of uropod 1 withoutsexual setae, uropod 2 with a long fine seta on the peduncle, epimeral plate 1 rounded and plates 2–3 slightly acuminateposterodistally, and sternal gills on pereonites 3–7. Hyalella domuyo sp. nov. is distinguished by its antenna 2 being muchlonger than antenna 1, a slight constriction on the palp of maxilla 1, pereopod 4 coxa bearing a thin serrate seta in theposterior cavity, pereopod 7 basis with three short subdistal setae on the outer surface, and telson with 13 thin setae onthe apical margin. Hyalella rioturbiensis sp. nov. differs from other species in the ‘patagonica complex’ by its uniquecombination of characters, including a row of plumose setae on the peduncular segment 4 of antenna 2, more than 12serrate setae on the inner face of the male propodus of gnathopod 1, tiny plumose setae on the dorsal surface of coxa 4,uropod 3 peduncle bearing three strong setae, one being flagellate-type, uropod 2 peduncle slightly shorter than the outerramus, and a telson apex with three main setae. Comments on the distribution of these new species are provided. With theaddition of these species, the known number of Hyalella species from Argentina and the Falkland Islands (Islas Malvinas)rises to 18, including three species complexes: H. curvispina, H. patagonica, and H. kochi. A key to the Hyalella speciesof Argentina is also presented.