Hyalella, Smith, 1874

Isa-Miranda, Águeda Verónica, Peralta, Marcela, Martin, Juan Pablo & Torres, Santiago Hernán, 2025, Freshwater Amphipod Crustaceans of Patagonia, Argentina: Two New Species of Hyalella Smith, 1874 with an Identification Key for the Genus, Zootaxa 5637 (1), pp. 57-82 : 78-79

Key for Identification of Hyalella Species from Argentina

This identification key includes 15 species and three species complexes of Hyalella , all valid and distributed within Argentine territory. The complexes are H. curvispina , H. patagonica , and H. kochi ( Gonzalez & Watling 2003; Jurado-Rivera et al. 2020). Considering that it is likely that there are still undiscovered species of Hyalella , this key should be used with caution, and it is recommended to review the original species descriptions and diagnoses for accurate identification. Considering that many Hyalella species remain undescribed, if there is no exact match with the character states in the key, the material should be identified only to the generic level.

Fig. 14 presents diagrams of key characters used in the identification process, aiding those unfamiliar with certain morphological details of Hyalella .

1. Eyes absent or reduced.....................................................................................2

1’. Eyes present and pigmented.................................................................................3

2(1). Coxa 4 excavated posteriorly................................................ H. rionegrina Grosso & Peralta, 1999

2’. Coxa 4 not excavated.................................................... H. cuyana Peralta & Isa-Miranda, 2023

3(1). Telson margin apically acute, apical margin with only two long simple setae, closely spaced and symmetrically distributed; pereonite 7 and pleonite 1 –2 with dorsoposterior carinae...................... H. pseudoazteca González & Watling, 2003

3’. Telson rounded or truncated at the apex, not pointed; apical margin with two or more simple, cuspidate or plumose setae; body smooth..................................................................................................4

4(3). Male gnathopod 2 propodus with irregular palm margin, anterior edge with a wide truncated or rounded process.............5

4’. Male gnathopod 2 propodus with regular palm margin............................................................6

5(4). Male uropod 1 inner ramus without modified (curved) setae; uropod 3 ramus length = peduncle..................................................................................................... H. misionensis Colla & César, 2015

5’. Male uropod 1 inner ramus with modified (curved) setae; uropod 3 ramus length> peduncle..... H. pampeana Cavalieri, 1968

6(4). Male gnathopod 2 propodus triangular, palm very oblique.........................................................7

6’. Male gnathopod 2 propodus quadrate or ovoid..................................................................8

7(6). Telson width> length; male uropod 1 inner ramus with two modified (curved) setae......... H. falklandensis Bousfield, 1996

7’. Telson length> width; male uropod 1 inner ramus without modified (curved) setae....... H. neonoma Stock & Platvoet, 1991

8(6). Male uropod 1 inner ramus with modified (curved) setae..........................................................9

8’. Male uropod 1 inner ramus without modified (curved) setae......................................................10

9(8). Telson apical margin with four to seven short and fine setae.......................................................11

9’. Telson apical margin with two main setae........................ H. inca Isa-Miranda, Peralta, González & Nieto, 2025

10(8). Telson apical margin with more than ten simple slender setae.....................................................13

10’. Telson apical margin with two to four simple slender setae........................................................14

11 (9) Maxilla 1 and maxilla 2 surface with several setules................. H. bonariensis Bond-Buckup, Araujo & Santos, 2008

11´Maxilla 1 and maxilla 2 surface without several setules..........................................................12

12(11). Male uropod 1, inner ramus with one modified (curved) seta; uropod 3 ramus distally with several slender setae and one cuspidate seta; apical margin of telson truncated................................... H. kochi complex González & Watling, 2001

12´. Male uropod 1, inner ramus with two modified (curved) setae; uropod 3 ramus distally with several slender setae and two cuspidate setae; apical margin of telson rounded....................................... H. curvispina complex Shoemaker, 1942

13(10). Uropod 3 ramus distally with four to six robust setae and one slender seta; sternal gills present on segments 2–7........................................................................................... H. fossamancinii Cavalieri, 1959

13’. Uropod 3 ramus distally with at most two robust setae, the rest slender; sternal gills present on segments 3–7...............17

14(10). Male gnathopod 1 propodus hammer-shaped.................................... H. puna Peralta & Isa-Miranda, 2019

14’. Male gnathopod 1 propodus hatchet-shaped...................................................................15

15(14). Uropod 3 peduncle with cuspidate setae and in addition to another flagellate-type seta; coxa 4 dorsal surface with three thin plumose setae......................................................................... H. rioturbiensis sp. nov.

15’. Uropod 3 peduncle with only typical cuspidate setae; coxa 4 dorsal surface without any thin plumose setae................16

16(15). Maxilla 1 palp with a constriction and two setae at the apex; pereiopod 7 basis with two short setae placed subdistally on outer surface................................................... H. oscari Isa-Miranda, Peralta, González & Nieto, 2025

16’. Maxilla 1 palp without constriction, with one seta at the apex; pereiopod 7 basis without any setae on outer surface.................................................................................. H. fatimae Isa-Miranda & Peralta, 2022

17(13). Uropod 2 peduncle dorsal surface without any seta; uropod 3 peduncle apically with four cuspidate setae...................................................................................... H. patagonica complex (Cunningham, 1871)

17’. Uropod 2 peduncle dorsal surface with a long serrate seta; uropod 3 peduncle apically with seven cuspidate setae..................................................................................................... H. domuyo sp. nov.

Figures

FIGURE 14. Schematic representation of the morphological characters used in the key. A, male gnathopod 1 propodus and dactylus, hammer-shaped; B, male gnathopod 1 propodus, hatchet-shaped; C, male gnathopod 2 propodus, non-triangular; D, male gnathopod 2 propodus, triangular-shaped; E, pereiopod 4, shaded in gray: showing non-excavated coxa; F, pereiopod 4, showing excavated coxa; G, pereiopod 7, with the basis shaded in gray, arrow indicating setae placed subdistally on the outer surface; H, types of cuspidate setae; I, flagellate seta; J, cross section of thorax.