Hyalella inca, Isa-Miranda, Águeda Verónica, Peralta, Marcela A., González, Juan Cruz & Nieto, Carolina, 2025

Hyalella inca sp.n.

Figs 8–13 View Fig View Fig View Fig View Fig View Fig View Fig .

Hyalella aff. puna — Hankel et al., 2023

MATERIAL EXAMINED. Holotype. Argentina: ♂, Catamarca Province, Laguna Antofagasta , – 26.1058° S – 67.42058° W, alt. 3338 m a.s.l, 13.XII.2015, J. Rodríguez leg., ( FML-CRUST 01335 ), 9.8 mm. GoogleMaps Paratypes: 1 ♀ measuring 7.35 mm, 2 ♂♂ and 1 ♀ ( FML-CRUST 01336 ); GoogleMaps 4 ♂♂ and 2 ♀♀ (IBN-EcoPP-23C); GoogleMaps same data as holotype. GoogleMaps Additional material: Argentina: 5 ♂♂ and 1 ♀, Salta Province, Aguas Calientes , – 24.39164° S – 66.56256° W, 3795 m a.s.l., 3.II.2014, GoogleMaps 3 ♂♂ and 2 ♀♀, Pastos Grandes , – 24.42852° S – 66.67161° W, 4048 m a.s.l, 3.II.2014, GoogleMaps 4 ♂ ♂ and 2 ♀♀, Catamarca Province, Laguna Antofagasta, – 26.10413889° S – 67.4185° W, 3331 m a.s.l, 14.XII.2015. J. Rodríguez leg. GoogleMaps

DIAGNOSIS. Body smooth. Palp of maxilla I asymmetrical, with right branch bearing two setae on tip vs. only one on left branch. Sternal gills present on pereonites 2 to 7. Epimeral plate 1 rounded; plates 2 and 3 acuminate. Uropod 3 elongated, peduncle longer than ramus; ramus thin, approximately twice as long as wide. Uropod 1 sexually-dimorphic, with male inner ramus displaying a distinct modified seta (‘copulatory spine’ of Bousfield, 1996).

TYPE LOCALITY AND REFERENCE SEQUENCES. Laguna Antofagasta, – 26.1058° S – 67.42058° W, 3338 m a.s.l, Catamarca Province, Argentina. GenBank accession numbers: COI: OR726344 ( Fig. 1 View Fig ) GoogleMaps .

ETYMOLOGY. The term “Inca ” in the specific epithet should be interpreted as a noun in conjunction with the generic name, in reference to the Inca Empire , which historically occupied vast areas of South America, including the highland and Puna regions.

DESCRIPTION OF MALE

Body: smooth. Maximum length observed 9.87 mm. Head: Eye ellipsoid, pigmented.

Antenna I ( Fig. 9 a, b View Fig ): shorter than antenna II but longer than its peduncle. Peduncular segments 1–3 progressively shorter, all segments with many simple and plumose setae, along with microtrichs Ib. Flagellum with eleven articles, with groups of simple setae (type A1) and some isolated plumose setae; aesthetascs ordinary occurring distally between articles 8–10.

Antenna II ( Fig. 9 c View Fig ): less than half body length. Peduncular segments 3–5 bearing groups of simple and plumose setae. Flagellum comprising 14 articles each bearing distal and subdistal simple setae of type A1.

Upper lip: Ordinary, with minute setae on the distal part ( Fig. 10 a View Fig ).

Mandible: Right mandible ( Fig. 10 b View Fig ) incisor 5-denticulate (three long, two short); lacinia mobilis complex with many denticles; setal row with 4 pappose setae; molar triturative, well developed. Left mandible ( Fig. 10 c View Fig ) incisor broadened, 5-denticulate; lacinia mobilis 4-denticulate (two long, two short); setal row with six pappose setae.

Lower lip: Ordinary, outer lobes covered with minute setae ( Fig. 10 d View Fig ).

Maxilla I: Asymmetrical. Outer plate with nine robust serrate setae F4 and setules on the inner surface. Inner plate shorter than outer one, with two apical papposerrate setae, and several marginal setules. Palp of right Maxilla I longer than wide, reaching more than half the length of the distance between the base of the palp and the apex of the outer plate, bearing two simple apical setae ( Fig. 10 e View Fig ). Palp of left maxilla shorter than right counterpart, with only one simple distal seta ( Fig. 10 f View Fig ).

Maxilla II ( Fig. 10 g View Fig ): Inner plate slightly shorter than outer plate, with 2 unequal strong pappose setae on inner margin; outer and inner plates with simple and plumose setae distally and few setules on the surface.

Maxilliped ( Fig. 10 h View Fig ): Inner plate with three apical robust cuspidate setae; distal and medial margins with plumose setae. Outer plate ovate, longer than first segment of palp; distal and medial margins with simple setae. Palp longer than plates, 4-segmented; segment 3 slender, longer than wide; segments 1–3 bearing both simple and serrated setae on medial margin and lateral margins; segment 4 unguiform, shorter than segment 3, with simple setae shorter than nail placed distally.

Gnathopod I ( Fig. 11 a View Fig ): Subchelate, coxal plate longer than wide, margin with small simple setae (type Ia). Basis hind margin with a single simple seta; basis, ischium and merus with denticles type T1 on margins. Posterior margin of basis and ischium with groups of 5 serrated setae. Carpus longer than wide, posterior pectinate lobe bordered with serrate setae. Propodus ( Fig. 11 b View Fig ) longer than broad, hammer-shaped, anterodistal margin with A1- type simple setae, inner face with 10–11 serrate setae type F3 arranged obliquely; palm margin bearing a subrectangular hump near the dactylus, lined with A1- type setae; palm angle with T1- type denticles, and two cuspidate setae with accessory seta. Dactylus with T1- type denticles. Palmar Index (sensu Ruffo [1973]) = 0.37.

Gnathopod II ( Fig. 11 c View Fig ): Subchelate. Coxal plate longer than wide. Basis, ischium and merus with groups of simple setae on posterior margin. Carpus subtriangular, notably shorter than propodus. Propodus ovate, with oblique palm; palm margin bordered with several rows of simple setae; palm angle with two cuspidate setae and T1- type denticles. Dactylus claw-like, congruent with the palm. Palmar Index (sensu Ruffo [1973]) = 0.43.

Pereiopods 3 and 4 ( Fig. 12 a, b View Fig ): Similar in size. Coxal plates: pereiopod 3 subrectangular, longer than wide; pereiopod 4 broad, excavated posteriorly, 1.2x as long as wide; both coxal plates with margins lined with thin simple setae type Ia; posterior margin of basis, ischium, merus, carpus and propodus with simple or cuspidate setae; dactylus elongated, approximately ½ length of propodus.

Pereiopods 5–7 ( Fig. 12 c–e View Fig ): Pereiopod 5 shorter than pereiopods 6 and 7, with the last two being equal in length. Coxal plate of pereiopod 5 bilobated, wider than long, with posterior lobe deeper than anterior lobe; coxa of pereiopod 6 as long as wide, with significantly reduced anterior lobe; coxa of pereiopod 7 wider than long; all coxal plates with thin simple setae along their margins (type Ia). Basis of pereiopods 5–7 expanded and finely serrated, anterior and posterior margin of ischium, merus, carpus and propodus with simple or cuspidate setae and few microtrichs type Ib. Dactylus of all limbs elongated, similar to pereiopods 3–4.

Coxal gills: Sacciform, present on gnathopod II to pereiopod 6 ( Fig. 12 a–d View Fig ). Sternal gills also sacciform but shorter, present on pereonites 2 to 7 ( Fig. 12 a View Fig ).

Pleopods: Biramous. Peduncle with pair of retinacula. Rami multiarticulate, provided with long plumose setae ( Fig. 13 a View Fig ).

Uropod 1 ( Fig. 13 b View Fig ): Peduncle longer than rami, with four dorsal cuspidate setae aligned in a longitudinal row and other three cuspidate setae on dorsolateral and dosomedial distal margin. Rami subequal in length with three dorsal cuspidate setae; inner ramus with seven distal setae, one of which notably elongated, slender and slightly curved, surpassing tip of ramus (‘copulatory spine’ sensu Bousfield [1996]); outer ramus with five distal setae, one of them larger than rest.

Uropod 2 ( Fig. 13 d View Fig ): slightly shorter than peduncle of uropod 1. Peduncle slightly longer than rami. Peduncle and both rami each with three dorsal cuspidate setae. Outer ramus with seven distal cuspidate setae, one notably longer and more robust than rest; inner ramus bearing five distal cuspidate setae, one of which longer and stronger than rest.

Uropod 3 ( Fig. 13 e View Fig ): subequal in length to peduncle of uropod 2; peduncle rectangular, wider and longer than ramus, with six robust distal setae and two additional marginal setae, all cuspidate. Outer ramus basal width nearly 2.5 times width at tip of ramus, with six to seven simple setae and one shorter cuspidate seta distally; another group of subdistal setae placed close to apex consisting of row of four long, thin simple setae (left uropod 3; Fig. 13 f View Fig ) or only one seta (right uropod 3) ( Fig. 13 e View Fig ).

Telson: subrectangular, with two widely spaced, long simple setae on distal margin (setae serrate in one of male paratypes); additionally, other two short plumose setae placed subdistally on each side (three setae in one of male paratypes) on dorsal surface of telson ( Fig. 13 g, h View Fig ).

Epimeral plates ( Fig. 13 i View Fig ): Plate 1 is rounded posterodistally; Plates 2 and 3 are acuminate posterodistally with angle strongly produced.

Intraspecific variability in males: Variations were observed, including differences in the setation of ramus of uropod 3, as outlined in the main description. Additionally, in one male an apparent notch was observed on coxa 5, and two setae were absent on the anterodistal part of the gnathopod I propodus. Some individuals exhibited 13 articles in antenna II flagellum (14 in holotype). Further variations were noted in the number and type of setae on the telson, as described in the main text.

FEMALE (PARATYPES). Maximum body length observed 7.32 mm. Female gnathopod II propodus ( Fig. 11 d View Fig ) smaller and slenderer than in male, with five serrate setae on the inner face. Oostegites subtriangular, featuring curled setae along margin ( Fig. 11 e View Fig ). Female Uropod 1 without modified seta (‘copulatory spine’) on inner ramus ( Fig. 13 c View Fig ).

TAXONOMICAL REMARKS

Hyalella oscari sp.n. was discovered in the Puna and High Andes ecoregions, specifically in Catamarca and La Rioja provinces to the east of the Andes, Argentina, at elevations ranging from approximately 3900 to 4400 m a.s.l. This species bears a close resemblance to Hyalella fatimae Isa-Miranda et Peralta, 2022 View in CoL , yet it can be primarily distinguished by distinct morphological features. Notably, H. oscari sp.n. is characterized by the morphology and chaetotaxy of maxilla I palp, particularly the presence of two plumose setae vs. only one seta present in H. fatimae View in CoL , the former being a feature unique within the genus Hyalella View in CoL . Additionally, in H. fatimae View in CoL , the antenna II extends notably longer than the head, about 25% of the body length, whereas in H. oscari sp.n., it is only slightly longer. The propod of male gnathopod I of H. oscari sp.n. has a slightly concave palm margin gradually increasing in height towards the palmar angle (vs. it is regularly convex in H. fatimae View in CoL ). The excavation of coxa 4 in H. oscari sp.n. is more pronounced than in H. fatimae View in CoL , and the former exhibits four cuspidate setae on the palm angle (vs. three in H. fatimae View in CoL ).

Hyalella oscari sp.n. also shows resemblances to H. fossamancinii Cavalieri, 1959 View in CoL , also reported in the Puna and High Andean region. However, notable differences exist, particularly in maxilla I: in H. fossamancinii View in CoL the palp is straight and bears only one simple distal seta, whereas H. oscari sp.n. features a slightly arched palp with a constriction and two plumose setae on tip. Additionally, regarding the setation on the peduncle of uropod 3, H. oscari sp.n. bears numerous fine marginal setae, which are absent in H. fossamancinii View in CoL . The shape of gnathopod I propodus male differs between the species, with H. fossamancinii View in CoL having a straight palm margin while H. oscari sp.n. exhibits a sinuous one.

Hyalella oscari sp.n. is further distinguished from both H. fatimae View in CoL and H. fossamancinii View in CoL by the presence of two short external setae on the basis of pereopod 7, a feature not observed in the other species. The only species exhibiting this trait is Hyalella gonzalezi Jaume, 2021 , endemic to Lake Titicaca, yet it differs primarily due to differences in uropod 3 setation, the distinctive maxilla I palp of H. oscari sp.n., and the longer and sharper coxa 4 in H. gonzalezi compared to H. oscari sp.n. Additionally, the body of H. gonzalezi presents a faint but distinct transverse hump along the posterodorsal margin of pereionites and pleonites, a feature not observed in H. oscari sp.n.

In molecular phylogenetic analyses, H. oscari sp.n. is genetically closely affiliated with H. armata View in CoL , H. krolli , and H. franciscae View in CoL . It is worth mentioning that H. oscari sp.n. displays a ‘smooth’ body whereas H. armata View in CoL (endemic to Lake Titicaca) exhibits extremely elongated, laterally directed spines on each of the pereiopodal coxal plates I–IV. In comparison to H. franciscae View in CoL (found in Patagonia, Chile, and southern South America), similarities were noted in the length of palp of maxilla I and setae on peduncle of uropod 3. However, distinctions arise in the length of uropod 3 ramus, a more ‘triangular’ male propod of male gnathopod II, and presence of 16 setae on the inner face of propodus of gnathopod I. In contrast to H. krolli (from Lake Titicaca), similarities were observed in the length of palp of maxilla I, but differences were evident, as H. krolli has a compact body, shorter antennae I and II, and notably elongated and narrow coxal plates.

Hyalella inca sp.n. was found in the Puna and High Andes ecoregions, precisely within the Salta and Catamarca provinces, situated to the east of the Andes, at elevations ranging from approximately 3300 to 4000 m a.s.l. This species exhibits several similarities to H. puna Peralta et Isa-Miranda 2019 View in CoL , which initially led to its designation as “ Hyalella aff. puna View in CoL ” in the study conducted by Hankel et al. [2023]. However, there are several diagnostic traits enabling the differentiation of both species. Notably, some individuals of H. puna View in CoL exhibit posterodorsal flanges on pleonites I–III, while other individuals of the same species have a smooth body. In contrast, H. inca sp.n. possesses a consistently smooth body (therefore, this feature cannot be used to distinguish these two species). Furthermore, in H. inca sp.n., the right maxilla I palp is longer than in H. puna View in CoL , and it features two simple setae at the apex, as opposed to H. puna View in CoL , which has only one. These two setae were also observed in Hyalella echinus ( Faxon, 1876) View in CoL from Lake Titicaca, although with significant differences, primarily associated with body structure, as H. echinus View in CoL has spines on each body somite. The left and right maxilla I are similar in H. puna View in CoL , while in H. inca sp.n., they are asymmetrical. Concerning the setation of male gnathopod I propodus, H. inca sp.n. features two reduced setae on dorsal margin, in contrast to H. puna View in CoL , which shows an unarmed margin.

Additionally, H. inca sp.n. has a notably larger uropod 3 ramus, with a basal width exceeding twice the height of the ramus, whereas H. puna View in CoL maintains a 1.7 ratio of base width to ramus height. Another distinguishing trait is the presence of a row of setae on the ramus of uropod 3 in H. inca sp.n., which is absent in H. puna View in CoL . H. inca sp.n. possesses also a modified seta on the inner ramus of uropod 1, not found in H. puna View in CoL . In molecular phylogenetic trees, H. inca sp.n. is closely related to H. kochi View in CoL , H. montforti View in CoL , and H. simplex View in CoL . They share the modified seta on the inner ramus of the male uropod 1. This curved seta is a diagnostic morphological character of the “curvispina View in CoL species complex” used by Bousfield [1996] to propose the subgenus Hyalella (Mesohyalella) View in CoL . The new species shares similarities with H. montforti (Lake Titicaca) View in CoL in the overall morphology of the male gnathopod II and male gnathopod I propodus. They differ primarily in the distinctive the dorso-posterior flanges on peraeon segments 7, pleonites 1, 2, and 3 of H. montforti View in CoL (compared to the smooth body of H. inca sp.n.), and the size and shape of the peduncle and ramus of uropod 3, which in H. montforti View in CoL is much smaller and stouter than in H. inca sp.n. Compared to H. simplex View in CoL (Southern Chile), there are similarities in the morphology and setation of the telson, as well as in the long palp of maxilla I. However, distinctions arise in the morphology and setation of uropod 3, and it is noteworthy that H. simplex View in CoL exhibits sternal gills on somites 3 to 7. Similarities with H. kochi View in CoL and the new species extend to the morphology of the propodus of male gnathopod I. However, notable differences are primarily observed in the reduced length of palp of maxilla I, the equal length of ramus and peduncle of uropod 3, and the presence of sternal gills on somites 3 to 7 in H. kochi View in CoL .

PHYLOGENETIC ANALYSES

Our phylogenetic analyses include a total of 36 species of both Hyaloidea (with 4 families represented) and Talitroidea (with 2 families represented) ( Table 2 View Table 2 ).

When considering South American species of Hyalella , there have been identified four clades (we maintained the same terminology for these clades as proposed previously by Adamowicz et al. [2018]). Clade A, housing H. kochi González et Watling, 2001 , H. nefrens González et Watling, 2003 , H. longipalma ( Faxon, 1876) , H. cuprea ( Faxon, 1876) , and H. hirsuta Jaume, 2021 , was strongly supported only by Bayesian inference (BI: 100) and weakly supported by maximum likelihood (ML: 79). Clade C (BI: 100, ML: 97) including H. franciscae González et Watling, 2003 , H. gonzalezi Jaume, 2021 in Jaume et al. [2021], K. krolli Jaume, 2021 in Jaume et al. [2021], H. armata ( Faxon, 1876) plus the new species H. oscari . Clade D (BI: 100, ML: 95) comprised species exclusively confined to the altiplano (Titicaca), namely H. tiwanaku González et Watling 2003 , H. longipes ( Faxon 1876) , and H. neveulemairei Chevreux 1904 . Clade E (BI: 100, ML: 98) including H. montforti Chevreux 1907 , H. simplex Schellenberg 1943 , H. kochi González et Watling 2001 , and the new species H. inca . All analyses agreed on locating the two new species within the clades C and E respectively ( Fig. 14 a, b View Fig ).