Hyalella roncador Penoni and Bueno 2025, sp. n.
Creators: name: Penoni, Ludmila Rocha
name: Bichuette, Maria Elina
name: Borges, Rayssa Karolina Ferreira
name: Bueno, Alessandra Angélica de Pádua
Publisher: name: Zenodo
Year: 2025
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Malacostraca
Amphipoda
Hyalellidae
Hyalella
Hyalella roncador

description: Hyalella roncador Penoni and Bueno sp. n.
(Figures 8–11)
Type material
Holotype male (Figure 8 (A)), body length = 8.81 mm, head length = 0.78 mm, Rio Roncador River, Parque Estadual Turístico do Alto Ribeira, Iporanga municipality, São Paulo state, Brazil (24.5308°S, 48.7017°W), MNRJcarcino 31351, February 2022, M.E. Bichuette, L.R. Penoni, T. Zepon colls.; allotype female (Figure 7 (B)), body length = 8.71 mm, head length = 0.73 mm, MNRJcarcino 31352 paratype 20+ whole individuals CCUFLA 461, one male on slide CCUFLA 459 and one female on slide CCUFLA 460 (same collection data as holotype).
h: hypothelminorheic; *: new species, under description; ª: superficial, but with ‘ troglomorphies’; Y/N/R: yes/no/reduced; bold: similar to Hyalella ceciliae sp. n.; italic: similar to H. caeca Pereira, 1989; A1/2: antenna 1/2; M1: maxilla 1; OP: outer plate; G1/2: gnathopod 1/2; CS: comb scales; PP: polygonal pattern; U1: uropod 1; BL: body length; DPC: disto-posterior corner.
Etymology
The species epithet roncador is a reference to the Roncador system, an important river of the Upper Ribeira karst area; its waters are mainly subterranean and form the Pérolas-Santana cave system.
Diagnosis
Maxilla 1 outer plate with 9 serrate setae. Gnathopod 1 of male and female identical, propodus 1.4× longer than wide, hammer shaped, coxa with 5 serrate setae on the posterior inner face, propodus with up to 9 pairs of simple setae on the posterior margin and with polygonal pattern on the disto-posterior margin. Gnathopod 2, coxa with 2 simple setae on the posterior inner face, propodus ovate, posterior margin with 5 groups of 1 to 3 simple setae and with a slender posterior excavation on the palm. Uropod 1 of the male without a curved seta on inner ramus. Uropod 3 ramus rectangular, with an excavation and up to 3 cuspidate setae midway to the apex. Telson longer than wide, apically rounded, and with 2 short cuspidate setae. Coxal gills on segments 2–6. Sternal gills on segments 2–7.
Description
Male. Mean body length 9.32 ± 0.46 mm (N = 3) (8.81–9.69 mm); mean head length 0.84 ± 0.06 mm (N = 3) (0.78–0.89 mm). Body surface smooth. Epimeral plates 2 and 3 accuminated (Figure 8 (J)). Coxae 1–3 similar, subequal in size, with some scattered microtrichs on the anterior margins on coxae 2 and 3; coxa 4 as wide as long, excavated posteriorly, with microtrichs. Eyes present, rounded and large.
Epimeron (Figure 9 (J)) 1 postero-distal margin rounded, 2 and 3 postero-distal margin acute; epimeron 2 longer than 1 and 3.
Antenna 1 (Figure 9 (A)) 0.3× the body length, 0.56× the length of antenna 2, 1.5× longer than the peduncle of antenna 2 and 0.9× the length of the flagellum of antenna 2. Flagellum with 19 to 21 articles; aesthetascs occurring distally on flagellum after article 5.
Antenna 2 (Figure 9 (B)) longer than half the body length (0.6× the body length); peduncle slender, 2.3× the length of the head; flagellum with 27 articles, 1.8× longer than the peduncle.
Mandible without palp; incisor toothed; left (Figure 9 (C)) lacinia mobilis with 6 teeth, row of setae with 3 pappose setae and a few setules, accessory seta on the molar process; right mandible (Figure 9 (D)) with 4 pappose setae and some setules; molar process cylindrical with a small accessory seta.
Upper lip (Figure 9 (E)) margin rounded; distal border covered by setules and a few scattered setules laterally. Lower lip (Figure 9 (F)) outer lobes rounded, distally notched, covered by setules apically.
Maxilla 1 (Figure 9 (G)) inner plate slender with 2 apical pappose setae and lateral setules. Outer plate with 9 serrate setae, a few setules on the inner margin, apically. Palp short, uniarticulate, longer than wide, reaching half the distance between base of the palp and base of the setae on the outer plate, with 1 long serrate seta apically.
Maxilla 2 (Figure 9 (H)) inner plate shorter than outer plate, inner plate with 1 strong pappose seta distally and some simple and papposerrate setae disto-apically, scattered setules laterally; outer plate with longer simple setae and one papposerrate seta, disto-apically, scattered setules laterally.
Maxilliped (Figure 9 (I)) without comb scales; inner plate with 3 large cuspidate distal setae apically, up to 15 pappose setae disto-apically, setules on the distal-outer margin, 4 simple setae on the outer margin; outer plate with several long simple setae with accessory seta on the inner margin, 3 simple setae on the inner face, and up to 5 simple setae on the outer margin; palp subequal to outer plate and shorter than inner plate, with 4 articles; article 1 inner margin with 2 simple setae with accessory seta and outer margin with 4 simple setae and 1 plumose seta; article 2 inner and disto-inner margins with several simple setae with accessory seta and disto-outer margin with 3 long and 2 simple setae and 1 long plumose seta; article 3 inner margin, outer and distal margins with long simple setae; article 4 (dactylus) unguiform with a short distal nail present, with up to 4 simple setae.
Gnathopod 1 (Figure 10 (A)) subchelate, identical on the male and the female; coxal plate 1.8× wider than long, with simple setae on the anterior margin, 5 serrate setae on the posterior inner face, close to the attachment of the basis; basis with posterior and disto-posterior serrate setae, posterior margin with four groups of, at maximum, 2 simple setae; ischium with 2 apical simple setae; merus with 6 papposerrate setae on distal margin; carpus longer than wide, with pappose setae on the lateral distal lobe, up to 4 papposerrate setae on inner face and up to 7 serrate setae distally; propodus 1.4× longer than wide, hammer shaped, up to 9 pairs of simple setae on the posterior margin, with polygonal pattern on the disto-posterior margin and some long and short simple setae on disto-anterior margin; palm slope transverse, with several long and short simple setae; 8 long pappose setae and some smaller ones on inner face; dactylus claw-like, small simple setae on the proximal margin, with a plumose seta distally.
Gnathopod 2 (Figure 10 (B)) subchelate; coxal plate 1.7× wider than long, with simple setae on the margin, 2 simple setae on the posterior inner face, close to the attachment of the basis, and some scattered microtrichs on the inner face; basis with 5 to 8 serrate setae on posterior margin, 1 short simple seta on anterior margin, and 3 serrate setae disto-posteriorly; ischium with 4 serrate setae disto-posteriorly; merus with up to 4 serrate setae and 3 simple setae with accessory seta on distal margin; carpus lobe slim, produced between merus and propodus, posterior margin with several pappose setae, disto-posterior corner with polygonal pattern, inner margin with some scattered simple and plumose setae, and disto-anterior margin with 4 serrate setae; propodus ovate, slope oblique, posterior margin with 5 groups of 1 to 3 simple setae, palm with a slight posterior excavation, 2 rows of short cuspidate setae with accessory setae and simple setae, anterior margin with several simple setae, inner face with a row of short simple setae; dactylus claw-like, congruent with palm, with small simple setae on the proximal margin and a plumose seta distally.
Pereopods 3–7 (Figure 10 (C–G)) simple. Coxae 3–7 with simple setae distally and microtrichs on inner face; coxa 3 similar to 1 and 2; coxa 4 as long as wide, excavated posteriorly; coxa 5 posterior lobe as long as anterior lobe; coxa 6 anterior lobe reduced; coxa 7 reduced. Pereopods 3 and 4 subequal in size, with 3 to 4 groups of 1 or 2 serrate setae on the posterior margins of their basis and on their basis and ischium disto-posterior margins, merus with 4 to 6 groups of 1 to 4 simple setae on the posterior margin, disto-anterior and disto-posterior margin with 4 to 7 serrate setae, carpus and propodus with 6 to 8 groups of up to 5 cuspidate setae with accessory seta and simple setae on the posterior margin, a plumose seta on the dactylus. Pereopod 5 is the shorter, 0.9× the length of P3 and P4 and 0.7× the length of P6 and P7, with groups of 1 to 3 cuspidate setae with accessory seta on the anterior margin of the basis and posterior margin of the merus, and groups of cuspidate setae with accessory seta and simple setae on the disto-posterior and disto-anterior margins of basis, ischium, merus, carpus and propodus, and the anterior margins of merus, carpus and propodus, a plumose seta on the dactylus. Pereopod 6 subequal in length to P7, longer than P3–P5. Pereopods 6 and 7 with 3 to 5 serrate setae on the proximo-anterior margin of basis, and 8 to 10 groups of 1 to 5 cuspidate setae with accessory seta on the anterior margins of their basis, merus, carpus and propodus and posterior margin of merus, a plumose seta on the dactylus of pereopod 6.
Pleopods (Figure 11 (A)) peduncle half the length of the rami, 2 coupling spines; both rami with several long plumose setae.
Uropod 1 (Figure 11 (B)) peduncle 1.2× longer than inner ramus and 1.4× longer than the outer ramus, with 5 cuspidate setae with accessory seta; inner ramus 1.2× longer than the outer ramus, with 2 cuspidate setae with accessory seta on dorsal margin and 6 cuspidate setae (2 longer, 2, medium and 2 shorter) apically, without curved seta; outer ramus with 3 cuspidate setae on dorsal margin and 4 cuspidate setae (2 longer, 2 shorter) apically.
Uropod 2 (Figure 11 (C)) 0.6× the total length of uropod 1, 1.2× longer than the peduncle of uropod 1, peduncle subequal in length to the inner ramus, peduncle and inner ramus 1.1× longer than the ramus, peduncle with 4 cuspidate setae with accessory seta disto-laterally; inner ramus with 3 cuspidate setae with accessory seta, each larger than the last, on dorsal margin and 6 cuspidate setae (2 longer, 2 medium with accessory seta, and 2 shorter) apically; outer ramus with 3 cuspidate setae with accessory seta on dorsal margin and 4 cuspidate setae (2 longer, 2 shorter) apically.
Uropod 3 (Figure 11 (D)) half the length of the peduncle of uropod 1 and 0.8× the length of peduncle of uropod 2, subequal to the telson; peduncle with up to 5 short cuspidate setae with accessory seta on outer distal margin; inner ramus absent; outer ramus rectangular, with 3 cuspidate setae with or without accessory seta halfway to the apex, and up to 6 cuspidate setae, with or without accessory seta, apically.
Telson (Figure 11 (E)) entire, longer than wide, apically rounded and with 2 short cuspidate setae; 3 small plumose setae on each side, symmetrically placed.
Coxal gills sac-like on pereonites 2–6. Sternal gills tubular on pereonites 2–7.
Female. (Figure 11 (F–G)) Mean body length 8.12 ± 0.88 mm (N = 3) (7.11–8.71 mm); mean head length 0.74 ± 0.11 mm (N = 3) (0.63–0.85 mm). Gnathopod 1 identical to the male. Gnathopod 2 (Figure 10 (F)) similar in size and shape to gnathopod 1; basis posterior and distal margins with 3 simple setae, ischium and merus posterior margin with simple and serrate setae; carpus with 2 pappose seta on the inner face; propodus with a row of approximately 8 simple and pappose setae on the inner margin; palm transverse, 0.6× the length of posterior margin, with a row of short simple setae and another of longer simple setae, polygonal pattern on the disto-posterior margin; dactylus claw-like with a distal plumose seta. Telson (Figure 10 (G)) identical to the male.
Habitat
Freshwater, epigean. Specimens of Hyalella roncador sp. n. were found associated to plant roots in the epigean stretches of Rio Roncador River, on the shallow and rapid waters (Figure 2 (C–D)). The abundance is high, surpassing 10 individuals.m −2. pH values varied from 6.8 to 7.4 and temperature from 18.5°C (winter season) to 21.2°C (summer season).
Conservation
We herein propose Hyalella roncador sp. n. as vulnerable (VU) based on IUCN subcategory D2 (restricted area of occurrence) (ICMBIO (Instituto Chico Mendes de ConservaÇão da Biodiversidade) 2013). It is worth mentioning that the species is possibly endemic.
Remarks
Hyalella roncador sp. n. can be easily distinguished from Hyalella ceciliae sp. n., H. caeca and all other subterranean Hyalella because it lacks the typical adaptations to life underground. Table 2 shows the morphological characteristics of superficial (ie nonsubterrenean) Hyalella species that occur in Brazil with some morphological similarities to Hyalella roncador sp. n. There are two characteristics easily used to group Hyalella and, hence, differentiate species: the presence/absence of a curved seta on the inner ramus of male’s uropod 1; and the presence/absence/position of flanges (a dorsoposterior carina on the thoracic and abdominal plates). Hyalella roncador sp. n. has neither a curved seta, which differentiates it from 21 Brazilian species, nor flanges, which differentiate it from the single other species from Brazil. Details of the remaining nine species can be found in Table 2, in comparison to Hyalella roncador sp. n.
description: Published as part of Penoni, Ludmila Rocha, Bichuette, Maria Elina, Borges, Rayssa Karolina Ferreira & Bueno, Alessandra Angélica de Pádua, 2025, New species of Hyalella Smith (Crustacea: Amphipoda: Hyalellidae): a contribution to the knowledge of a widely distributed genus in the Upper Ribeira karst, with redescription of the rare and endangered Hyalella caeca Pereira, pp. 195-226 in Journal of Natural History 59 (1 - 4) on pages 207-215, DOI: 10.1080/00222933.2024.2448565, http://zenodo.org/record/14764987