Hyalella ceciliae 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 ceciliae

description: Hyalella ceciliae Penoni and Bueno sp. n.
(Figures 3–6)
Type material
Holotype male (Figure 3 (A)), body length = 6.44 mm, head length = 0.53 mm, preserved in permanent slides (with Canada Balsam as the medium), Santana Cave, Parque Estadual Turístico do Alto Ribeira, Iporanga municipality, São Paulo state, Brazil (24.5308°S, 48.7017°W), MNRJcarcino 31349 November 2017, M.E. Bichuette, coll; allotype female (Figure 3 (B)), body length = 5.06 mm, head length = 0.5 mm, MNRJcarcino 31350 February 2022, M.E. Bichuette, L.R. Penoni, T. Zepon, colls.; paratype, one male on slide CCUFLA 457 and one female on slide CCUFLA 458 (same collection data as allotype).
Etymology
The species epithet ceciliae is in honour of Cecília Torres (in memoriam), a Brazilian speleologist who dedicated her life to the study of caves and their fauna, mainly in the Ribeira Valley, a pioneer in these studies. Cecília was part of many expeditions on which several species were discovered.
Diagnosis
Maxilla 1 palp longer than wide, shorter than half the distance between the base of the palp and the base of setae on outer plate; outer plate with 8 serrate setae. Maxilliped heavily setose on the inner margin of palp and of outer ramus. Gnathopod 1 of male and female identical, propodus 1.3× longer than wide, hammer shaped, inner face with a row of 7 papposerrate setae, with comb scales on the merus. Gnathopod 2 propodus ovate, palm subequal to posterior margin of propodus, slope oblique. Uropod 1 of the male without a curved seta on inner ramus. Uropod 3 longer than the telson, peduncle wider and shorter than the ramus. Telson almost square, no observed setae apically, 2 small plumose setae on each side, placed symmetrically. Coxal gills on segments 2–6. Sternal gills on segments 2–7.
Description
Male. Mean body length 5.87 ± 0.81 mm (N = 2) (5.29–6.44 mm); mean head length 0.48 ± 0.07 mm (N = 2) (0.43–0.53 mm). Body surface smooth. Epimeral plates 2 and 3 accuminated (Figure 4 (J)). Coxae 1–3 similar, subequal in size, with some scattered microtrichs; coxa 4 as wide as long, excavated posteriorly. Eyes absent.
Epimeron (Figure 4 (J)) 2 and 3 postero-distal margin acute; first and third epimeron shorter than the second one.
Antenna 1 (Figure 4 (A)) almost half the body length (0.4×), 0.8× shorter than antenna 2, 2.3× longer than the peduncle of antenna 2 and 1.2× longer than the flagellum of antenna 2. Peduncle articles 1–3 relative lengths 1:0.82:0.76; flagellum with 13 articles; aesthetascs occurring distally on flagellum after article 6.
Antenna 2 (Figure 4 (B)) 1.1× longer than half the body length; peduncle slender, double the length of the head; flagellum with 17 articles, 1.9× longer than the peduncle.
Mandible without palp; incisor toothed; left (Figure 4 (C)) lacinia mobilis with 4 teeth, setae row with 4 pappose setae and a few setules, no observed accessory seta on the molar process; right mandible (Figure 4 (D)) with 4 pappose setae and some setules; molar process cylindrical with an accessory seta.
Upper lip (Figure 4 (E)) margin rounded; distal border covered by setules. Lower lip (Figure 4 (F)) outer lobes rounded, distally notched, covered by setules apically.
Maxilla 1 (Figure 4 (G)) inner plate slender, with 2 apical pappose setae and lateral setules. Outer plate with 8 serrate setae, and a few setules on the inner margin, apically. Palp short, uniarticulate, longer than wide, reaching less than half the distance between base of the palp and base of the setae on the outer plate, with no apparent seta distally, only some short setules on the outer margin.
Maxilla 2 (Figure 4 (H)) inner plate shorter than outer plate, inner plate with 2 strong pappose setae distally and some simple setae disto-apically, and setules laterally; outer plate with longer simple setae and some papposerrate setae, disto-apically, and setules laterally.
Maxilliped (Figure 4 (I)) without comb scales; inner plate with 3 cuspidate distal setae apically, a few pappose setae disto-apically, 3 simple setae on the ventral margin, setules on the distal-outer margin and 2 simple setae on the outer margin; outer plate with several long simple setae on the inner margin and 2 smaller simple setae on the outer margin; palp longer than inner and outer plates, with 4 articles; article 1 inner margin with up to 4 long simple setae and outer margin with 1 simple seta; article 2 inner margin with several long simple setae and outer margin with 2 simple setae; article 3 inner margin with simple and papposerrate setae, and outer and distal margins with long simple setae; article 4 (dactylus) unguiform with distal nail present, with up to 6 simple setae, shorter than nail.
Gnathopod 1 (Figure 5 (A)) subchelate, identical on the male and the female; coxal plate 1.7× wider than long, with simple setae on the margin and a microtrich on the internal margin; basis with 5 posterior and disto-posterior simple setae, with or without accessory seta; ischium with 1 apical simple seta; merus with serrate, papposerrate and simple seta on distal margin, and a slender row of comb scales distally; carpus longer than wide, with pappose setae on the lateral distal lobe, up to 5 pappose setae on inner margin and some simple or serrate setae distally; propodus 1.3× longer than wide, hammer shaped, 2 long simple setae with accessory seta on disto-posterior margin, some long and short simple setae on disto-anterior margin with no comb scale present; palm slope transverse, with up to 10 long simple setae and 5 short simple setae; up to 6 pappose setae on inner face; dactylus claw-like, with a plumose seta distally.
Gnathopod 2 (Figure 5 (B)) subchelate, without comb scales or polygonal pattern; coxal plate 1.6× wider than long, with simple setae on the margin and some scattered microtrichs on the inner margin; basis with 5 long simple setae with accessory seta on posterior margin, 1 short simple seta on anterior margin, and up to 2 simple setae disto-posteriorly; ischium with 2 simple setae disto-posteriorly; merus with up to 6 serrate setae on distal margin; carpus lobe slim, produced between merus and propodus, posterior margin with pappose setae, inner margin with 2 small pappose setae and disto-anterior margin with 2 long serrate setae; propodus ovate, palm and posterior margin subequal in length, slope oblique, posterior margin with 2 simple setae, palm with a slight posterior excavation, some short cuspidate setae with accessory setae and some simple setae, anterior margin with a few simple setae; dactylus claw-like, congruent with palm and with 1 plumose seta distally.
Pereopods 3–7 (Figure 5 (C–G)) simple. Coxae 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 longer than anterior lobe; coxa 6 anterior lobe reduced; coxa 7 reduced. Pereopods 3 and 4 subequal in size, with 2 to 3 groups of 1 or 2 setae on the posterior margins of their basis, merus, carpus and propodus, with a plumose seta on the dactylus. Pereopod 5 1.1× longer than P3 and P4, with groups of 1 to 2 cuspidate setae with accessory seta on the anterior margins of the basis, merus, carpus and propodus. Pereopod 6 1.3× longer than P5 and 0.9× the length of P7. Pereopods 6 and 7 with groups of 1 to 3 simple and/or cuspidate setae with accessory seta on the anterior margins of their basis, merus, carpus and propodus, with a plumose seta on the dactylus.
Pleopods (Figure 6 (A)) peduncle 0.7× the length of the rami, no coupling spines observed, both rami with several long plumose setae.
Uropod 1 (Figure 6 (B)) peduncle 1.1× longer than inner ramus and 1.2× longer than the outer ramus, with 5 cuspidate setae with accessory seta and 2 short simple setae; inner ramus subequal in size to outer ramus, slightly longer, with 3 cuspidate setae with accessory seta on dorsal margin and 5 cuspidate setae (2 longer, 2 medium length, 1 shorter) apically, without curved seta; outer ramus with 3 cuspidate setae with accessory seta on dorsal margin and 4 cuspidate setae (1 longer, 3 shorter) apically.
Uropod 2 (Figure 6 (C)) 0.6× the total length of uropod 1, peduncle 0.7× the length of inner ramus, subequal to outer ramus, with 4 cuspidate setae with accessory seta and 1 short simple seta; inner ramus 1.3× longer than outer ramus, with 2 cuspidate setae with accessory seta on dorsal margin and 5 cuspidate setae (2 longer, 1 shorter) apically; outer ramus with 3 cuspidate setae with accessory seta on dorsal margin and 4 cuspidate setae (3 longer, 1 shorter) apically.
Uropod 3 (Figure 6 (D)) half the length of the peduncle of uropod 1 and subequal to the peduncle of uropod 2, 1.2× longer than the telson; peduncle with 2 cuspidate setae on outer distal margin; inner ramus absent; outer ramus subtriangular, longer than peduncle, with 3 cuspidate setae apically, 1 shorter.
Telson (Figure 6 (E)) entire, as long as wide, apically rounded and with no apparent setae; 2 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 6 (F–G)) Mean body length 5.54 ± 0.67 mm (N = 2) (5.06–6.01 mm); mean head length 0.49 ± 0.01 mm (N = 2) (0.49–0.5 mm). Gnathopod 1 identical to that of male. Gnathopod 2 (Figure 6 (F)) similar in size and shape to Gnathopod 1; merus with 6 long papposerrate setae; carpus with 2 pappose seta on the inner face; propodus elongated, with several long simple setae on the inner face and short simple setae on the palm; palm transverse; dactylus claw-like with a distal plumose seta. Telson (Figure 6 (G)) similar to the male, but with an observed cuspidate seta apically, and 3 small plumose setae laterally on each side, symmetrically placed.
Habitat
Freshwater, hypogean, troglobite, stygobite. A very few specimens (3–5 individuals) of Hyalella ceciliae sp. n. were found swimming freely or burying themselves on the sandy bottom of the lentic pools of Santana Cave, and were found always in the same locale, close to the touristic passage (Figure 2). pH values varied from 7.4 to 8.1 and temperature from 18.8°C (winter season) to 20.2°C (summer season).
Conservation
We herein propose Hyalella ceciliae sp. n. as endangered (EN) based on the International Union for Conservation of Nature (IUCN) subcategories B1 (<5.000 km 2 in area of occurrence extension) and D1 (<250 mature individuals) (ICMBIO, 2013).
Remarks
Hyalella ceciliae sp. n. is hypogean, with two important specialisations for subterranean life: the absence of eyes and loss of pigmentation (see Figure 7, live specimen in the natural habitat). These features can be used to differentiate it from most of the known Hyalella species. It is similar, however, to other cave species from Brazil that are also blind and unpigmented, namely: H. caeca, H. epikarstica Rodrigues, Bueno and Ferreira, 2014 and H. formosa Cardoso and Araujo, 2014 (Cardoso et al. 2014). Table 1 presents morphological characteristics of the subterranean and troglomorphic Hyalella species that occur in Brazil. There are also H. veredae Cardoso and Bueno, 2014 (Araújo et al. 2014) and H. speleae Bueno and Cardoso, 2011 (Cardoso et al. 2011), but the eyes can be present, reduced or absent in these populations; and the hypothelimnorheic Hyalella imbya Rodrigues and Bueno in Rodrigues et al. (2012) Hyalella ceciliae sp. n. can be set apart from H. formosa and H. epikarstica because the new species has antenna 1 longer than antenna 2, while for the other two species it is the opposite. There are several differences between Hyalella ceciliae sp. n. and H. caeca, which will be detailed later in this paper.
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 200-206, DOI: 10.1080/00222933.2024.2448565, http://zenodo.org/record/14764987