Hyalella bocaina, Bichuette, 2025

Bichuette, Alessandra Angélica de Pádua Bueno Carolina Mendes Deotti Ludmila Rocha Penoni Maria Elina, 2025, Expanding the knowledge of Hyalella Smith, 1874 (Amphipoda: Hyalellidae) for southeast Brazil: two new troglophilic species from caves of the Atlantic Rainforest, Nauplius (e 20250478) 33, pp. 1-27 : 4-12

publication ID	https://doi.org/10.1590/2358-2936e20250478
publication LSID	lsid:zoobank.org:pub:B768EB87-0EE4-4AEC-82F5-838040380786ABSTRACT
persistent identifier	https://treatment.plazi.org/id/03A16507-FFBC-384F-5764-FCA2DC3743BF
treatment provided by	Felipe
scientific name	Hyalella bocaina
status	sp. nov.

Treatment

Hyalella bocaina View in CoL sp. nov.

Deotti, Penoni and Bueno

( Fig. 2–8 View Figure 2 View Figure 3 View Figure 4 View Figure 5 View Figure 6 View Figure 7 View Figure 8 )

Zoobank: urn:lsid:zoobank.org:act:174DC621-15A2-41DE-AC97-EF20266B2257

Typematerial. Holotype: adult male, (body length [L] 10.29 mm; head length [HL] 0.69 mm), MZUSP 45191 View Materials , Brazil, state of São Paulo, municipality of R ibeirão Grande, Parque Estadual Intervales (24°16’18.42”S 048°25’29.3”W), March 2000, P.C. Bispo coll. GoogleMaps — Paratypes: 1 adult female (L 9.8 mm; HL 0.50 mm), MZUSP 45192 View Materials ; 31 whole individuals and 3 males and females on slides CCUFLA 453 (same collection data as the holotype) GoogleMaps ; 1 male on slides, CCUFLA 454; Brazil, state of São Paulo state, municipality of Iporanga, Parque Estadual Intervales, Gruta do Minotauro cave entrance (24°16’34.7”S 48°27’22.7”W), October 2009, M.E. Bichuette; T. L.C. Scatolini; A. Pereira and D. Monteiro-Neto colls GoogleMaps .

Diagnosis. Body surface smooth. Eyes round, pigmented. Epimeron 1 and 3 postero-distal margin acute (acute angle). Antenna 2 not half the body length. Maxilla 1 palp longer than wide, reaching almost half of distance between base of palp and base of setae on outer plate. Gnathopod 1 propodus inner face with 10 serrate setae, anterior and posterior margins with comb-scales. Pleopods with 2 coupling spines and several setules present on margins. Uropod 3 shorter than telson, peduncle longer than ramus, with 6 cuspidate setae with accessory seta and ramus with distal cuspidate seta with accessory seta and some simple setae. Telson with 2 to 4 apical simple and symmetrical setae, with 3 simple setae on both sides, laterally. Coxal gills sac-like and present on segments 2 to 6. Sternal gills present on segments 3 to 7.

Description of male ( Fig.2A View Figure 2 ). Mean body length: 8.7 ± 1.3 mm (N = 7); mean head length: 0.68 mm ± 0.16 mm (N = 7). Body surface smooth. Epimeral plates 2–3 accuminate ( Fig.4B View Figure 4 ). Coxae 1–4 subequal in size and shape, slightly overlapping. Coxa1 similar to 2 and 3.Coxa 4longer than wide, excavated posteriorly.Coxa 5 posterior lobe narrower than anterior lobe. Coxa 6 and 7 longer than wide. Eyes round and pigmented.

Antenna 1 ( Fig. 3A View Figure 3 ) about 3.8× smaller than body length,1.4 × smaller than antenna 2, 1.6× longer than peduncle of antenna 2; peduncle 1.4 × longer than head; article 1 1.2 ×longer than 2, article 3 1.1× shorter than 1 and 1 × shorter than article 2; flagellum with 14 articles, 1.7 × longer than peduncle; aesthetascs ( Fig. 3A View Figure 3 , highlighted) occurring on flagellum from article 3 distally.

Antenna 2( Fig.3B View Figure 3 ) 2.6 × smaller than body length; peduncle slender, 2.2 × longer than head; article 4 with similar size than article 5; flagellum with 17 articles, 1.4 × longer than peduncle.

Mandiblewithoutpalp;incisortoothed;left( Fig.3C View Figure 3 ) mandible with 5 teeth and setal row with 5 pappose setae and some setules on apical margin, lacinia mobilis with 3 teeth, molar process with accessory seta; right mandible ( Fig. 3D View Figure 3 ) with abundant setules on apical margin, setal row with 3 pappose setae;broad and cylindrical molar process with accessory seta.

Upper lip ( Fig. 3E View Figure 3 ) margin rounded; distal border covered by setules on ventral and dorsal face. Lower lip ( Fig. 3F View Figure 3 ) outer lobes rounded and distally notched, with several setules on dorsal and ventral face.

Maxilla 1 ( Fig. 3G View Figure 3 ) inner plate slender, with 2 pappose setae and several setules distally. Outer plate with 9 papposerrate setae apically. Palp short, uniarticulate, longer than wide, reaching almost half of distance between base of palp and base of seta on outer plate, with distal short seta and some setules on margin.

Maxilla 2 ( Fig. 3H View Figure 3 ) inner plate subequal to outer plate, inner plate with 1 papposerrate seta, 6 pappose setae and several simple distal setae; outer plate with 3 pappose setae and several simple distal setae; inner and outer plates covered by several setules.

Maxilliped ( Fig. 4A View Figure 4 ) inner plate with 3 cuspidate distal setae and several pappose setae, without comb-scales; outer plate 1.4 × smaller than inner plate, with several simple setae, without comb-scales; palp longer than outer plate and subequal to inner plate, with 4 articles, covered with several simple long setae on the inner margin; article 1 outer margin with few simple setae; article 2 outer margin with few long simple setae; article 3 outer margin with few long pappose setae, without comb-scales; article 4 (dactylus) unguiform, 2.2 × shorter than third article, with some pappose setae, shorter than nail, without comb-scales, and distal nail present. Variation: one specimen was also found with 7 cuspidate distal setae and several pappose setae on inner plate; outer plate with several simple and few pappose setae; article 2 of palp with some serrate setae apically on outer margin; article 4 (dactylus) with serrate setae instead of pappose.

Gnathopod 1 ( Fig. 5A View Figure 5 ) subchelate; coxal plate 1.8 × wider than longer, with several short simple setae on margin; basis and ischium with dorsal and apical serrate setae and comb-scales on posterior margin of ischium; merus with some pappose setae on distal margin and polygonal pattern present; carpus 1.8 × longer than wide, 1.3 × longer than propodus, with lateral distal lobe produced, with 5 serrate setae, without comb-scales; posterior lobe, with polygonal pattern and pectinate border expressed, without comb-scales and with several serrate setae on margin and 4 pappose setae on inner face; propodus 1.4 × longer than wide, hammer-shaped, with several simple long setae on disto-anterior margin and polygonal pattern present, inner face with 10 serrate setae, with few simple setae and comb-scales absent; palm slope transverse, with row of many simple setae, posterior distal corner with 1long and strong cuspidate seta with accessory seta, polygonal pattern present, and comb-scales absent; dactylus claw-like, polygonal pattern present on disto-anterior margin, terminal simple setae and polygonal pattern present on proximal margin, with 1 plumose seta dorsally.

Gnathopod 2 ( Fig. 5B View Figure 5 ) subchelate; coxal plate 1.8 × wider than long, with simple setae on margin; basis and ischium with several serrate setae and polygonal pattern on posterior margin of ischium; merus with few serrate setae on posterior margin and polygonal pattern; carpus 3.6 × wider than long, posterior lobe slim produced between merus and propodus, forming scoop-like structure, margin with several pappose setae, polygonal pattern, pectinate border and serrate setae on lateral distal lobe, without comb-scales; propodus ovate, 1.4 × longer than wide, comb-scales absent; palm shorter than posterior margin of propodus, slope transverse, margin with 1 row of several cuspidate setae with accessory seta and simple setae, posterior distal corner with 2 long and strong cuspidate setae and with cup for dactylus, polygonal pattern present; dactylus claw-like, congruent with palm, plumose seta dorsally, and terminal simple setae and polygonal pattern present on the proximal and disto-anterior margin.

Pereopods 3 to 7 ( Fig. 6A–E View Figure 6 ) simple. Pereopods 3 and 4 merus and carpus posterior margin with several serrate and simple setae and some simple with accessory seta in carpus; propodus posterior margin of pereopod 3 and 4 with some simple setae and several cuspidate with accessory seta; dactylus 3.6 × and 4.1 × shorter than propodus, respectively, with plumose seta dorsally. Pereopods 5 to 7 merus, carpus and propodus posterior margin with several cuspidate setae some of them with accessory seta and few simple setae, dactylus 4.0 ×, 3.9 ×, and 4.3× shorter than propodus, respectively, with plumose seta dorsally. Pereopod 3 and pereopod 5 similar in size; pereopod 4 smaller than others; pereopod 6 longer than pereopod 7.

Pleopods ( Fig. 7A View Figure 7 ) peduncle 3.3 × longer than wide, 1.7 × mean size of rami, with 2 coupling spines and several setules present on margins; both rami with several plumose setae.

Uropod 1( Fig.7B View Figure 7 ) peduncle3.1 × longer than outer ramus and subequal to inner ramus, with 4 cuspidate setae with accessory seta and 1 simple seta; inner ramus slightly longer than outer ramus, with 3 dorsal cuspidate setae with accessory seta on margin and 7 cuspidate setae with accessory seta apically, without curved seta;outer ramus with 5 dorsal cuspidate setae with accessory seta on the margin and 3 cuspidate setae with accessory seta apically.

Uropod 2 ( Fig. 7C View Figure 7 ) 1.4 × shorter than uropod 1, peduncle longer than inner ramus, with 4 cuspidate setae with accessory seta; inner ramus with 4 dorsal cuspidate setae and 6 cuspidate setae apically, all with accessory seta; outer ramus with 4 dorsal cuspidate setae and 4 apical cuspidate setae, all with accessory seta.

Uropod 3 ( Fig. 7D View Figure 7 ) 0.7 × shorter than peduncle of uropod 1 and 0.6 × than peduncle of uropod 2; 1.1 × shorter than telson; peduncle with 6 cuspidate setae with accessory seta; inner ramus absent; outer ramus uniarticulate, subequal to peduncle, with one cuspidate with accessory seta and some simple setae.

Telson ( Fig. 7E View Figure 7 ) entire, 1.1 × longer than wide, apically rounded, with 2 to 4 apical simple setae, symmetrically, with 3 simple setae laterally on both sides.Variations:3 plumose setae laterally on each side.

Epimeron ( Fig. 4B View Figure 4 ) 2 and 3 postero-distal margin acute. Coxal gills sac-like and present on pereonites 2 to 7. Sternal gills tubular and present on pereonites 3 to 7.

Description of female. ( Fig. 2A View Figure 2 ) Mean body length: 8.3 ± 1.1 mm (N = 7); mean head length: 0.68 ± 0.07 mm (N = 7).

Gnathopod 1 ( Fig. 8A View Figure 8 ) similar to male gnathopod 1 in size and shape; ischium with polygonal pattern; carpus 2.2 longer than wide, without polygonal pattern and comb-scales, with pectinate border and some serrate and simple setae; propodus 1.7 × longer than wide, disto-anterior margin with few simple setae and polygonal pattern present, inner face with 10 serrate setae; palm transverse with several long simple setae, posterior distal corner with 2 long and strong cuspidate setae with accessory seta, without comb-scales and polygonal pattern; dactylus claw-like, with polygonal pattern on disto-anterior margin, with 1 plumose seta dorsally and terminal simple setae on proximal margin.

Gnathopod 2 ( Fig.8B View Figure 8 ) similar in size and shape to gnathopod 1; ischium and merus with comb scales; carpus 2.3 × longer than wide, without comb-scales, posterior lobe produced and forming scoop-like structure, without pectinate margin and polygonal pattern, with several serrate setae and 2 long serrate setae on inner face; propodus 2.3 × longer than wide, hammer-shaped, inner face with some pappose setae; palm 1.1 × shorter than posterior margin of propodus, without polygonal pattern, inner margin with few simple setae, palm slope transverse, posterior distal corner with 2 long and strong cuspidate seta with accessory seta and comb-scales present; dactylus claw-like, with comb-scales on disto-anterior margin, with 1 plumose seta dorsally and terminal simple setae on proximal margin.

Telson( Fig. 8C View Figure 8 ) 1.1 × longer than wide, similar in shape to male, with 2 to 4 simple apical setae and 1 to 3 plumose setae on each side of margin.

Etymology. The epithet bocaina is a recognition of the river where the two populations of this new species are found.

Habitat. Freshwater, troglophilic. The species is categorized as troglophilic because it has wellestablished subterranean and epigean (surface) populations. They are sometimes also called facultative cave-dwellers. Specimens of H. bocaina sp. nov. were collected at two different sites, including the rapids of the Roda d’Água tourist route and at the cave entrance zone of the Gruta do Minotauro. The surrounding forest is well preserved.The rapids of PEI present an irregular flow, allowing their interaction with the substrate and, thus, the formation of microcurrents with different speeds. In addition, from this interaction, microhabitats are formed between the rocks, allowing the accumulation of sand and leaves ( de Paula Paciência, 2011).

Remarks. Among all Hyalella species that occur in Brazil, H. bocaina sp. nov. is distinguished from the other 26 species by the absence of a curved seta on the inner ramus of uropod 1 of the male. Table 1 presents the main morphological differences between H. bocaina sp. nov. and the other Hyalella species from Brazil. We highlight that H. bocaina sp. nov., differs from H. caeca , H. spelaea and Hyalella troglofugia Bastos-Pereira, Oliveira and Ferreira, 2018 , for being epigean, with no evident troglomorphic features; also, H. bocaina sp. nov. presents a pectinate border expressed on the carpus of the female and male gnathopod 1, which is different from Hyalella montana Rodrigues, Senna, Quadra and Bueno, 2017 ; there are no flanges — or dorsal carina — in the new species, different from Hyalella pseudoazteca González and Watling, 2003b ; and H. bocaina sp. nov. has antenna 2 shorter than half the body length, which is different from Hyalella longipropodus Limberger, Graichen and Castiglioni, 2021 .