Hyalella montana, Rodrigues & Senna & Quadra & Bueno, 2017

Rodrigues, Stella Gomes, Senna, André R., Quadra, Adriana & Bueno, Alessandra Angélica De Pádua, 2017, A new species of Hyalella (Crustacea: Amphipoda: Hyalellidae) from Itatiaia National Park, Brazil: an epigean freshwater amphipod with troglobiotic traits at 2,200 meters of altitude, Zootaxa 4344 (1), pp. 147-159 : 149-157

Hyalella montana n. sp. Rodrigues, S.G., Senna, A.R., Quadra, A. & Bueno, A.A.P.

( Figs 2–6 )

Material examined: Holotype male, body length = 5.7 mm, head length = 0.5 mm, Brazil, Itatiaia National Park (22°22′13,3″S – 44°42′32,6″W), Minas Gerais state, Itamonte municipality, small stream next to the Alsene river (pH: 7.5; water temperature: 9.7 °C), 30.XI.2012, coll. A. Quadra, R. Figueiró and A.R. Senna, CRFFP 86. Paratypes (same collection data of the holotype): 1 male (dissected and draw), CRFFP 87; 1 female (dissected and draw), CRFFP 88; 55 males and 44 females, CRFFP 89.

Type locality. Brazil, Minas Gerais state: Itatiaia National Park (22°22′13,3″S 44°42′32,6″W), near to the antique Alsene Hotel, Minas Gerais state, Itamonte municipality, small stream next to the Alsene river, 2,217 meters of altitude.

Diagnosis. Body surface smooth. Eyes round, pigmented (few individuals present reduced eyes or absent eyes). Rostrum absent. Antenna 1 shorter than antenna 2, flagellum with 9 articles. Antenna 2 less than half body length, flagellum with 7 articles. Maxilla 2 inner plate with only one long and strong papposerrate apical seta. Maxilliped with palp smaller than inner plate and as the same size as outer plate. Gnathopod 1 propodus width about 1/2 of maximum length, hammer-shaped, comb-scales absent, inner face with 7 serrate setae. Gnathopod 2 carpus wider than long, posterior lobe border with denticles and polygonal patterns; propodus ovate, length 1.3 maximum width, comb-scales absent; palm sub-equal to posterior margin of propodus, slope oblique. Peraeopod 6 and 7 longer than others. Uropod 1 peduncle longer 1.5X than rami, male without curved seta on inner ramus. Uropod 3 shorter than telson, than peduncle of uropod 1 and peduncle of uropod 2; peduncle with five long cuspidate seta; ramus shorter than peduncle. Telson as long as wide, without apical setae, but with pin-shaped setae laterally. Coxal gills sac-like on pereonites 2 to 6 and sternal gills tubular on pereonites 3 to 7.

Description of male. Mean body length: 6.1 ± 0.4 mm, mean head length: 0.52 mm ± 0.08 mm (n=4). Body surface smooth; epimeral plates slightly acuminate.

Head 1.7X longer than first pereon segment, rostrum absent. Eyes round, pigmented, however, few individuals present reduced eyes or absent eyes.

Antenna 1 shorter than antenna 2, shorter than half body length; peduncle slightly shorter than head length; flagellum with 9 articles, longer than peduncle; aesthetascs occurring on flagellum from the article 3 to article 8.

Antenna 2 peduncle not surpassing the second pereonite, less than half body length, peduncle slender, 1.25X longer than head; flagellum with 15 articles, longer than peduncle.

Basic amphipodan mandible, without palp; incisor toothed; molar large, cylindrical and triturative; left lacinia mobilis with five teeth, setal row on left mandible with four main pappose setae plus accessory setae; right lacinia mobilis with six teeth; setal row on right mandible with three main pappose setae plus accessory setae.

Upper lip margin rounded; distal border covered by setules on ventral and dorsal faces.

Lower lip outer lobes rounded and distally notched, with setules on ventral and dorsal faces.

Maxilla 1 palp uniarticulate, short, longer than wide, reaching the half length the distance between the base of the palp and tip of setae on outer plate, with a long setae; inner plate slender, shorter than outer plate, with two long papposerrate apical setae presenting long setules, with many setae on the inner margin; outer plate with eight serrate setae.

Maxilla 2 inner plate as the same size as outer plate, with only one long and nine short papposerrate apical seta, several simple apical setae; outer plate with abundant long simple setae; inner and outer plates covered by several setules.

Maxilliped inner plate longer than wide, with three strong cuspidate setae apically, several pappose setae on apical and inner borders; outer plate smaller than inner plate, with several pappose setae and short simple setae; palp as the same size as inner plate and longer than outer plate, four articles; article 1 longer than wide, outer face with simple setae; article 2 longer than wide, inner face with several long simple setae; article 3 longer than wide, outer and inner faces with several long simple setae; dactylus unguiform with few simple setae, shorter than other articles, inner border with several simple setae; distal nail shorter than dactylus.

Gnathopod 1 subchelate; coxal plate wider than long, with simple setae on the border; basis and ischium with simple setae dorsally; merus with serrate setae; carpus longer than wide, shorter than propodus, with lateral distal lobe produced and forming a scoop-like structure, border with denticles and polygonal pattern; propodus width about 1/2 of maximum length, hammer-shaped, with several simple long setae on disto-anterior border, combscales absent, inner face with 7 serrate setae, with few simple seta on the disto-posterior border; palm slope oblique, margin slightly concave, palm with many simple setae, posterior distal corner with one long and strong cuspidate seta with an accessory seta; dactylus claw-like, comb-scales absent, with one plumose seta dorsally.

Gnathopod 2 subchelate; coxal plate wider than long, with simple setae on the border; basis with several simple setae on posterior margin; merus with few serrate setae on posterior margin; carpus wider than long, posterior lobe slim produced between merus and propodus, border with denticles and polygonal pattern; propodus ovate, length 1.3 maximum width, comb-scales absent; palm sub-equal to posterior margin of propodus, slope oblique, with one row of several cuspidate setae with an accessory setae and simple setae, posterior distal corner with two long and strong cuspidate setae and with a cup for dactylus; dactylus claw-like, congruent with palm, plumose seta dorsally, comb-scales absent.

Peraeopods 3 to 7 simple. Peraeopods 3 and 4 merus and carpus posterior margin with clusters of simple setae; propodus posterior margin of peraeopod 3 with simple setae and peraeopod 4 with cuspidate and simple setae; dactylus less than half-length of propodus. Peraeopods 5 to 7 dactylus less than half-length of propodus; merus, carpus and propodus posterior margin with 11–14 marginal clusters of 1–6 cuspidate seta. Peraeopod 3 sub-qual to peraeopod 5; peraeopod 4 sub-equal to peraeopod 5; peraeopod 6 sub-equal to peraeopod 7, and both are longer than others. Coxal plates: peraeopod 3: longer than wide, width about 1/2 of maximum length; peraeopod 4: excavated posteriorly, as long as wide; peraeopod 5: wider than long, with two lobes; peraeopod 6: wider than long, with two lobes; peraeopod 7: wider than long. All coxal plates with small simple setae on the border.

Pleopods peduncle shorter than rami, with two coupling spines; both rami with several plumose setae.

Uropod 1 peduncle longer 1.5X than rami; outer ramus longer than inner ramus; outer ramus with four dorsal cuspidate setae with an accessory seta and four cuspidate setae with an accessory seta apically; inner ramus with three dorsal cuspidate setae with an accessory seta and three cuspidate setae with an accessory seta apically; peduncle with seven cuspidate setae with an accessory seta dorsally; male without curved seta on inner ramus.

Uropod 2 shorter than uropod 1; inner ramus with four dorsal cuspidate setae with an accessory seta and three cuspidate setae with an accessory seta apically; outer ramus with four dorsal cuspidate setae with an accessory seta and three distal cuspidate setae with an accessory setae; peduncle longer and wider than rami, with four cuspidate setae with an accessory seta.

Uropod 3 shorter than telson, than peduncle of uropod 1 and peduncle of uropod 2; inner ramus absent; outer ramus uniarticulate; peduncle longer than wide, with five long cuspidate seta; ramus shorter than peduncle; basal width 2.8X the width of ramus apex, with three simple setae and one strong seta apically.

Telson entire, apically rounded, as long as wide, without apical setae; few small simple setae and pin-shaped setae laterally.

Coxal gills sac-like, present on pereonites 2 to 6. Sternal gills tubular present on pereonites 3 to 7.

Female. Mean body length: 6.0 ± 1.1 mm, mean head length: 0.55 ± 0.15 mm (n=4). Antenna 1 similar in shape to male, flagellum with 4 articles; antenna 2 similar in shape to male, flagellum with 6 articles. Gnathopod 1 similar to male gnathopod 1; carpus longer than wide, without comb-scales; with posterior lobe produced and forming a scoop-like structure, with pectinate margin, with several serrate setae; propodus longer than wide, hammer-shaped, palm shorter than posterior margin of propodus, without comb-scales, inner face with few simple setae, palm slope transverse, dactylus claw-like. Gnathopod 2 similar in size and shape to gnathopod 1; different in shape to male gnathopod 2 and smaller; propodus as long as wide, subchelate, inner face with few simple setae, palm transverse with several long simple setae, without comb-scales. Telson similar in shape to male.

Habitat. Freshwater, epigean.

Conservation. 'Itatiaia' means 'pointed stone' in Tupi-Guarani language (Brazilian Indian language) and it refers to the remarkable relief of the Park. The relief of the INP is characterized by rocky peaks and steep sloped hills on the middle of the plateau (Agulhas Negras 2,791 m, Pedra do Altar 2,661 m) or on its edges (Pedra do Couto 2,682 m, Prateleiras 2,515 m), contrasting with relatively broad floodplain sectors filled with peaty sediments (Modenesi-Gauttieri & de Toledo 1996). The INP was the first National Park established in Brazil in June 1937 and currently covers an area of approximately 30,000 hectares (ICMBio 2015). This Park is considered one of the most relevant conservation areas of the world for housing an extensive area of the threatened Atlantic Rain Forest biome and tens of endemic and endangered species (ICMBio 2015). The plateau area of the INP houses the headwaters of 12 important regional watersheds, which drain to the Grande, Paraná and Paraíba do Sul Rivers, the most important ones of the southeast Brazil. The aquatic fauna of the INP is still poorly known, but in the last few years new species of freshwater invertebrates have been described ( Ermilov et al. 2014; Sousa et al., 2014). The habitat of the new species is protected, since it is located within a Conservation Unit. Tourist visits are allowed, however the relief makes it difficult the access to the higher areas of the INP, assisting in the conservation of the new species.

Etymology. The species epithet " montana " is in Latin and it means "mountain", referring to the habitat of the new species. Montana is also the name of a typical phytophysiognomy in the INP that occurs above 1,800 m of altitude (Modenesi-Gauttieri & de Toledo 1996).

Remarks. Using the taxonomic key of Rodrigues et al. (2014) for the Brazilian species of the genus, H. montana does not match to any described species for the country, both epigean as the hypogean. The new species does not present curved seta on inner ramus of the uropod 1, one of the most remarkable characteristics of Hyalella , as well as the epigean species H. dielaii Pereira, 2004 , H. longistila (Faxon, 1876) , H. meinerti Stebbing, 1899 , H. warmingi Stebbing, 1899 , H. minensis Bastos-Pereira & Bueno, 2013 and H. gracilicornis (Faxon, 1876) . However, H. montana differs from all species mentioned mainly by the reduced size of the uropod 3, by presenting a telson without apical setae, by the absence of comb-scales on propodus of gnathopod 1 and 2, and the sternall gills occurring only on pereonites 3 to 7.

Unexpectedly, as occurs in a superficial system, the individuals of H. montana present morphological traits similar to the subterranean species of the genus ( Rodrigues et al. 2014), as: anophthalmy (in few individuals); extreme reduction of the size of the uropod 3; telson without apical setae; absence of comb-scales of gnathopods 1 and 2; and sternal gills tubular present on pereonites 3 to 7. Of all epigean species of Hyalella described until now, H. montana is the first one to present individuals with transitional morphological traits to the troglomorphism, and it is unique in the genus so far. The fact that it was found buried under rocks and sediment suggests that H. montana is troglophile, and may be still in the process of adaptation to the hypogean environment. Moreover, we observed during the samples that the stream where the new species was found sprouted from the ground, supporting the hypothesis that this new species originates from hyporheic environment and/or is adapting to it.

The species H. pernix Moreira, 1903 was described for the INP more than a century ago. Its description is very brief, absent of taxonomic details and with very few illustrations. Pereira (1985) when collected in Esgotada Lake in the INP, identified the material as H. pernix , and also stated that the species was a senior synonym of H. curvispina Shoemaker, 1942 . However, González & Watling (2003) concluded that the specimens sampled by Pereira (1985) do not correspond to H. pernix described by Moreira (1903) or to H. curvispina described by Shoemaker (1942) and it refers to a new species, which was never formally renamed.

Hyalella montana does not correspond either to the species of Pereira (1985) or to H. pernix , mainly by not presenting curved seta on inner ramus of the uropod 1, comb-scales on gnathopod 1 and 2 and apical setae on telson. González & Watling (2003) also suggest that H. pernix must be redescribed in order to avoid new mistakes as in Pereira (1985), moreover, it is not possible to distinguish it from other Brazilian species based solely on the description of Moreira (1903). Unfortunately, the type material is unknown or is lost, so it is not possible to confirm the validity of H. pernix .

Figures

FIGURE 2. Hyalella montana n. sp., Itatiaia National Park (22 ° 22 ′ 13,3 ″ S – 44 ° 42 ′ 32,6 ″ W), Minas Gerais state, Itamonte municipality, Brazil. Holotype, male, 5.7 mm, CRFFP 86; paratype, female, 5.0 mm, CRFFP 88. Scale bars: 1.0 mm.

FIGURE 3. Hyalella montana n. sp., Itatiaia National Park (22 ° 22 ′ 13,3 ″ S – 44 ° 42 ′ 32,6 ″ W), Minas Gerais state, Itamonte municipality, Brazil. Paratype, male, 5.8 mm, CRFFP 87. Scale bars: 0.5 mm for A 1 – 2; 0.2 mm for rMd; 0.1 mm for the remainder.

FIGURE 4. Hyalella montana n. sp., Itatiaia National Park (22 ° 22 ′ 13,3 ″ S – 44 ° 42 ′ 32,6 ″ W), Minas Gerais state, Itamonte municipality, Brazil. Holotype, male, 5.8 mm, CRFFP 87; paratype, female, 5.0 mm, CRFFP 88. Scale bars: 0.1 mm for LL; 0.5 mm for the remainder.

FIGURE 5. Hyalella montana n. sp., Itatiaia National Park (22 ° 22 ′ 13,3 ″ S – 44 ° 42 ′ 32,6 ″ W), Minas Gerais state, Itamonte municipality, Brazil. Holotype, male, 5.8 mm, CRFFP 87; paratype, female, 5.0 mm, CRFFP 88. Scale bars: 0.1 mm for Pl; 0.2 mm for Mp; 0.5 mm for the remainder.

FIGURE 6. Hyalella montana n. sp., Itatiaia National Park (22 ° 22 ′ 13,3 ″ S – 44 ° 42 ′ 32,6 ″ W), Minas Gerais state, Itamonte municipality, Brazil. Holotype, male, 5.8 mm, CRFFP 87. Scale bars: 0.1 mm for T; 0.2 mm for U 1 – 3; 0.5 mm for the remainder.