Hyalella nebula, Cardoso & Oliveira & Ferreira, 2025

Hyalella nebula sp. nov.

urn:lsid:zoobank.org:act:

Figures 1 View FIGURE 1 , 2 E,F View FIGURE 2 , 9–11 View FIGURE 9 View FIGURE 10 View FIGURE 11 , 15D View FIGURE 15

Type material: Brazil, Minas Gerais state, Brumadinho municipality, MJ_0005 cave (-20.0949º-44.0772º): Holotype ♂ (ISLA97004), V.2024, leg. R. Zampaulo. Paratypes: 9♂, 14♀ ( ISLA 97005, in slide), same data as holotype .

Diagnosis: Male with absent eyes,; antenna 1 shorter than antenna 2; flagellum of 11 articles; antenna 2 less than half body length, flagellum with 16 articles; gnathopod 1 ventral face with seven serrate setae; gnathopod 2 palm shorter than posterior margin of propodus, slope oblique; inner ramus of uropod 1 with one curved seta; telson with two cuspidate setae with accessory seta and three plumose setae laterally. Females with eyes present, reduced; antenna 1 shorter than antenna 2; flagellum of 7 articles; antenna 2 with flagellum with 11 articles; inner ramus of uropod 1 without curved seta.

Description

Male: Body length 4.6 mm; cephalothorax length 0.36 mm.Body surface smooth.Epimeral plates not acuminate. Cephalothorax slightly longer than first thoracic segment, rostrum absent. Eyes reduced ( Fig. 15D View FIGURE 15 ). Antenna 1 ( Fig. 9A View FIGURE 9 ) shorter than antenna 2; flagellum of 11 articles, longer than peduncle. Antenna 2 ( Fig. 9B View FIGURE 9 ) less than half body length, peduncle longer than cephalothorax, flagellum with 16 articles, longer than peduncle. Mandible ( Fig. 9C,D View FIGURE 9 ) incisor with five to six teeth; lacinia mobilis denticulate; left mandible setal row with three long and robust pappose setae; right mandible with two main pappose setae; molar large, cylindrical, and triturative; accessory seta present. Upper-lip ( Fig. 9E View FIGURE 9 ) margin rounded, and distal margin covered by setules. Lower-lip ( Fig. 9F View FIGURE 9 ) bilobed, outer lobes rounded with setules on ventral and dorsal faces, outer margin smooth. Maxilla 1 ( Fig. 9G View FIGURE 9 ) palp short, uniarticulate, longer than wide, with one strong seta; inner plate slender, smaller than outer plate, with two strong pappose apical setae and several simple setae on inner and outer margin; outer plate with ten serrate setae. Maxilla 2 ( Fig. 9H View FIGURE 9 ) inner plate shorter than outer plate, with two strong papposerrate setae, medial margin with several simple and serrate setae on anterior margin. Maxilliped ( Fig. 9I View FIGURE 9 ) inner plates apically rounded, with three cuspidate and pappose setae apically, medially and on outer margin; outer plate slender than inner plate, tapering apex with simple setae; palp longer than outer plate, with four articles, with simple setae; dactylus unguiform, shorter than article 3; distal nail present.

Gnathopod 1 ( Fig. 9J View FIGURE 9 ) subchelate; dactylus claw-like, with one plumose seta; propodus length less than two times maximum width, hammer shaped, ventral face with seven serrate setae, anterodistal margin cluster of simple setae, posterodistal margin with two strong cuspidate setae with accessory seta, and comb scales; carpus longer than wide, longer than propodus, posterior lobe with pectinate border with several serrate setae; base, ischium and merus with simple setae on posterodistal margin.

Gnathopod 2 ( Fig. 9K View FIGURE 9 ) subchelate; dactylus claw-like, short, reaching 1/3 of propodus length; propodus ovate, length about 1.6 maximum width; palm shorter than posterior margin of propodus, slope oblique, with several cuspidate setae with accessory seta and simple setae; carpus wider than long with posterior lobe elongated produced between propodus and merus, border pectinate with several pappose setae.

Pereopods 3–5 ( Fig. 10A–C View FIGURE 10 ) progressively shorter, propodus, carpus, merus, ischium, and base with several simple and cuspidate setae with accessory seta on posterior and anterior margin, dactylus less than half the length of propodus. Pereopod 6 ( Fig. 10D View FIGURE 10 ) longest, pereopod 7 ( Fig. 10E View FIGURE 10 ) slightly shorter than pereopod 6. Coxal plate of pereopods longer than wide, excavated posteriorly on pereopod 4; round on pereopod 5, trapezoidal on pereopod 6, and reduced on pereopod 7.

Pleopods ( Fig. 10F View FIGURE 10 ) not modified; peduncle slender, shorter than rami, with two coupling spines distally; rami with several plumose setae on both margins.

Uropod 1 ( Fig. 10G View FIGURE 10 ) longer than uropod 2; peduncle longer than rami, with four dorsal cuspidate setae with accessory seta; inner ramus with two dorsal cuspidate setae with accessory seta, one curved seta followed by five cuspidate setae apically; outer ramus with two dorsal cuspidate setae with an accessory seta and four cuspidate setae apically. Uropod 2 ( Fig. 10H View FIGURE 10 ) peduncle as long as rami, with four dorsal setae; rami subequal in length; inner ramus with two dorsal cuspidate setae with accessory seta and five cuspidate setae apically, outer ramus with two dorsal cuspidate setae with accessory seta and five distal setae. Uropod 3 ( Fig. 10I View FIGURE 10 ) shorter than other uropods; peduncle slightly longer than wide, with two cuspidate setae with accessory seta; inner ramus absent; outer ramus uniarticulate, sub-equal to peduncle, with three cuspidate setae apically.

Telson ( Fig. 10J View FIGURE 10 ) as long as wide, entire, apically rounded, bearing two cuspidate setae with accessory seta and three plumose setae laterally.

Coxal gills sac-like, present on gnathopod 2 to pereopod 6. Sternal gills tubular, present on segments 2 to 7.

Female ( Fig. 11 View FIGURE 11 ): Body length of 2.7 mm; cephalothorax length of 0.2 mm. Antenna 1 flagellum of 7 articles. Antenna 2 flagellum of 11 articles. Gnathopod 1 ( Fig. 11A View FIGURE 11 ) similar in size and shape to male gnathopod 1; propodus inner face with four serrate setae; carpus posterior lobe with pectinate border with several serrate setae. Gnathopod 2 ( Fig. 11B View FIGURE 11 ) propodus rectangular, slightly longer than gnathopod 1, length about than two times maximum width, subchelate; propodus inner face with four serrate setae; carpus posterior lobe with pectinate border with of several serrate setae. Uropod 1 ( Fig. 11C View FIGURE 11 ) longer than uropod 2; peduncle longer than rami, with four dorsal cuspidate setae with accessory seta; inner ramus with one dorsal cuspidate seta, apex with four cuspidate setae without curved seta; outer ramus one dorsal cuspidate seta and three cuspidate setae apically. Uropod 2 ( Fig. 11D View FIGURE 11 ) peduncle as long as rami, with three dorsal setae; inner ramus longer than outer ramus, with one dorsal cuspidate seta and five cuspidate setae apically, outer ramus with one dorsal cuspidate seta and three distal setae. Uropod 3 ( Fig. 11E View FIGURE 11 ) and telson ( Fig. 11F View FIGURE 11 ) similar to male.

Etymology: The epithet nebula refers to the mist commonly associated with mountains of the region, which also inspired the city’s name.

Morphological remarks: Hyalella nebula sp. nov. resembles H. troglofugia , that occurs in the nearby municipality of Nova Lima, in Minas Gerais state. Both species present 2 cuspidate setae on telson. However, Hyalella nebula sp. nov. differs from H. troglofugia , by the presence of reduced eyes, that are absent in H. troglofugia ; and the number of articles on antennae, 11 on antenna 1 and 16 on antenna 2; while the number of articles on H. troglofugia are 9–11 and 9–12 respectively; the number of setae in gnathopod 1 propodus, 7 in Hyalella nebula sp. nov. and 4 in H. troglofugia ; and the shape of gnathopod 2 propodus, slender in Hyalella nebula sp. nov. (1.5 times longer than wide), and the presence of the curved seta on uropod 1, absent in H. troglofugia ( Bastos-Pereira et al. 2018) .

The presence of the curved setae is seen in other species in the region, such as the epigean species of H. carstica Bastos-Pereira & Bueno, 2012 , recorded in the municipality of Arcos (MG), and H. xakriaba Bueno & Araujo, 2013 , recorded in the municipality of Itacarambi (MG); and in other stygobite species, H. veredae ; H. formosa , H. imbya and H. epikarstica .