Hyalella formosa Cardoso & Araujo

Cardoso, Giovanna Monticelli, Araujo, Paula Beatriz, Bueno, Alessandra Angélica De Pádua & Ferreira, Rodrigo Lopes, 2014, Two new subterranean species of Hyalella Smith, 1874 (Crustacea: Amphipoda: Hyalellidae) from Brazil, Zootaxa 3814 (3), pp. 353-368 : 362-367

publication ID	https://doi.org/ 10.11646/zootaxa.3814.3.3
publication LSID	lsid:zoobank.org:pub:2D820F30-55A5-4B4E-8064-FBB45DD49013
DOI	https://doi.org/10.5281/zenodo.6133286
persistent identifier	https://treatment.plazi.org/id/03DF87D1-FFDE-FF80-FF0C-FE02DB396F9D
treatment provided by	Plazi
scientific name	Hyalella formosa Cardoso & Araujo
status	sp. nov.

Treatment

Hyalella formosa Cardoso & Araujo View in CoL , sp. n.

( Figs. 7–10 View FIGURE 7 View FIGURE 8 View FIGURE 9 View FIGURE 10 )

Type material. Holotype: male, cephalothorax length 0.4 mm, total length 5.6 mm, Brazil, Paraná state, Ponta Grossa municipality, Andorinhas Cave (25°08’39”S 49°55’58”W), MZUSP 28419; 24.VII.2011, Ferreira R.L. & cols. Paratypes: UFRGS 5543 (2 males on slides, 1 female on slide), UFLA 0 260 (1 male, 1 female). All samples have the same data as holotype.

Diagnosis. Eyes absent. Antenna 1 flagellum with 11 to 13 articles, longer than antenna 2. Antenna 2 with eight to ten articles. Gnathopod 1 and 2 carpus posterior lobe with polygonal pattern and one row of serrate setae. Gnathopod 1 propodus oval shape, without projections on the posterior margin, inner face with five serrate setae. Gnathopod 2 propodus elongated, oval shape, without projections on the posterior margin; palm smooth, slope oblique, strongly inclined, longer than posterior margin; dactylus long, exceeding half length of propodus. Uropod 1 inner ramus of male with one curved seta and four apical cuspidate setae. Uropod 3 peduncle with one cuspidate seta distally; ramus with one cuspidate seta and two to three distal simple setae.

Description of male. ( Figs 2 View FIGURE 2 E and 7A). Mean body length: 5.4 ± 0.9 mm (n=3); mean cephalothorax length: 0.4 ± 0.08 mm. Body surface smooth, epimeral plates not acuminate. Eyes absent.

Antenna 1 ( Fig. 7 View FIGURE 7 B) longer than antenna 2; total length reaches fourth pereonite; peduncle not surpassing first pereonite; flagellum with 11 to 13 articles, each with one or two aesthetascs after article 2.

Antenna 2 ( Fig. 7 View FIGURE 7 C) total length reaches fourth segment; peduncle not surpassing first pereonite; flagellum with eight to ten articles.

Upper lip ( Fig. 7 View FIGURE 7 D) margin rounded, distal border covered by setules on dorsal and ventral faces.

Mandible ( Fig. 7 View FIGURE 7 E) basic amphipodan (in the sense of Watling 1993), but without palp; incisor toothed; left lacinia mobilis with five teeth and setal row with two pappose setae, right mandible with three pappose setae; molar process broad and cylindrical with accessory seta.

Lower lip ( Fig. 7 View FIGURE 7 F) lobes rounded, with setules on dorsal and ventral faces.

Maxilla 1 ( Fig. 7 View FIGURE 7 G) inner plate shorter than outer plate, with two distal papposerrate setae and several setules on the margin. Outer plate with nine serrate setae; palp short, uniarticulated with one distal setae.

Maxilla 2 ( Fig. 7 View FIGURE 7 H) inner and outer plate of similar sizes, inner ramus with two papposerrate setae, nine serrulate and several simple setae; outer plate with several simple setae and one long plumose seta distally.

Maxilliped ( Fig. 7 View FIGURE 7 I) inner ramus with three cuspidate distal setae and several pappose and simple setae on the margin; outer ramus with simple setae and two serrate setae on the margin; palp with four articles with several simple setae; dactylus unguiform, shorter (1/2) than the article 3, with simple seta and distal nail.

Gnathopod 1 ( Fig. 8 View FIGURE 8 A) subchelate; basis, ischium and merus with simple setae; carpus longer than wider, shorter than propodus, lobe posterior margin with polygonal pattern and one row of serrate seta; propodus length 1.5 times the width (rectangular), oval shape, without projections on the posterior margin, inner face with five serrate setae; dactylus claw-like with simple setae and one plumose seta ( Fig. 8 View FIGURE 8 B).

Gnathopod 2 ( Fig. 8 View FIGURE 8 C) subchelate; basis, ischium and merus with simple setae on the posterior margin; carpus wider than longer, lobe posterior margin with polygonal pattern and one row of serrate setae; propodus elongated, oval shape, without projections on the posterior margin, length 1.4 times the width (rectangular); smooth palm, slope oblique, strongly inclined, palm 1.5 times longer than posterior margin, with 12 to 20 cuspidate setae with accessory seta; dactylus claw-like, long, exceeding half the length of the propodus ( Fig. 8 View FIGURE 8 D).

Pereopods 3 to 7 ( Figs. 8 View FIGURE 8 E and 8F) merus, carpus, propodus posterior margin with cluster of cuspidate setae with accessory seta; dactylus length 1/3 of propodus; propodus dorsal and distal margins with simple setae; pereopod 3 and 4 with similar sizes; pereopod 5 smaller than others; pereopod 6 smaller than pereopod 7; which is about 1.5 times greater than pereopod 3.

Pleopods ( Fig. 9 View FIGURE 9 A) peduncle shorter than rami, with distal coupling spines; both rami with several plumose setae.

Uropod 1 ( Fig. 9 View FIGURE 9 B) peduncle longer than rami, with four cuspidate setae with accessory seta; inner ramus with one curved seta and four apical cuspidate setae ( Fig. 9 View FIGURE 9 C); outer ramus with three cuspidate setae with accessory seta on inner margin, and apex with four cuspidate setae, one of them with accessory seta (U1 about 5 times the length of U3).

Uropod 2 ( Fig. 9 View FIGURE 9 D) shorter than uropod 1; peduncle with four cuspidate setae with accessory seta on the margin; inner ramus longer than outer ramus with one or two cuspidate setae with accessory seta on the margin, apex with five cuspidate setae with accessory seta; outer ramus with three cuspidate setae with accessory seta, apex with three to four cuspidate setae, two of them with accessory seta.

Uropod 3 ( Fig. 9 View FIGURE 9 E) shorter than uropod 2, peduncle longer than ramus, longer than wide with one distal cuspidate setae; ramus uniarticulated with one cuspidate setae and two to three distal simple setae.

Telson ( Fig. 9 View FIGURE 9 F) longer than wider, with two long simple setae and three short simple setae laterally.

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

Female. Cephalothorax length: 0.4 mm, body length: 5.0 mm (n = 1). Gnathopod 1 ( Fig. 10 View FIGURE 10 A) smaller than gnathopod 2; carpus wider than longer, lobe posterior margin with polygonal pattern; propodus longer than wider, inner face with five serrate setae. Gnathopod 2 ( Fig. 10 View FIGURE 10 B) similar to gnathopod 1, slightly larger, with carpus wider than longer, lobe posterior margin with polygonal pattern; propodus rectangular, longer than wider, inner face with five serrate setae. Uropod 1 peduncle longer than rami, inner margin with five cuspidate setae with accessory seta; inner ramus with two apical cuspidate setae; outer ramus with two cuspidate setae with accessory seta on the margin and apex with four cuspidate setae ( Fig. 10 View FIGURE 10 C).

Habitat and ecological considerations. Hyalella . formosa was found in an underground lake in Andorinhas Cave, located near Ponta Grossa city ( Fig. 2 View FIGURE 2 A). The cave is mainly composed of sandstone; its entrance is within a fracture covered by dense vegetation, while the surrounding is quite modified, especially due to agricultural activities ( Fig. 2 View FIGURE 2 B). The cave comprises an elliptical hall approximately 140 meters long, its floor is strongly declined ( Fig. 1 View FIGURE 1 D) and, in the deepest portion, there is the lake ( Fig. 1 View FIGURE 1 C) where the species was found ( Spinardi & Lopes, 1990). Dozens of individuals were observed swimming in the water column. There is organic material composed by plant fragments that are flushed in from the outside by water during rainy periods. The water table appears to vary over the year so the configuration of the pond level may be variable depending on the season. Other fractures were observed in the region, although apparently not connected with the water table. Although the only possible habitat for this species appears to be Andorinhas Cave, it is quite likely that the distribution of the species is more extensive, comprising part of the water table in the area.

Remarks. The troglomorphic features found in H. formosa , such as the absence of eyes resembles H. caeca , H. imbya , H. anophthalma and H. muerta ; and the antenna 1 being longer than antenna 2, resemble H. imbya and H. muerta . The propodus of gnathopod 2 with a smooth palm in H. formosa is similar to H. caeca and H. imbya , while in H. spelaea , H. anophthalma and H. muerta the palm is irregular. In addition H. formosa shares with H. imbya the strongly inclinated palm of gnathopod 2, the absence of denticles on the posterior margin of gnathopod 2 carpus (Fig. 23), the presence of one curved seta in uropod 1 and long pereopods 6 and 7. The new species has unique characteristics such as the shape of gnathopod 1 distinct from the hammer-shape type, which is present in all other species ( González & Watling, 2003), as well as different numbers of setae on the gnathopod propodus, uropod 1 and 3.