Hyallela troglofugia, Bastos-Pereira & Oliveira & Ferreira, 2018

Bastos-Pereira, Rafaela, Oliveira, Marcus Paulo Alves De & Ferreira, Rodrigo L., 2018, Anophtalmic and epigean? Description of an intriguing new species of Hyalella (Amphipoda, Hyalellidae) from Brazil, Zootaxa 4407 (2), pp. 254-266 : 256-262

Hyallela troglofugia sp. nov.

( Figs. 2–6 )

Material examined. Type material ( Fig 2 ): holotype male, cephalothorax length 0.37 mm, total length 3.76 mm, Brazil, Minas Gerais state, municipality of Nova Lima , collection point P1 (UTM geographical coordinates: E 617842 N 7795039), ISLA21114, July 2013, Oliveira, M. P. A & cols . Paratypes: ISLA 21116 (2 males and 3 females entire), ISLA 21117 (8 males and 2 females on slides), collected at the points P1, P2 (E 618000 N 7795048) and P3 (E 618193 N 7795085).

Diagnosis. Body surface smooth. Eyes absent. Antenna 1 shorter than antenna 2. Gnathopod 1 propodus inner face with four setae. Gnathopod 2 propodus posterior margin longer than palm, dactylus slightly longer than palm. Pereopod 5 shorter than others. Pereopod 6 slightly longer than 7. Uropod 1 inner ramus without curved seta. Uropod 3 shorter than telson. Telson longer than wide with two strong and two small apical and three small lateral setae. Sternal gills present on pereonites segments 2 to 7.

Description of male. Body surface smooth. Mean body length: 6.43 ± 2.9 mm, mean cephalothorax length: 0.53 ± 0.21 mm (n=5). Body surface smooth, epimeral plates not acuminate. Eyes absent.

Antenna 1 ( Fig. 3 ) total length reaches second pereonite; flagellum with 9 to 11 articles, with one or two aesthetascs from first to sixth article. Antenna 2 ( Fig. 3 ) total length reaches third pereonite; peduncle surpasses the first pereonite; flagellum with 9 to 12 articles. Upper lip ( Fig. 3 ) margin rounded, distal border covered by setules on dorsal and ventral faces. Mandible ( Fig. 3 ) as described by Watling (1993) without palp; incisor toothed; left lacinia mobilis with five teeth and setal row with three pappose setae; right mandible with two pappose setae; molar process broad and cylindrical with accessory seta. Lower lip ( Fig. 3 ) lobes rounded, with setules on dorsal and ventral faces. Maxilla 1 ( Fig. 3 ) inner plate shorter than outer plate, with two distal papposerrate setae, and several marginal setules. Outer plate with eight serrate setae. Palp short, uni-articulated with few distal setules. Maxilla 2 ( Fig. 3 ) inner and outer plates of similar sizes, inner plate with two papposerrate setae, seven or eight serrulate setae and several simple setae; outer plate with several simple distal setae. Maxilliped ( Fig. 3 ) inner plate with three cuspidate distal setae and several pappose and simple setae; outer plate with simple setae on the margin; palp with four articles with several simple setae. Dactylus unguiform, smaller than third article, with simple seta and distal nail.

Gnathopod 1 ( Fig. 4 ) subchelate; basis, ischium and merus with simple setae; carpus longer than wide, shorter than propodus, lobe posterior margin without polygonal pattern and comb scales and row of serrate setae present; propodus length about 1.8 times the width (rectangular), hammer-shaped, inner face with four or five serrate setae, posterior margin with denticles as comb scales; dactylus claw-like with simple setae and one dorsal plumose seta ( Fig. 4 ).

Gnathopod 2 ( Fig. 4 ) subchelate; basis, ischium and merus with simple setae on the posterior margin; carpus wider than longer, lobe posterior margin elongated without polygonal pattern and comb scales, row of four serrate setae present; propodus 1.4 times longer than wide (rectangular), posterior margin with denticles as comb scales, irregular palm, slope oblique and slightly inclined, palm shorter than posterior margin, palm margin convex with several simple setae and at least 20 cuspidate setae with accessory seta; dactylus claw-like with a dorsal plumose seta.

Pereopods 3 to 7 reduced in length ( Fig. 4 ); merus, carpus, propodus posterior margin with sets of two or three cuspidate setae with accessory seta; propodus length about 4.5 times the dactylus length; pereopod 3 and 4 with similar sizes; pereopod 5 smaller than others; pereopod 6 slightly longer than pereopod 7, which is as long as pereopod 3.

Pleopods ( Fig. 5 ) peduncle about half the rami length, with distal coupling spines; both rami with several plumose setae.

Uropod 1 ( Fig. 5 ) peduncle longer than rami, with two to four lateral and 1 or 2 apical cuspidate setae with accessory seta; inner ramus slightly longer than outer ramus with three to five cuspidate setae on inner margin, without curved seta and with four apical cuspidate setae; outer ramus with two or three cuspidate setae with accessory seta on inner margin, and apex with four to seven cuspidate setae; U1 about 3 times the length of U3. Uropod 2 ( Fig. 5 ) about 0.6 times the length of uropod 1; peduncle slightly longer than rami, with three to four lateral and two apical cuspidate setae; inner and outer ramus similar in length, inner ramus margin with two cuspidate setae with accessory seta, apex with six cuspidate setae, two of them with accessory seta; outer ramus with two to three cuspidate setae with accessory seta in the margin and 4 apical cuspidate setae, one of them with accessory seta.

Uropod 3 ( Fig. 5 ) half the length of uropod 2; peduncle longer than wide with three distal cuspidate setae with accessory seta; ramus uni-articulated, half the peduncle length, with four distal cuspidate setae.

Telson ( Fig. 5 ) longer than wide, with two long and two short apical cuspidate setae and three plumose setae laterally.

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

Female differences. Cephalothorax length: 0.62 ± 0.03 mm, mean body length: 6.07 ± 1.17 mm (n=2). Antenna 1 flagellum with 8 articles. Antenna 2 flagellum with 11 articles. Gnathopod 1 ( Fig. 6 ) shorter than gnathopod 2; carpus and propodus longer than wide, propodus inner face with three serrate setae. Gnathopod 2 ( Fig. 6 ) carpus longer than wide; propodus rectangular, 2 times longer than wide, inner face with four serrate setae, palm with 10 simple setae, shorter than posterior margin.

Etymology. From the Latin expressions troglo = cave, fugia = fugitive. For details, see the session ‘Remarks’.

Affinities. In general, the new species shares some characteristics of taxonomic importance with all the described subterranean species of Hyalella from Brazil ( H. caeca Pereira, 1989 , H. spelaea Bueno & Cardoso, 2011 , H. imbya Rodrigues & Bueno, 2012 , H. formosa Cardoso & Araujo, 2014 , H. veredae Cardoso & Bueno, 2014 , H. epikarstica Rodrigues, Bueno & Ferreira, 2014 ) and H. montana Rodrigues, Senna, Quadra & Bueno, 2017 (Table 1). As well as most of these species (except for H. spelaea and H. veredae in which eyes are reduced), eyes are absent in H. troglofugia sp nov. Regarding the length of antennae, H. veredae presents a similar number of articles both for A1 and A2 (9 to 11), but in such species A1 and A2 are subequal in length, while the new species presents A1 shorter than A2. This characteristic (A1 shorter than A2) is present in the genus diagnosis, but some species like H. imbya , H. formosa and H. epikarstica present A2 longer than A1. Hyalella troglofugia sp nov also shares the presence of sternal gills from pereonites 2 to 7 with H. veredae .

The new species presents four similarities with H. formosa : G1 dactylus longer than propodus palm, P5 shorter than other pereopods, telson longer than wide and sternal gills on pereonites 2 to 7. However, these species differs in relation to the proportion of A1 and A2 length ( H. formosa : A1 longer than A2; H. troglofugia sp nov: A1 shorter than A2), curved seta on U1 (present in H. formosa and absent in the new species), as well as in the proportion between G1 propodus palm and posterior margin ( H. formosa : palm longer than posterior margin; H. troglofugia sp nov: palm shorter than posterior margin) and between U3 and telson ( H. formosa : U3 and telson similar in length; H. troglofugia sp nov: U3 shorter than telson).

Regarding the two first subterranean species of Hyalella described in Brazil ( H. caeca and H. spelaea ), the new species is similar due to the absence of curved setae and A1 shorter than A2, but in H. caeca the G1 propodus palm is longer than the posterior margin. In relation to H. spelaea , H. troglofugia sp nov differs mainly in function of the longer G2 dactylus, number of setae on inner face of G1 propodus and absence of eyes. Hyalella troglofugia sp nov also shares the presence of U3 shorter than telson with H. imbya and H. epikarstica , but differs in relation to the length of antennae and length proportions in gnathopods and pereopods.

In relation to H. montana , H. troglofugia is similar regarding the A1 flagellum articles, proportion between A1 and A2 length and proportion among pereopods length, as well as the absence of curved seta on U1 and reduced U3 size. However, these two species differ in relation to the number of articles of A2 flagellum, number of setae on inner face of G1 propodus, proportion between G2 propodus palm and posterior margin length and between dactylus and palm length. These species differ mainly in relation to the eyes, since only some individuals of H. montana presented reduction or absence of them, while all individuals of H. troglofugia are anophtalmic.

Habitat and Threats. The landscape where Fazenda Stream is inserted, the habitat of H. troglofugia sp nov, may be characterized as a mosaic compounded by urban areas, quarries, pastures and forest fragments ( Figure 1A ). The metropolitan region of Belo Horizonte is also close to the study site, the third largest urban agglomeration of Brazil and the 88th of the world (Worldatlas 2017). Among the impacts caused by urban expansion, the excessive consumption and alteration of water quality are potential risks for this new species ( Larson et al. 2009). The presence of urban centers affects the natural cycle of hydric infiltration in the soil, thus altering the rainwater drainage, reducing the level of water table and increasing the probability of contamination of adjacent springs by anthropic wastes ( White et al. 1986, Sharp et al. 2003). The substitution of native vegetation by areas of livestock and/or crops represents secondary effects of such high demographic density and causes several environmental problems such as fragmentation, invasive species, erosion and pollution of soil, water pollution, imbalances in the carbon cycle, among others ( Klink & Machado 2005). Moreover, this region comprises one of the main areas of surface iron ore exploration in the world. This type of mineral extraction removes and discards the ferruginous crust that covers the mineral reserves, thus modifying the landscape and causing a huge impact for the local and regional biodiversity ( Ferreira et al. 2015). During the extraction and processing of iron ore, the indiscriminate use of water alters the balance between the aquifer recharge and residence time of groundwater, what limits the system capacity of hydric resilience ( Gama & Matias 2015). Other threat to the habitat of H. troglofugia sp nov. refers to the use of such streams as motorcycle tracks during recreational activities especially in the weekends, what promotes the silting, homogenization of substrates, removal of macrophytes and roots in the streams, thus suppressing potential micro-habitats for the new species. Finally, areas surrounding the Fazenda Stream present several unfinished works of railway infrastructure, such as stretches of abandoned tunnels, pillars and bridges built in the 70’s for a federal project called Ferrovia do Aço ( Teixeira 2011). Such constructions demonstrate that the landscape presents a long history of anthropic modifications without inventories and adequate management of the associated fauna.

Figures

FIGURE 3. Hyalella troglofugia sp nov found in streams located in the Iron Ore region, state of Minas Gerais, Brazil. Paratype male.Scale bars:0.1 mm.

FIGURE2. Hyalella troglofugia sp nov.Holotype male, foundin streams located inthe Iron Ore region, state of Minas Gerais, Brazil, ISLA21114.Paratype female, ISLA21116.

FIGURE4. Hyalella troglofugia spnov found instreams located in theIron Ore region, state of Minas Gerais,Brazil.Paratype male.Scale bars: 0.1 mm.

FIGURE5. Hyalella troglofugia spnov found instreams located in theIron Ore region, state of Minas Gerais,Brazil.Paratype male.Scale bars: 0.1 mm.

FIGURE6. Hyalella troglofugia spnov found instreams located in theIron Ore region, state of Minas Gerais,Brazil.Paratype female, ISLA21116 Scale bars: 0.1 mm.

FIGURE1. (A) First and second order streams along the Northernborder of Iron Quadrangle withhighlight for urban (yellow) and mining areas (purple); (B) Hydrogeological units that composes the Fazenda Stream and sampling sites of Hyalella troglofugia sp nov.; (C) The first sampling point (P1) represents a small channel built for recreational purposes, which deviates part of the hydric volume of Fazenda Stream; (D) The second sampling point (P2) starts in an artifical cavity (hypogean) and (E)continues as a small stream on slope for 20 m until accessing the second order stream;(F) P3 representsa first order stream 70 m far from the main channel.