Oxarthrius (Oxarthrius) inexpectatus Asenjo, 2018

Asenjo, Angélico, Zampaulo, Robson De Almeida & Ferreira, Rodrigo Lopes, 2018, Two new troglobitic species of Oxarthrius Reitter (Coleoptera, Staphylinidae, Pselaphinae) from Brazil, Zootaxa 4462 (3), pp. 404-414 : 405-407

Oxarthrius (Oxarthrius) inexpectatus Asenjo sp. nov.

( Figs. 1–11 )

Type material (8 ♂♂, 6 ♀♀). Holotype: BRAZIL: ♂, labeled “BRAZIL: Minas Gerais[state], / Cave RM_0033[code name of cave], 23S / 605163mE 7784344mN, / SAD 69, 07.ii [February].2016, R.A. / Zampaulo & A.S. Reis leg.”; “Cav.[cave]RM_0033, Parcela 30, / Piso sedimento grosso, / temperatura 27.3°C, / umidade 92%, / luminosidade 0”; “HOLOTYPE / Oxarthrius (Oxarthrius) / inexpectatus Asenjo sp. nov. / Desig. Asenjo et al., 2018” (CEMT).

Paratype: (7 ♂♂, 6 ♀♀), labeled: “ BRAZIL: Minas Gerais [state], / Cave RM_0033[code name of cave], 23S / 605163mE 7784344mN, / SAD 69, 07.ii [February].2016, R.A. / Zampaulo & A.S. Reis leg. ”; “Cav.[cave]RM_0033, Parcela 0 6, / Piso sedimento grosso, / temperatura 22.6°C, / umidade 89%, / luminosidade 0” (1♂ CEMT). “ BRAZIL: Minas Gerais [state], / Cave RM_0033[code name of cave], 23S / 605163mE 7784344mN, / SAD 69, 07.ii [February].2016, R.A. / Zampaulo & A.S. Reis leg. ”; “Cav.[cave]RM_0033, Parcela 22, / Piso sedimento grosso, / temperatura 23.1°C, / umidade 92%, / luminosidade 0” (1♂ CEMT). “ BRAZIL: Minas Gerais [state], / Cave RM_0033[code name of cave], 23S / 605163mE 7784344mN, / SAD 69, 07.ii [February].2016, R.A. / Zampaulo & A.S. Reis leg. ”; “Cav.[cave]RM_0033, Parcela 25, / Piso rocha e blocos, / temperatura 23.4°C, / umidade 92%, / luminosidade 0” (2♀ CEMT). “ BRAZIL: Minas Gerais [state], / Cave RM_0033[code name of cave], 23S / 605163mE 7784344mN, / SAD 69, 07.ii [February].2016, R.A. / Zampaulo & A.S. Reis leg. ”; “Cav.[cave]RM_0033, Parcela 27, / Piso sedimento fino, / temperatura 23.6°C, / umidade 92%, / luminosidade 0” (1♂, 2[teneral specimens] ♀ CEMT). “ BRAZIL: Minas Gerais [state], / Cave RM_0033[code name of cave], 23S / 605163mE 7784344mN, / SAD 69, 07.ii [February].2016, R.A. / Zampaulo & A.S. Reis leg. ”; “Cav.[cave]RM_0033, Parcela 30, / Piso sedimento grosso, / temperatura 27.3°C, / umidade 92%, / luminosidade 0” (2♂, 1♀ CEMT). All paratypes with label “ PARATYPE / Oxarthrius (Oxarthrius) / inexpectatus Asenjo sp. nov. / Desig. Asenjo et al., 2018”.

Other specimens. BRAZIL: Minas Gerais: Parque Estadual da Lapa Grande, Gruta Boqueirão da Nascente , 16°42’45.53”S, 43°56’30.03”W, 30.iii.2015, L.M. Rabelo leg. (4♂♂, 3♀♀ teneral ISLA). Nova Lima, Capão Xavier, Cave N 05, iii.2014, BioEspeleo Consultoria leg. (1♂ ISLA). Nova Lima, Capão Xavier, artificial gallery, pitfall trap, iii.2014, BioEspeleo Consultoria leg. (1teneral ♂, 1♀ ISLA). Nova Lima, Capitão do Mato , Cave CPMT _0015, 15.iii.2017, R.A. Zampaulo leg. (1♂ CEMT) .

Diagnosis. Oxarthrius inexpectatus sp. nov., is similar to O. bispinosus and O. aurora sp. nov. but can be differentiated by the following characters in the male: antennal segment 10, two times longer than wide ( O. inexpectatus sp. nov.) or tree time longer than wide ( O. aurora sp. nov.), and trapezoidal ( O. bispinosus ); mesotibiae without strong tooth in the ventro-posterior face ( O. inexpectatus sp. nov. and O. aurora sp. nov.) or present ( O. bispinosus ).

Description. Holotype male, BL: 1.92. Body, mouthparts, antennae, and tarsi reddish-brown ( Figs. 1–2 ). Tegument polished and shiny with sparse long setae, setae granulated at their base.

Head ( Figs. 3–4 ): slightly oval (HW: 0.45; HL: 0.45), with large antennal tubercle at lateral margin of frontal ridge. Antennal insertions of head not visible in dorsal view. Region of lateral margins before eyes narrowing and lateral genal edge rounded. Eyes prominent, situated at middle of head length. Neck strongly constricted (NW: 0.20). Head with two vertexal fovea [vf] connected by one transverse sulcus. Small longitudinal carina between vertexal fovea [vf] and another on the neck dorsally. Ocular-mandibular carinae present, starting at the superior edge of eyes; another small carina present that starts between eyes and joins with ocular-mandibular carinae at anterior region of head. Median gular sulcus shallow. Gular foveae [gf] present in posterior region of head. Antenna thin and long, with scape short and ventral side curved, last three antennomeres gradually thickening. Scape with base thicker than apex (length 0.20: width 0.09), pedicel thinner and shorter than scape (length 0.10: width 0.06), segment 3–11 longer than wide: 3 (length 0.12: width 0.06), 4 (length 0.12: width 0.05), 5 (length 0.18: width 0.05), 6 (length 0.16: width 0.05), 7 (length 0.18: width 0.05), 8 (length 0.13: width 0.05), 9 (length 0.20: width 0.07), 10 (length 0.16: width 0.08), 11 (length 0.39: width 0.10); all antennomeres covered with microsetae; segments 9–11 with microsetae denser.

Thorax ( Figs. 3–4 ): Pronotum slightly wider than long (PL: 0.47; PW: 0.45), edge of anterior half almost semicircular, posterior half with sides slightly convergent and posterior margin almost straight, postero-lateral angles with right angle. In posterior half with pair of prominent basolateral spines adjacent to elongate lateral antebasal foveae [laf], median antebasal fovea [maf] absent. Outer [oblf] and inner basolateral foveae [iblf] at basal margin present. Prosternum with lateral procoxal fovea [lpcf], proepimeral fovea [pef], and distinct paranotal carinae. Transversae sulcus with long setae at anterior margin of mesoventrite and into the anterior sulcus with one pair of median mesosternal foveae [mmsf]; one pair of small anterolateral mesosternal fovea [almsf]. Metaventrite with lateral mesocoxal fovea [lmcf].

Elytra ( Fig. 1 ): wider than pronotum (EL: 0.70; EW: 0.67), sides gradually narrowing anteriorly. Anterior margin straight and each elytron with two small basal elytral foveae [bef], humeri prominent, shallow sutural stria [ss] complete with short shallow discal stria [ds]. Elytron with epipleural carina that vanishes at anterior third, with small apicolateral clefts. Metathoracic wings longer than elytra but not reaching apex of abdomen.

Legs ( Figs. 5–6 ): thin and long. Procoxae and mesocoxae conical, prominent and contiguous. Metacoxae transversely elongate and moderately separate. Femora thickened medially; mesofemora with a long sinuate spine on basal half with one small tooth in posterior edge ( Fig. 5 ). Tibiae similar in length to femora, all tibiae thickening towards the apex. Tarsi 3-segmented, first segment very short and last two segments relatively long; protarsi and mesotarsi with second and third segments subequal in length, metatarsi with second segment longer than third; all tarsi with one single claw and one minute accessory seta.

Abdomen ( Fig. 1 ): slightly wider medially, with terga and sterna not fused and without paratergite; the intersegmental membranes with pattern of minute rectangular sclerites like brick wall. Tergite IV (first visible tergite) longest, V–VI very short in their lengths. Tergite IV with strong inner marginal carinae (imc); mediobasal fovea [mbf] and basolateral fovea [blf] connected internally; both mediobasal foveae [mbf] connected by deep longitudinal basal sulcus. Tergite IV at anterior margin with weak curved impressed line. Tergite VII and IV similar in length. Tergite VIII with apical edge deeply emarginated and with a small protuberance before the apical margin emarginate.Sternite IV with one basolateral fovea [blf] at each side, one mediobasal fovea [mbf] and one medial fovea at each side, all connected by a deep longitudinal basal sulcus.Sternites V–VII very short. Sternite VIII transverse, with large medial depression; posterior margin nearly straight. Tergum IX visible ( Fig. 10 ).

Aedeagus ( Figs. 7–10 ): strongly asymmetric, with parameres fused to form slim elongate plate that is curved at apex; median lobe slightly bulbous at base, elongate and narrow, curving laterally at apex.

Female. Characters of head, eyes, pronotum and elytra as described in male. Mesofemur without spine near the base. Tergite VIII with apical margin straight, with dorsal small protuberance pointed. Sternite VIII with central area almost flat, apical margin curved.

Etymology. The specific epithet refers to the Latin term inexpectatus , meaning unexpected, given the disjunct distribution of the species (which occur in both limestone and iron-rich caves). This in a noun in apposition.

Distribution. Known from iron-rich caves in the “Quadrilátero Ferífero” area (Parque Estadual Sera do Rola Moça—PESRM, Capão Xavier and Capitão do Mato), and in a limestone cave located in the Parque Estadual da Lapa Grande (Montes Claros municipality) in Minas Gerais state, Brazil.

Habitat and ecological notes. Specimens were collected in two quite distinct subterranean environments. The first one the limestone caves located in the Montes Claros municipality. Such caves are placed in the Bambuí geological group (Neoproterozoic age) and located in a conservation unit (Parque Estadual de Lapa Grande). The specimens were observed in at limestone cave (Boqueirão da Nascente cave), and were only found in deep portions of the cave, especially those areas covered by speleothems. All individuals were found in an upper gallery, located at least 20 meters above the subterranean stream that passes through the cave system, and at least 250 meters from the single entrance (the cave extends about 300 meters). Specimens were observed walking on speleothems or compacted sediments on the floor. The organic resources occurring in this area comprised of mainly guano piles. Six other caves were sampled in the region, but no specimens of Oxarthrius inexpectatus sp. nov. were found.

The second area where specimens were found corresponds to subterranean environments (mainly caves, although specimens were also observed in artificial galleries) associated with the “Quadrilátero Ferríferro” region, one of the most important iron ore landscapes in Brazil and Minas Gerais State ( Piló & Auler, 2005). The region holds more than 700 caves, most of them small, in average 22 meters long in a linear length ( Piló & Auler, 2005). Although several caves were sampled in this area, specimens of Oxarthrius inexpectatus sp. nov. were observed in only three caves (RM_0033, N_005, CPMT_0015) and one artificial gallery (Capão Xavier subterranean gallery). In most caves only a few specimens were observed, with the exception of the cave RM_0033 (the type-locality), where many specimens were found.

The RM_0033 cave presents the largest known population of this species. It is located in a high slope of the headwaters of the Mutuca stream in the Serra do Rola Moça State Park. The epigean environment is mainly composed of rupestrian vegetation with small shrubs often associated with the entrances of the caves ( Fig. 24 ). Its single entrance consists of a small passage ( Fig. 25 ) which determines the existence of an extensive aphotic zone along almost the whole cave. It is inserted in the contact of the ferrugineous topmost breccia (regionally known as “canga”) ant the iron ore rock (Itabirite), presenting around 70 meters of horizontal projection. The organic resources observed in this cave are litter from the external vegetation (mainly accumulated near the entrance), roots of epigean vegetation, which grows in several points of cave and ant middens (especially from the Apterostigma ants). Dozens of Oxarthrius inexpectatus sp. nov. were observed in almost all the aphotic areas of the cave, in both rainy and dry seasons. They were observed under rocks or moving on the floor in places formed by sandy or clayey sediment, or even on the bare rock ( Figs. 26, 27 ). Specimens are extremely sensitive to light, exhibiting escape behavior when exposed to artificial lighting.

Important information regarding this species is that it can also live (or at least disperse) in the small channels (canaliculus) present in the canga formation. Some years ago, an artificial gallery was built in a hill devoid of caves, near the Serra do Rola Moça State Park. Many specimens of Oxarthrius inexpectatus sp. nov. actively colonized this gallery, thus demonstrating their capability to disperse and probably to live in such small shallow subterranean habitats.

An intriguing aspect regarding this species consist of its disjunct distribution. The occurrence of specimens in a limestone cave and in ferrugineous caves (located approximately 380 km from the iron caves), is undoubtedly puzzling. Troglobites cannot survive for long periods in epigean habitats, so that dispersion between caves across external environments is quite uncommon ( Barr 1967; Culver 1982; Barr & Holsinger 1985; Holsinger & Culver 1988). Accordingly, troglobitic species with wide distributions can represent: i) a single species represented by populations with mechanisms that enable gene flow between caves ( Miller 2005); ii) genetically isolated populations that have not diverged due to insufficient time or low rates of change or iii) several distinct cryptic species, erroneously grouped into a single species ( Niemiller et al. 2013). There are different rock formations between these occurrences ( Fig. 23 ) although most of them represent rocks with considerable porosity (especially limestones), which do not preclude the possibilities of subterranean migration (CPRM 2008).

Figures

FIGURES 1–11. Oxarthrius (Oxarthrius) inexpectatus sp. nov., holotype, 1, habitus, dorsal view; 2, habitus, lateral view; 3, head and pronotum, dorsal view; 4, head and pronotum, ventral view; 5, meso leg, external face; 6, meta leg, external face (coxa absent); 7, aedeagus, ventral view; 8, aedeagus, lateral view; 9, aedeagus, dorsal view; 10, tergum IX;11, tergum VIII (T8) and sternum VIII (T8), lateral view. Scale bars: 1 mm (1–2); 0.5 mm (3–6); 0.2 mm (7–11).

FIGURES 23–27. 23, Elevation map of South America, Minas Gereais state, Bambui geological formation lead color, blue triangles; 24, RM_0033 cave in Nova Lima; 25, Boqueirão da Nascentes cave in Montes Claros; 26, Oxarthrius (Oxarthrius) inexpectatus sp. nov. in RM_0033 cave; 27, Oxarthrius (Oxarthrius) inexpectatus sp. nov. in Boqueirão da Nascentes cave.