Ardistomis ferreirai, Balkenohl & Pellegrini & Zampaulo, 2018

Balkenohl, Michael, Pellegrini, Thais Giovannini & Zampaulo, Robson De Almeida, 2018, A peculiar new beetle from Brazil associated with a cave habitat (Coleoptera, Carabidae, Clivinini), Zootaxa 4497 (3), pp. 398-410 : 400-405

Ardistomis ferreirai sp. nov.

( Figs. 1–6, 8b )

Type material. Holotype: Male , with labels and data: white, black framed, black printed “ Brazil (PA) - ISLA Projeto NSS—Morro I Parauapebas— 01/09/2010 Cav. GEM-1195 (Est. Seca) Carabidae sp5 Col. CARSTE” / white, handwritten, pencil “7397 ISLA ” ( ISLA) .

Paratype: 1 male, with labels and data: white, handwritten, Nankin pen “ Brazil, Pará, Floresta (National Serra dos Carajás), 596716mE 9327033mN, 07–12/X2008, leg. R. Andrade, et al., cavidade N5S21, amostra 907B” / white, handwritten, pencil “ Carabidae sp6” / white, black framed, black printed “ MZSP 4810” ( MZSP).

Remarks: In the holotype the two apical antennomeres of the right antenna are missing. Antennomere nine is blackish at tip. The paratype is somewhat paler as the holotype indicating it is immature.

The coordinates are given verbatim as they appear on the labels. For completeness an alternative format is given here in addition: Holotype: -06° 06' 33,02124"S; 50° 08' 05,69962"W. Paratype 1—N5S_0021, -06° 05' 15,30694"S; 50° 07' 33,52114"W.

Description. Measurements (holotype / paratype): Length 3.38 / 3.40 mm; width 0.93 / 0.96 mm; ratio length/ width of pronotum 1.05 / 1.00; ratio length/width of elytra 1.81 / 1.71.

Colour: Dorsal and ventral surface glossy; fuscous to hinnuleus, without any metallic tinge; mandibles fuscous, other mouthparts, antennae and tarsi more pale rufus-fuscous.

Head ( Figs. 2–5 ) with dorsal surface smooth, glossy. One third narrower than pronotum. Clypeus as wide as labrum, with convex reflexed margin anteriorly, with indistinct clypeal suture, wings of clypeus of moderate size, convex, not projecting as far as middle part of clypeus, separated from clypeus by obtuse emargination. Supraantennal plates vaulted, elongated, anteriorly separated from clypeal wings by indistinct notches. Frons elongated anteriorly, slightly convex, with indistinct central pore at eye-level. Supraorbital furrows deep, wide, nearly parallel anteriorly, diverging posterior to eye-level, bilaterally with two supraorbital setae situated at posterior eye- and posterior gena-level. Supraorbital carinae small. Vertex transverse groove well impressed, sharp, postero-laterally with isodiametric reticulation. Eyes small, conspicuously reduced, slightly convex, omatidiae not visible (160 times), surrounded by dark pigment. Genae broad, flattened, surface smooth. Antenna elongated, reaching over base of elytra, antennomere two and three of equal length, scapus with indistinct irregular reticulation, with the seta situated dorso-frontally at apical quarter. Labrum as wide as clypeus, emargined, sevensetose, with indistinct isodiametric reticulation. Mandible elongate (ratio length/width 2.88), narrow, straight, arcuate apically, with blunt tubercle-like tooth dorsally in basal third, premolar acute. Apical segment of maxillary palpus slender, elongated, securiform. Segment two of labial palpus bisetose, segment three a quarter longer as segment two, apical segment guttuliform. Ligula pointed, the two apical setae close together. Mentum with paralateral carina, small acutely toothed antero-laterally, with rounded central lobe projecting as far as lateral teeth, surface completely covered with roughly meshed reticulation. Pronotum ( Figs. 1, 4, 5 ) with outline longitudinal cordiform, flattened on disc (lateral view), distinctly convex in frontal view. Anterior angles rounded. Posterior angles not visibly developed. Reflexed lateral margin convex, reaching from anterior angles up to base. Marginal channel distinct. Lateral anterior and posterior setigerous punctures situated in distinct foveae, removed from lateral channel by diameter of pore. Reflexed margin as wide as lateral channel. Pleura swollen, visible in dorsal view. Anterior transverse line deep, sharp, joining with lateral margin at anterior angles, joining with median line. Median line deep, sharp, joining base. Surface with few indistinct wrinkles, basal impressions traceable bilaterally (100 times), formed by small fields of transverse reticulation. Base wide, with transverse rugae. Elytron ( Fig. 1) with outline long-ovate, slightly convex on disc (lateral view), flattened at middle and convex laterally in frontal view. Lateral margin convex, contracted to base and in apical third. Humerus rounded off. Base concave. Reflexed lateral margin crenulate in anterior two thirds, marginal channel with uninterrupted series of setigerous punctures, preapical epipleural plica displaced outward and interrupting outline of elytra. Setigerous tubercle at base of first stria. Scutellar stria absent. Striae impunctuate, subcrenulated, with irregular reticulation, stria one joining basal tubercle, stria two free at base, three joining with lateral channel. Striae one and two reaching apex, three to six ending apically at apical carina of interval seven, stria seven ending apically at level of preapical epipleural plica. Intervals convex, convexity more evident laterally, seventh carinate apically. Inner intervals slightly broadened basally. Third interval with four setigerous punctures, all approaching third stria, setae upright, of moderate length. Hind wings reduced to minute seta-like rudiment, length of rudiment comparable to seta of scapus of antenna. Ventral surface with proepisternum nearly smooth medially and laterally, with wide band of isodiametric reticulation at middle running parallel to lateral margin ( Fig. 5 ). Epipleuron and mesosternum smooth. Mesocoxa with isodiametric reticulation anteriorly. Abdomen at middle with transverse and laterally with isodiametric reticulation, the last four tergites with two accessory setae approaching base and a pair of setae laterally, terminal segment with transverse reticulation, with the two apical setigerous punctures widely separated. Legs with profemur less robust as in other species of the genus, medially with isodiametric reticulation. Protibia with terminal spine long, curved distinctly ventrally and laterally; movable spur shorter than spine, turned slightly ventrally, with one moderately long and one short praeapical lateral denticles. First tarsomere of protarsus as long as segments two to five together. Intermediate tibia with tubercles apically furnished with evident setae. In comparison to the hind legs, tarsomeres of front legs are conspicuously widened, those of intermediate legs distinctly widened and of hind legs slender (only two males were available for study). Sexual differences unknown. Male genitalia ( Fig. 6) with median lobe moderately slender, arcuate basally and at middle, nearly straight apically, with few minute pili in apical half, apical lamella somewhat distorted, spatula-like. Endophallus with two groups of microtrichia. Parameres asymmetric, ventral one slender, arcuate, with one seta of moderate length at apex; dorsal paramere wide, somewhat distorted, asetose, lateral apophysis blunt, basal apophysis acute. Female genitalia unknown. Variation was observed in the size of the two specimens (see measurements). The paratype is paler in total indicating it is still immature to a certain degree.

Distribution. Known from the type locality in Pará State, Brazil. The two specimens were collected in two different caves with a distance of 2.5 km but in the same massif.

Differential diagnosis. A smaller sized, slender and flattened Ardistomis species with uniform brown colour, a longitudinal cordiform pronotum, long ovate elytra, and segment two of the labial palpus as long as segment three.

Taking the features for Middle American species into account, the new species resembles specimens of the fasciolatus species group ( Valdés 2009). However, all of the species of this group have fully developed eyes, exhibit a subovate or subglobose pronotum, the elytron has a developed humerus, and the third interval of the elytron shows five setigerous punctures. The species seems to be more related to members of the venustulus species group, but those species are fully winged, the pronotum has a different shape, and the chetotaxy of the elytron is different ( Valdés 2007, 2009).

The new species can be easily distinguished from all other members of the genus by the distinctly elongated mandibles, the crenulated lateral margin of the elytra, the missing hind wings, and the nearly subparallel outline of the elytra. The only other Ardistomis which also shows such conspicuously reduced eyes as A. ferreirai sp. nov. is A. franki Nichols MS from Jamaica ( Nichols 1988b, quoted as ‘manuscript name’ by Valdés 2009) and according to personal information communicated kindly by Valdés. The most striking differences shown by A. franki are the convex elytra with interval three five-punctate, shorter mandibles, absence of crenulation of the elytra, larger size (length 5.5 mm), and a more convex pronotum.

Etymology. The species is dedicated to Rodrigo Lopes Ferreira (Federal University of Lavras, Brazil), renowned specialist in biospeleology, during the last 20 years describing not less than 100 invertebrate species found in Brazilian caves, and is expressed as a Latinised adjective.

Habitat, ecological considerations and threats. The region is covered by a submontane Ombrofila forest and the caves concerned are located in the average slope area at an altitude of about 600 m NN ( Fig. 7 ). Despite several research visits in caves of the high slope and low slope area ( Fig. 7 ), A. ferreirai sp. nov. seems to inhabit only the caves in the average slope area.

The specimens were found on the moist ground of the cave and under blocks in the inner aphotic parts of the caves ( Fig. 8 ). The caves are located in a complex iron ore outcrop known as “Serra Norte”. This formation is situated in the Carajás National Forest, a federal conservation unit of sustainable use with nearly 400 thousand hectares. The area preserves 1.31 thousand hectares of Amazon forest and “rupestrian fields” growing over a superficial ferruginous breccia (canga formation), merged between pastures and urban areas ( Rolim et al. 2006; Souza-Filho et al. 2016).

More than two thousand natural iron ore caves are known to exist in the area, while at the same time mining practices are withdrawing about 164 million tons of ore per year (Departamento Nacional de Produção Mineral— DNPM 2017). The two Ardistomis ferreirai sp. nov. specimens were collected in two different caves, located in the south portion of “Serra Norte”, numbered as caves N5S_0021 and N5SM1_0027. The region is enclosed by the rivers Rio Catete and Rio Itacaiúnas, both of them tributaries of the Tocantins River system. Despite the intensive mining operations, both caves are legally protected due to their dimensions marking their importance in the region and any irreversible negative impacts are forbidden ( BRASIL 2008; MMA 2017). Cave N5SM1_0027 has a wide entrance with a constricted passage a few meters ahead. Organic inputs are apparently predominated by large roots hanging from the ceiling and a few small ones on the cave floor; leaf litter is restricted to the entrance area. The cave substrate consists of fine sediment, gravel and matrix rock. In the final portion of the cave there are blocks and dripping areas forming small intermittent pools of water. The cave has 59.5 meters of horizontal projection, an area of 655 m 2, 2.42 m slope, 589 m NN and is situated a distance of 670 m from the mining area. Many of these characteristics are shared by cave N5S_0021 ( Fig 8a ), except for the small intermittent pools of water, as well as its development proceeding by narrower passages with a low ceiling and narrow ascending conduits giving access to larger halls. It possesses 285 meters of horizontal projection, an area of 207 m 2, 30 m slope, 663 m NN and is situated about 150–200 m from the mining area.

The conditions in the inner aphotic parts of the caves in which the specimens were found differ substantially from those observed in the entrance chamber. In the caves specimens of spiders ( Carajas paraua Brescovit & Sánchez-Ruiz, 2016 ), isopods ( Circoniscus buckupi Campos-Filho & Araújo, 2011 ) and whip spiders ( Charinus carajas Giupponi & Miranda, 2016 ) were found as well as other undetermined species. Carajas paraua and C. buckupi are restricted to the subterranean environment. In general, such troglobitic species are widely distributed throughout the iron ore outcrop complex of “Serra Norte”. This pattern occurs due to a huge network of small channels (canaliculi) connecting the caves ( Ferreira et al. 2015).

Figures

FIGURE 7. Habitat of Ardistomis ferreirai sp. nov. with location of cave N5SM1_0027, entrance of cave in the submontane Ombrofila forest (a), schematic drawing of the slope (b). Arrows: entrance of cave.

FIGURE 8. Cave N5S_0021, conduit located in the most distal portion of the cave in a complete aphotic part (a). Ardistomis ferreirai sp. nov. live specimen found in the cave Cave N5SM1_0027 (b).

FIGURES 2–5. Ardistomis ferreirai sp. nov.; 2. Head, dorsal view;—3. Head, ventral view;—4. Head, lateral view; 5. Head and prothorax, lateral view showing the band of isodiametric reticulation running in parallel to lateral margin.