Duvalius abyssimus Reboleira & Ortuno, n. sp.

Duvalius abyssimus Reboleira & Ortuño n. sp.

(Figs. 2–5)

Type series. Holotype: 1 ♂, Krubera-Voronya Cave (UTM: 43°24′35″N, 40°21′44″E), Caucasus (Abhkazia), 27.VII.2010, S. Reboleira & A. Sendra leg. (SR/UA).

Paratype: 1 ♀, same data as holotype, 09.VIII.2010 (VMO/UAH).

Diagnosic features (Figs. 2 and 4): Micropthalmous and micropterous trechine species. Body elongated, with long antenna and legs. Integument depigmented and testaceous, slightly shiny and with soft microreticulation. Cordiform pronotum, nearly as wide as long, with the anterior part largely protruding and posterior angles acute and sinuate toward the straight base. Ovate elytra with the shoulders not marked, seven striae visible, but only the first three punctuate. Male protarsi with the first tarsomeres enlarged. Median lobe of the aedeagus thin and long, with the apex of the apical blade slightly curved towards the dorsal part and the inner sac with a symmetric sclerotized piece, channel-shaped, of which a thin and fine structure is projected rearward.

Description: Large species, total body length: 6.60–6.77 mm.

Head: (Fig. 2) longer than wide (width/length ≈ 0.64–0.65, excluding mandibles), neck well marked, temples convex and very long (four times the diameter of the eye), deep and complete frontal furrows bordering all the supraocular area and slightly reduced in the posterior part, eyes reduced and not convex with a few ommatidia, two supraocular setae (the anterior is placed slightly behind the level of the posterior edge of the eye and the posterior almost adjacent to the rear of the supraocular groove); clypeus with two setae on each side; labrum slightly notched and fringed with six setae near the anterior margin; mandibles long and very sharp; labial and maxillar pieces typical of the genus; labium lobulated and bisetulated at the base of labial tooth which is truncated (Fig. 3), articulated with the labium in the prebasilar area, bordered with six long setae (Fig. 3); antennae very long and full of setae, reaching the level of the 6th umbilical setae.

Pronotum (Fig. 2): cordiform, nearly as wide as long (width/length ≈ 1,03), its greatest width in its anterior third; lateral margin markedly sinuated; basal margin slightly notched with the posterior angles protruding backwards; lateral channel of moderately width and marked in all its length; basal grooves deep and not punctuated; convex disk with well marked median sulcus; two pronotal bilateral setae (the anterior situated in the first third part and the posterior slightly forward the rear angle).

Elytra (Fig. 2) oval and narrow (width/length ≈ 0.64–0.66), reaching maximum width slightly behind half; base of elytra oblique with effaced shoulders; striae 1st–3rd well marked by a punctured groove; striae 4th–7th only punctuate, becoming progressively weaker toward the outer striae; scutellar striole short and located at the base of the first interstria; apical striole short but well defined; internal interstriae very slightly convex, being the external ones flat; lateral channel width; discal setae inserted over the 3rd stria, the anterior located in the basal fifth and the posterior discal setae roughly central, next to 3/5; scutellar pore at the origin (anastomosis) of the 1st–2nd stria; apical triangle present, formed by the subapical seta (inserted at the end of the 2nd stria), first apical seta close to the elytral apex at the level of the second stria), second apical seta contiguous to the recurrent striole; umbilical series typical of the genus, with four equidistant setae in the humeral group and four setae in the apical group (two anterior and two posterior).

Legs (Fig. 2) very long; anterior tibia furrowed longitudinally in the outer margin of the dorsum; anterior first two tarsomeres of the male clearly widened and toothed on the inner margin.

Aedeagus (Fig. 4) large (1.38 mm), median lobe thin and elongated; basal bulb slightly dilated, arcuate in a regular curve and with a very small sagittal aileron; apical blade formed by a small sclerotized surface with blunt contour in dorsal view (Fig. 4 c) and slightly raised towards the dorsal part (Figs. 4 a, b); inner sack with a symmetrical sclerotized piece, channel-shaped, of which a piliform structure is projected rearward (Fig. 4 a–c); parameres slender, subequal, each with three apical setae of different thickness (Fig. 4 d–e).

Female genitalia (Fig. 5). External genitalia (Fig. 5 a) formed by dimerous IX gonopods (gonocoxites and gonosubcoxites) and IX laterotergites; gonocoxites unguiform, wide, with 3 to 4 spiniform setae inserted in the dorsal surface and with a small ventral groove that harbours two small sensorial setae; gonosubcoxite trapezoidal, slightly longer than wide, with 3 or 4 large spiniform setae in the inner margin (near the corner) and two large setae on the ventral basal margin; laterotergite IX wing-shaped, slightly sclerotized and with more than 30 setae in the basal half. Internal genitalia (Fig. 5 b) membranous and voluminous (length ≈ 1.07 mm; Ø ≈ 0.19–0.28), the vagina is short and wide, and leads to a large copulatrix bursa, pleated longitudinally in bellows; the distal half of the complex (spermatheca) is poorly folded, hyaline, ending as a “cul-de-sac”.

Etymology. abyssimus from the Latin name for abyss, once it was discovered in Krubera-Voronja, world’s deepest cave since 2001 and as far, the only cave surpassing the depth of -2000 meters below the surface.

Affinities and biogeographical remarks. Duvalius abyssimus n. sp. is the third species of the genus in the Western Caucasus region. Two cave-dwelling species were previously known: D. miroshnikovi Belousov & Zamotajlov, 1995, from Bariban Cave, Sochi, Alek massif, in Russia and D. sokolovi Ljovuschkin, 1963, from the Arabika massif, Abkhazia (Belousov 1991, Belousov et al. 1995, Kryzhanovskij et al. 1995, Ljovuschkin 1963, 1972).

Duvalius miroshnikovi from Alek massif, a small mountain ridge that is located approximately 40 km west of Arabika, seems to be the closest species to D. abyssimus. D. miroshnikovi is distinguished by the size and by the distinct shape of the aedeagus, especially the shape of the median lobe, and by the presence of 4 to 5 setae in the parameres, although the number of these setae is often variable in Trechini (Belousov et al. 1995).

Duvalius sokolovi was described based on a short diagnosis and a general habitus illustration of one single female from the Arabika massif. The type locality called as “ Trechus Cave ” is described as a small cave (≈ 6 meters) where the female holotype was found walking among limestone debris (commonly known as MSS). Without providing further information in the description, the type locality is impossible to be identified by local people or speleologists within the Arabika massif. It is also impossible to revise the type specimen of D. sokolovi because it was lost (Golovatch pers. comm.). Furthermore, the available description of D. sokolovi is short and does not include many diagnostic features. Even so, D. sokolovi can be distinguished from D. abyssimus n. sp. by its incomplete frontal furrows, the proportional head size related to pronotum and by the posterior border of the elytra, much more prominent (Ljovuschkin 1963).

Given the problems concerning the identity of D. sokolovi, this name could be eventually considered as nomem dubium.

Ecology and habitat. The specimens of Duvalius abyssimus n. sp. were collected in the Krubera-Voronja cave by active search in the upper part of the cave, at -60 meters depth, where temperature is about 3 ºC and humidity is 100%. This cave harbours the world’s deepest terrestrial subterranean invertebrate community and it is inhabited by arthropods with different degrees of adaptation to subterranean life (Sendra & Reboleira 2012). The richest part of the cave is the basis of the first shaft, where Duvalius abyssimus n. sp. was found. It has a major input of nutrients from surface and consequently higher richness (Sendra & Reboleira 2012). The pseudoscorpion Neobisium (Blothrus) birsteini Lapschoff, 1940 (Neobisiidae), is the main predator widespread along the deepest branch of the cave, together with the opilion and spider of the genera Nemaspela Šilhavý, 1966 (Nemastomatidae) and Troglohyphantes Joseph, 1881 (Linyphiidae), only found in the upper parts of the cave. A major proportion of this biocoenosis is composed by decomposers: a millipede of the order Chordeumatida and a species of Leucogeorgia Verhoeff, 1930 (Julidae); the springtails Plutomurus ortobalaganensis Jordana & Baquero, 2012 (Tomoceridae), Deuteraphorura kruberaensis Jordana & Baquero, 2012 (Onychiuridae), Schaefferia profundissima Jordana & Baquero, 2012 (Hypogastruridae) and Anurida stereoodorata Jordana & Baquero, 2012 (Neanuridae) (Jordana et al. 2012) and the beetle Catops cavicis Giachino, 2011 (Leiodidae) (Giachino 2011).