The family Ctenobelbidae (Acari, Oribatida), with description of a new species and discussion on systematic placement and taxonomic status of the genus Berndamerus Mahunka, 1977

Abstract The oribatid mite genus Berndamerus Mahunka, 1977 is transferred into the family Ctenobelbidae as the subgenus Ctenobelba (Berndamerus) Mahunka, 1977, stat. n. from the family Amerobelbidae. The known species of Berndamerus combined: C. (B.) bicostata (Berlese, 1910), comb. n., C. (B.) eremuloides (Berlese, 1910), comb. n., C. (B.) hellenica (Mahunka, 1977), comb. n. A new species, Ctenobelba (Berndamerus) bugiamapensis sp. n., is described from soil, Bu Gia Map National Park, southern Vietnam. It differs from the other species of the subgenus by the heterotrichy of notogastral setae, presence of adanal neotrichy and localization of adanal lyrifissures. Ctenobelbidae is recorded in Vietnam for the first time. A new diagnosis of the family Ctenobelbidae and the identification keys to the known subgenera of the genus Ctenobelba and species of the subgenus Ctenobelba (Berndamerus) are provided.

The primary purpose of paper is to discuss the systematic placement and taxonomic status of the subgenus Ctenobelba (Berndamerus) stat. n., which was described as the genus Berndamerus Mahunka, 1977 of the family Amerobelbidae.
During taxonomic survey of oribatid fauna of the Bu Gia Map National Park in southern Vietnam (a brief geographical and floristic descriptions of this park was given earlier -Ermilov et al. 2012a), we found a new species of Ctenobelba (Berndamerus) stat. n. It is a first representative of the Ctenobelbidae recorded from Vietnam. The secondary purpose of the present paper is to describe and illustrate this new species.
We provide a new diagnosis of the family Ctenobelbidae and present the identification keys to the known subgenera of the genus Ctenobelba and species of the subgenus Ctenobelba (Berndamerus) stat. n.
Soil samples were collected by taking 10 soil cores (diameter: 7.8 cm; depth: 10 cm). The samples collected were left in the metal cores to minimize disturbance during transportation from the field to the laboratory. Oribatid mites were extracted into 75 per cent ethanol using Berlese's funnels with electric lamps (40 W) during ten days. Specimens of the new species were found in three samples out of 10.
Holotype and paratypes were mounted in lactic acid on temporary cavity slides for measurement and illustration. The body length was measured in lateral view, from the tip of the rostrum to the posterior edge of the ventral plate. The notogastral width refers to the maximum width in dorsal aspect (without pteromorphs). Lengths of body setae were measured in lateral aspect. All body measurements are presented in micrometers. Formulae for leg setation are given in parentheses according to the sequence trochanter-femur-genu-tibia-tarsus (famulus included). Formulae for leg solenidia are given in square brackets according to the sequence genu-tibia-tarsus. General terminology used in this paper follows that of Grandjean (summarized by Norton and Behan-Pelletier 2009). Mahunka, 1977Mahunka (1977 described the genus Berndamerus with Berndamerus hellenicus Mahunka, 1977, as the type species, and included it in the family Amerobelbidae. Later, Mahunka and Mahunka-Papp (1995), Subías (2004), Ermilov (2011) supported Berndamerus in this family.

Systematic placement and taxonomic status of the genus Berndamerus
However, mites of the family Amerobelbidae differ from those of the family Ctenobelbidae by an important morphological character -absence (versus presence) of prodorsal costulae (Norton and Behan-Pelletier 2009). All species of Berndamerus are with well developed costulae. Therefore inclusion of this genus in Amerobelbidae is doubtful. Thus, we suggest the genus Berndamerus should be transferred to the family Ctenobelbidae.
The main generic morphological character of Berndamerus is the arrangement of notogastral setae (located dorsally, usually in two longitudinal rows). This character state is not an apomorphy, because it is inherent also for some other taxa in the Ameroidea, including the ctenobelbid subgenus Ctenobelba (Caucasiobelba) Subías & Shtanchaeva, 2010. Thus, the generic status of Berndamerus cannot be supported, and we consider that it should be included as the subgenus in the genus Ctenobelba, differing from Ctenobelba (Caucasiobelba) by the absence of reticulate body surface: Ctenobelba (Berndamerus) Mahunka, 1977 stat. n setae setiform, barbed; lamellar setae longest and thickest. Sensilli setiform, ciliate Notogastral setae c longest, barbed; p 1 -p 3 of medium size, barbed; other setae short, smooth. Setae c, la, lm inserted in one longitudinal row; lp, h 2 , h 3 inserted close to each other. Aggenito-adanal neotrichy present: eight pairs of setiform, barbed setae developed.
Integument. Body color yellow-brownish to brown. Dorsal body surface smooth; ventral body surface (including subcapitular mentum, genital and anal plates) microfoveolate (diameter of foveolae up to 0.5), which is visible only under high magnification (× 1500). The region adjacent to the anal aperture striate.

New diagnosis of the family Ctenobelbidae
Prodorsum with long, parallel one pair of costulae. Rostrum rounded or dentate. Lamellar setae inserted on the costular ends. Sensilli bifurcate or setiform, with cilia (three to 25) or long branches unilaterally. Tutoria absent. Cerotegument presented by granules or reticulate ornamentation, rarely absent. Anterior margin of notogaster with one pair of tubercles. Ten pairs of notogastral setae present; they of diverse shape (thickened or leaf-like or with long, bent thin tip) or simple. Pedotecta I and II well developed. Epimeral formula: 3-1-3-3 (rarely: 3-1-3-4 or 3-1-4-4); epimeral setae 1b often longest, directed forward. Six pairs of genital, two to five aggenital (rarely more than five), two pair of anal and three pairs of adanal setae present (rarely more aggenital and adanal setae). Lyrifissures iad located posteriad to adanal setae ad 3 . Solenidia of tibiae and genua not coupled with dorsal seta. Legs monodactylous.