Two new species of oribatid mites of the family Galumnidae (Acari, Oribatida) from Vietnam

Abstract Two new species of oribatid mites of the family Galumnidae, Allogalumna monodactyla sp. n. and Galumna (Galumna) paracalcicola sp. n., are described from dark loamy soil under crown of Ficus sp. in southern Vietnam. Allogalumna monodactyla sp. n. is the first identified member of Allogalumna recorded for Vietnam. The identification keys to the species of Allogalumna from the Oriental region and species of Galumna (Galumna) from Vietnam and the calcicola-group are given.


Introduction
During taxonomic identification of oribatid mites from Dong Nai Biosphere Reserve of southern Vietnam, we found two new species of Galumnidae; one belonging to the genus Allogalumna Grandjean, 1936, other to Galumna (Galumna) Heyden, 1826. The main goal of this paper is to describe these species.
Allogalumna is a genus that was proposed by Grandjean (1936) with Galumna alamellae Jacot, 1935 as type species. Currently, it comprises more than 30 species having a cosmopolitan distribution collectively (data summarized by Subías (2004Subías ( , updated 2013). In the Vietnamese fauna, Allogalumna has been recorded earlier, but some unidentified species has been referred (Vu et al. 1985;Ermilov and Anichkin 2013a). Thus, the new species described here is the first identified member of this genus recorded for Vietnam. We compared our present material with that of previously found one specimen of Allogalumna sp. (Ermilov and Anichkin 2013a), and clarified that the latter was the same species.
The generic diagnoses of the genera Allogalumna and Galumna are summarized earlier by .
Additionally, the identification keys to the Allogalumna-species from the Oriental region and Galumna (Galumna)-species from Vietnam and the calcicola-group are given in the present work.
Soil samples were collected by taking 10 soil-cores (diameter: 7.8 cm; depth: 10 cm). Samples were left in the metal cores to minimize disturbance during transport from the field to the laboratory. Mites were extracted into 75% ethanol using Berlese's funnels with electric lamps (40 W) for ten days.
Holotypes 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 F. Grandjean (summarized by Norton and Behan-Pelletier 2009). Integument. Body color yellowish-brown to brown. Body and legs covered by the microgranular cerotegument. Granules (up to 1) visible only under high magnification. Body surface smooth. Pteromorphs with distinct radiate wrinkles.
Notogaster. Anterior notogastral margin not developed. Dorsophragmata absent. Notogastral setae represented by 10 pairs of alveoli. Four pairs of porose areas small, round (Aa, 4-6; A1-A3, 4), poorly visible, punctiform, without distinct borders. Alveoli of setae la inserted latero-posteriorly to Aa. Lyrifissures im located between lm and lp. Opisthonotal gland openings not evident. Median pore (mp) present in all specimens, located in centrodorsal part of notogaster between the virtual lines connecting lm and lm, lp and lp.
Legs. Monodactylous; claw of each leg smooth. Morphology of leg segments, setae and solenidia typical for most Galumnidae (for example : Ermilov and Anichkin 2010, 2011aErmilov et al. , 2011, but solenidion of genua III weakly dilated in medial part. Formulae of leg setation and solenidia: ; homology of setae and solenidia indicated in Table 1.
Type deposition. The holotype is deposited in the collection of the Zoological Institute of the Russian Academy of Sciences, St. Petersburg, Russia; one paratype in deposited in the collection of the Siberian Zoological Museum, Novosibirsk, Russia; one paratype is deposited in the collection of the Tyumen State University Museum of Zoology, Tyumen, Russia.
Etymology. The specific name "monodactyla" refers to the monodactylous legs of the new species.
Comparison. Allogalumna monodactyla sp. n. differs from other known species of the genus Allogalumna by the median pore located in centrodorsal part of notogaster (versus in posterior part) and monodactylous legs (versus tridactylous).   Integument. Body color yellowish-brown. Body surface smooth, but some transverse stria located posteriorly to the genital apertures. Pteromorphs with distinct radiate wrinkles.
Legs. Three claws of each leg smooth. Morphology of leg segments, setae and solenidia typical for most Galumnidae (for example : Ermilov and Anichkin 2010, 2011aErmilov et al. , 2011.  Table 1.
Type deposition. The holotype is deposited in the collection of the Zoological Institute of the Russian Academy of Sciences, St. Petersburg, Russia; paratype is deposited in the collection of the Tyumen State University Museum of Zoology, Tyumen, Russia.
Etymology. The prefix para is Latin meaning "near" and refers the similarity between the new species and the species Galumna calcicola (Aoki & Hu, 1993).
Comparison. Galumna (Galumna) paracalcicola sp. n. can be included in calcicola-group. Species of this group have the short (clearly not reaching the insertions of rostral setae), almost straight lamellar lines.  Aoki (1965) described Galumna flabellifera orientalis Aoki, 1965from Thailand. However, later he (1982 has come to opinion that the subgeneric status of G. flabellifera orientalis is impossible, and has counted it as a junior synonym of the type species.