Contributions to the knowledge of oribatid mites of Indonesia. 2. The genus Pergalumna (Galumnidae) with description of a new species and key to known species in the Oriental region (Acari, Oribatida)

Abstract A new species of oribatid mite of the genus Pergalumna (Oribatida, Galumnidae) is described from litter and soil materials in Sumatra, Indonesia. Pergalumna paraindistincta sp. n. is morphologically most similar to Pergalumna indistincta Ermilov & Anichkin, 2011, Pergalumna pertrichosa Mahunka, 1995 and Pergalumna sura Balogh, 1997; however, the new species differs from Pergalumna indistincta by the smaller body size, presence of long adanal setae ad1, and large, single median pore in females and males; from Pergalumna pertrichosa by the smaller body size, presence of three pairs of notogastral porose areas, elongated A1 and minute anal setae; from Pergalumna sura by the presence of strong adanal setae ad1, large, single median pore in females and males, and shorter bothridial setae. Furthermore, Pergalumna hawaiiensis hawaiiensis (Jacot, 1934) and Pergalumna panayensis Ermilov & Corpuz-Raros, 2015 are recorded for the first time in the Indonesian fauna. An identification key to the known species of Pergalumna in the Oriental region is given.


Introduction
This work is a part of a continuing study on the Indonesian fauna of oribatid mites, and it includes the data on the genus Pergalumna Grandjean, 1936 (Oribatida, Galumnidae). During taxonomic identification, four species were identified, including one new to science. The primary goal of the paper is to present data on the specific localities, notes on new records and overall known distributions of registered taxa and to describe the new species.
Pergalumna is a genus that was proposed by Grandjean (1936) with Oribata nervosa Berlese, 1914 as type species. Based on an updated generic diagnosis (Ermilov et al. 2013b), it comprises more than 140 species (Subías 2004(Subías , updated 2015Ermilov and Bayartogtokh 2015;Ermilov and Corpuz-Raros 2015) having collectively a cosmopolitan distribution (Subías 2004(Subías , updated 2015. The identification keys to selected species were given by Shaldybina (1975), Balogh (1990, 2002), Weigmann (2006), and Ermilov et al. (2014b). The secondary goal of the paper is to provide an identification key to known species of Pergalumna in the Oriental region.

Materials and methods
Exact collection locality and habitat are given in the respective "Material examined" section for each species.
Specimens 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. Notogastral width refers to the maximum width in dorsal aspect. Lengths of body setae were measured in lateral aspect. All body measurements are presented in micrometers. Formulas for leg setation are given in parentheses according to the sequence trochanter-femur-genu-tibia-tarsus (famulus included). Formulas 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).
Drawings were made with a camera lucida using a Carl Zeiss transmission light microscope "Axioskop-2 Plus". Integument. Body color brown. Body surface microgranulate, visible under high magnification, ×1000 (diameter of granules less than 1).
Type deposition. The holotype is deposited in LIPI (Indonesian Institute of Science) Cibinong, Indonesia; three paratypes are in the collection of the Senckenberg Museum, Görlitz, Germany; seven paratypes are in the collection of the Tyumen State University Museum of Zoology, Tyumen, Russia.    Etymology. The specific name paraindistincta refers to the morphological similarity of the new species to Pergalumna indistincta Ermilov & Anichkin, 2011. Remarks. Pergalumna paraindistincta sp. n. is morphologically most similar to P. indistincta Ermilov & Anichkin, 2011 from Vietnam (see Ermilov and Anichkin 2011b) and P. sura Balogh, 1997 from the Neotropical region (see Balogh 1997;Ermilov et al. 2014a) in having rounded rostrum, well-developed prodorsal setae, setiform and ciliate of bothridial setae, three pairs of notogastral porose areas, transversally oriented Aa and strongly elongated, longitudinally oriented A1, and the absence of anterior notogastral margin as well as postanal porose area. However, the new species differs from both by the presence of strong adanal setae ad 1 (vs. minute in P. indistincta and P. sura) and large, single median pore in females and males (vs. median pore absent in males and represented by several foveae in females in P. indistincta, and absent in females and males in P. sura). Additionally, the new species is smaller than P. indistincta (415-481 × 298-365 vs. 547-614 × 381-415) and has shorter bothridial setae than P. sura.
Furthermore, P. paraindistincta sp. n. is morphologically similar to P. pertrichosa Mahunka, 1995 from Borneo (see Mahunka 1995) in having a rounded rostrum, well developed prodorsal setae, setiform and ciliate bothridial setae, strong adanal setae ad 1 , a single median pore, and the absence of an anterior notogastral margin. However, the new species differs from the latter by the smaller body size (415-481 × 298-365 vs. 550-608 × 413-454 in P. pertrichosa), presence of three pairs of notogastral porose areas with elongated A1 (vs. four pairs of porose areas with A1 rounded in P. pertrichosa) and minute anal setae (vs. well developed in P. pertrichosa).

Key to known species of Pergalumna in the Oriental region
At present, 45 species/subspecies of Pergalumna are known in the Oriental region (Subías 2004(Subías , updated 2015; including present and personal data of the first author). Pergalumna heroica (Willmann, 1931) from Java (see Willmann 1931), P. medialis (Sellnick, 1925) from Sumatra (see Sellnick 1925) and P. obsessa Subías, 2004 from Taiwan (see Tseng 1984 as Galumna pallida Tseng, 1984) are excluded from the key because these species have been poorly described.