The genus Scapheremaeus (Acari, Oribatida, Cymbaeremaeidae) in the oribatid mite fauna of New Zealand, with description of two new species

Abstract Two new species of oribatid mites of the genus Scapheremaeus (Oribatida, Cymbaeremaeidae), Scapheremaeus gibbus sp. n. and Scapheremaeus luxtoni sp. n., are described from New Zealand. Scapheremaeus gibbus sp. n. is morphologically most similar to Scapheremaeus humeratus Balogh & Mahunka, 1967, but differs from the latter by the number of notogastral, genital and adanal setae, morphology of bothridial setae, position of adanal lyrifissures and absence of humeral processes. Scapheremaeus luxtoni sp. n. is morphologically most similar to Scapheremaeus yamashitai Aoki, 1970, but differs from the latter by the morphology of notogastral and rostral setae, morphology of leg solenidia φ2 and development of humeral processes. The species Scapheremaeus zephyrus Colloff, 2010 is recorded for the first time in New Zealand. An identification key to the known New Zealand species of Scapheremaeus is provided.


Introduction
Scapheremaeus is a large genus of oribatid mites (Acari, Oribatida, Cymbaeremaeidae), which was proposed by Berlese (1910) with Eremaeus patella Berlese, 1886 as type species. At present, the genus comprises more than 110 species and has a cosmopolitan distribution (except the Antarctic region) (Subías 2004(Subías , updated 2015Ermilov and Anichkin 2015). The generic characters of Scapheremaeus are summarized by Colloff (2009). The identification keys to species from some regions and countries have been presented by Sitnikova (1975), Rios and Palacios-Vargas (1998), Balogh and Balogh (2002), Colloff (2010), Norton et al. (2010), and Ermilov and Anichkin (2015). The information about juvenile instars is summarized by Norton and Ermilov (2014), with some new data added by .
During studies of oribatid mites from New Zealand, we discovered two new species of Scapheremaeus, S. gibbus sp. n. and S. luxtoni sp. n., and also found a known species, S. zephyrus Colloff, 2010, which was previously recorded only in Australia. The primary aim of our paper is to describe these species.
Three other species of Scapheremaeus are known from New Zealand (Hammer 1966): S. emarginatus Hammer, 1966, S. insularis Hammer, 1966 andS. patella (Berlese, 1886). The second aim of our paper is to provide an identification key for all known species of this genus in New Zealand.

Materials and methods
The collection lo cality and habitat for each new species are given in the "Material examined" sections. Additionally, two specimens (female and male) of S. zephyrus were collected from: New Zealand, South Island, Central Otago, Old Man's Range, 45°18'58"S, 169°11'45"E, 1646 m a.s.l., in soil and debris under Dracophyllum muscoides cushion, 17 February 2014 (M. Minor).
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;Colloff 2009).
Legs. Monodactylous. Femora I and II with extremely large ventral expansions. Porose areas (p.a) slightly visible, oval. Formulas of leg setation and solenidia:   Etymology. The specific name gibbus refers to the clearly convex centrodorsal notogastral region, forming longitudinal elongate hump-like structure.
Remarks. The new species is most similar to S. humeratus Balogh & Mahunka, 1967 from Congo (see Balogh and Mahunka 1967) in having small body size, monodactylous legs, simple notogastral setae, areolate body surface, and absence of circumdorsal furrow. However, it differs from the latter by the presence of 13 pairs of notogastral setae (versus 11), globular bothridial setae (versus fusiform), five pairs of genital setae (versus six), two pairs of adanal setae (versus three), transverse position of adanal lyrifissures (versus longitudinal) and absence of humeral processes (versus well developed). Integument. Body color light yellow-brownish. Anterior part of prodorsum and centro-dorsal part of notogaster with areolate sculpturing. Dorso-lateral parts of notogaster and ventral plate with elongated ridge-like tubercles.
Legs. Tridactylous. Porose areas slightly visible, oval. Formulas of leg setation and solenidia as in S. gibbus sp. n.; homology of setae and solenidia as indicated in Table 1. Famuli short, slightly dilated distally. Solenidia (except simple ω on tarsi and φ 1 , and thin σ on genua I) dilated distally. Setae l on tibiae I setiform, not modified.
Type deposition. The holotype and one paratype are deposited in the New Zealand National Arthropod Collection, Auckland, New Zealand; one paratype is deposited in the collection of the Senckenberg Institution, Frankfurt, Germany; one paratype is deposited in the collection of the Tyumen State University Museum of Zoology, Tyumen, Russia.
Etymology. The specific name is dedicated to the well-known acarologist Malcolm Luxton, for his extensive contributions to our knowledge of New Zealand oribatid mite fauna.
Remarks. The new species is similar to S. yamashitai Aoki, 1970 from Japan (see Aoki 1970;Fujikawa 2002) in having circumdorsal furrow, tridactylous legs, costulae and transcostula, ten pairs of minute notogastral setae and areolate centrodorsal region of notogaster. However, it differs from the latter by the presence of thin notogastral setae (versus thickened), straight rostral setae (versus curved medially), short and dilated distally leg solenidia φ 2 (versus long and simple) and slightly developed humeral processes (versus well developed).  Also, in having circumdorsal furrow, tridactylous legs, costulae, minute notogastral setae, straight rostral setae and areolate centrodorsal region of notogaster, S. luxtoni sp. n. is similar to S. zephyrus Colloff, 2010 from Australia (see Colloff 2010) and New Zealand (our data). However, it differs from the latter by the presence of large tubercle-like distal parts of costulae (versus small), strong transcostula (versus absent), ten pairs of thin notogastral setae (versus nine pairs and thickened) and three pairs of adanal setae (versus two pairs).