Two new species of the genus Trichoribates (Acari: Oribatida: Ceratozetidae) from Central Japan

The present paper deals with two species of oribatid mites of the genus Trichoribates Berlese, 1910 from the subalpine zone of high mountains in Central Japan. Trichoribates aokii n. sp. and Trichoribates hirauchiae n. sp. are proposed on the basis of adults. The first species is characterized by narrow lamellar cusps and translamella, and very closely situated notogastral setae h2 and h3. The second species is readily distinguishable from other closely related species by the specific structure of porose areas A1 and A2, the larger body size, the longer interlamellar and rostral setae, and anteriorly converging lamellae. A key to the Japanese species of Trichoribatesis provided along with data on their geographical distribution and habitat ecology.


INTRODUCTION
The oribatid mite genus Trichoribates was established by Berlese (1910) with Murcia trimaculata C. L. Koch, 1835 as type species. Weigmann and Norton (2009) discussed recently the validity of this species and interpreted the type of Trichoribates. The genus is one of the most common and taxonomically diverse taxa of oribatid mites in the northern hemisphere. According to authors' estimation, the genus now comprises 52 valid species, but only a few of them, such as T. berlesei Jacot, 1929, T. novus (Sellnick, 1928 and T. copperminensis Hammer, 1952 are widely distributed in the Holarctic region. Most other representatives seem to be relatively rare and are found only in restricted areas or are only known from the type localities. Among the biogeographical realms, the Palaearctic region is distinguished from other regions by its high species richness (36 spp.), followed by the Nearctic region (17 spp.). The other biogeographical regions contain less than three species.
Currently, only four species of Trichoribates (T. alpinus Aoki, 1982, T. berlesei Jacot, 1929, T. novus (Sellnick, 1928 and T. rausensis Aoki, 1982) are known from Japan, and two additional species were found recently, which we describe here as new to science.
The primary goal of this work is to describe two unknown species of Trichoribates. Providing additional remarks on the biogeography and habitat ecology, and constructing an identification key to the Japanese species of Trichoribates are the other goals of this work.
This work is based on material collected in the frame of ecological studies on the oribatid mite communities from the subalpine zone of Mt. Naeba, and the first author collected 145 species from litter and soil samples (Maruyama 2003). Among those, several new taxa were found including two species of Trichoribates (T. aokii n. sp. was indicated as Trichoribates sp. MC, and T. hirauchiae n. sp. as Trichoribates sp. MA in Maruyama [2003]).
Morphological terminology used in this work is based mostly on that developed over many years by Grandjean (e.g. 1936) as summarized by Norton and Behan-Pelletier (2009). All measurements are given as a range, with the mean in parentheses. Setal formulas of legs are given as numbers per segment for appendages (from trochanter to tarsus), and as number per podosomal segment.

Genus Trichoribates Berlese, 1910
Diagnosis of adult -Rostrum rounded; lamellae wide, with well-developed cusps and translamella; lamellar cusps with or without lateral and median dens; bothridia cup-shaped; sensilli with clavate or oval head, rounded or flattened distally; tutoria broad, with cusps pointed or dentate distally; custodia with short to long narrowly pointed cusps; notogaster with large pteromorphs curved ventrally, line of desclerotization absent; lenticulus present or absent; 10 or 11 pairs of notogastral setae, setae dp present or absent; four pairs of notogastral porose areas (exception, sacculi in T. polaris Hammer, 1953), porose areas Am and Ah present; six pairs of genital setae; all legs heterotridactylous; tibiae I with dorsodistal apophysis bearing solenidion φ 2 ; seta l" of tibiae and genua I, II, and sometimes that of tibiae and genua III, IV thick, heavily barbed (see also Behan-Pelletier 1985;Bayartogtokh and Schatz 2008).
Integument -Body colour deep reddish to yellowish brown. Surface of body and leg segments with thick cerotegument, roughened by small granules. Faintly microtuberculate on cuticle of prodorsum, notogaster, ventral plate and leg segments.
Prodorsum -Rostrum widely rounded, with pair of minute lateral dens and nose-like protuberance dorsally ( Figure 1B). Lamellae narrow, gradually converging anteriorly, about 2/3 of prodorsal length ( Figure 1A). Translamella narrow, but distinctly developed. Length of lamellar cusps about 1/5 length of whole lamellae, with distinct lateral dens, but medial dens minute or sometimes absent ( Figure 1D). Prodorsal setae distinctly barbed in their distal half; interlamellar setae slightly extending beyond rostrum, about 1.5 times as long as lamellar setae, almost twice as long as rostral setae. Sensilli short, with clavate head slightly bending medially, its surface roughened. Alveoli of interlamellar setae and bothridia completely concealed under anterior marginal part of notogaster ( Figure  1E). Tutoria long and broad, extending beyond alveoli of rostral setae, finely striated along dorsal edge, with three to five dentations at the distal end (Figure 3A, B).
Notogaster -Longer than wide, anterior margin broadly rounded; lenticulus poorly developed. Pteromorphs well developed, curved ventrally, with rounded margin ( Figure 1E). Ten pairs of notogastral setae short, thin, finely barbed. Relative length of posterior notogastral setae: h 1 > h 2 > h 3 ; p 1 > p 2 > p 3 . Mutual distance of la-la wider than that of c-c; distance between h 1 -h 1 little wider than that of p 1 -p 1 . Setae h 2 and h 3 inserted close to each other. Among four pairs of porose areas Aa largest, its real shape almost circular or slightly oval; A 2 smallest and sometimes missing; A 1 and A 3 similar in shape and medium in size ( Figure 1C). Lyrifissures im situated between la and lp. Openings of opisthosomal glands (gla) located anterolateral to setae lp.
Ano-genital region -Anal and genital plates smooth, both genital and anal openings slightly wider than long ( Figure 1F). All ano-genital setae short, thin, minutely barbed. Relative length of their mutual distance: g 3 -g 3 ≈ g 5 -g 5 ≈ g 4 -g 4 > g 2 -g 2 > g 6 -g 6 > g 1 -g 1 . Distance between alveoli of aggenital setae slightly shorter than that of adanal setae ad 3ad 3 . Setae ad 3 situated in paranal position, at level posterior to anal setae an 2 . Adanal lyrifissures iad situated at same level as setae an 2 , adjacent to anterolateral margins of anal perture.
Legs -Median claw thicker than lateral claws ( Figure 2). Solenidia ω 1 on tarsi I slightly longer than ω 2 ; solenidia φ 1 on tibiae I nearly four times as long as φ 2 . Legs I and IV subequal in length, leg II shortest. Femora I-IV, tibiae, genua, femora and trochanters of leg IV with narrow ventral blade. Type-series -Holotype (NSMT-Ac 11521, male): Southwest from the summit of Mt. Naeba, 36°50'37"N, 138°41'16"E, 2130 m a.s.l., Sakae-mura in Shimominauchi-gun, Nagano Prefecture, from litter and soil of a wetland dominated by Molinia japonica Hackel, 26 August 1996, collected by I. Maruyama. Three paratypes (NSMT-Ac 11522-11524, males): same data as holotype; four paratypes (NSMT-Ac 11525-11528, three males and one female): same data as holotype except for altitude, 2040 m. The holotype and paratypes (mounted on slides) will be deposited in the National Science Museum, Tokyo, Japan. Additional non-type specimens (four females and seven males) from the same locality as holotype, are preserved in the collection of S. Shimano.
Remarks -This species is similar to T. alpinus, described by Aoki (1982) from Mt. Norikura, Gifu Prefecture, Central Japan, in the very small notogastral porose areas A 2 , clavate sensilli and distal structure of lamellar cusps. However, T. aokii sp. nov. is distinguishable from T. alpinus by the much narrower lamellar cusps and translamella, and closely situated notogastral setae h 2 and h 3 . In T. alpinus, the lamellae are wide, and becoming broader distally with very broad lamellar cusps and translamella (twice as broad as chitinized median margin of lamellae). Also in T. alpinus, the notogastral setae h 2 and h 3 are widely spaced from each other, and the distance between these setae is nearly as long as that between setae p 2 and p 3 .
Another Japanese species, T. rausensis, also has small porose areas A 2 and narrow lamellae. However, T. rausensis is different from T. aokii sp. nov. in having widely spaced lamellar cusps; the smooth sensilli; the distinctly shorter rostral and interlamellar setae, and very closely situated porose areas A 1 and A 2 .
Two other species found in Japan, T. berlesei and T. novus are distinguishable from T. aokii n. sp. by having much broader lamellae and lamellar cusps; much larger lateral dens of cusps; far longer notogastral setae with rough barbs; dorso-distally projected tutorial tips; anteriorly protruding pteromorphs, and distinctly larger body size.
Etymology -This species is named after Dr. Jun-ichi Aoki, professor emeritus of the Yokohama National University, Japan. His superb teaching and enthusiasm for soil zoology, acarology, taxonomy and ecology influenced the lives and careers of many students.

Trichoribates hirauchiae n. sp.
[Japanese name: Hirauchi-kobanedani] (Figures 3-5) Diagnosis -Large in size; rostrum with pair of minute lateral dens a nose-like protuberance dorsally; rostral, lamellar and interlamellar setae long, barbed; lamellae narrow, translamella very weakly developed, sometimes absent; lamellar cusps with distinct lateral dens, but medial dens minute or absent; sensilli short, with clavate head, its surface roughened; tutoria long and broad, with five or six dentations at the distal end; 10 pairs of short, thin notogastral setae finely barbed; porose areas round to elongate oval, Aa largest, A 1 smallest, located very close to A 2 , sometimes A 1 joined to A 2 ; epimeral and ano-genital setae minutely barbed.
Integument -Body color yellowish brown to reddish brown. With thick cerotegument, roughened by minute granules. Faintly microtuberculate on cuticle of prodorsum, notogaster, ventral plate and leg segments.
Notogaster -Longer than wide, anterior margin broadly rounded; lenticulus poorly developed. Pteromorphs well developed, curved ventrally, with rounded margin ( Figure 4E). Ten pairs of notogastral setae short, weakly barbed; relative length of the setae: c > la > lm, p 1 > p 2 > p 3 , h 3 ≥ h 1 > h 2 . Relative mutual distance between pairs of setae: p 3p 3 > la-la > h 3 -h 3 > c-c > h 2 -h 2 > lm-lm > lp-lp ≈ p 2 -p 2 > h 1 -h 1 > p 1 -p 1 . Among four pairs of porose areas, Aa largest, oval; A 1 smallest, round to oval, located very close to A 2 ; A 2 and A 3 of medium size, elliptical or oval ( Figure 4C); sometimes A 1 joined to A 2 , but in one specimen A 2 divided into two parts. Lyrifissures im situated at level midway between setae la and lp. Openings of opisthosomal glands (gla) located anterior to setae h 3 .
Ano-genital region -Anal and genital plates smooth; both genital and anal openings slightly wider than long ( Figure 4F). Genital and aggenital setae thin, minutely barbed; relative length of distance between pairs of setae: g 4 -g 4 > g 5 -g 5 > g 3 -g 3 > g 6 -g 6 > g 2 -g 2 ≈ g 1 -g 1 . Anal and adanal setae thin, minutely barbed; relative length of their mutual distance an 2 -an 2 > an 1 -an 1 . Setae ad 3 situated in paranal position, at level posterior to anal setae an 2 . Adanal lyrifissure (iad) aligned obliquely, situated slightly anterior to level of setae an 2 , adjacent to anterolateral margins of anal aperture.
Type-series -Holotype (NSMT-Ac 11518, male): Near summit of Mt. Naeba, 36°50'28"N, 138°41'15"E, 2110 m a.s.l., Sakae-mura in Shimominauchi-gun, Nagano Prefecture; from litter and soil of a wetland dominated by Veratrum stamineum Maxim, 26 August 1996, collected by I. Maruyama. Two paratypes (NSMT-Ac 11519-11520, males): the same data as holotype. The holotype and paratypes (mounted on slides) will be deposited in the National Science Museum, Tokyo, Japan. Additional non-type specimens (three females and four males) from the same locality as holotype are preserved in the collection of S. Shimano.
Remarks -Trichoribates hirauchiae sp. nov. is similar to T. rausensis described by Aoki (1982) from Hokkaido, Ishikawa, Yamanashi and Nagano Prefectures (northern and central Japan) in the narrow lamellae, the weakly-developed translamella, and the clavate sensilli. However, T. hirauchiae sp. nov. is readily distinguishable from T. rausensis by the different structure of porose areas A 1 and A 2 (A 1 is larger than A 2 in T. rausensis); the much larger body size (body length: 524 -564 µm width: 332 -420 µm in T. rausensis); the far longer interlamellar and rostral setae, extending beyond the rostral tip (setae in and ro of T. rausensis not reaching tip of rostrum); the lamellae gradually converging anteriorly (lamellae of T. rausensis nearly parallel to each other).
Etymology -This species is named in memory of our colleague, late acarologist, Mrs. Yoshiko Hi-rauchi for her generous contribution to the knowledge of oribatid mites of the Toyama Prefecture, Central Japan.

DISCUSSION
As mentioned above, only four species of Trichoribates have been recorded from Japan, and are mainly known from moist, warm soil and litter on the temperate habitats.
Two other species, T. alpinus and T. rausensis have been known only from Japan until recent time, but later the former species was recorded from the Kunashir Island of the Russian Far East (Ryabinin 2015), whereas the second species was found in northern India (Mondal and Kundu 1999).
In Japan, these species are basically distributed in the mountainous areas. Aoki (1964) recorded T. novus from Zizoudaira, Tanzawa Mountains, Kanagawa Prefecture, at about 1600 m a.s.l., however, Ohkubo et al. (2015) excluded this species from the revised Japanese faunistic list of oribatid mites, because they suspected the previous record was made by misidentified.
The third species, T. alpinus also occurs in high altitudes, and found at elevations about 1360-2835 m a.s.l. This species is currently known from Yamagata, Niigata, Miyagi, Fukushima, Iwate, Akita, Yamanashi, Nagano Prefectures (Aoki and Harada 1983;Harada 1988Harada , 1993Harada , 1994Harada , 1999. The above-mentioned two species, T. rausensis and T. alpinus were also considered as two of the most common species below the alpine zone (Aoki and Harada 1983;Harada 1994).
The fourth species, T. berlesei was found only from moss cushion on city construction in Kushiro, Hokkaido Prefecture (Aoki 2000).
Concerning the habitat ecology, in Japan, these species are litter inhabitants in various types of forests (i.e. Harada 1993Harada , 1994Harada , 1999, but also occur in moss cushion in urban area (Aoki 2000).
Finally, the following key can be used to identify adults of Trichoribates species in Japan.  Aoki, 1982