Oribatid fauna (Acari, Oribatida) from a cave in south Nippon (Japan), with a description of a new species

Representatives of six oribatid mite species belonging to the cohort Brachypylina were collected from the upper wall and soil surface at the entrance of Kumaso cave in South Nippon (Japan). Of these, three were known species: Fissicepheus (Fissicepheus) takenouchiensis Fujikawa and Nishi, 2013, Scheloribates latipes C. L. Koch, 1841 and Peloribates (Peloribates) latus Fujikawa, 2006. One species of Humerobates (Humerobates) was described as a new species. Two other individuals did not match any described species and may represent two new species. However, as single individuals, we could not decide with certainty about their specific status. These individuals were respectively assigned to the genera Protoribates and Spatiodamaeus. Here, we provide only morphological descriptions of these single specimens. No typically cave-dwelling oribatid mites were found in the present investigation.

In the first survey of oribatid fauna living in a cave in Japan, a total of 11 species, all belonging to Brachypylina, was recorded (Nakamura et al., 2010). Brachypylina has are characterized by the following combination of characters: holoid body type, brachypiline venter, genua of legs I-III shorter than tibiae and presence of Trägårdh's organ (Norton and Behan-Pelletier, 2009). The strongly chi-tinized cuticle of adult brachypylinid species might have the ability to resist drought as suggested by Ducarme et al. (2004).
In order to get an overview of the Oribatid fauna living in another Japanese cave, we sampled soil inside and at the entrance (photic zone) of the Kumaso cave and recorded Oribatid mites found in both types of samples.
This article brings together the survey of Oribatid species found in these samples and the description of some specimens unassigned to any known species, with a designation of Humerobates (Humerobates) kumasoi as a new species.

METHODS
Study site -Kumaso cave (31°48'50"N; 130°45'19"E, about 82 m a.s.l, in the subtropical zone) is located at Hayato-cho, Kirishima-shi, Kagoshima Prefecture, South Japan (Fig. 1). The cave formed in welded tuff 3 million years ago (personal communication from Mr. M. Harada, 2013), and is now situated in a thick forest of Cryptomeria japonica, Castanopsis spp. and Quercus spp. on a hill on a property belonging to President T. Ishihara of Myoken Ishiharaso Co. Ltd. On the day of sampling (22 Sept. 2011), the temperature inside the cave (at 5 p.m.) was 21°C at the floor surface and 18°C 1 m above it. The temperature outside the entrance at 5.30 p.m. was 18.5°C at the soil surface and 19°C 1 m above it.
Sampling -Eight samples of about 200 cm 3 each were collected by hand-picking from sands in the cave and soil materials of top most part and the surface of the ground at the entrance on 22 Sept. 2011, by K. Nakamura. After extraction with a modified Tullgren apparatus, mites were kept in lactic acid for clearing during twenty days, then mounted on glass slides.

RESULTS
The survey of Oribatid fauna from soil sampled inside and at the entrance of the Kumaso cave was carried out on 22 Sept. 2011. The only mite found inside the cave was a specimen of the mesostigmatid genus Gamasiphis (Rhodacaridae). No oribatid mites were found inside the cave. However, representatives of seven oribatid species including one new species, were collected from soil materials of the top most part and the surface of the ground at the entrance, ie. from the photic zone. Yet, as found in the Kumaya Cave of Iheya Village (Nakamura et al., 2010), all oribatid species belonged to the cohort Brachypylina. Six oribatid species are detailed in the present study. One specimen of Drepanoppia could not be studied because the body was broken.
Material examined -Holotype (Adult female) (NSMT-Ac 13788) from the soil surface at the entrance of Kumaso cave; 4 paratypes (2 adult females and 2 adult males) (NSMT-Ac 13789): same data as holotype; 1 additional paratype (adult male) used in scanning electron microscopy: same data as holotype. Type specimens (NSMT-Ac 13788 and 13789) are deposited in the National Museum of Nature and Science, Tokyo. The other type specimen is deposited in the National Agricultural Research Center for Kyushu Okinawa Region, Kumamoto Prefecture.

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Nakamura K. et al. Etymology -Named in honour of Kumaso, one of the former human races in Nippon (Japan).
Notogaster -Nearly as long as wide, anterior margin rounded, bearing 10 pairs of vestigial notogastral setae. Anterior margin of pteromorphae not extending beyond dorsosejugal suture. Porose areas Aa (the major axis: ca. 7 µm) located between la and lm; A1 between lp and h3; A2 antero-lateral to h 3 ; A3 lateral to h 1 . Opisthonotal gland opening (gla) situated lateral to A1. Lyrifissures ia, im, ih and ips aligned obliquely, located posterior to c 2 , anterior to gla, antero-lateral to gla and anterior to p 3 , respectively. Lyrifissure ip aligned perpendicular to notogastral outline, located between p 1 and p 2 .
Remarks -According to Subías (2004), 15 species and three subspecies are known as members of the genus Humerobates (Humerobates) Sellnick, 1928, and a single species of the subgenus Humerobates (Cordylobates) Luxton, 1995 is known. The new species has some remarkable features in common with known species of Humerobates (Humerobates) such as narrow lamella without long cusp ot translamella, lamellar seta originating from tip of lamella, long tutorium, sensillum with broad head, immovable pteromorph, 10 pairs of notogastral setae, four pairs of porose areas, opisthonotal gland opening, genito-anal setal formula 6-1-2-3, and heterotridactylous legs. However, the new species is different from congeners in having anterior rostral margin projecting as a point on each side, bothridia with large ventromedial scale dentate on the anterior margin, sensilla composed of thin smooth short stems and broad spatulate heads verrucose throughout length, expanded distally without narrower apex, vestigial notogastral setae, vestigial adanal setae, thick medial subcapitular setae, and small body size (< 310 µm in length). All known members of subgenus Humerobates have round or straight anterior rostral margins and adanal setae. Moreover, most have notogastral setae. Humerobates (H.) varius Ohkubo, 1982 recorded from Japan has vestigial notogastral setae like the new species. However, the new species differs from Humerobates (H.) varius by anterior rostral margin projecting as a point on each side and vestigial adanal setae. Females and males of the new species had same range of body lengths and different ranges of widths. The cause of the fact is unknown in the present work.

(Figs. 5 -9)
In the present paper, one specimen was described as Spatiodamaeus sp. Although it may prove in the future being representatives of new species, it was not designed as new species in the present paper because only a single, damaged specimen was found.
Material examined -One adult female (NSMT-Ac 13786) from the soil surface at the entrance of Kumaso cave. The specimen is deposited in the National Museum of Nature and Science, Tokyo.
Material examined -One adult female (NSMT-Ac 13790) from the soil surface at the entrance of Kumaso cave. Specimen is deposited in the National Museum of Nature and Science, Tokyo.
Measurements and body appearance -Body length, 557µm; width, 329 µm. Body colour light brown; body surface smooth.
Remarks -The genus Protoribates (Protoribates) contains 40 known species and three known subspecies worldwide, of which two species bear a superficial resemblance to the present specimen. P. (P.) mollicoma (Hammer, 1973) and P. (P.) yezoensis (Fujikawa, 1983) have straight anterior notogastral margin, long lamellar and interlamellar setae, and ad 1, 2 aligned in post-anal position as seen in the present specimen. However, the present specimen is different from P. (P.) mollicoma in length of ad 1 and ad 2 , and insertion of ad 3 . The former has adanal setae ad 1-3 of the same length, and ad 3 inserted the anterior margin of the anal aperture, while the latter had adanal setae ad 1, 2 longer than ad 3 and ad 3 inserted in front of anterior margin of the anal aperture. The present specimen is different from P. (P.) yezoensis in the form of rostrum and insertion of an 1, 2 . The former has a round rostrum, and setae an 1, 2 inserted near midway along the plates, while the latter has a rostrum with a median elevation, and seta an 1 inserted near the posterior margin of the anal plate.