Three new species of the subgenus Otocepheus (Acrotocepheus) (Acari, Oribatida, Otocepheidae) from China

Abstract Three new species of subgenus Otocepheus (Acrotocepheus): O. (A.) digitatussp. nov., O. (A.) multigranulatussp. nov., and O. (A.) occultatussp. nov. are proposed and described based on adult material collected from China, and O. (A.) duplicornutus Aoki, 1965 is reported in China for the first time. A key to Chinese species of the subgenus Acrotocepheus is provided.

The subgenus Otocepheus (Acrotocepheus) was proposed by Aoki (1965), with O. (A.) quateorum Aoki, 1965 as type. The subgeneric characters of Otocepheus (Acrotocepheus) were summarized by Aoki (1965), and identification keys to species from some regions and countries were presented by Aoki (1965) and Corpuz-Raros (2007). Chen et al. (1992) recorded O. (A.) gracilis (Aoki, 1973) from Anhui, China, which was the first report of genus Otocepheus in China. The following year, Wen (1993) proposed the subgenus Otocepheus (Hexatocepheus) with O. (Hexatocepheus) emeiensis from Sichuan, China as type. Until now, only two subgenera and two species of Otocepheus were recorded in China (Chen et al. 2010). During studies of oribatid mites from China, we discovered three new species of subgenus Otocepheus ( Aoki, 1965. All four of these species are described, and an identification key for all known species of this subgenus in China is provided.

Materials and methods
The collection locality and habitat for each new species are given in the "Material examined".
Specimens were mounted in lactic acid on temporary cavity slides for measurement and illustration, except one specimen of O. (A.) digitatus sp. nov., which was mounted on a permanent slide with Hoyer's medium. 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.
Integument. Body color light yellow-brownish. Body surface densely foveolate. Prodorsum. Rostrum broadly rounded. Rostral seta moderately curved inward, densely barbed outside. Lamellar seta inserted behind tip of costula, curved inward, roughened externally. Interlamellar seta barbed, blunt at tip. Bothridial seta with a long fusiform head and a strongly curved peduncle. Exobothridial seta short. Bothridium opening laterally, dorsal bothridial plate straight or curved outward slightly, ventral bothridial plate broadly triangular in dorsal view. Tutorium well developed. Two pairs of prodorsal condyles present, lateral prodorsal condyles broadly rounded, median prodorsal condyles large and rounded, well separated from each other. Mutual distance between ventral bothridial plates nearly equal with that between lateral prodorsal condyles. Subpedotectum well developed.
Notogaster. L/W of notogaster about 1.8. Surface of notogaster densely punctate. Anterior margin of notogater strait. Lateral notogastral condyles finger-shaped, with wide base. Median notogastral condyles absent. Ten pairs of notogastral setae glabrous, setae c, la, h 3 , p 1 , p 3 setiform and relatively short in length, while the rest notogastral setae lm, lp, h 1 , h 2 , p 2 flagelliform and longer in length. Setae c, la, lm nearly located on the same line. All lyrifissures well visible, ip located between setae p 2 and p 3 , ips between setae h 3 and p 3 . Opisthonotal gland opening located anterior and very close to lyrifissure im. Vitta marginalis distinct.
Anogenital region. Genital plates each with 2 longitudinal, slant furrows. Four pairs of genital setae (mutual distances g 1 -g 1 ≈g 2 -g 2 ≈g 4 -g 4 <g 3 -g 3 ). Aggenital lyrifissure located close and anterolateral to genital aperture. One pair of aggenital, two pairs of anal (mutual distances an 1 -an 1 <an 2 -an 2 ) and three pairs of adanal setae similar in length. Setae ad 3 -ad 3 below level of anterior margin of anal opening. Adanal lyrifissure located in diagonal position and close to anal aperture, below level of anterior margin of anal opening.
Legs. Monodactylous. Claw of each leg strong and smooth. Formulae of leg setation and solenidia: Leg seta u setiform (L-type) on tarsi I, thorn-like (S-type) on tarsi II-IV. Homology of setae and solenidia indicated in Table 1.    Etymology. The specific name "digitatus" is from Latin for "finger-like" refers to the finger-shaped lateral notogastral condyles.
Notogaster. L/W of notogaster about 1.2. Surface of notogaster densely and obviously granulate. Anterior margin of notogaster straight. The largest width of notogaster medially, near level of seta lp. Lateral notogastral condyles wide, like a lateral view of staircase with two to three steps mainly. Median notogastral condyles absent. Ten pairs of notogastral setae nearly same in length, barbed. A faint, short ridge present lateral to insertion of seta c. Mutual distance between setae p 1 lager than that between p 1 and p 2 . Seta lm and lyriffissure im nearly on same line. Five pairs of lyrifissures visible, ip located between setae p 2 and p 3 , ips between setae h 3 and p 3 . Opisthonotal gland opening located anterior to lyriffissure im. Vitta marginalis well developed, fainted anteriorly.
Anogenital region. A pair of longitudinal ridges posterior to epimeral seta 4a. Genital plates smooth. Four pairs of genital setae (mutual distances g 1 -g 1 ≈g 2 -g 2 <g 4 -g 4 <g 3g 3 ). Aggenital lyrifissure located close and anterolateral to genital aperture. One pair of aggenital, two pairs of anal (mutual distances an 1 -an 1 <an 2 -an 2 ) and three pairs of adanal setae. Anal and adanal setae barbed like notogastral setae. Setae ad 3 -ad 3 below level of anterior margin of anal opening. Adanal lyrifissure situated anterior to level of seta ad 3 .
Remarks Diagnosis. Body size (n = 4): 1240-1410 × 560-670. Bothridial seta with a long fusiform head and a short peduncle. Lateral prodorsal condyles on prodorsum small, rounded, lateral prodorsal condyles markedly anterior to medial prodorsal condyles. An extra pair of condyles located posterior to lateral prodorsal condyles, covered by lateral notogastral condyles. Lateral notogastral condyles large, width nearly equal with their mutual distance, tips markedly anterior to medial prodorsal condyles. Anterior median part of mentum with a lower lip ridge.
Integument. Body color light yellow-brownish. Body surface densely foveolate. Prodorsum. Rostrum rounded. Rostral seta curved inward, densely barbed outside. Lamellar seta inserted behind tip of costula, moderately curved inward, roughened outside. Interlamellar seta barbed, setiform. Bothridial seta with a long fusiform head and a short peduncle. Exobothridial seta short. Costula straight, nearly paralleled. Bothridium opening laterally, dorsal bothridial plate straight, ventral bothridial plate broadly rounded in dorsal view. Lamelliform expansion pointing to bottom of seta ro. Two pairs of prodorsal condyles present. Lateral prodorsal condyles small, rounded, markedly anterior to medial prodorsal condyle. Median prodorsal condyles small, rounded, well separated from each other. An extra pair of condyles located posterior to lateral prodorsal condyles, covered by lateral notogastral condyles. Mutual distance between ventral bothridial plates larger than that between lateral prodorsal condyles. Subpedotectum well developed.
Notogaster. L/W of notogaster about 1.3. Surface of notogaster densely punctate. Lateral notogastral condyles large, triangular and rounded distally, inner part with a narrow base, anteromedial margins distinctly excavated, width nearly equal with their mutual distance, tips markedly anterior to medial prodorsal condyles. Medial notogastral condyles absent. Ten pairs of notogastral setae, slightly barbed, setae located posteriorly tend whip-like at tips. All lyrifissures well visible, ip located between setae p 2 and p 3 , ips between setae h 3 and p 3 . Opisthonotal gland opening located posterior to lyrifissure im. Vitta marginalis distinct.
Anogenital region. A pair of longitudinal ridges posterior to epimeral setae 4a. Genital plates with two or three longitudinal ridges on both sides. Four pairs of genital setae smooth (mutual distances g 1 -g 1 ≈g 2 -g 2 ≈g 4 -g 4 <g 3 -g 3 ). Aggenital lyrifissure located close and anterolateral to genital aperture. One pair of aggenital, two pairs of anal (mutual distances an 1 -an 1 <an 2 -an 2 ), and three pairs of adanal setae. Anal setae barbed and blunt at tips, adanal setae barbed and whip-like at tips. Seta an 2 well separated from outer margin of anal plate. Location of adanal setae normal, inside external margin of ventral plate. Setae ad 3 -ad 3 below level of anterior margin of anal opening. Adanal lyrifissure located in diagonal position and close to anal aperture.
Type deposition. All type specimens are deposited in the collection of IZAS. Etymology. The specific name "occultatus" is from Latin for "hiding", in reference to the extra condyles which are covered by the large lateral notogastral condyles.
Integument. Body color light brown, but genital plates and legs dark brown. Body surface densely foveolate. Prodorsum. Rostrum rounded. Seta ro moderately curved inward, densely barbed outside. Seta le removed backward from tip of costula, curved inward, roughened externally. Setae le and in slightly barbed, with blunt tips. Bothridium opening laterally, dorsal bothridial plate nearly straight, ventral bothridial plate broadly triangular in dorsal view. Bothridial seta with lanceolate head, slightly roughened. Seta ex short, setiform. Tutorium developed. Lamelliform expansion pointing to bottom of seta ro. Costula well developed. Prodorsal condyles broadly rounded, well separated from each other. Subpedotectum well developed. Extra condyles posterior to lateral prodorsal condyles invisible.
Anogenital region. Aggenital lyrifissure located close and anterolateral to genital aperture. A pair of longitudinal ridges posterior to epimeral seta 4a present. Genital plates smooth. Four pairs of genital setae (mutual distances g 1 -g 1 ≈g 2 -g 2 ≈g 4 -g 4 <g 3 -g 3 ) and one pair of aggenital setae present, setiform and slightly barbed. Three pairs of adanal and two pairs of anal setae (mutual distance an 1 -an 1 <an 2 -an 2 ) slightly barbed. Setae ad 3 -ad 3 below level of anterior margin of anal opening. Adanal lyrifissure located in diagonal position and close to anal aperture (in some specimens one of the adanal lyrifissures aligned transversely while the other one aligned diagonally), below level of anterior margin of anal opening.
Material examined. One male (ZLH-12-72): China, Guangxi Province, Longzhou County, 22°25'19"N, 106°58'12"E, 149 m a.s.l., in soil and debris beside deadwood, 3 August 2012; one male (ZLH-12-73): same locality as ZLH-12-72, 22°25'11"N,  Remarks. The morphological characters of specimens checked in this study are almost coincident with the original description of this species by Aoki (1965), which was based on material collected from Sara Buri, Thailand, except for the following delicate differences: arc degrees of prodorsal condyles (broadly rounded versus semicircular) and alignment of adanal lyrrifissure (located in diagonal position versus generally aligned transversely). Though these characters are relatively constant in our limited specimens, the shape of prodorsal or notogastral condyles, as well as the alignment of adanal lyrrifissure, sometimes vary. So, we temporarily treat these minor differences as normal individual variation.
Key to known species of Otocepheus (Acrotocepheus) from China