Trichoribates aokii, Maruyama & Shimano & Bayartogtokh, 2016

Maruyama, I., Shimano, S. & Bayartogtokh, B., 2016, Two new species of the genus Trichoribates (Acari: Oribatida: Ceratozetidae) from Central Japan, Acarologia 56 (2), pp. 213-224 : 214-218

Trichoribates aokii n. sp.

[Japanese name: Aoki-kobanedani] ( Figures 1-3 )

Diagnosis — Medium in size; rostrum widely rounded, with a nose-like protuberance dorsally; rostral, lamellar and interlamellar setae long, barbed; lamellae narrow, with long, but narrow translamella; lamellar cusps with distinct lateral dens, but medial dens minute or sometimes absent; sensilli short, with clavate head; tutoria long and broad, with three to five dentations at the distal end; 10 pairs of short, thin notogastral setae finely barbed; porose areas round to oval, A 2 much smaller than others; epimeral and ano-genital setae minutely barbed.

Measurements — Body length: 504 – 569 (538) µm; width: 338 – 408 (380) µm (n = 14).

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,

Acarologia 56(2): 213–224 (2016)

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.

Gnathosoma — Subcapitular mentum nearly as long as wide, without noticeable microtubercles. Hypostomal setae m, a and h finely barbed ( Figure 1F ). Chelicerae with strongly sclerotized blunt teeth; setae cha and chb barbed. Palps typical for family, palpal setation 0-2-1-3-10 including both ventral setae and solenidion ω of tarsi.

Epimeral region — Apodemes apo.2, apo.sj and apo.3 well developed, dark-colored. Epimeral setae short, thin, finely barbed, setal formula: 3-1- 3-3. Custodia reaching anterior margin of pedotecta II; discidia well developed, conspicuously projected laterally ( Figure 1F ). Pedotecta I large, surface smooth, without striation.

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 3 - ad 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. Formula of leg setation (including famuli): I (1-5-3- 4-20), II (1-5-3-4-15), III (2-2-1-3-15), IV (1-2-2-3-12); formula of solenidia: (Ge-Ti-Ta): I (1-2-2), II (1-1-0), III (1-1-0), IV (0-1-0).

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.

Figures

FIGURE 1: Trichoribates aokii n. sp.: A – prodorsum; B – rosrum; C – notogastral porose areas; D – variation of lamellar cusps; E – dorsal aspect of body, legs omitted; F – ventral aspect of body, legs omitted. B-D and E, F to same scale.

FIGURE 2: Trichoribates aokii n. sp.: A – leg I (left, antiaxial aspect); B – leg II (left, antiaxial aspect); C – leg III (left, paraxial aspect); D – leg IV (left, paraxial aspect).

FIGURE 3: Variation of tutoria in two species of Trichoribates: A – Left and right tutoria of Trichoribates aokii n. sp.; B – Variation of tutorial distal dentations of Trichoribates aokii n. sp.; C – Left and right tutoria of Trichoribates hirauchiae n. sp.