Trichogalumna ekaterinae, Bayartogtokh & Shimano, 2019

Bayartogtokh, Badamdorj & Shimano, Satoshi, 2019, Contribution to the knowledge of Galumnidae (Acari: Oribatida) in the Oriental region, Zootaxa 4647 (1), pp. 368-377 : 369-371

Trichogalumna ekaterinae sp. nov.

( Fig. 1 )

Diagnosis. Small species, body length 253–262 µm, width of notogaster 173–182 µm; rostrum widely rounded in dorsal view, but protruding in lateral view; rostral, lamellar and interlamellar setae medium long, thin, smooth; sensillus with thin, long stalk and widely lanceolate head with small, pointed tip; anterior margin of notogaster not developed; notogastral setae well developed; three pairs of porose areas (Aa, A 1 and A 3).

Measurements. Holotype (female): body length of 253 µm, width of notogaster 176 µm; paratypes (three females): 256–262 (259) µm, width of notogaster 173–182 (178) µm.

Integument ( Figs. 1A ). Body color yellowish brown to dark brown. Body surface nearly smooth, with microgranules on prodorsum and pteromorph.

Prodorsum ( Fig. 1A, B, C, E ). Rostrum widely rounded in dorsal view, but protruding in lateral view; inner rostral tooth (irt) of rostrum distinct ( Fig. 1B ). Tutorial (S) and lamellar (L) ridges distinct, nearly parallel, curving backwards. Rostral (ro) and lamellar (le) setae 30–32 µm in length, interlamellar seta (in) ∼ 22 µm long, setiform, thin, smooth. Sensillus (ss) having thin stalk and large, asymmetrically dilated, almost semicircular head with small, pointed tip. Dorsosejugal porose area (Ad) oval, located posterolaterad to seta in. Exobothridial seta and porose area Al not evident.

Notogaster ( Fig. 1A ). Anterior margin of notogaster not developed. Dorsophragma (D) elongated longitudinally. Notogastral setae 18–32 µm long, thin, smooth. Three pairs of notogastral porose areas, Aa, A 1 and A 3 circular to oval in shape (in holotype, left A 1 was divided into two parts); A 1 located anterior to seta h 2; A 3 situated posterior to seta h 1. Notogastral lyrifissures (ia, im, ih, ips and ip) and opisthonotal gland opening (gla) well developed; ip visible in posterior view.

Gnathosoma ( Fig. 1D ). Morphology of subcapitulum, palp and chelicera typical for genus (e.g. see Ermilov & Corpuz-Raros 2016). Subcapitular setae short, setiform, smooth. Palp setation: 0-2-1-3-9+1ω; axillary saccules distinct, elongated. Cheliceral setae setiform, barbed, cha longer than chb; Trägårdh’s organ elongate triangular, rounded distally.

Epimeral region ( Fig. 1D ). Only three pairs of epimeral setae (1a, 3b, 4b) distinct, thin, smooth; seta 1a ∼ 21 µm long, 3b and 4b ∼ 11 µm long. Discidium broadly conical; pedotectum I rounded, pedotectum II scale-like, subtriangular in ventral view. Circumpedal carina well developed.

Ano-genital region ( Fig. 1D ). All ano-genital setae medium long (12-18 µm), thin, smooth; g 1, g 2 and g 3 inserted on anterior margin of genital plate, g 4, g 5 arranged longitudinally, g 6 inserted on posterior margin of genital plate. Adanal setae ad 1 and ad 2 inserted posterior to anal plates; ad 3 inserted in paraanal position; lyrifissure iad situated anterolateral to anal aperture. Postanal porose area (Ap) oval, transversely oriented, visible only in posterior view.

Legs. Morphology of leg segments, setae and solenidia typical for Trichogalumna (e.g. Ermilov et al. 2011). Claws smooth dorsally. Famulus short, with slight distal expansion. Formulas of leg setation: I (1-4-3-4-20), II (1- 4-3-4-15), III (1-2-1-3-15), IV (1-2-2-3-12); formula of solenidia: I (1-2-2); II (1-2–2), III (0-1-1), IV (0-1-0).

Material examined. Holotype (female) and three paratypes (females): Raelkelat , Island of Babeldaob, Republic of Palau, from moss sample growing on bark of fallen tree in a secondary forest , 7°28’59”N, 134°29’32”E, coll. S. Shimano, 17 December 2017.

Type depository. Holotype and all paratypes are deposited in NSMT—the National Museum of Nature and Science, Tsukuba, Japan ( Zhang 2018).

Etymology. This species is named in honor of our esteemed colleague and friend Dr. Ekaterina A. Sidorchuk, who made a great contribution to the knowledge of mite diversity in Baltic amber inclusions.

Remarks. Trichogalumna seminuda Balogh, 1960 known from Angola, Trichogalumna arborea Ohkubo, 1984 from Japan, Trichogalumna vietnamica Mahunka, 1987 from Vietnam, Trichogalumna africana Ermilov, Sidorchuk & Rybalov, 2011 from Ethiopia, and a semicosmopolitan species, Trichogalumna nipponica ( Aoki, 1966) (see Balogh 1960; Aoki 1966; Ohkubo 1984; Mahunka 1987; Ermilov et al. 2011) are similar to Trichogalumna ekaterinae sp. nov. in the morphology of asymmetrically dilated sensillus. However, all these known species have clearly developed four pairs of porose areas (vs. A 1 absent in the new species), and a much larger body size (body sizes more than 350 × 240 µm vs. 259 × 178 µm). Additionally, T. seminuda differs from the present new species by the very long interlamellar seta extending beyond the rostrum, and distinctly barbed rostral setae. The other African species, T. africana is different from the present new species in the relatively slender sensillus with a small notch behind the tip of the sensillar head. The Japanese species, T. arborea differs from the new species in the well-developed transverse bands on the notogaster and ano-genital region, as well as in the finely wrinkled and granulated structure of the humeral region. The Oriental species, T. vietnamica can easily be distinguished from T. ekaterinae sp. nov. by the long, barbed rostral seta. The semicosmopolitan species, T. nipponica has a much slender, distally barbed lanceolate sensillus rather than the largely dilated, smooth sensillus shown in the present new species.

It should be noted here that the holotype of Trichogalumna ekaterinae sp. nov. has the left porose area A 1 divided into two parts, which seems to be an abnormal character. Klimov & Ermilov (2017) studied the evolutionary dynamics of gain and loss of the notogastral porose areas of Galumnoidea Jacot, 1925 with respect to the various modifications of their properties, such as shape and position. These authors concluded that patterns of expression of porose areas in abnormal individuals and rare species suggest that this may be a complex, non-Mendelian character, encoded by several genes (i.e. a polygenic trait). They also proposed that the loss of porose areas is not likely to be down-regulated by a third gene.

Genus Galumna Heyden, 1826

Type species: Notaspis alatus Hermann, 1804

Figures

FIGURE 1. Adult of Trichogalumna ekaterinae sp. nov., holotype. A—Dorsal view of body, B—Rostrum, dorso-frontal view, C—Anterior part of prodorsum, lateral view, D—Ventral view of body, legs not shown, E—Sensillus, lateral view. A, B, C and D to same scale.