Eustigmaeus extremiorientalis Khaustov, 2016

Ikeda, Satsuki, Imada, Yume & Nakano, Takafumi, 2024, A new species of the genus Eustigmaeus (Trombidiformes: Prostigmata: Stigmaeidae) and the first record of E. extremiorientalis in Japan, Zootaxa 5538 (3), pp. 233-246 : 240-242

Eustigmaeus extremiorientalis Khaustov, 2016

[New Japanese name: Ichigo-maruhishi-dani]

( Figs 6–10 )

Eustigmaeus extremiorientalis Khaustov, 2016: 322 , figs 1–6.

Eustigmaeus sp. 4 — Ikeda et al. (2024: 734, fig. 4).

Material examined. Eight specimens: 7 females, KUZ Z4528 , Z4529 , Z5169 , Z5170 , Z5171 , Z5172 , and Z5173 , from moss colony on a wet concrete wall along the pavement road, 33°43′52.7″N 132°56′16.8″E, approx. 1,020 m elev., Kumakogen , Kamiukena, Ehime Prefecture, Japan, 10 September 2020 and 16 March 2021, coll. S. Ikeda [locality code 4 in Ikeda et al. (2024)]; 1 female, KUZ Z4715 , from moss on a wet tree root along the mountain path, 35°14′13.0″N 138°16′48.4″E, approx. 1,460 m elev., Aoi , Shizuoka, Shizuoka Prefecture, Japan, 19 April 2022, coll. S. Ikeda [locality code 29 in Ikeda et al. (2024)].

Description. FEMALE (Japanese population). Most characteristics of the Japanese populations coincide well with those in the original description (see Khaustov 2016). Some variations of the Japanese populations are highlighted below.

Idiosomal length 320–349 (n = 7), idiosomal width 245–289 (n = 5).

Idiosomal dorsum ( Figs 6–7 ). Ornamentation of dorsal shields and shape of dorsal setae as described in Khaustov (2016). Suranal shield located ventrally, with shallow dimples enclosed in subcuticular reticulum (reticulum absent in KUZ Z5169). Lengths of dorsal setae (n = 8 unless otherwise stated): vi 37–44, ve 48–59, sci 30–42, sce 28–41, c1 35–47, c2 24–33, d1 33–43, d2 31–39, e1 36 –47, f1 39–52, h1 27–36, h2 12–16 (n = 7). Distances between setae (n = 7 unless otherwise stated): vi–vi 30–36, ve–ve 93–104, sci–sci 154–176, sce–sce 228–244 (n = 6), vi–ve 57–64, ve–sci 37–43, sci–sce 44–49, c1–c1 80–91, d1–d1 119–124, d2–d2 217–243, e1–e1 108–119, f1–f1 70–83, h1–h1 29–37 (n = 5), h2–h2 63–72 (n = 5), c1–d1 75–82, c1–d2 81–93, e1–d2 107–117, d1–d2 59–67, d1– e1 58–69, e1–f1 32–43, h1–h2 23–30.

Idiosomal venter ( Figs 6–7 ). Characteristics of callosities, coxisternal plates, endopodal plates, and anal cover identical to those in original description. Humeral shield with shallow dimples enclosed in subcuticular reticulum and dim shield boundary ( Figs 6B and 7B ). Aggenital plate weakly reticulated. Lengths of setae: ag1 11–15 (n = 8), ag2 11–14 (n = 8), ps1 10–12 (n = 5), ps2 8–10 (n = 6), ps3 11–12 (n = 6).

Gnathosoma ( Fig. 8 ). Palpal and subcapitular traits as described in Khaustov (2016). Chelicera and its short movable digit 82–91 (n = 8) and 18–22 (n = 8) in length, respectively. Lengths of subcapitular setae as follows: m 15–17 (n = 7), n 13–16 (n = 8), or1 8–11 (n = 8), or2 10–13 (n = 7). Distances between subcapitular setae follows (n = 7): m–m 25–27, n–n 31–34, m–n 11–13.

Leg ( Figs 9–10 ). Leg setation as described in Khaustov (2016). Leg lengths: Leg I 157–165 (n = 8), Leg II 133–147 (n = 8), Leg III 127–137 (n = 5), Leg IV 156–170 (n = 8). Minor differences in leg setae shapes: setae (a) and (u) on tarsi of leg I–IV smooth or serrated; seta pl ′ on tarsus of leg II barbed and pointed. Leg I ( Fig. 9A ). Seta lengths: k 6–9 (n = 7), φp 8–10 (n = 6), φ 6–7 (n = 7), ω 12–14 (n = 7). Leg II ( Fig. 9B ). Seta lengths: k 4–7 (n = 7), φp 6–8 (n = 6), ω 7–9 (n = 7). Leg III ( Fig. 10A ). Seta lengths: φp 3–4 (n = 5), ω 3–4 (n = 6). Leg IV ( Fig. 10B ). Seta lengths: φp 2–4 (n = 7), ω 2–3 (n = 7).

DNA sequences. One sequence was determined and deposited with INSD by Ikeda et al. (2024). INSD accession number LC789964 ( KUZ Z4801 ) for COI.

Host plants. One species from the Hypnaceae and one from the Brachytheciaceae have been recorded ( Ikeda et al. 2024): Hypnaceae , Gollania ruginosa ; Brachytheciaceae , Okamuraea hakoniensis .

Etymology. The Japanese name “Ichigo” means “strawberry,” referring to the inverted subtriangle-shaped hysterosomal shields with large round dimples resembling a strawberry’s pseudocarp.

Remarks. Eustigmaeus extremiorientalis was originally described from the Russian Far East ( Khaustov 2016). The examined specimens from Japan were identified as E. extremiorientalis based on the following characters (see Khaustov 2016): large round dimples on dorsal shields, absence of dorsal seta e2, distally widened strongly barbed dorsal setae, and presence of two pairs of callosities. Other characteristics such as idiosomal dimensions and setae lengths did not differ from those of Russian E. extremiorientalis . Although examined specimens exhibited a suite of minor differences, these were found to vary intraspecifically, as all other mentioned characteristics unequivocally matched those of Russian E. extremiorientali s. This record on Honshu and Shikoku Islands of the Japanese Archipelago represents the first record of E. extremiorientalis in Japan. Although the elevation of the type locality was not provided ( Khaustov 2016), Japanese specimens were found at relatively high elevations (approximately 1,020 and 1,460 m elev.).

Figures

FIGURE 6. Eustigmaeus extremiorientalis Khaustov, 2016, female (KUZ Z5171). A—surface of prodorsal shield; B—humeral shield. Scale bar = 20 μm.

FIGURE 7. Eustigmaeus extremiorientalis Khaustov, 2016, female (KUZ Z5171).A—idiosomal dorsum; B—idiosomal venter. Punctation is not shown.

FIGURE 8. Eustigmaeus extremiorientalis Khaustov, 2016, female.A—left palp and chelicera (KUZ Z5173); B—ventral view of subcapitulum (KUZ Z5169). Punctation is not shown.

FIGURE 9. Eustigmaeus extremiorientalis Khaustov, 2016, female (KUZ Z5172). A—left leg I, dorsal view; B—left leg II, dorsal view.

FIGURE 10. Eustigmaeus extremiorientalis Khaustov, 2016, female (KUZ Z5172). A—left leg III, dorsal view; B—left leg IV, dorsal view.