Feltria (Feltria) ishikariensis Imamura, 1954

Tuzovskij, Petr V., 2022, On the systematic of the water mite Feltria ishikariensis Imamura (Acari, Hydrachnidia, Feltriidae), Amurian Zoological Journal XIV (2), pp. 180-185 : 181-184

Feltria (Feltria) ishikariensis Imamura, 1954

(Figs. 1–8)

Material examined. Asia, Russia, Primorye Territory, Ussurijsky State Nature

Reserve, 1 male 17.07.1983, 2 females 27.11.1983, 2 females 20.09.1984, 1 female 30.07.1986, Komarovka stream, depth 40– 50 cm, substrates: stones, gravel, sand, leg. T. S. Vshivkova .

Description. Male. Idiosoma flat and almost circular (L/W ratio 1.08), all frontal setae (Fch, Fp, Vi, Ve) located on separate sclerites (Fig. 1). Dorsum with a large shield and one pair of narrow posterior plates. Dorsal shield broad (L/W ratio 1.17), occupying almost all dorsal idiosoma surface, and bearing four pairs of setae: Oi, Oe, Sci and Li, Sci thicker than other setae. Setae Hi, He, Sce and Le located on soft integument along dorsolateral portions of dorsum. Posterodorsal pair of plates narrow (L/W ratio 3.4), bearing seta and glandularium Si on each side. First pairs of slit organs free or fused with sclerite bearing seta and glandularium Vi on each side; second pair of slit organs fused with glandularia Hi, other slit organs (i 3– i 5) lying free on soft integument along lateral portions of idiosoma.

Leg coxae incorporated into four groups, close to each other, and occupy more than half of the idiosoma ventral surface (Fig. 2). Anterior coxal groups with moderately developed posterior apodemes, seta and glandularium Hv situated laterally on posterior margin of coxal plate II on each side. Coxal plates IV subrectangular, posterior margin perpendicular to longitudinal axis. Medial margins of coxal plates III/IV straight, medial margin of Cx-IV longer than medial margins of Cx-III. Genital plate large transverse, anterior margin convex and slightly undulating, posteromedial margin deeply indented, close to coxal field, leaving a narrow membranous interspace containing the paired glandularia (Se, Pe) and ventrolateral platelets; gonopore small and narrow, slightly shifted anteriorly; 40–50 pairs of subequal acetabula scattered over the whole plate, and four pairs of thin medial setae. Seta Pi fused with glandularia Ci, located close to genital plates posterior margin on each side. Excretory pore in posteroventral position and fused with genital field posterior margin. Capitulum with short anchoral process.

Shape and chaetotaxy of pedipalp as in ( Fig. 3 ): P-1 short, with single dorsodistal seta; P-2 expanded (L/H ratio 1.09), with slightly concave ventral margin, two proximal and three thick subequal dorsodistal setae; P-3 short (L/H ratio 0.82), with single short, thick proximal seta and two thin dorsodistal setae; P-4 slightly tapering distally, with straight ventral margin (L/H ratio 2.72), longer than P-2 (P-2/P-4 ratio 0.9), with two unequal distoventral setae, two thin dorsal ones, mediodistal seta thin and short; P-5 a little shorter than P-3, with three pointed distal spines.

III-Leg-6 with short ventrodistal projection directed to distal part of segment, bearing four to five slender pointed setae ( Fig. 4 ). First four segments of all legs with mainly thick setae, terminal segments (especially tarsi) with several thin setae. Leg claws with three pointed clawlets: median clawlet largest, internal clawlet thicker and longer than external one ( Fig. 5 ).

Measurements (n = 1). Idiosoma L 325, W 300; dorsal shield L 288, W 245; capitulum L 108; pedipalp segments (P-1–5) L/H: 19/25, 58/48, 35/36, 70/32, 32/15; leg segments L: I- Leg-1–6: 35, 40, 38, 50, 58, 60; II-Leg-1–6: 35, 38, 38, 56, 67, 74; III-Leg-1–6: 48, 40, 45, 67, 75, 83; IV-Leg-1–6: 70, 45, 48, 70, 83, 93.

Female. Idiosoma flat and nearly circular (L/W ratio 1.03–1.05), frontal setae (Fch, Fp, Vi, Ve) located on separate platelets (Fig. 7). Dorsum with large shield and four pairs of unequal lateral plates. Dorsal shield broad (L/W ratio 1.08–1.15), anteriorly narrowed, distally widely rounded, bearing two pairs of pairs of setae (Oi, Sci). Setae He, Sce and Le located on soft integument along lateral portions of dorsum. Posterior pair of plates largest (L/ W 2.5 – 3.3), bearing seta and glandularium Si in medial half, anterior pair plates bearing seta and glandularium Oe on each side. First pair of slit organs located close to glandularia Vi, second pair of slit organs free or fused with glandularia Hi, i3–i5 lying free on soft integument along lateral portions of dorsum. Capitulum with short anchoral process. Pedipalps, especially P-4, more slender than in male ( Fig. 6 ). III-Leg-6 without modified setae.

Leg coxae incorporated into four groups and covering about half of ventral surface (Fig. 8). Anterior coxal groups with short posterior apodemes directed laterally. Coxal plate IV with slightly convex medial margin which is much longer than coxal plate III medial margin. Acetabular plates wider than long, with straight or weakly convex medial margin, 40–50 genital acetabula and four to six thin setae on each side, gonopore usually surrounded by frame. Pregenital sclerite small, fused to anterior genital sclerite. Setae Pi fused with glandularia Ci and placed on common sclerite on each side. Excretory pore surrounded by sclerotised ring contiguous or fused with posterior margin genital frame. Ventrolateral plates relatively large triangular and lying free between posterolateral extensions of fourth coxae and acetabular plates.

Measurements (n = 5). Idiosoma L 450– 470, W 435–450; dorsal shield L 280–310, W 220–275; capitulum L 95–110; cheliceral segments: base L 75–80, chela L 23–25; pedipalp segments (P-1–5) L/H: 18–24, 42–50, 30– 36, 60–69, 33–35; leg segments L: I-Leg-1–6: 35–37, 35–42, 35–42, 54–60, 54–66, 60–72; II- Leg-1–6: 35–42, 35–42, 38–48, 48–60, 57–69, 70–78; III-Leg-1–6: 40–45, 35–45, 45–48, 60– 67, 65–85, 70–90; IV-Leg-1–6: 65–75, 48–52, 50–58, 75–85, 75–95, 85–95.

Remaks. The present species is closely related to F. minuta Koenike, 1892 . Differences between F. ishikariensis and F. minuta are found in the following characters (character states of F. minuta are given in parentheses, data from Gerecke 2009 and Gerecke et al. 2016): Male: The genital field with 40–50 pairs of acetabula (with 65–82 pairs of acetabula); III-Leg-6 with short stout projection bearing four to five slender setae, Fig. 4 (with finger-shaped projection bearing two to three setae, Fig. 9 ); Female: The dorsal shield anteriorly narrowed, Fig. 7 (widely rounded, Fig. 10 ), the genital field with 40–50 pairs of acetabula (with 62–110 pairs of acetabula); the excretory pore plate relatively small in posteroventral position, Fig. 8 (large in terminal position, Fig. 11 ).

Habitat. Running waters.

Distribution. Asia, Japan, Russia: Primorye territory.

Figures

Figs. 3–6. Feltria ishikariensis: 3, 6 — pedipalp; 4 — III-Leg-5–6; 5 — leg claw; 3–5 — male; 6 — female. Scale bar: 50 μm Рис. 3–6. Feltria ishikariensis: 3, 6 — пеÃипаΛьпа; 4 — коΛено, гоΛень и Λапка ноги III; 5 — коготок ног; 3–5 — самец; 6 — самка. ШкаΛы: 50 μm

Figs. 9–11. Feltria minuta: 9 — III-Leg-6; 10 — idiosoma, dorsal view; 11 — idiosoma, ventral view; 9 — male; 10–11 — female (after Gerecke et al. 2009) Рис. 9–11. Feltria minuta: 9 — Λапка ноги III; 10 — иÃиосома, ÃорсаΛьная сторона; 11 — иÃио- сома; вентраΛьная сторона; 9 — самец; 10–11 — самка (по Гереке и Ãр. 2009)