Piona neumani (Koenike, 1883)

Tuzovskij, Petr V., 2020, Deutonymphal morphology of the water mite Piona neumani (Koenike, 1883) (Acari, Hydrachnidia, Pionidae), Amurian Zoological Journal XII (1), pp. 8-11 : 9-11

Piona neumani (Koenike, 1883)

( Figs 1–7 )

Diagnosis. Deutonymph. Dorsum without plates; genital plates separately, acetabula small and subequal in size, distance between acetabula a little large than diameter any acetabulum on each side; P–2 ventral margin straight, P–3 lateral seta long and situated proximally to middle of segment, IV–Leg–6 with two to three thick, long setae.

Deutonymph, description. Color yellowish-brownish, idiosoma oval, integument soft and finely striated. Dorsum without platelets. The number and position of idiosomal setae typical for the genus Piona . All dorsal setae thin and approximately equal in length, but setae Fch ( Fig. 1 ) longer and a little thicker than others idiosomal setae.

Coxae of legs ( Fig. 2 ) in four groups, cover about half ventral surface in mature specimens. Capitulum with short anchoral projection. Anterior coxal plates with short apodemes. Sclerites bearing setae setae Hv free and located between anterior and posterior coxal groups. Suture line between coxal plates III and IV complete. Medial margin of coxal plate IV 2.0– 2.5 times longer than medial margin of coxal plate III. Posterior margins of coxal plates IV forming obtuse angle, apodemes moderately developed. Gonopore is absent, acetabular plates separately, with two subequal acetabula and three thin, short setae, distance between acetabula large than diameter any acetabulum on each side. Genital sclerite larger than pregenital sclerite. Excretory pore surrounded by narrow sclerotized ring and placed anterior to flanking setae (Pi and Ci).

Chelicera ( Fig. 3 ) with large basal segment and short crescent chela.

Pedipalp ( Fig. 4 ) short and stout: P–1 short, without seta; P–2 large, with straight ventral margin and bearing three dorsodistal setae; P–3 with concave ventral margin, two unequal setae, base of lateral seta situated proximally to middle of segment; P–4 comparatively short, with straight ventral margin, ventral setae well separated, ventral setal tubercle larger than distal one, distoventral peglike seta short; P–5 with two short proximal and two long distal spine-like setae.

Legs 6–segmented slender: I–Leg–4/5 with two short swimming setae ( Fig. 5 ). Legs II–IV with long swimming setae, their number as following: three setae on II–Leg–4/5 and III– Leg–4, four on III–Leg-5, six on IV–Leg-5; IV– Leg–6 with two to three thick, long setae ( Fig. 6 ). Leg claws with subequal internal clawlets, lamella with convex ventral margin ( Fig. 7 ).

Measurements (n=2). Idiosoma L 650–775; medial margin of coxal plates III L 24–30; medial margin of coxal plates IV L 48–55; acetabular plates L 72–74, W 36–42; cheliceral segments: base L 125, chela L 48–50; pedipalp segments (P–1–5) L: 30-35, 77–80, 45–48, 72–73, 30; legs segments L: I–Leg–1–6: 47–50, 54–66, 72–85, 105–110, 120–125, 150–155; II–Leg–1–6: 47– 50, 60–65, 72–85, 125–127, 135–145, 160–168; III–Leg–1–6: 54–60, 65–67, 78–85, 128–132, 150–160, 165–170; IV–Leg–1–6: 72–78, 66–72, 95–102, 138–145, 150–155, 145–148.

Remarks. The described deutonymph is similar to P. nodata (Müller, 1781) , but it is without dorsal platelets, the color yellowishbrownish, P–4 with unequal ventral setal tubercles ( Fig. 4 ). In contrast, in the deutonymph of P. nodata the dorsal platelets present, the color red, P–4 with subequal ventral setal tubercles ( Tuzovskij 1990).

Figures

Figs 1–4. Piona neumani (Koenike, 1883), deutonymph: 1 — seta Fch; 2 — idiosoma, ventral view; 3 — chelicera; 4 — pedipalp. Scale bars: 16, 18 = 100 μm; 17, 19 = 50 μm Рис 1–4. Piona neumani (Koenike, 1883), Ãейтонимфа: 1 — seta Fch; 2 — иÃиосома, вентраΛьная сторона; 3 — хеΛицера; 4 — пеÃипаΛьпа. ШкаΛы: 1–2 = 100 μm; 3, 4 = 50 μm

Figs 5–7. Piona neumani (Koenike, 1883), deutonymph: 5 — I–Leg–5–6; 6 — IV–Leg–5–6; 7 — claw of leg I. Scale bars: 5–6, 7 = 50 μm Рис. 5–7. Piona neumani (Koenike, 1883), Ãейтонимфа: 5 — гоΛень и Λапка ноги I; 6 — гоΛень и Λапка ноги IV; 7 — коготок ноги I. ШкаΛы: 5–6, 7 = 50 μm