Piona nodatella Tuzovskij, 2015

Tuzovskij, Petr V., ., .., ., -, -, -, -, -, -, -, -, -, -, -, -, -, -, -, -, -, -, ., -, P-, ., I- & I-, .., 2017, Larval morphology of the water mite Piona nodatella Tuzovskij, 2015 (Acari: Hydrachnidia, Pionidae), Ecologica Montenegrina 11, pp. 37-41 : 37-40

Piona nodatella Tuzovskij, 2015

( Figs 1-12 )

Material examined. 35 larvae, Russia, Yaroslavl Province, Nekouz District, temporary waters near settlement Borok and village Pogorelka , April-June, P. V. Tuzovskij; larvae reared from four females in laboratory (IBIW), duration of the embryonic period 8-13 days.

Diagnosis. Dorsal shield elongate (ratio length/width 1.55-1.70) and bearing four pairs of setae, Fch shorter than Vi; Oe longest, Hi slightly shorter than He, Sce longer than Sci, and Li longer than Le; C3 longer than other coxal setae; dorsal shield and all coxal plates porous and with reticulation; excretory pore plate wider than long with convex anterior margin; P-4 with two setae, III-Leg-3 with two heavy setae.

Description.

Larva. Idiosoma flat, dorsal plate elongate, in unengorged larvae covering almost the whole dorsum ( Fig. 1 ), bearing four pairs setae (Fch, Fp, Vi, Oi) with convex lateral margins, its anterior margin straight or slightly convex, posterior margin rounded; setae Fch shorter than Vi, trichobothria Fp and Oi relatively short and equal in length. Setae Oe, Hi, He, Sci, Sce, Li and Le situated in soft membrane, Oe longest, Hi slightly shorter than He, Sce slightly longer than Sce, and Li slightly longer than Le.

Coxal plates ( Fig. 2 ) moderately large and elongate, first plates with short apodemes directed laterally, plates II-III with single rudimentary apodeme near middle of their medial margin on each side. Setae C1 shorter than C2; C4 relatively thick, not reaching to posterior margin of coxal plates III and slightly shorter than C3. Setae Ci very long thickened, located on small tubercles. Setae Pi and Pe subequal and moderately in length. Excretory pore plate ( Figs 3–4 ) wider than long (L/W ratio 0.5-0.6) with convex anterior margin; setae Ai and Ae forming true transverse row and located near posterior margin of the plate, Ae slightly longer than Ai, bases of Ai close to each other, located laterally to excretory pore.

Capitulum ( Fig. 5 ) with wide base and relatively narrow rostrum, anterior hypostomal setae longer than posterior ones. Basal segments of chelicerae ( Fig. 6 ) fused to each other medially, longer than wide, expanded proximally and tapering distally; chela small, pointed.

Pedipalps short and stocky ( Fig. 7 ): P–1 short and without seta; P–2 large with slightly convex dorsal margin, with single dorsodistal seta distally; P–3 with very long, thick proximolateral seta and relatively short dorsodistal one; P–4 with two unequal thin setae and large dorsodistal claw; P–5 small, with single solenidion, two long and four relatively short unequal simple setae.

Legs 5–segmented, shape and arrangement of setae on legs segments as shown in Figs 8–10. Total number of leg setae, excluding eupathidia, as follows (specialized setae indicated in parentheses): I– Leg-1– 5: 1, 7, 5 (s), 11 (2s), 14 (s, ac); II–Leg-1–5: 1, 7, 5 (s), 11 (2s), 13 (s, ac); III–Leg-1–5: 1, 6, 5 (s), 10, 11 (ac). Number of thickened distal setae from trochanter to tarsus: I-Leg: 0, 1, 1, 1, 0; II–Leg: 0, 1, 2, 3, 0; III- Leg: 0, 2, 2, 4, 0. I–Leg-1 with relatively short seta, II–Leg-1 and III–Leg-1 each with long seta. Solenidion or solenidia on I/II–Leg-3/4 located distally, solenidion on III–Leg-3/4 and II-Leg-5 located a little dorsodistal to middle of these segments; I–Leg-4 and II–Leg-4 with subequal solenidia. Acanthoid seta comparatively short and setose, located distally on tarsus of all legs. Lateral claws and empodial claw nearly equal in length, but lateral claws comparatively thin ( Figs. 11-12 ).

Measurements, n=10. Dorsal plate L 285–310, W 185–195; setae Fch and Vi L 48–55, setae Vi L 60- 65, setae Fp and Oi L 20-25; setae L Oe 95–115; setae Hi and Sci L 70-80, setae He L 80-90, setae Sce L 85- 93, setae Li L 80-85, setae Le L 67-75; setae Si L 32-39; setae Se L 65–74, setae Ci L 130–140, setae Pi and Pe L 38–45; setae Ai L 28–32; setae Ae L 35–45; setae C1 L 65–77, setae C2 L 80-85, setae C3 L 90–102, setae C4 L 90–96; medial edge of coxa I L 80–90, medial edges of coxae II+III L 125–140; urostigma D 11- 13; excretory pore plate L 22–26, W 33–42; cheliceral segments: base L 86–93, chela L 16–19; pedipalpal segments (P–1–5) L: 6–9, 35-39, 25-32, 9-19, 6–7; legs segments L: I–Leg-1–5: 32-40, 35-38, 38-45, 52-58, 64-70; II–Leg-1–5: 35-40, 38-45, 38-45, 57-65, 80-87; III–Leg-1–5: 44-48, 40-45, 41-45, 64-68, 90-96.

Remarks. The larva of Piona nodatella is similar to P. nodata (Müller, 1781) . However, the following clear differences can be found in the morphology larva of P. nodatella (character states of larva P. nodata are given in parenthesis after Wainstein 1980): setae C2 shorter than C3 and C4, Fig. 2 (much longer than C3 and C4); excretory pore plate with convex anterior margin, Figs 3-4 (with concave anterior margin); III-Leg- 3 with two heavy setae, Fig. 10 (with three heavy setae); P-4 with two setae, Fig. 8 (with three setae).

Figures

Figures 1–2. Piona nodatella Tuzovskij, 2015, larva: 1 – dorsal view; 2 – ventral view. Scale bar: 1-2 = 50 μm.

Figures 3-7. Piona nodatella Tuzovskij, 2015, larva: 3-4 excretory pore plate; 5 – capitulum, 6 – chelicera, dorsal view; 7 - pedipalp, lateral view. Scale bars: 3-4, 7 = 20 μm; 5 -6 = 50 μm.

Figures 9-13. Piona nodatella Tuzovskij, 2015, larva: 8 - Leg I; 9 - Leg II; 10 - Leg III; 11 - claws of leg I; 12 - claws of leg III. Scale bars: 8-10 =50 μm, 11 -12 =20 μm.