Piona neumaniella, V.Tuzovskij, 2022

V. Tuzovskij, Petr, 2022, Description of a new water mite species of the genus Piona Koch (Acari, Hydrachnidia, Pionidae) from European Russia, Zootaxa 5190 (3), pp. 438-446 : 438-446

Piona neumaniella , sp. n.

( Figs 1–29 )

Type series. Holotype: female, slide 1596, Europe, Russia, Samara Province, Stavropol District, National natural Park “Samarskaya Luka”, small lake near village Koltsovo , depth 30–90 cm, substrates silt and vegetation along a coastal line, 21.05.1996, leg P. Tuzovskij . Paratypes: same locality as holotype, 3 females and 3 males 21.05.1996, 3 females and 3 males 23.05.1996; 3 females and 2 males 02.06.1996, 2 mature deutonymphs 15.06.1996. The females produce eggs from which develop directly the deutonymphal stage. Larvae and deutonymphs were reared from seven females, the duration of the embryonic period was 10–13 days .

Description. Larva. Idiosoma flat, dorsal plate elongate (L/W ratio 1.58–1.85), covering almost the whole dorsum ( Fig. 1 ), bearing four pairs setae (Fch, Fp, Vi, Oi) with convex lateral margins, anterior margin straight or slightly convex, posterior margin rounded; simple setae Fch shorter than Vi, trichobothria Fp and Oi relatively long, thin and subequal in length. Surface of dorsal shield slightly sclerotized with indistinct reticulation. Coxal plates I ( Fig. 2 ) with short apodemes directed laterally. Coxal plates III elongate and much larger than coxal plate II, with rounded posterior margin, suture line between coxal plates incomplete obliterated medially. Setae C1 shorter than C2, C3 longer than C4; C4 relatively thick, a little not reaching to posterior margin of coxal plates III, base of coxal seta C4 and suture line between coxal plates II+III well separated. Excretory pore plate ( Figs 3–4 ) subtriangular wider than long (L/W ratio 0.85–0.92), with almost straight posterior margin, slightly convex lateral margins; both pairs of anal setae and excretory pore located near posterior margin of plate; anal setae in trapezoid arrangement, bases of setae Ai situated anterior and medial to Ae, Ai shorter than Ae. Basal segments of chelicerae ( Fig. 5 ) fused to each other medially, expanded proximally and tapering distally, with short pointed crescent chela ( Fig. 6 ). Pedipalps stocky ( Fig. 7 ): P-1 short and without seta; P-2 large, with a single dorsal seta; P-3 a little shorter than P-2, with very long, thick lateroproximal seta and relatively short dorsodistal one; P-4 short, with three thin setae and large dorsodistal claw; P-5 small, with single solenidion, two unequal long and five 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(s), 11(ac). Number of thickened distal setae from trochanter to tarsus: I-Leg: 0, 1, 1, 2, 0; II-Leg: 0, 1, 2, 3, 0; III-Leg: 0, 2, 2, 4, 0. I-Leg-1with relatively short seta, II/III-Leg-1 with long seta each. Solenidion or solenidia on I/II-Leg-3/4 and III-Leg-3 located dorsodistally, solenidion on III-Leg-4 situated near to middle of segment; I/II-Leg-4 with subequal solenidia. Acanthoid seta comparatively short and setose, located distally on tarsus of all legs. Leg claws subequal in length but central claw a little thicker than lateral claws on tarsi all legs ( Fig. 11 ). Measurements (n=5). Dorsal plate L 335–345, W 25–265; medial margin of coxa I L 60–69, medial margin of coxae II+III L 130–140; urstigma D 16–17; excretory pore plate L 35–38, W 39–40; setae Fch L 50, setae Fp and Oi L 41, setae Vi L 56, L 48; setae Oe L 95–101; setae C1 L 48, setae C2 L 55, setae C3 L 78, setae C4 L 65; cheliceral segments: base L 90–95, chela L 15–18; pedipalpal segments (P–1–5) L: 12-15, 33–36, 27–30,12–15, 9–10; leg segments L: I-Leg-1–5: 30–36, 30–36, 36–42, 48–50, 48–51; II-Leg-1–5: 33–37, 33–37, 42–48, 57–66, 60–66; III-Leg-1–5: 42–46, 40–42, 42–48, 60–66, 66–72.

Deutonymph. Color red, idiosoma oval, integument soft and with large wrinkles. Setae Fch ( Fig. 12 ) longer and thicker than other idiosomal setae. Coxal plates in four groups ( Fig. 13 ). Anterior coxal groups with short apodemes. Glandularium and seta Hv free, located between anterior and posterior coxal groups on each side. Suture line between coxal plates III and IV complete. Medial margin of coxal plate IV 2.0–3.0 times longer than medial margin of coxal plate III. Posterior margins of coxal plates IV forming obtuse angle, apodemes slightly developed. Acetabular plates separated, with two subequal acetabula and three short, thin setae on each side, distance between acetabula equal or large than diameter of acetabula. Genital and pregenital sclerites fused. Excretory pore surrounded by a sclerotized ring and placed anterior to setae Pi. Pedipalp thicker than anterior pairs of legs ( Fig. 14 ): P-1 short, without seta; P-2 large, with straight ventral margin and bearing three short subequal dorsal setae; P-3 short with concave ventral margin, two unequal setae, lateral seta equal or a little shorter than dorsal margin of segment, its base located near middle of segment; P-4 tapering distally, with two well separate ventral setae (proximal seta associated with small tubercle, distal one usually not associated with tubercle or tubercle very minute), distal peg-like seta very small; P-5 with proximal solenidion, four unequal distal spines and three thin setae. Legs 6-segmented slender, I-Leg-4/5 with relatively short swimming setae ( Fig. 15 ), legs II–IV with long swimming setae ( Fig. 16 ), their number as following: two on I-Leg-5 and II-Leg-4; three to four on II-Leg-5, four on III-Leg-5, five on IV-Leg-5, IV-Leg-6 with three to four thick setae. Leg claws with long pointed external and comparatively short, thick internal clawlets, lamella moderately developed with slightly convex ventral margin ( Fig. 17 ). Measurements (n=10). Idiosoma L 390–540; seta Fch 72–80; acetabular plate L 60–72, W 30–36; genital acetabula (ac-1-2) L 18–21, 18–24; cheliceral segments L: base 115–135, chela 48–54; pedipalp segments (P-1-5) L: 18–24, 90–96, 48–55, 90–96, 35–40; leg segments L: I-Leg-1-6: 35–50, 75–85, 75–90, 110–115, 110–120, 140–160; II-Leg-1-6: 50–65, 65–80, 80–90, 125–40, 135–150, 160–170; III-Leg-1-6: 50–65, 75–90, 85–95, 130–140, 155–165, 155–170; IV-Leg-1-6: 75–90, 75–100, 100–105, 130–150, 160–190, 175–190.

Adults. Both sexes. Color red. All dorsal setae thin and approximately equal in length, but setae Fch ( Fig. 18 ) longer and thicker than others idiosomal setae. Dorsum usually without platelets, occasionally two platelets present, which are hardly visible. Pedipalps thicker than anterior pair of legs. P-2 ventral margin straight or slightly convex; P-4 with sexual dimorphism. Male. Idiosoma oval, integument soft with rather large wrinkles ( Fig. 19 ). Anterior coxal groups separated with short apodemes. Sclerites bearing setae Hv fused with posterior margins of coxal plates II, but suture line present on each side. Posterior coxal groups fused medially but suture line present. Suture line between third and fourth coxal plates incomplete obliterated medially on each side. Genital plates broadly wing-shaped, anteromedially fused to coxal plates IV, their posterior margin not extending laterally beyond posterior projections of these plates. Gonopore narrow transverse, wider than long, genital pit moderately deep, with 8–12 genital acetabula on each side. Excretory pore surrounded by sclerotized ring, located between flanking setae (Pi, Ci). Chelicera with large basal segment and short crescent chela ( Fig. 20 ). Pedipalp ( Fig. 21 ) thicker than legs: P-1 short, with single short dorsodistal seta; P-2 ventral margin straight or slightly convex, with six to seven short subequal dorsal setae; P-3 short, with one long lateral seta and two short subequal setae, lateral seta located near middle of segment its length equal or shorter than dorsal margin of segment; P-4 stocky, ventral margin with an extension bearing two pointed subequal comparatively large setal tubercles, and several thin setae associated or not associated with small tubercles, ventrodistal peg-like seta short and directed ventrally; P-5 relatively long with proximal solenidion, four very short, thick distal spines and several thin setae. Ejaculatory complex ( Fig. 22 ) proximal chamber relatively large, with a curving proximal projection forming single incomplete coil, proximal and distal arms subequal in length.

Legs with swimming setae. I/II-Leg–6 thickened distally ( Fig. 23 ); III-Leg-5 much longer than III-Leg-6 (III-Leg-5/III-Leg-6 L ratio 1.77–1.92.), subequal in thickness along entire length, with long distal seta; III-Leg-6 short, weakly thickened distally, with convex dorsal margin ( Fig. 24 ); IV–Leg-4 comparatively thick, with a concavity bearing rather numerous unequal spine-like setae, IV-Leg-5 longer than IV-Leg-4 a little thickened distally, IV-Leg-6 thin straight, with three to five thick setae ( Fig. 25 ). Number of swimming setae as follows: three to four on I–Leg-4, four to five on I-Leg-5, five to six on II-Leg-4/5, one on III-Leg-5, three to four on IV-Leg-4, eight to ten on IV-Leg-5. Claws of legs III small and subequal in shape and size ( Fig.6 ). Measurements (n=5). Idiosoma L 675–725; seta Fch L 75–80; genital field W 325– 350; cheliceral segments L: base 200–225, chela 60–65; pedipalp segments (P–1–5) L: 37–50, 150–170, 85–105, 160–175, 50–55; leg segments L: I-Leg-1–6: 75–90, 110–125, 135–155, 205–215, 215–240, 235–245; II-Leg-1–6: 75–90, 110–140, 150–175, 225–240, 250–265, 235–255; III-Leg-1–6: 85–100, 125–150, 150–175, 235–250, 300–315, 160–170; IV-Leg-1–6: 150–165, 125–150, 135–155, 200–240, 250–290, 250–265. Female. Integument lineated. All coxal groups separated ( Fig. 28 ). Anterior coxal groups with a short apodeme each. Sclerites bearing setae Hv free. Suture line between third and fourth coxal plates complete, coxal plate IV posterior margins forming obtuse angle, apodeme moderately developed. Genital field with two pairs of plates: small anterior plates usually bearing one acetabulum and surrounded by six to eight short, thin setae, posterior plates irregular wider than long, with 8–13 acetabula and three to six short, thin setae on each side; in addition, (occasionally two or three) acetabula lying free in the integument between anterior and posterior plates on each side. Anterior genital sclerite large than posterior one. Excretory pore located between setae Pi and surrounded by sclerotized ring. P-2 ventral margin straight or slightly convex; P-3 with three subequal setae which much shorter than dorsal margin of segment; P-4 slender slightly tapering distally, ventral margin without extension, with two small well separated setal tubercles and several short, thin setae not associated with tubercles ( Fig. 29 ). Legs thin and slender. I/II-Leg-6 not thickened. Legs with swimming setae, their number as following: four to five on I-Leg-4, five to seven on I-Leg-5, six to eight on II-Leg-4 and IV-Leg-4, seven to ten on II-Leg-5 and III-Leg-4; 1-11 on III-Leg-5, 8–11 on IV-Leg-5. Swimming setae on anterior pairs of legs shorter than on posterior ones. Leg claws as in the male I/II-Leg claws. Measurements, n=5. Idiosoma L 1250–1600; cheliceral segments L: base 260–290, chela 87–90; pedipalp segments (P-1-5) L: 37–50, 165–200, 100–112, 200–225, 62–75; leg segments L: I-Leg-1-6: 100–115, 160–175, 210–225, 325–340, 325–340, 310–325; II-Leg-1-6: 100–115, 175–190, 200–265, 350–365, 350–375, 325–350; III-Leg-1-6: 110–125, 185– 200, 200–265, 360–375, 360–375, 325–340; IV-Leg-1-6: 185–215, 200–215, 285–300, 385–415, 425–440, 335–360. Remarks. The present species is similar to Piona neumani (Koenike, 1883) , P. circularis Piersig, 1896 and P. litoralis Viets, 1936 ; however, K. Viets (1956) and K. O. Viets (1987) regarded two last species as a junior synonym of the first species. Differences between P. neumaniella sp. n. and P.neumani are found in the following characters (characters states of larva, deutonymph and adults P. neumani are indicated in parentheses, data from Wainstein 1980 for larva, Tuzovskij 2020 for deutonymph, K. Viets 1936, Lundblad 1962 and Gerecke et al. 2016 for adults, respectively): Larva: the dorsal shield, coxal plates and excretory pore plate very slightly sclerotized (well sclerotized), larvae develop without parasitism to deutonymphal stages (a host necessary for development); base of coxal seta C4 and suture line between coxal plates II+III well separated on each side, Fig. 2 (close to each other, Fig. 30 ); basal segments of chelicerae distinctly thickened in proximal half, with straight lateral margins, Fig. 5 (almost all length equal in width, with irregular lateral margins, Fig. 31 ); anal setae in trapezoid arrangement, Figs 3–4 (in straight transverse line, Fig. 32 ); all leg clawlets subequal in length (lateral clawlets longer than central clawlets); Deutonymph: pregenital and genital sclerites fused to each other (separated), P-5 all thick spine-like setae located close to each distally, Fig. 13 (two short spines located proximally and two comparatively long spines located distally, Fig. 33 ), II-Leg-5 with two swimming setae (with three swimming setae); Adults: Dorsal plates not developed (present); Male: Integument with wrinkles (lineated), gonopore narrow, Fig. 19 (rather wide, Fig. 34 ), ejaculatory complex proximal chamber with a curving rather thick, short proximal projection forming incomplete coil, Fig. 22 (with relatively thin, long projection, forming 1.5 coils, Fig. 27 ); Female: coxal plate IV posterior margins with short obtuse projection, Fig. 28 (with rather long pointed projection, Fig. 35 ).

Etymology. The species is named neumaniella as it has many features in common with the species P. neumani .

Habitat. Lakes.

Distribution. Europe ( Russia, Samara Province).

Figures

FIGURES 1–7. Piona neumaniella sp. n., larva: 1, dorsal shield; 2, idiosoma, coxal plates; 3–4, excretory pore plate; 5, chelicerae, dorsal view; 6, chela, lateral view; 7, pedipalp. Scale bars: 1–2, 3–4, 5 = 50 μm, 6, 7 = 25 μm.

FIGURES 8–11. Piona neumaniella sp. n., larva: 8, I-Leg-1–5; 9, II-Leg-1–5; 10, III-Leg-1–5; 11, leg claws. Scale bars: 8–10 = 50 μm, 11 = 25 μm.

FIGURES 12–14. Piona neumaniella sp. n., deutonymph: 12, seta Fch; 13, ventral view; 14,pedipalp. Scale bars: 12–13 = 100 μm, 14 = 50 μm.

FIGURES 15–17. Piona neumaniella sp. n., deutonymph: 15, I-Leg-4–6; 16, IV-Leg-4–6; 17, leg claw.Scale bars: 15–16= 100 μm, 17 = 50 μm.

FIGURES 18–21. Piona neumaniella sp. n., male: 18, seta Fch; 19, ventral view; 20, chelicera; 21, pedipalp. Scale bars: 18, 20 = 100 μm, 19 = 200 μm; 21 = 50 μm.

FIGURES 22–27. 22–26. Piona neumaniella sp. n., male: 22, ejaculatory complex; 23, I-Leg-5–6; 24, II-Leg-5-6; 25, IV-Leg- 4–6; 26, III leg claws. 27. Piona neumani, ejaculatory complex. Scale bars: 22, 26, 27= 50 μm, 23–25 = 100 μm.

FIGURES 28–29. Piona neumaniella sp. n., female: 28, ventral view; 29, pedipalp.Scale bars: 28 = 200 μm, 29 = 100 μm.

FIGURES 30–35. Piona neumani: 30–32, larva; 33, deutonymph; 34, male; 35, female; 30, coxal plate I–III; 31, chelicerae, 32, excretory pore plate (30–32 after Wainstein 1980); 33, pedipalp (after Tuzovskij 2020); 34–35, genital field (after Gerecke et al. 2016).