Piona magadanensis, Tuzovskij, Petr V., 2013

Tuzovskij, Petr V., 2013, New water mite species of the genus Piona Koch, 1842 (Acari, Hydrachnidia: Pionidae) from Northeastern Russia, Zootaxa 3664 (3), pp. 321-334 : 322-327

Piona magadanensis sp. n.

( Figs 1–23 )

Type series. Holotype: male, slide 2430, Russia, Magadan Province, Ola District, small forest pond near settlement Ola, depth 0.3–0.5 m, 2 June 1979, leg. P.V. Tuzovskij. Paratypes: two females and one deutonymph; Magadan city, small pond near Gertner bay, depth 0.3–0.5 m, 7 August 1978, leg. P.V. Tuzovskij.

Description. Female. Idiosoma oval, integument soft and striated. Dorsum with small elongated platelets, ratio L/ W 5.1 –5.6 ( Fig. 1 ). 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. 2 ) thicker than others idiosomal setae associated with glandularia ( Fig. 3 ) and trichobothria ( Fig. 4 ). Coxae of legs cover about half ventral surface ( Fig. 5 ). 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 incomplete and obliterated medially. Medial margin of coxal plate IV 2.5–3 times longer than medial margin of coxal plate III. Posterior margins of coxal plates IV forming obtuse angle, apodemes slightly developed. Genital opening and acetabular plates approximately equal in length. Acetabular plates sickle-shaped, well indented on medial margin; 14–16 pairs of genital acetabula, two pairs of which much larger than others; all acetabula and genital setae located on the plates, three setae located anteromedially and three setae located posteromedially on each side. Anterior large acetabulum located in anteromedial corner of acetabular plate, second large acetabulum located near middle of the medial margin of the plate. Excretory pore surrounded by narrow sclerotized ring ( Fig. 6 ) and placed between setae Pi.

Pedipalp rather slender ( Fig. 7 ): P–1 with a single short dorsodistal seta; P–2 large, with straight ventral margin and bearing five dorsal setae; P–3 with three short subequal setae, base of lateral seta located near middle of segment; P–4 stocky, shorter than P–2, ventral setae located on small subequal tubercles which are well separated, distoventral spine short; P–5 with proximal solenidion, five thin setae and four thick distal spines.

Legs thin and slender. I–Leg-4 with one or two, I–Leg-5 with two short swimming setae ( Fig. 8 ). Legs II–IV with long swimming setae, their number as following: three or four on II–Leg-4 and II–Leg-5, four or five on III– Leg-4, five on III–Leg-5 and IV–Leg-4; seven or eight on IV–Leg-5. Claws with long external and short internal clawlets, lamella with convex ventral margin ( Fig. 9 ).

Measurements (n=2). L of idiosoma 1100–1150; L of acetabular plates 175–185, W of acetabular plates 150– 185; L of cheliceral segments: base 175–180, claw 57–60; dorsal L of pedipalp segments (P–1–5): 40–42, 138–150, 78–85, 125–140, 57–60; L of leg segments: I–Leg-1–6: 78–85, 95–102, 120–138, 165–175, 170–185, 165–170; II– Leg-1–6: 78–85, 100–105, 130–140, 180–195, 190–200, 210–225; III–Leg-1–6: 90–96, 100–115, 130–140, 195– 210, 220–235, 210–225; IV–Leg-1–5: 120–125, 120–125, 160–175, 230–245, 230–240.

Male. Dorsum similar those of the female, setae Fch long ( Fig. 10 ). Anterior coxal plates with short apodemes ( Fig. 11 ). Genital field fused with fourth coxal plates. Genital field extending laterally slightly beyond posterior corner of fourth coxal plates, with a large, deep genital pit; 23 genital acetabula on each side, two pairs of which much larger than others. Genital opening triangular, with small anteromedian incision. Setae Pe free or fused with coxal plate IV. Excretory pore surrounded by narrow sclerotized ring.

Chelicera ( Fig.12 ) with large basal segment and short crescent stylet. Pedipalp ( Fig. 13 ) short and stout: P–2 with five–six short setae; P–3 with three short subequal setae, lateral seta located anterior to middle of segment; P– 4 shorter than P–2, both ventral setae located on small subequal tubercles, distolateral spine short; P–5 with proximal solenidion, five thin setae and four thick distal spines.

I–Leg-5–6 and II–Leg-5–6 expanded towards distal end ( Fig. 14 ); III–Leg-5 long, straight and expanded distally, III–Leg-6 short and club–shaped ( Fig. 15 ); IV–Leg-4 thick and has a deep concavity bearing numerous unequal spine–like setae ( Fig. 16 ), IV–Leg-5 slightly expanded in distal half. I–Leg-4 with one, I–Leg-5 with two short swimming setae. Legs II–IV with long swimming setae, their number as following: three on II–Leg-4 and IV–Leg-4, four on II–Leg-5 and III–Leg-4, five on III–Leg-5; eight or nine on IV–Leg-5. Claws of tarsi I–II with long, thin clawlets, external clawlet slightly longer than ventral one ( Fig. 17 ). Claws of legs III asymmetric ( Fig. 18 ); large claw with moderately developed lamella, with thick, long dorsal clawlet and relatively thin ventral one; small claw with relatively large lamella, with thick pointed dorsal clawlet and thin ventral one. I–Leg-4 with one swimming seta, I–Leg-5 with two short swimming setae. Legs II–IV with long swimming setae, their number as following: seven on II–Leg-4, 8–10 on II–Leg-5, III–Leg-4 and IV–Leg-4; 11–13 on III–Leg-5 and IV–Leg-5.

Measurements (n=1). L of idiosoma 660; W of acetabular plates 348; L of cheliceral segments: base 160, stylet 48; dorsal L of pedipalpal segments (P–1–5): 42, 125, 69, 102, 54; L of leg segments: I–Leg-1–6: 65, 85, 108, 138, 145, 168 II–Leg-1–6: 72, 90, 108, 145, 155, 175; III–Leg-1–6: 78, 90, 105, 175, 215, 160; IV–Leg-1–6: 85, 90, 95, 170, 180, 170.

Deutonymph. Dorsum without true dorsal platelets. Setae Fch long ( Fig. 19 ). Coxal plates like those the female, but with smaller number of setae ( Fig. 20 ). Suture line between coxal plates III and IV oblique, incomplete and obliterated medially. Posterior apodemes on coxal plates IV well developed. Acetabular plates separated, oblique, directed anteromedially, bearing three acetabula and three setae each. Median acetabulum larger than anterior and posterior acetabula, distance between anterior and median acetabulum approximately twice longer than distance between median and posterior acetabula. Genital sclerite much larger than pregenital sclerite.

Pedipalp stout ( Fig. 21 ): P–1 short, without seta; P–2 large, with straight ventral margin and bearing three subequal dorsodistal setae; P–3 with two short unequal setae, base of lateral seta located proximally to middle of segment; P–4 and P–2 approximately equal in length, ventral setae located on very small subequal tubercles which well separated, distoventral spine short pointed; P–5 with proximal solenidion, three thin setae and four thick distal unequal spines.

Legs thin and slender. I–Leg-4 with one swimming seta, I–Leg-5 with two short swimming setae ( Fig. 22 ). Legs II–IV with long swimming setae ( Fig. 23 ), their number as following: one seta on II–Leg-4 and IV–Leg-4, two setae on II–Leg-5 and III–Leg-4, three on III–Leg-5, six or seven on IV–Leg-5.

Measurements (n=1). L of idiosoma 410; L of seta Fch 90; L of acetabular plates 80, W of acetabular plates 36; diameter of genital acetabula (ac. 1–3): 10–12, 15–18, 10–12; L of cheliceral segments: base 130, stylet 40; dorsal L of pedipalpal segments (P–1–5): 30, 90, 48, 85, 39; L of leg segments: I–Leg-1–6: 50, 60, 72, 115, 120, 135; II–Leg-1–6: 55, 60, 78, 125, 145, 155; III–Leg-1–6: 55, 60, 85, 130, 160, 160; IV–Leg-1–6: 80, 70, 102, 150, 160, 150.

Differential diagnosis. The present species is similar to the American species Piona pinguipalpis Cook, 1960 and to the European species P. l a m i n a t a (Thor, 1901). Piona magadanensis sp. n. differs from P. pinguipalpis in the following characters (character states of P. pinguipalpis are indicated in parenthesis after Cook 1960): In the adults of P. magadanensis sp. n. the genital field has 22–25 acetabula on each side (7–12 acetabula on each side), two genital acetabula on each side much larger than the others (all acetabula subequal), the setal tubercles of P–4 well developed (poorly developed); the genital opening in the male triangular (oval, transverse). The medial margin of the genital plate in female P. laminata slightly concave, the medial margin of P–2 convex, I–Leg-5 with five or six swimming setae, claw of leg I equal in length (Lundblad 1962); while in female Piona magadanensis sp.n. the genital plate is well indented on medial margin, the medial margin of P–2 straight, I–Leg-5 with two swimming setae, claw of leg I unequal in length. The deutonymph of the new species is similar to deutonymphs the following species: P. latigenitalia Marshall, 1924 , P. spinulosa (Wolcott, 1902) , P. annulata (Thor, 1900) , P. co с cinoides (Thor, 1896) and P. inflata (Sokolow, 1927) by having three pairs of the genital acetabula. All genital acetabula in the named species are subequal ( Marshall 1924; Tuzovskij 1990), while in the deutonymph of P. magadanensis sp. n. the median acetabulum considerably larger than both others acetabula on each side ( Fig. 41 ).

Etymology. The species epithet magadanensi s is derived from the name of the Province where it was collected (Magadan).

Habitat. Standing waters.

Distribution. Asia ( Russia, Magadan Province).

Figures

FIGURES 1 – 6. Piona magadanensis sp. n., female: 1, dorsal plates; 2, seta Fch; 3, seta with glandularia; 4, trichobothria Oi; 5, coxal plates and genital field; 6, excretory pore. Scale bars: 1, 5 = 100 μm; 2 – 4, 6 = 50 μm.

FIGURES 7 – 9. Piona magadanensis sp. n., female: 7, pedipalp, lateral view; 8, tibia and tarsus of leg I; 9, claw of leg II. Scale bars: 7 = 50 μm; 8 – 9 = 100 μm.

FIGURES 10 – 13. Piona magadanensis sp. n., male: 10, seta Fch; 11, coxal plates and genital field; 12, chelicera; 13 — pedipalp. Scale bars: 10, 12 – 13 = 50 μm; 11 = 100 μm.

FIGURES 14 – 18. Piona magadanensis sp. n., male: 14, tibia and tarsus of leg I; 15, tibia and tarsus of leg III; 16, genu and tibia of leg IV; 17, claw of leg I; 18, claws of leg III. Scale bars: 14 – 16 = 100 μm; 17 – 18 = 20 μm.

FIGURES 19 – 21. Piona magadanensis sp. n., deutonymph: 19, seta Fch; 20, idiosoma, ventral view; 21 — pedipalp. Scale bars: 19, 21 = 50 μm; 20 = 100 μm.

FIGURES 22 – 23. Piona magadanensis sp. n., deutonymph: 22, tibia and tarsus of leg I; 23, tibia and tarsus of leg IV. Scale bar: 100 μm.

FIGURES 39 – 43. Piona anadyrensis sp. n., deutonymph: 39, dorsal platelets; 40, seta Fch; 41, idiosoma, ventral view; 42, pedipalp, lateral view; 43, genu, tibia and tarsus of leg IV. Scale bars: 39, 41 = 100 μm, 40, 42 – 43 = 50 μm.