Piona discrepaniella Tuzovskij, 1990

Tuzovskij, Petr V., 2019, On the systematics of the water mite Piona discrepans (Koenike, 1895) and Piona discrepaniella Tuzovskij, 1990 (Acari, Hydrachnidia, Pionidae), Zootaxa 4629 (3), pp. 397-404 : 400-403

Piona discrepaniella Tuzovskij, 1990

( Figs 12–19 , 20 )

1990 Piona discrepaniella . Key to deutonymphs (in Russian): 186–188

Material examined. 1 male and 1female: Asia, Russia, Chukotka, Anadyr District, small lake near settlement Markovo , 19 August 1981, leg. P. Tuzovskij.

Both sexes. Color brown. Soft integument finely striated. Legs long and slender. Pedipalps thicker than anterior pairs of legs. P-2 ventral margin straight or slightly convex; P-3 with three setae, these shorter than dorsal margin of segment; P-4 ventrally with two setal tubercles, several short, thin setae not associated with tubercles and short distal peg-like seta. Male. Dorsum ( Fig. 12 ) with large shield covering about one half of dorsal surface and bearing five pairs of setae: Oi, Oe, Hi, Sci, Li. Setae Fch, Fp, Vi, Ve, He, Le and four pairs of slit organs (i1–i4) located on soft integument. Setae Fch thicker than other idiosomal setae. Anterior coxal groups separated, with short apodemes ( Fig. 13 ). Sclerites bearing glandularia and setae Hv not fused with posterior margin of coxal plates II. Posterior coxal groups close together, but not fused. Suture line between third and fourth coxal plates incomplete medially. Genital field, excretory pore plate and setae Pi, Pe included into ventral sclerotization. Setae Si, Ci, Sce, Hv and i5 located on soft integument. Genital plates broad, with distinct outline and two deep, narrow anterior indentations on each side, with 29–35pairs of acetabula, one of these and four to five thin setae located on an anterior platelet on each side. Gonopore small oval, genital pit comparatively shallow with two pairs of thin setae. Small transverse sclerite located close to posterior margin of genital plate on each side. Pedipalp ( Fig. 14 ) compact: P-1 short, with a single short dorsodistal seta; P-2 large, with straight ventral margin and six short, subequal dorsal setae; P-3 with three unequal setae, these shorter than dorsal margin of segment, lateral seta located slightly anteriorly to middle of segment; P-4 ventrally with two distinct setal tubercles, lying behind each other, several thin setae not associated with tubercles and short distal peg-like seta. I/II-Leg-6 hardly thickened distally. III-Leg-5 straight, with several stout distal setae, one of these occasionally longer than others, III-Leg-6 straight and much shorter than III-Leg-5 ( Fig. 15 ). IV-Leg-4 rather thick, with a deep concavity bearing a few unequal stout setae ( Fig. 16 ). Legs with swimming setae, their number as following: one on I-Leg-4, two on I-Leg-5 and II-Leg-4, three on II-Leg-5; two to three on III/IV-Leg-4, one on III-Leg-5, four on IV-Leg-5. Swimming setae on anterior pairs of legs shorter than on posterior ones. I/II-Legs claws ( Fig. 17 ) with moderately developed lamella and two pointed clawlets: long, thin external and comparatively short, thick internal. Claws of legs III small and with subequal pointed clawlets ( Fig. 18 ).

Measurements, n=1. Idiosoma L 725; cheliceral segments L: base 180, chela 60; pedipalp segments (P-1-5) L: 35, 145, 78, 138, 48; leg segments L: I-Leg-1–6: 60, 100, 125, 160, 185, 185; II-Leg-1–6: 70, 110, 135, 200, 200, 200; III-Leg-1–6: 80, 125, 135, 210, 240, 135; IV-Leg-1–6: 135, 110, 140, 185, 210, 210.

Female. Dorsal plates not developed. All coxal groups separated ( Fig. 19 ). Anterior coxal groups with a short apodeme each. Suture line between third and fourth coxal plates incomplete medially, posterior margins of coxal plate IV forming obtuse angles, apodeme rather well developed.

Gonopore longer than acetabular plates, anterior and posterior genital sclerites slightly developed. Acetabular plate wider than long, with two to three deep, narrow unequal anterior indentations, three to four short, thin medial setae and 28–33 pairs of acetabula, one of these and five to six thin setae located on an anterior platelet on each side. Excretory pore located between setae Pi and surrounded by sclerotized ring. Shape of pedipalps and chelicerae as in male.

Legs thin and slender. I/II-Leg-6 not thickened. Legs with swimming setae, their number as following: one on I-Leg-4, two on I-Leg-5 and II-Leg-4, three on II-Leg-5and III/IV-Leg-4; five on III/IV-Leg-5. Swimming setae on anterior pairs of legs shorter than on posterior ones. Leg claws as in the male I/II-Legs claws.

Measurements, n=1. Idiosoma L 850; acetabular plate L 54–60, W 90–95; cheliceral segments L: base 85, chela 30; pedipalp segments (P-1–5) L: 35, 150, 78, 132, 54; leg segments L: I-Leg-1–6: 75, 85, 125, 160, 175, 180; II- Leg-1–6: 75, 110, 135, 200, 210, 200; III-Leg-1–6: 85, 115, 150, 200, 230, 200; IV-Leg-1–6: 135, 125, 165, 235, 250, 225.

Habitat. Standing waters.

Distribution. Asia, ( Russia, Chikotka).

Remarks. Piona discrepaniella is similar to P. discrepans but differs in the following characters (characters states of adults P. discrepans are indicated in parentheses): both sexes: P-4 ventrally with two distinct setal tubercles and several thin setae not associated with tubercles, Fig. 14 (P-4 ventrally with two rather larger and several very small setal tubercles, Fig. 20 ); male: dorsal shield covering about ½ surface of dorsum and bearing five pairs of setae, Fig. 12 (dorsum nearly entirely covered by a shield and bearing six pairs of setae ( Fig. 22 ), genital plates with a distinct suture line and bearing 28–33 of acetabula, Fig. 13 (genital plates without suture line and bearing 12–18 acetabula each, Fig. 23 ), setae Sce not included into ventral sclerotization, Fig. 13 (setae Sce included into ventral sclerotization, Fig. 23 ); female: genital plates with 28–33 acetabula each, their anterior margins with two to three unequal, narrow indentations, Fig. 19 (genital plates with 10–25 acetabula each, their anterior margin without any indentations, Fig. 21 ).

Figures

FIGURES 12–13. Piona discrepaniella Tuzovskij, 1990, male: 12, idiosoma, dorsal view; 13, idiosoma, ventral view.Scale bars: 12–13=200 μm.

FIGURES 14–19. Piona discrepaniella Tuzovskij, 1990, adults: 14, pedipalp; 15, III-Leg-5-6; 16, IV-Leg-4-5; 17, claw of leg I; 18, claws of leg III; 19, idiosoma, ventral view. 12–18, male, 19, female. Scale bars: 14–16=100 μm, 17–18=50 μm, 19=200μm.

FIGURES 20–21. Piona discrepans (Koenike, 1895) and Piona discrepaniella Tuzovskij, 1990, adults: 20, pedipalp of P. discrepaniella; 21, idiosoma of P. discrepans, ventral view. Scale bar: 21=50 μm, 22=200μm.

FIGURES 22–23. Piona discrepans (Koenike, 1895), male: 22, idiosoma, dorsal view; 23, idiosoma, ventral view. Scale bars: 22–23=200 μm.