Piona interrupta subsp. interruptella Tuzovskij, 2013, ssp. n.

Piona interrupta interruptella ssp. n.

(Figs 44–52)

Type series. Holotype: female, slide 2305, Russia, Chukotka, Anadyr District, Majorskoe Lake near settlement Markovo, depth 0.5–0.8 m, 29 June 1978, leg. P.V. Tuzovskij. Paratype: one female from the same locality and collection date as holotype.

Description. Female. Idiosoma oval, integument soft and striated. Dorsum with small elongated platelets (Fig.

44). 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. 45) thicker than other idiosomal setae associated with glandularia (Fig. 46) and trichobothria (Fig. 47).

Coxae of legs cover about half ventral surface (Fig. 48). Anterior coxal groups with short apodemes. Sclerites bearing setae setae Hv lying free and located between anterior and posterior coxal groups. Medial margin of coxal plates IV nearly twice longer than medial margin of coxal plates III. Posterior margins of coxal plates IV forming obtuse angle, apodemes slightly developed.

Genital opening longer than acetabular plates, three pairs of genital setae located in integument between acetabular plates and pregenital sclerite and five pairs of thin setae placed in acetabular plates, four of which are located in posteromedial corner. Acetabular plates well indented on medial margin, with numerous genital acetabula (40–55), two pairs of which much larger than others; anterior large acetabulum located in anteromedial corner of acetabular plate, second large acetabulum situated approximately in center of the plate. Excretory pore surrounded by narrow sclerotized ring.

Pedipalp rather slender (Fig. 49): P–1 with a single short dorsodistal seta; P–2 large, with straight ventral margin, bearing seven or eight dorsal setae; P–3 with one long and two relatively short unequal setae, base long seta located near middle of segment; P–4 longer than P–2, ventral setae located on tubercles, proximal tubercle a little smaller than distal one, distoventral spine short; P–5 with one proximal solenidion, five thin setae and four thick distal spines.

Legs thin and slender; I–Leg-4 with two, I–Leg-5 with seven short swimming setae (Fig. 50); 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 (Fig. 51). Claws with long external clawlet and short internal one, lamella with convex ventral margin (Fig. 52).

Measurements, μm (n=2). L of idiosoma 1800–2375; L of acetabular plates 235–250, W of acetabular plates 260–275; L of cheliceral segments: base 390, claw 175; dorsal L of pedipalp segments (P–1–5): 85–90, 325–340, 170–180, 385–400, 173–175; L of leg segments: I–Leg-1–6: 150–160, 225–240, 275–290, 435–450, 485–515, 410– 425; II–Leg-1–6: 155–165, 235–250, 310–325, 475–490, 535–550, 435–450; III–Leg-1–6: 155–175, 250–265, 310–325, 485–500, 560–575, 450–465; IV–Leg-1–6: 260–275, 275–290, 385–400, 560–575, 600–615, 435–465.

Differential diagnosis. The present subspecies is similar to the North American species Piona interrupta Marshall, 1929 (Cook 1960, Smith 1976) from which it is easily distinguishable by the size of the idiosoma and setae Fch, and the shape of the coxal plates IV and P–4. The female of P. interrupta is characterized by following features: the setae Fch (= antennary bristles after Marshall 1929) short, the idiosoma relatively small (945–1700 μm); the posterior margins of the coxal plates IV forming an acute angle; P–4 bears two large tubercles and one small tubercle or two small pointed tubercles (Marshall 1929, 1937). In contrast, in the female P. interrupta interruptella ssp. n. the setae Fch are long (Fig. 45) and the idiosoma is large (1800–2375 μm); the posterior margins of the coxal plates IV forming obtuse angle (Fig. 48); P–4 bears only two large tubercles, small tubercle(s) absent (Fig. 49).

The female of P. interrupta interrupta, briefly described by Cook (1960) as P. interrupta, differs from the original description of this subspecies (Marshall 1929, 1937) and from the here presented subspecies by the following features: the acetabular plate only slightly indented on the medial margin, the anterior large acetabulum located near the middle of medial margin of the plate, I–Leg-5 without swimming setae; while in the female P. interrupta interuptella ssp. n. the acetabular plate deeply indented on the medial margin, the anterior large acetabulum located in the anteromedial corner of this plate, I–Leg-5 with swimming setae. Thus, the female described by Cook (1960) as P. interrupta possibly belongs to another subspecies or species.

Etymology. The subspecies epithet interruptella is derived from the name of the North American subspecies Piona interrupta interrupta.

Habitat. Standing waters.

Distribution. Asia (Russia: Chukotka).

Acknowledgements

The author expresses sincerely gratitude to Peter Martin, Vladimir Peşic and an anonymous referee for their careful work and critical comments.