Arrenurus (Arrenurus) udalzowi, Tuzovskij, 2022

Tuzovskij, Petr V., 2022, A new water mite species of the genus Arrenurus Dugès, 1834 (Acari, Hydrachnidia: Arrenuridae) from Russia, Zootaxa 5133 (4), pp. 594-600 : 594-599

Arrenurus (Arrenurus) udalzowi sp. n.

( Figs 1–19 )

Type series. Holotype: male, slide 8403, Europea, Russia, Yaroslavl Province, Nekouz District, small pond near village Pogorelka , 9.08.2001, leg P. Tuzovskij . Paratypes: From the same locality as holotype , 1 male 5. 08.2001, 1 male 7. 07.2005, 1 female 27.05.1974, 1 female 16. 06.1974; Asia, West Siberia, Kemerovo Province, Prokopevsk District , small pond near village Sharap , 2 males 22.08.1973, leg. P. Tuzovskij.

Description.

Larva. Colour red. Dorsal plate ( Fig. 1 ) in unengorged larva covers nearly whole dorsum, bearing five pairs of setae (Fch, Fp, Vi, Oi and Hi), narrow and truncate anteriorly, indented near anterior eyes, widest in the middle of its length, distinctly narrowing in posterior part. Anterolateral indentations deep with obtuse angle, reaching to about one-sixth length of dorsal shield. Setae Fch shortest, setae Vi, Oi and Hi subequal in length and a little longer than Fp. Five pairs of setae (Oe, He, Sci, Sce, Li,) situated in soft integument, Oe longest, other setae subequal in length.

Medial margin of coxal plates I and III longer than medial margin of coxal plates II ( Fig. 2 ). Coxal plates I and II each with posteromedial apodemes directed laterally. Setae C2 longer than C1, C4 shorter than C3 and not reaching posterior margin of coxal plate III; Pi longer than Pe. All coxal plates and dorsal plate with reticulation. Setae Ci longest, Si shortest, Se much longer than Le, Pi a little longer than Pe. Setae Pi longer than Pe. All coxal plates and dorsal plate with reticulation. Setae Ci much longer than Se, Pe longer than Pi. Coxal plates I and II each with posteromedial apodemes directed laterally ( Fig. 2 .). Excretory pore plate wider than long (L/W ratio 0.80–0.82), widest near the middle of its length, anterior margin convex with short median projection ( Fig. 3 ) or with small median indentation ( Fig. 4 ).

Excretory pore plate setae (Ai and Ae) reduced and represent by alveoli, Ai located close to anterior margin, Ae situated near middle of excretory pore plate. Excretory pore located in the center or slightly anterior to middle excretory pore plate between bases setae Ae. Distance between setae Ae-Ae almost three times longer than distance between setae Ai-Ai.

Basal segment of chelicera relatively large, with slightly concave ventral margin; chela small crescent-shaped ( Fig. 5 ). Pedipalp short ( Fig. 6 ): P-1 very short, without setae; P-2 with single dorsal seta near middle of segment; P-3 with very long, thick proximal seta and comparatively short, fine dorsodistal one; P-4 with two thin proximal setae, one thick, spine-like seta and massive dorsodistal claw; P-5 small with one solenidion, and seven simple setae: one very long, thick seta, three setae moderately long, thick, one curved pectinate seta and two short setae (thick and thin).

Legs moderately slender. Shape and arrangement of setae on legs segments as shown in Figs 7–9 . Total number of leg setae, excluding eupathidia, as follows (specialized setae indicated in parenthesis): I-Leg-1–5: 1, 7, 5 (s), 9 (2s), 14 (s, ac); II-Leg-1–5: 1, 7, 5 (s), 11 (2s), 14 (s, ac); III-Leg-1–5): 1, 6, 5 (s), 10 (s), 11. I–III-Leg-2 setae Fe6 (after Prasad & Cook 1972) represented in form of setal bases only and usually hardly visible. II/III-Leg-1each with rather long seta which longer than seta on I-Leg-1. Solenidia on I/II-Leg-4 located distally, solenidion on I–III-Leg-3 placed near to the middle of these segments. Acantoid seta situated distally on tarsi of legs I and II. Central claws of all legs thicker than lateral claws and bearing two ventral teeth ( Fig. 10 ), claws of III-Legs a little large than claws of I/II-Legs.

Measurements (n=7). Dorsal plate L 225–235, W 160–170; setae Fch L 42–46; setae Fp L 48–52, setae Vi, Oi and Hi L 63-67; setae Oe L 70-75; setae He, Sci L 65-70; setae Sce, Li L 70-75; setae Le L 55–60; setae Si L 32–35; setae Se L 83–90, setae Ci L 125–135, setae Pi L 25–30; setae Pe L 32–35; setae C1 L 52–55, setae C2 L 70–75, setae C3 L 65–70, setae C4 L 55–60; medial margins of coxae I–III L 73–77, 32–36, 65–70; excretory pore plate L 25–29, W 32–36; basal segment of chelicera L 88–-93, chela L 31–33; pedipalpal segments (P-1–5) L: 15–17, 40–49, 34–36, 15–17, 15–17; legs segments L: I–Leg-1–5: 35–38, 32–35, 40–45, 55–60, 83–85; II-Leg-1–5: 35–38, 40–45, 43–47, 63–65, 92–96; III-Leg-1–5: 40–45, 48–52, 45–50, 65–70, 95–102.

Male. Colour red. Idiosoma wide (L/W ratio 1.05–1.15), anterior margin slightly concave or almost straight, lateral margins straight; cauda short and distinctly set of from the anterior part of the idiosoma; pygal lobes comparatively short and directed posterolaterally ( Fig. 11 ). Dorsal shield moderately large, convex anteriorly, bearing four pairs of setae (Oi, Hi, Sci, and Li); setae and glandularia Sci a little separated, glandularia open on somewhat small rounded tubercles distally to the middle of the shield; bases of setae Li close together, Le near distal end of pygal lobes, the latter with concave posterior margin and pointed lateral corners. Dorsal furrow complete passing onto sides of idiosoma at base of pygal lobes. Setae Fp, Oi and Pi without glandularia, other idiosomal setae associated with glandularia. Distance between setae Oi-Oi nearly twice shorter than distance between setae Hi-Hi. Hyaline membrane weakly developed. Base of petiole situated on ventral side ( Fig.12 ). Petiole rather large, narrowed anteriorly, widest distally, ligulate process not extending beyond posterior margin ( Fig. 13 ). Anterolateral corners of coxal plates I and II pointed, reaching to anterior idiosoma margin. Coxal plates I fused to each other medially, suture line weakly developed. Posterior coxal groups close to each other medially. Medial margin of coxal plate III nearly three times shorter than medial margin of coxal plates IV. Lateral projection of coxal plates IV with rounded tip, not extending beyond lateral idiosoma margin. Gonopore small, acetabular plates narrow and not reaching the lateral margins of the idiosoma, with numerous acetabula. Setae Ci longest, Se relatively thin a little shorter than Ci. Setae Hv located near posterolateral margin of coxal plates II. Setae Pi thick, Se considerably shorter and thinner than Pi. Excretory pore open on a small tubercle in the integument between posterior margin of genital field and base of petiole. Setae Hv situated near posterolateral margin of coxal plates II, Pe located beyond acetabular plates, setae and glandularia Se distinctly separated setae and located on pygal lobes. Pedipalp stocky ( Fig. 14 ): P-1 short with a single dorsodistal setae; P-2 stocky with straight ventral margin, with three to four dorsodistal, one to two ventrodistal and one to two mediodistal setae, all these setae approximately equal in length; P-3 relatively short, with one long, thin median and comparatively short, thick lateral seta; P-4 longer than P-2, with a stout and rather long antagonistic seta, two fine dorsodistal setae and two short distal setae, P-5 with a single solenidion, four thin setae and three unequal spines. Legs III and IV with swimming setae. IV-Leg-4 large, with well-developed distoventral projection bearing six to eight long setae ( Fig. 15 ). Claws of leg I–III with long pointed external clawlet and short internal clawlet ( Fig. 16 ); claws of leg IV with two subequal pointed clawlets ( Fig. 17 ).

Measurements (n=5). Idiosoma L 1120–1150, W 1000–1060; dorsal plate L 750–800, W 560–600; distance between medial margins of coxal plates IV 25–40; petiole L 225–240, W 150–155; pedipalpal segments (P-1–5) L: 35–40, 100–112, 80–90, 125–140, 62–75; legs segments L: I-Leg-1-6: 75–90, 110–140, 160–175, 210–240, 200–215, 225–250; II-Leg-1–6: 85–90, 150–165, 170–180, 235–265, 210–240, 235–265; III-Leg-1–6: 95–105, 150–165, 160–175, 250–265, 225–250, 235–250; IV-Leg-1–6: 185–215, 175–240, 250–265, 435–465, 160–175, 210–225.

Female. Idiosoma nearly circular (L/W ratio 1.0-1.06), widest near middle, without dorsal humps or tubercles, posterolateral corners not developed ( Figs 18-19 ). Dorsal furrow complete. Dorsal shield moderately large (L/W ratio 1.18- 1.20), widest in the middle of its length, with slightly convex anterior margin, a little narrowed anteriorly and bearing setae Oi, Hi, Sci, Li. Anterolateral corners of coxal plates I and II pointed, anterolateral corners of coxal plates III rounded. Medial margins of coxal plate III and IV subequal in length or medial margin of coxal plate III a little shorter than medial margin of coxal plate IV. Posterior coxal groups well separated, lateral projection of coxal plates IV reaching the lateral margin of the idiosoma. Gonopore elongate subrectangular, placed a little posterior to middle of idiosoma; each genital flap with two triangular elongate patches which contiguous by acute angles. Genital flaps elongate (L/W ratio 2.5–2.6). Width of gonopore and distance between medial margins of coxal plates IV nearly equal in size. Acetabular plates broad and directed posterolaterally. Pedipalp as in male.

Measurements (n=2). Idiosoma L 1250–1310, W 1240–1300; dorsal plate L 880–940, W 750–775; distance between medial margins of coxal plates IV 70–85; genital flap L 160–185, W 62–75; pedipalpal segments (P-1–5) L: 45–50, 125–137, 75–87, 135–143, 62–70; legs segments L: I-Leg-1–6: 60-75, 125–200, 175–200, 210–225, 175–200, 200–225; II-Leg-1–6: 60–75, 135–150, 200–215, 225–250, 185-240, 250–275; III-Leg-1-5: 100–115, 150–165, 160–190, 235–250, 210–240, 235–250; IV-Leg-1–6: 150–175, 225–240, 225–250, 310–325, 225–250, 225–250.

Differential diagnosis. The new species is similar to Arrenurus primoryensis Tuzovskij & Semenchenko, 2011 and A. virens Neuman, 1880 . The present species is similar to Asian species in the shape of the idiosoma, differences between A. udalzowi sp. n. and A. primoryensis are found in the following characters (characters states of male A. primoryensis are given in parenthesis, data from Tuzovskij & Semenchenko, 2011): idiosoma large, L/W 1120–1150/1000–1060, Figs 11 –22 (comparatively small, L/W 885/810, Figs 20–21 ); setae Sci long, thin (very short with blunt tip); petiole broad, L/ W 1.5 –1.6, located posteroventrally (elongate, L/ W 2.4, located caudally); IV-Leg-4 longer than IV-Leg-5+IV-Leg-6 (IV-Leg-4 much shorter than IV-Leg-5+IV-Leg-6). The male of A. virens differs by rather elongate idiosoma (L/W ratio 1.36–1.38), petiole widest in the middle of its length, distinctly narrowing in posterior part; the female idiosoma widest in posterior half with posterolateral corners, gonopore a little wider than distance between medial margins of coxal plates IV ( Cassagne-Mèjean 1966).

Etymology. The species is named the Russian researcher A.D. Udalzow.

Distrbution. Europe, Asia, Russia.

Habitat. Ponds, running waters.

Figures

FIGURES 1–4. Arrenurus udalzowi sp. n., larva: 1, dorsal view; 2, idiosoma ventral view; 3–4, excretory pore plate. Scale bars: 1–2 = 50 μm., 3–4 = 20 μm.

FIGURES 5–10. Arrenurus udalzowi sp. n., larva: 5, chelicera, lateral view; 6, pedipalp; 7, I-Leg-1–5; 8, II-Leg-1–5; 9, III- Leg-1–5; 10, leg claw. Scale bar: 5–9 = 50 μm, 10 = 25 μm.

FIGURES 11–12. Arrenurus udalzowi sp. n., male:11, idiosoma, dorsal view; 12, idiosoma, ventral view. Scale bar: 11–12 = 200 μm.

FIGURES 13–17. Arrenurus udalzowi sp. n., male:13, petiole; 14, pedipalp; 15, IV-Leg-4–6; 16, claw of legII; 17, claw of leg IV. Scale bars: 14, 13, 16–17 = 50 μm, 15 = 200 μm.

FIGURES 18–19. Arrenurus udalzowi sp. n., female:18, idiosoma, dorsal view; 19, idiosoma, ventral view. Scale bar: 18–19 = 200 μm.

FIGURES 20–21. Arrenurus primoryensis, male: 20, idiosoma, dorsal view; 21, idiosoma, ventral view (after Tuzovskij & Semenchenko 2011). Scale bar: 20–21 = 100 μm.