Hydryphantes ildensis, Tuzovskij, 2016

Tuzovskij, Petr. V., 2016, A new water mite species of the genus Hydryphantes Koch (Acari, Hydrachnidia, Hydryphantidae) from the Yaroslavl Province of Russia, Ecologica Montenegrina 5, pp. 35-40 : 36-40

Hydryphantes ildensis T uzovskij, sp. n.

( Figs 1– 22 )

Holotype: female, slide 8958, Russia, Yaroslavl Province, Nekouz District, Ild stream near village Mar’ino , 15 June 2004, P. V. Tuzovskij . Paratypes: 23 larvae reared from holotype. The holotype is deposited in the collection of the Institute for Biology of Inland Waters (Borok, Russia) .

Diagnosis. Female: Integument soft with short rounded papillae; frontal plate compact with convex anterior margin, concave posterior margin and moderately long posterior projection, median eye situated posterior to anterior setae of plate; coxal plates I-IV with a few long, fine setae each; P-1 with 7-8 short setae, P-3 with 8 dorsal setae; capitulum with short rostrum, capitular base convex; acetabular plates elongate, with 20-23 medial and 12-15 lateral setae on each plate. Larva: D istance between bases of trichobothria Oi larger than their length; median eye situated between setae Vi; all dorsal hysterosomal setae subequal; basal segment of chelicera with narrow strips; urstigma oval; posterior margin of coxal plate II slightly convex; excretory pore plate as long as wide or slightly wider than long; P-4 with two subequal clawlets; I–Leg-4 solenidion and eupathidium nearly equal in length, II–Leg-4 solenidion 1.5 times longer than eupathidium, I/II–Leg-5 with subequal solenidia; III-Leg-4 solenidion longer than III-Leg-5 solenidion, I–Leg-6 de <ds.

Description. Female. Idiosoma soft oval. Integument with short rounded papillae ( Fig. 1 ). Lateral eyes in capsules. Number and position of idiosomal setae typical for genus Hydryphantes . Frontal plate ( Fig. 2 ) compact with convex anterior margin, posterior margin concave, posterior projections moderately long, median eye situated posterior to anterior setae. Coxal plates I-IV with numerous setae ( Fig. 3 ). Coxal plates I+II forming subcutaneous posteromedial extensions embracing gnathosomal bay, but medially separated by a membranous strip. Genital flap elongate (L/W ratio 2.1), with 20-23 medial and 12-17 lateral setae ( Fig. 4 ). Excretory pore surrounded by sclerotized ring ( Fig. 5 ).

Capitulum ( Fig. 6 ) with short rostrum, capitular base convex. Chelicera ( Fig. 7 ) with large basal segment and comparatively short chela.

Pedipalp slender ( Fig. 8 ): P-1 with 7-8 short dorsodistal setae; P-2 with 18-21 setae; P-3 with 8 setae; P-4 with short dorsodistal spine and 3 thin distal setae.

Legs II-IV with long swimming setae ( Fig. 9 ), their number as following: one to two on II–Leg-4; 10-11 on II–Leg-5; two to three on III-Leg-3; 9-11 on III-Leg-4; 11-15 on III-Leg-5; three to four on IV– Leg-3; 14-16 on IV-Leg-4-5. Leg claws hook-like, without claw lamella ( Fig. 10 ).

Measurements (n=1). Idiosoma L 1750; coxal plates I+II L 335, W 435; coxal plates III+IV L 560, W 450; genital flap L 260, W 125; capitulum L 300; rostrum L 43; chelicera L 435, chela L 135; pedipalpal segments (P–1–5) L: 87, 137, 100, 200, 50; leg segments L: I–Leg-1–6: 110, 125, 150, 260, 285, 260; II– Leg–1–6: 110, 135, 195, 335, 375, 375; III–Leg–1–6: 125, 150, 210, 350, 395, 360; IV–Leg–1–6: 225, 225, 300, 460, 450, 385.

Larva. Colour red. Anterior pair of platelets small, oval or triangular; posterior plate relatively large, anteriorly narrow, posteriorly widening; median eye weakly developed (usually hardly visible) and situated between setae Vi ( Fig.11 ). Both pairs of trichobothria thin, Fp very long, Oi short. Distance between bases of trichobothria Oi–Oi larger than their length. Simple proterosomal setae (Fch and Vi) thick, but Fch shorter than Vi. Other dorsal setae (Oe, Hi, He, Sci, Sce, Li and Le) thick and subequal.

Coxal plates II triangular without setae, coxal plates I and III more or less trapezoidal and rounded medially ( Fig. 12 ); all coxal setae relatively short and subequal. Urstigma oval, wider than long. Setae Si longer and thicker than other ventral idiosomal setae. Setae Se, Ci, Pi and Pe subequal and slightly longer and thicker than both pairs of anal setae (Ai and Ae).

Excretory pore plate small, usually as long as wide or slightly wider than long ( Figs 13–14 ), excretory pore situated near posterior plate margin. Bases of setae Ae situated anterior to excretory pore, setae Ai situated posterior to excretory pore plate.

Chelicera with large basal segment ( Fig.15 ) and small pointed chela ( Fig.16 ). Basal segment with rather numerous narrow strips.

Pedipalps stout ( Fig. 17 ): P–1 short, without seta; P–2 large, with convex dorsal margin and single dorsal seta proximally to middle of segment; P–3 long, with two subequal setae (proximal and distal); P–4 with three thin unequal setae, dorsodistal claw large, distally bifurcate, with subequal clawlets; P–5 small, with a single, long solenidion and seven simple setae, five long and thick, two short and thin.

Legs 6–segmented. Shape and arrangement of specialized setae on terminal legs segments as shown in Figs 18–20. I –Leg-4 solenidion and eupathidium nearly equal in length, I/II–Leg-5 proximal solenidia subequal; I–Leg-6 de shorter ds; III–Leg-4 proximal solenidion longer than III–Leg-5 proximal solenidion. Lateral claws shorter and thinner than strong empodial claw ( Figs. 21-22 ).

Measurements, n=10. Dorsal plate L 43–49, W 43–47; setae Fch L 27–31, setae Fp L 70–75, setae Vi L 37–44, setae Oi L 11–13, distance between setae Vi–Vi 36–38, distance between setae Oi–Oi 16–19; setae Oe, Hi, He, Sci, Li, Le and Si L 32-38, setae Si L 25-29; setae Ci, Se, Pi and Pe 16-19; setae Ai and Ae 9-12; excretory pore plate L 10–12, W 11–13; urstigma L 6-8, W 10-12; basal segments of chelicerae L 68– 76, chela L 17–19; pedipalpal segments (P–1–5) L: 6–7, 27–28, 26–28, 13–16, 11–12; leg segments L: I– Leg-1–6: 22– 25, 20–24, 15–18, 25–28, 33–37, 60–64; II–Leg-1–6: 25–27, 18–23, 12–14, 16–19, 30–32, 50– 54; III–Leg-1–6: 25–28, 16–20, 12–15, 20–23, 31–34, 47–50.

Remarks. The female of the new water mite is similar to the female Hydryphantes nonundulatus Viets, 1919 . However, the following clear differences can be found in their morphology (character states of H. nonundulatus are given in parenthesis after Tuzovskij 2015): the acetabular plates with 12-15 lateral setae each, Fig. 4 (with 2-4 lateral setae each); the capitular rostrum short, L = 43 μm, Fig. 6 (comparatively long, L = 60-75 μm); P-1 with 7-8 dorsodistal setae, Fig. 8 (with three to five setae); P-3 height smaller than length of segment, with eight 8 setae (larger than length of segment, with four setae).

The larva of the present species is similar to the larva of H. planus Thon, 1899 . The latter species differs at the larval stage in: (1) P-3 short, L = 16-19 μm; (2) P-5 solenidion shorter than segment; (3) I-Leg- 5 solenidia subequal; (4) Fp comparatively short L = 55-65 μm ( Tuzovskij 2014).

Etymology. The species is named after the stream (Ild) where it was collected.

Habitat. Running waters.

Distribution. Europe, Russia: Yaroslavl Province.

Figures

Figures 1–5. Hydryphantes ildensis sp. n., female: 1 – fragment of integument, 2 – frontal plate; 3 – coxal plates; 4 – genital field; 5 – excretory pore. Scale bars: 1, 4, 5 = 100 μm; 2-3 = 200 μm.

Figures 6–10. Hydryphantes ildensis sp. n., female: 6 – capitulum; 7 – chelicera; 8 – pedipalp; 9 – III–Leg-3–6, 10 - claws. Scale bars: 6–8 = 100 μm; 9 = 200 μm; 10 = 50 μm.

Figures 11–12. Hydryphantes ildensis sp. n., larva: 11 – dorsal view; 22 – ventral view. Scale bar: 50 μm.

Figures 13–22. Hydryphantes ildensis sp. n., larva: 13–14 – excretory pore plate; 15 – basal segment of chelicera, dorsal view, 16 – chela, lateral view; 17 – pedipalp, lateral view; 18 – I–Leg-4–6; 19 – II–Leg–4–6; 20 – III–Leg–4–6; 21 – claws of leg I; 22 – claws of leg III. Simple setae on I–III–Leg-4–6 are not shown. Scale bars: 13–14, 16–17, 18– 22 = 20 μm, 15 = 50 μm.