Hydryphantes prolongatus Thon, 1899

Tuzovskij, Petr V., 2015, On the systematic of the water mite Hydryphantes prolongatus Thon, 1899 (Acari, Hydrachnidia, Hydryphantidae), Ecologica Montenegrina 2 (2), pp. 78-87 : 79-86

Hydryphantes prolongatus Thon, 1899

( Figs 1–29 )

Material examined. 11 females, 4 males and 4 deutonymphs, Russia, Yaroslavl Province, Nekouz District, April-July 2000-2002, 2004, sedge bogs near village Postyltsevo, leg. P. V. Tuzovskij. Larvae (n = 38) were reared from six females in laboratory conditions, two females 28 May 2000, one female 4 July 2001, two females 27 May 2002 and one female 17 June 2004. The duration of the embryonic period was 12-15 days .

Diagnosis. Larvae: Distance between bases of trichobothria Oi larger than their length; all dorsal hysterosomal setae subequal; excretory pore plate wider than long; basal segment of chelicera with narrow strips; I/II–Leg-4 solenidion much longer than eupathidium, I–Leg-6 de <ds; adults: frontal plate subquadrate (L/W ratio 0.88–1.05), anterolateral extensions much wider than posterolateral extensions, anterior margin obtuse angled or slightly convex, posterior margin straight, posterior projections short, their length equal to 1/4–1/6 length of basal portion of plate, median eye situated at level of anterior setae of plate; capitulum long (base of capitulum/rostrum L ratio 2.4-3.0); P–3 with 6–10 setae; deutonymphs: frontal plate subquadrate (L/W ratio 0.95–1.05), anterolateral extensions much wider than posterolateral extensions; anterior margin slightly convex, posterior margin straight; posterior projections short, their length equal to 1/4–1/5 length of basal portion of plate; capitulum with long rostrum; P–3 with two long, thin setae; genital field with two pairs of subequal acetabula and four to five pairs of thin setae.

Description

Larvae. Colour red. Idiosoma oval, all setae not associated with glandularia. Proterosoma with two pairs of trichobothria (Fp, Oi) and three pairs of simple setae: Fch, Vi, Oe (figure 1). Anterior pair of dorsal platelets triangular or oval. Posterior plate slightly wider than long (L/W ratio 0.81–0.95), narrowed anteriorly and widened posteriorly; median eye slightly developed and situated between setae Vi; Fch shorter Vi; Oi short, distance between Oi–Oi larger than their length; trichobothria Fp very long and well extending to posterior tips of setae Vi. Hysterosomal setae Hi, He, Sci, Sce, Li, Le and Si subequal, their bases situated on very small sclerites.

All coxal plates separated on each side (figure 2). Coxal plates II triangular with convex posterior margin, coxal plates I and III more or less trapezoidal and broadly rounded medially, all coxal setae short and subequal. Urstigma comparatively large oval and wider than long. Setae Se, Ci, Pi and Pe subequal and slightly longer than both pairs of anal setae (Ai, Ae).

Excretory pore plate small, wider than long (L/W ratio 0.81–0.91), its shape variable (figures 3–5).

Capitulum (figure 6) with short, wide base, ventral setae slightly shorter than dorsal ones. The mouth opening surrounded by numerous long papillae. Posterior portion of basal part of capitulum with distinct reticulations. Basal segment of chelicera (figure 7) with narrow strips, cheliceral stylet heavy and without apical teeth.

Pedipalps moderately long (figure 8): P–1 short, without setae; P–2 large with convex dorsal margin and single dorsal seta located in proximal part of segment; P–3 with two unequal setae (thick proximal and relatively long, thin distal); P–4 with three unequal setae and large dorsodistal bifurcate claw; P–5 small, with a moderately long solenidion and seven setae, five long an thick, two relatively short and thin.

Legs 6–segmented. Leg II distinctly shorter than anterior and posterior ones. Number of leg setae (specialized setae indicated in parenthesis): I–Leg-1–6 – 1, 2, 5, 6 (s, e), 13 (2s, e), 22 (s, e, ac); II–Leg-1–6 – 1, 2, 5, 6 (s, e), 12 (2s), 22 (s, e, ac); III–Leg-1–6 – 1, 2, 5, 5 (s, e), 11 (s), 20. Shape and arrangement of specialized setae on terminal legs segments as shown in figure 9–11. All simple setae heavy and usually with long serration. I/II–Leg-4 solenidion much longer than eupathidium, I–Leg-5 with two subequal long proximal solenidia and short distal eupathidium, I–Leg-6 de <ds; II–Leg-5 with unequal proximal solenidia, II–Leg-6 solenidion proximal, eupathidium submedial; III–Leg-4 proximal solenidion longer than III–Leg-5 solenidion. Empodium large and crescent-shaped on all tarsi, ambulacra I ( Fig. 12 ) shorter than ambulacra II and III ( Fig. 13 ).

Measurements, n=10. Dorsal plate L 43–48, W 50–54; setae Fch L 33–38, setae Fp L 80–88, setae Vi L 41–47, setae Oi L 10–15, setae Oe, Hi, He, Sci, Sce, Li, Le and Si L 35–42; setae Ci, Se, Pi, Pe 19–22; setae Ai and Ae 13–15; distance between setae Vi–Vi 42–48, distance between setae Oi–Oi 18–23; excretory pore plate L 11–13, W 13–14; urstigma L 10–11, W 12–15; basal segments of chelicerae L 80–85, cheliceral stylet L 22–25; strips on basal segment of chelicera W 0.6 –1.0; pedipalpal segments (P–1–5) L: 6–7, 33–36, 27–30, 21–24, 11–14; legs segments L: I–Leg-1–6: 28–32, 25-28, 18–24, 31–38, 41–48, 80–90; II–Leg-1–6: 28–30, 21–24, 15–19, 21–24, 43–49, 68–72; III–Leg-1–6: 30–33, 18–24, 16–19, 25–28, 43–47, 61–68; de1= 5–6, ds1= 10–15; de2= 32–38, ds2= 6–9.

Deutonymphs. Colour red. Idiosoma oval and somewhat flattened dorsoventrally. Trichobothria Fp, Oi and setae Pi not associated with glandularia, other idiosomal setae associated with glandularia (figures 14–15). Frontal plate (figures 14, 16) subquadrate (L/W ratio 0.95–1.05), anterolateral extensions much wider than posterolateral extensions (anterolateral extentions/posterolateral extensions W ratio 1.37-1.57); anterior margin slightly convex, posterior margin straight; posterior projections short, their length equal to 1/4–1/5 length of basal portion of plate; frontal eye situated posterior to trichobothria Fp. Coxal plates in four groups, with a few fine setae each. Coxal plates I+II with a small subcutaneous posteromedial extension on each side. Genital field (figure 17) with two pairs of subequal acetabula and four to six pairs of thin setae. Excretory pore surrounded by a sclerotized ring. Integument with short, flat papillae (figure 18).

Capitulum (figure 19) with long rostrum (base of capitulum/rostrum L ratio 3.0-4.0) and convex basal part. Chelicera (figure 20) rather slender, basal segment with large dorsal obtuse-angled hump near middle, cheliceral stylet moderately long. Pedipalp compact (figure 21): P–1 with one to two setae, P–2 with 9–13 short, thick setae, P–3 with two long, thin setae; P–4 slightly tapering distally, with three distal setae and a short, thick dorsodistal spine.

II–Leg-5 (figure 22) and III/IV–Leg-3–5 (figure 23) with long swimming setae. Number of swimming setae: II–Leg-5, 6–10; III–Leg-3–5, 0–2, 5–10, 9–14; IV–Leg-3–5, 2–4, 8–12, 10–14. All legs with simple hook– like claws (figure 24).

Measurements (n=4). Idiosoma L 1200–1450; coxal plates I+II L 225–265; coxal plates III+IV L 325–400; genital plate L 85–100, W 62–75; anterior genital acetabula D 35–40, posterior genital acetabula D 32–38; capitulum L 230–275; basal segment of chelicera L 225–275, cheliceral stylet L 115–125; pedipalpal segments (P–1–5) L: 55–62, 85–105, 65–75, 135–155, 25–28; leg segments L: I–Leg-1–6: 65–90, 75–100, 85–125, 135–175, 160–200, 175–200; II–Leg-1–6: 75–90, 85–100, 100–125, 175–240, 210–285, 225–290; III–Leg-1–6: 75–90, 90–115, 100–125, 200–215, 235–315, 235–300; IV–Leg-1–6: 130–150, 135–150, 160– 215, 260–340, 270–350, 235–315.

Adults. Females and males are similar to deutonymph, but differ in structure of the external genital organ, larger size, number of idiosomal glandularia (setae Pi associated with glandularia) and more numerous setae on all segments of appendages. Males and females do not exhibit external sexual dimorphism, but mature females are larger than males.

Frontal shield subquadrate (L/W ratio 0.88–1.05), anterolateral extensions much wider than posterolateral extensions (anterolateral extentions/posterolateral extensions W ratio 1.35-1.62), anterior margin obtuse–angled (figure 25) or slightly convex, posterior margin straight, posterior projections short, their length equal to 1/4–1/6 length of basal portion of plate. Median eye small and situated almost at level of anterior setae.

All coxal plates with numerous setae (figure 26). Genital field (figure 27) with three pairs of acetabula, anterior pair of acetabula larger than second pair but slightly smaller than posterior pair of acetabula. Acetabular plate elongate (L/W ratio 2.18–2.42), with 15–20 pairs of medial setae; posterior margin of plate oblique in antero-lateral direction.

Capitulum (figure 28) with long rostrum (base of capitulum/rostrum L ratio 2.4–3.0) and convex basal part. Pedipalp compact (figure 30): P–1 with 3–5 dorsodistal setae; P–2 with 11–20 setae; P–3 with 6– 10 setae; P–4 slender with four thin setae and short, thick dorsodistal spine.

Number of swimming setae: II–Leg-4–5, 1–4, 10–16; III–Leg-3–5, 2–5, 11–15, 12–22; IV–Leg-3–5, 3–5, 16–23, 18–25.

Measurements, female (n=10). Idiosoma L 1620–2200; dorsal plate L 560–600, W 500–590; genital flaps L 310–350, W 135–165; genital acetabula (ac.1–ac.3) D 50–62, 37–45, 65–80; capitulum L 400–500, rostrum L 100–125, basal segment of chelicera L 435–525, cheliceral stylet L 210–240; pedipalpal segments (P–1–5) L: 100–115, 150–175, 110–150, 250–290, 25–35; legs segments L: I–Leg-1–6: 125–140, 135–165, 185–200, 275–300, 300–340, 310–350; II–Leg-1–6: 125–150, 175–200, 210–240, 375–415, 450–475, 435– 490; III–Leg-1–6: 130–150, 160–200, 235–265, 425–465, 485–515, 460–500; IV–Leg-1–6: 235–275, 235– 275, 350–390, 535–615, 535–600, 460–515.

Measurements, male (n=4). Idiosoma L 1500–1900; dorsal plate L 435–575, W 560–650; genital flaps L 300–350, W 135–150; genital acetabula (ac.1– ac.3) D 42–50, 35–39, 50–63; capitulum L 410–440, rostrum L 105–140; chelicera: basal segment L 360–415, cheliceral stylet L 150–200; pedipalpal segments (P–1–5) L: 85–100, 125–150, 105–120, 225–245, 30–37; legs segments L: I–Leg-1–6: 90–120, 135–150, 160–190, 225–300, 275–340, 310–375; II–Leg-1–6: 100–115, 135–165, 200–250, 325–400, 385–465, 410– 500; III–Leg-1–6: 125–140, 160–190, 210–250, 360–490, 410–475, 425–515; IV–Leg-1–6: 210–250, 210– 250, 310–350, 460–565, 460–560, 425–515

Remarks. The water mite Hydryphantes prolongatus Thon, 1899 is similar to H. ruber (Geer, 1778) . However, the following clear differences can be found in the morphology of larvae, deutonymphs and adults of H. prolongatus (character states of H. ruber are given in parenthesis, for larvae after Wainstein 1980 and Tuzovskij 2014, for deutonymphs and adults after Gerecke 1996 and Tuzovskij 2014, respectively): larvae: distance between bases of trichobothria Oi larger than their length, Fig. 1 (smaller than their length), longer trichobothria, Fp L 80–88µm (short, L 56–63µm); excretory pore plate wider than long, Figs 3–5 (as long as wide); deutonymphs and adults: Frontal plate with anterolateral extensions much wider than posterolateral extensions, anterolateral extentions/posterolateral extensions W ratio 1.35-1.62, Figs 14 , 16 , 25 (slightly wider, anterolateral extentions/posterolateral extensions W ratio 1.12-1.30); capitulum with a long rostrum, Fig. 28 (with a relatively short rostrum).

Thus, the morphology of all active stages of H. prolongatus clear differs from that of H. ruber , and H. prolongatus should be treated as a separate species.

Distribution. Widely distributed in Europe (K. Viets 1936, 1956; K.O. Viets 1978, 1987).

Figures

Figures 1–2. Hydryphantes prolongatus Thon, 1899, larva: 1- dorsal view, 2- ventral view. Scale bar: 50µm.

Figures 3–8.Hydryphantes prolongatus Thon, 1899, larva: 3–5 – excretory pore plate, 6 – capitulum, 7 – chelicera, dorsal view, 8 – pedipalp. Scale bars: 3–5, 8 = 20 µm, 6–7 = 50µm.

Figures 9–13. Hydryphantes prolongatus Thon, 1899, larva: 9 – I–Leg-4–6; 10 – II–Leg-4–6; 11– III–Leg-4–6; 12 – claws of leg I; 13 – claws of leg III. Simple setae on I–III–Leg-4–6 are not shown. Scale bars: 100µm.

Figures 14–15. Hydryphantes prolongatus Thon, 1899, deutonymph: 14 – dorsal view, 15 – ventral view. Scale bar: 200µm.

Figures 16–21. Hydryphantes prolongatus Thon, 1899, deutonymph: 16 – frontal plate; 17 – genital field; 18 – fragment of integument; 19 – capitulum; 20 – chelicera; 21 – pedipalp. Scale bars: 16, 19–20 = 100µm, 17–18, 21 = 50 µm.

Figures 22–24. Hydryphantes prolongatus Thon, 1899, deutonymph: 22 – II–Leg-4–5; 23 – IV–Leg-3–6; 24 – claw. Scale bars: 22–23 = 200µm, 24 = 50µm.

Figures 25–29. Hydryphantes prolongatus Thon, 1899, adults: 25 – frontal plate; 26 – coxal plates; 27 – genital field; 28 –capitulum; 29 – pedipalp. Scale bars: 25–26, 28 = 200µm, 27, 29 = 100µm.