Lebertia fimbriatella, Tuzovskij, 2019

Tuzovskij, Petr V., 2019, Description of a new water mite species of the genus Lebertia Neuman, 1880 (Acari, Hydrachnidae: Lebertiidae) from Russia, Zootaxa 4550 (3), pp. 444-450 : 444-450

Lebertia fimbriatella sp. n. ( Figs 1–21 )

Type series. Holotype: female, slide 8533, Europe, Russia, Yaroslavl Province, Nekouz District, brook near village Maloe Dyakonovo , depth 0.2–0.4 m, substrate: slit, detritus, stones, 1.06. 2002, leg. P. V. Tuzovskij . Paratypes: From the same locality as holotype; 1 female 1.07.2002, 1 female 9.07.2002, 1 male 11.07.2002, 1 male 17.07.2001, 1 male 18.07. 2001, 2 males 20.07.2001, 2 males 27.06.2001, 1 female 1.06.2003, 1 male 22.08.2003, 2 males 2.08.2005, 1 male and 1 female 24.08.2005. Additional material: Yaroslavl Province, Breitovo District, Kamenka stream near settlement Pokrovskoe on Sit , depth 0.2–0.4 m, substrate: stones, gravel, sand, 1 male, 20.08.2003, leg. P. V. Tuzovskij. Larvae (n=10) were reared 0 1.06.2002 and 10.06.2003 from two females, the duration of the embryonic period was 10–13 days. Larva. Description. Dorsal plate large elongate (L/W ratio 0.9–1.0), posteriorly pointed, covering about 3/5 of idiosoma surface in unengorged larvae and bearing four pairs of setae (Fch, Fp, Vi and Oi), simple setae long and thick, but setae Fch much shorter than Vi, trichobothria Fp and Oi thin, short and equal in length ( Fig. 1 ). Eight pairs of setae (Oe, Hi, He, Sci, Sce, Li, Le, Si) situated in soft membrane. All idiosomal setae not associated with glandularia .

Ventral idiosoma surface is nearly completely covered by the coxal plates ( Fig. 2 ). Coxal setae C1 shorter than C2, C3 and C4 subequal in length. Idiosomal setae Pi shorter than Pe and located at posterior end of coxal plate III on each side. Ci longest, whip-like and borne on small tubercles. Urstigma relatively large, oval. Excretory pore plate as long as wide or slightly longer than wide (L/W ratio 1.0–1.1), excretory pore located near posterior end of plate and a little posteriorly to setae Ae, bases of setae Ai located close to anterior margin; distance between bases of setae Ae–Ae almost two times longer than distance between Ai–Ai ( Figs 3–4 ). Coxal shield and dorsal plate with cell-shaped reticulations.

Capitulum ( Fig. 5 ) with rather broad base and comparatively narrow rostrum, anterior hypostomal pair of setae longer and thicker than posterior pair of setae.

Basal segments of chelicerae fused to each other medially, with convex dorsal and concave ventral margin ( Fig. 6 ). Chela small, crescent–shaped with two minute subapical teeth.

Pedipalps compact ( Fig. 7 ): P–1 very short, without seta; P–2 relatively large, with single long dorsoproximal seta; P–3 with a very long, thick lateroproximal seta and relatively short, thin dorsoproximal seta; P–4 rather long, its length larger than height, with two unequal proximal setae and single dorsodistal thin seta, and massive hook-like dorsodistal claw; P–5 small, with one short solenidion, two long and five relatively short unequal simple setae, one of them very short.

Shape and arrangement of setae on legs segments as shown in Figs 8–10 . Total number of setae on legs I-III except for eupathidia as follows (number of sensilla shown in parentheses): I-Leg-1-5: 1, 7, 5(s), 11(2s), 15(s, ac); II-Leg-1-5: 1, 7, 5(s), 11(2s), 15(s, ac); III-Leg-1-5: 1, 6, 5(s), 10(s), 11. Basifemur and telofemur of all legs fused to each other, with indistinct suture line. Number of heavy setae from trochanter to tarsus: I–Leg: 1, 1, 1, 1, 0; II–Leg: 0, 2, 2, 1, 0; III–Leg: 0, 1, 1, 1, 0. Solenidion on I/II-Leg-3 and both solenidia on I-Leg-4 located distally, proximal solenidion on II-Leg-4 and solenidion on III-Leg-IV located near middle of segment. Claws of legs I and II ( Fig. 11 ) smaller than claws of legs III ( Fig. 12 ).

Measurements, n=10. Dorsal plate L 250–270, W 145–175; setae Fch L 80–90, Fp and Oi L 25–32, Vi L 140–155, Oe L 140–155, Hi and He L 110–120, Sci and Sce L 100–110; Li, Le L 95–105, Si and Se L 80–95, Ci L 120–130, Pi L 44–48, Pe L 50–65, setae C1 L 65–70, C2 L 80–95, C3 and C4 L 90–105; medial margins of coxae I L 80–90, medial margins of coxae II+III L 95–105; excretory pore plate L 32–35, W 35–38; capitulum L 70–80; cheliceral segments L: base 67–70, chela L 12–13; pedipalpal segments (P–1–5) L: 12–13, 32–36, 22–35, 19–23, 12–15; legs segments L: I– Leg-1–5: 32–39, 38–42, 38–45, 50–55, 60–65; II–Leg-1–5: 38–42, 44–48, 38–45, 55–65, 67–74; III–Leg-1–5: 42–52, 43–55, 48–55, 64–70, 80–88.

Adults: Both sexes. Colour yellow to brown. Integument smooth. Setae Fch ( Fig.13 ) longer and thicker than other idiosomal setae. Trichobothria Fp, Oi and setae Pi not associated with glandularia, other idiosomal setae associated with glandularia.

Coxal shield ( Fig. 14 ) nearly as long as wide (L/W ratio 0.8–1.1). Suture line between coxal plates II usually a little longer than median length of coxal plates I, occasionally they are nearly equal in length or even suture line between coxal plates II shorter than medial length of coxal plates I (Cx-I/Cx II ratio mL 0.9—1.1). Coxal shield bearing two pairs of glandularia (Hv and Pe), Pe l ocated near tips of coxal plates I. Posterior margin of coxal plates II comparatively narrow. Coxal plates IV embracing the genital field ¾ to 4/5, with obtuse-angled or rounded posteromedial edges. Genital field with three pairs of acetabula, posterior pair smaller than anterior pairs of acetabula. Excretory pore ( Fig. 15 ) elongate, with slightly thickened lips but without additional sclerotization.

Pedipalp moderately long ( Fig. 16 ): P-1 short, with single dorsodistal setae; P-2 with three unequal dorsoproximal and two long unequal dorsodistal setae, ventral margin of segment concave, ventrodistal seta thick and inserted slightly away from ventrodistal segment edge; P-3 rather long, dorsal setae close to each other, inserted slightly proximally from the center of the segment, medio- and dorsodistal setae close to each other, mediodistal seta longest, ventrodistal seta inserted slightly away from ventrodistal segment edge; P-4 slender, proximal and distal edges of the segment nearly equal in height, with straight ventral margin, divided by seta insertions into three sectors: 1:1:1, rarely 2:1:2, 2:1:3 or 3:2:2, mediodistal peg-like seta pointed, its length about 1/3 length of P-5.

Legs III–IV with swimming setae, their number as following: one or two on III-Leg-5 and IV-Leg-4; three, occasionally two or four, on IV-Leg-5; swimming setae on III/IV-Leg-5 longer than ½ L III/IV-Leg-6 but not reaching tips of these segments; IV-Leg-5 with 5–7 ventral thick setae, IV-Leg-6 usually with three, occasionally two or four, minute spine-like setae ( Figs 17–18 ). Leg claws ( Fig. 19 ) with moderately developed lamella and two clawlets: short internal and comparatively long external.

Capitulum with short rostrum, posterodorsal projections long and pointed ( Fig. 19 ). Basal segment of chelicera large with convex dorsal and nearly straight ventral margin, chela small, sickle-shaped.

Female. Genital field with 10–15 pairs of medial and 3–5 pairs of lateral thin setae. Measurements (n=5). Idiosoma L 600–1125; coxal shield L 560–615, W 525–615; coxal plate I mL 135–150, coxal plate II mL 150–165; genital flap L 165–175, W 70–77, genital acetabula (ac-1–3) L 55–63, 40–60, 30–38; cheliceral segments L: base 185–195, chela 30– 37; pedipalp segments (P–1–5) L: 24–30, 65–72, 75–85, 90–96, 27–30, P-4 medio-distal peg-like seta L 14–16; leg segments L: Leg-1–6: 60–75, 75–85, 80–100, 125–140, 110–140, 135–150; II–Leg-1–6: 60–75, 75– 85, 8 5 –100, 140–150, 160–170, 155–175; III–Leg-1–6: 75–88, 85–100, 100–115, 175–190, 205–220, 185–200; IV–Leg-1–6: 135–165, 100– 115, 160–175, 210–230, 225–250, 210–225.

Male. Genital field with 20–28 pairs of medial and 5–7 pairs of lateral thin setae ( Fig. 21 ). Measurements (n=10). Idiosoma L 600–875; coxal shield L 550–600, W 525–600; coxal plate I mL 125–140, coxal plate II mL 135–160; genital flap L 135–150, W 50–62, genital acetabula (ac-1–3) L 42–48, 36–42, 20–30; cheliceral segments L: base 165– 175, chela 30–35; pedipalp segments (P–1–5) L: 24–30, 65–72, 60–66, 77–84, 18–24, P-4 medio-distal peg-like seta L 12– 15; leg segments L: Leg-1–6: 50–65, 75–90, 75–90, 105–125, 110–125, 125–140; II–Leg-1–6: 60– 75, 7 5 –90, 75–90, 125– 140, 135–165, 135–150; III–Leg-1–6: 75–85, 85–100, 100–115, 150–175, 185–195, 170–190; IV–Leg-1–6: 125–140, 100–110, 145–155, 200–205, 210–225, 175–200.

Differential diagnosis. The new species is similar to Lebertia fimbriata Thor, 1899 , L. ignatowi Sokolow, 1930 and L. pusilla Koenike, 1911 . The coxal shield in adult L. ignatowi is clearly longer than the width, Cx-I shorter than Cx-II (Cx-1/CxII ratio mL 0.7–0.9), swimming setae on III/IV-Leg-5 are not longer than 1/2 L of III/IV-Leg-6, III/IV-Leg-4 without swimming setae ( Sokolow 1940, Gerecke 2009, Semenchenko 2010). Adults of L. pusilla especially well differs from L. fimbriatella sp. n. in the length of swimming setae on posterior pairs of legs: III/IV-Leg-5 each with 3-4 long swimming setae arranged in a longitudinal line near distal segment margin, in length is similar to, or exceeding, terminal segment ( Gerecke 2009, Di Sabatino et al. 2010).

The new species close related to Lebertia fimbriata Thor, 1899 , however, the following clear differences can be found in the morphology of larva and adults of Lebertia fimbriatella sp.n. and L. fimbriata (character states of larva and adults of L. fimbriata are given in parenthesis after Martin 2000 and Müller 2015 for larvae, Gerecke 2009 and Di Sabatino et al. 2010 for adults): larva: III-Leg-2 with single heavy seta, Fig. 9 (two heavy setae), III-Leg-5 with 11 simple setae, Fig. 10 (10 simple setae + one solenidion), the excretory pore plate located near posterior end of the excretory pore plate and a little posterior to setae Ae, Figs 3–4 (centrally located on the excretory pore plate between setae Ae =E2); adults: integument smooth (finely striated); IV-Leg-5 with three swimming setae, Fig. 17 (with two swimming setae); IV-Leg-6 with three to four ventral minute spine-like setae (with two spine-like setae). Thus, L. fimbriatella sp.n. is a sister species and possibly belong to Lebertia fimbriata complex.

Etymology. The species epithet “ fimbriatella ” is derived from the name of the similar species, Lebertia fimbriata .

Habitat. Running waters.

Distribution. Europe ( Russia: Yaroslavl Province).

Figures

FIGURES 1–2. Lebertia fimbriatella sp. n., larva: 1, dorsal view; 2, ventral view. Scale bar: 50 µm.

FIGURES 3–7. Lebertia fimbriatella sp. n., larva: 3–4, excretory pore plate; 5, capitulum, ventral view; 6, chelicera, lateral view; 7, pedipalp. Scale bars: 3–4 = 50 µm, 5–7 = 20 µm.

FIGURES 8–12. Lebertia fimbriatella sp. n., larva: 8, leg I; 9, leg II; 10, leg III; 11, claws of leg I; 12, claws of leg III. Scale bars: 8– 10 = 50 µm, 8, 11–12 = 20 µm.

FIGURES 13–16. Lebertia fimbriatella sp. n., female: 13, seta Fch; 14, coxal shield and genital field; 15, excretory pore; 16, pedipalp. Scale bars: 13, 15, 16 = 50 µm, 14 = 100 µm.

FIGURES 17–21. Lebertia fimbriatella sp. n.: 17, IV-Leg-4-6; 18, IV-Leg-6; 19, leg claw; 20, capitulum and chelicera, lateral view; 21, genital field; 17–20 female, 21, male. Scale bars: 17–18, 21 = 100 µm, 19, 20 = 50 µm.