Hygrobates (Hygrobates) trigonicus Koenike, 1895

Tuzovskij, Petr V., 2018, Larval morphology of Hygrobates foreli (Lebert, 1874), H. longiporus Thor, 1898 and H. trigonicus Koenike, 1895 (Acari, Hydrachnidia, Hygrobatidae), Zootaxa 4374 (2), pp. 249-262 : 258-261

Hygrobates (Hygrobates) trigonicus Koenike, 1895

( FigS 29–44 )

Material examined. Larvae (n=6): RuSSia, YaroSlavl Province, Nekouz DiStrict , RybinSk reServoir, near village Pogorelka , July 1976. Larvae were reared from a Single female, the duration of the embryonic period waS 11 dayS.

Diagnosis. Larva. DorSal plate elongate (L/W ratio 1.45–1.50) with convex lateral marginS; tmas on coxae III abSent; Setae Fch Shorter than Vi; Setae Pe Slightly longer than Pi; excretory pore plate wider than long without muScle attachment ScarS anteriorly; II-Leg-3 with three heavy Setae; III-Leg4 with two heavy Setae; II-Leg-5 Solenidion located dorSodiStally.

Description. DorSal plate elongate (L/W ratio 1. 1.45 –1.50), covering large part of dorSum, acute anteriorly, with Slightly convex lateral marginS; Simple Setae long and thick, Setae Fch Shorter than Vi; trichobothria Fp, Oi thin, Short and equal in length ( Fig. 29 ). Eight pairS of Setae (Oe, Hi, He, Sci, Sce, Li, Le, Si) Situated in Soft membrane; Oe longeSt, Si ShorteSt, Hi and Sce Subequal in length and longer than other Setae Situated in the membrane. Surface of dorSal plate with reticulated patternS conSiSting of elongated cellS.

Coxal Setae C1 and C2 relatively Short and Subequal; C3 and C4 almoSt Subequal and longer and thicker than C1 and C2 ( Fig. 30 ). TranSverSe muScle attachment Scar on coxae III abSent. Setae Pe Slightly longer than Pi. UrStigma oval and moderately in Size. All coxae with reticulated patternS conSiSting of elongated cellS. Setae Ci very long, well thickened, Situated on moderately long projection. Excretory pore plate wider than long (L/W ratio 0.47–0.60), convex poSteriorly, without muScle attachment ScarS anteriorly, excretory pore Situated Slightly poSteriorly to baSeS of Setae Ae, baSeS of Setae Ai located cloSe to anterior margin; diStance between baSeS of Setae Ae–Ae two timeS longer than diStance between Ai–Ai.

BaSal SegmentS of chelicerae fuSed to each other medially ( Fig. 31 ), with Slightly convex lateral marginS, their anterior edgeS Straight. Chela relatively Small, creScent–Shaped, with two minute, Subapical teeth ( Fig. 32 ).

PedipalpS Stout ( Fig. 33 ): P–1 very Short, without Setae; P–2 relatively large, with Single dorSodiStal Seta; P–3 with a very long, thick lateroproximal Seta and one Short, fine dorSodiStal Seta; P–4 with two unequal Setae and a maSSive dorSodiStal claw; P–5 Small, with one long Solenidion and unequal Simple Setae, one of them very Short.

Shape and arrangement of Setae, excluding eupathidia, on legS SegmentS aS Shown in FigS 34–36 . Number of thickened Setae from trochanter to tarSuS: I-III-Leg: I: 1-1-1-0-0, II: 0-1-3-1-0, III: 0-1-3-2-0. II-Leg-5 Solenidion located dorSodiStally, all other Solenidia on other SegmentS of legS Situated alSo diStally. Central claw and lateral clawS in all legS nearly Subequal in Size and with two hair-like projectionS each. ClawS of legS III ( Fig. 38 ) larger than clawS of legS I and II ( Fig. 37 ). Central claw and lateral clawS in all legS nearly Subequal in Size.

MeaSurementS, n=6. DorSal plate L 210–225, W 140–150; Setae Fch L 35–39; Hi, Sci L 48–52, Fp and Oi L 15–18, Vi L 41–48, Oe L 51–55; He L 37–42; Sce L 25–29; Li L 28–35; Le L 37–40; Si L 25–29, Se L 32–39, Ci L 145–160, Pi and Pe L 19–23, Setae C1 and C2 L 35–40, C3 L 55–60, C4 L 67–71; medial marginS of coxae I–III L 150–155; gnathoSomal bay L 44–48; urStigma L 12–13; excetory pore plate L 35–42, W 70–75; baSal SegmentS of chelicerae L 64–70, chela L 13–16; pedipalpal SegmentS (P-1-5) L: 5–6, 22–26, 12–15, 5–6, 4–5; leg SegmentS L: I–Leg-1-5: 25–29, 41–45, 35–39, 44–47, 43–47; II-Leg-1-5: 25–29, 38–42, 37–40, 46–48, 48–52; III-Leg-1-5: 38– 42, 35–42, 41–45, 54–58, 60–65.

Female. IdioSoma oval and Somewhat flattened dorSoventrally. Integument Soft and finely Striated. Setae Fch ( Fig. 39 ) much thicker than other idioSomal Setae. Anterior coxal plateS with Short apodemeS, poSteromedial margin convexity rounded ( Fig. 40 ). Coxal plate IV Subtriangular in Shape, with anterior and poSterior marginS converging to medial line. Genital plateS elongated (L/W 75 ratio 3.0–3.5) Sickle-Shaped, with concave medial margin; acetabula in an obtuSe triangle; both genital ScleriteS Small and nearly equal in width ( Fig. 41 ). Pregenital Sclerite uSually with two (occaSionally with one or three) pairS of Setae.

Pedipalp moderately long ( Fig. 42 ); P-1 with Single dorSodiStal Seta; P-2 with five to Six thick dorSal Setae; ventral margin concave, diStally protruding in a Slightly knob-Shaped projection covered by relatively large Scattered denticleS; P-3 with two dorSoproximal, two dorSodiStal thick Subequal Setae and Single thin diStal Seta; ventral margin convex, with a few denticleS in the diStal half of Segment; P-4 ventral Setae Separated, anterior Seta longer than poSterior one.

LegS Slender, with Swimming Setae. I-Leg-5 with two Subequal diStoventral Setae ( Fig. 43 ). II-IV-Leg-5 with Single Swimming Seta each ( Fig. 44 ).

MeaSurementS (n=5). IdioSoma L 600–940; Seta Fch L 45–50; coxal plateS I + capitulum mL 285–300; genital plateS L 150–175, W 48–55, genital acetabula (ac-1-3) L/W 60–65/20–25, 48–52/20–25, 35–40/30–40; cheliceral SegmentS L: baSe 223–230, chela 98–105; pedipalp SegmentS (P-1-5) L: 25–32, 100–125, 75–85, 135–150, 45–50; legS SegmentS L: I-Leg-1-6: 60–65, 72–77, 85–100, 135–150, 135–150, 135–145; II-Leg-1-6: 60–65, 80–90, 110–120, 160–190, 185–200, 175–180; III-Leg-1-6: 70–78, 100–105, 135–150, 200–225,235–255, 210–225; IV-Leg-1-6: 135–150, 110–125, 185–200, 260–290, 275–290, 210–240.

Remarks. The adult miteS of the preSent SpecieS well differS from moSt known SpecieS of the genuS Hygrobates by preSence Swimming Seta on II-IV-Leg-5. The Swimming Seta on II-IV-Leg-5 are alSo preSent in the deutonymph of thiS SpecieS ( TuzovSkij 1990).

Figures

FIGURES 29–30. Hygrobates trigonicus Koenike, 1895, larva:29, dorsal view; 30, ventral view. Scale bar: 50 µm.

FIGURES31–38.Hygrobates trigonicusKoenike, 1895,larva:31, chelicera, dorsalview;32, chela, lateral view; 33, pedipalp; 34, Leg I; 35, Leg II; 36, Leg III; 37, claws of leg I; 38, claws of leg III. Scale bars: 31–33, 37–38 = 20µm, 34–36 = 50 µm.

FIGURES 39–44. Hygrobates trigonicus Koenike, 1895, female: 39, seta Fch; 40, coxal plates I–IV; 41, genital field; 42, pedipalp; 43, I-Leg-5-6; 44, IV-Leg-5-6. Scale bars:39, 42 = 100 µm, 40, 41, 43, 44 = 100 µm.