Hygrobates (Hygrobates) longiporus Thor, 1879

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 : 254-258

Hygrobates (Hygrobates) longiporus Thor, 1879

( FigS 16–28 )

Material examined. Larvae (n=19), RuSSia, YaroSlavl Province: 6 larvae , 3 July 2003, Nekouz DiStrict, Ild Stream near village Mar’ino , and 13 larvae, Breitowo DiStrict , Kamenka Stream near Settlement Sit’-PokrovSkoe , 7 July 2003. The duration of the embryonic period waS 11–13 dayS.

Diagnosis. Larva. DorSal plate elongate (L/W ratio 1.8–1.9) with parallel lateral marginS; tmas on coxae III preSent; Setae Fch Slightly Shorter than Vi, Setae Pi and Pe equal in length; II-Leg-5 Solenidion located proximally to the middle of the Segment; II-Leg-3 and III-Leg-4 with three heavy Setae each.

Description. DorSal plate ( Fig. 16 ) elongate (L/W ratio 1.8–1.9), covering large part of dorSum, acute anteriorly, with parallel lateral marginS; Simple Setae long and thick, but Setae Fch Slightly Shorter than Vi, trichobothria Fp, Oi thin, Short and equal in length. Eight pairS of Setae (Oe, Hi, He, Sci, Sce, Li, Le, Si) Situated in Soft membrane; Oe longeSt, Hi and Sce Subequal in length and longer than other Setae Situated in the membrane. Surface of dorSal plate with reticulation.

Coxal Setae C1 and C2 relatively Short and Subequal; C3 and C4 long, C4 a little longer than C3; tranSverSe muScle attachment Scar on coxae III preSent. Setae Pe longer than Pi ( Fig. 17 ). UrStigma relatively large, oval. 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 0.38–0.42), Slightly convex anteriorly, “W” — Shaped poSteriorly and with muScle attachment ScarS anteriorly; excretory pore and Setae Ae on the Same level in the center or excretory pore Slightly anteriorly to 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. 18 ), with Straight lateral marginS, their anterior edgeS Straight or Slightly concave. Chela relatively Small, creScent-Shaped, with two minute Subapical teeth.

PedipalpS Stout ( Fig. 19 ): P-1 very Short, without Setae; P-2 relatively large, with Single dorSal Seta diStally to middle of Segment; P-3 with a very long, thick lateroproximal Seta and Short, fine dorSoproximal Seta; P-4 with two unequal Setae and a maSSive dorSodiStal claw; P-5 Small, with one rather 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 20–22 . Number of thickened Setae from trochanter to tarSuS: I-III-LegS: I: 1-1-1-0-0, II: 0-1-3-1-0, III: 0-1-3-3-0. Solenidion on II- Leg-5 located proximally to middle of Segment, and Solenidion or Solenidia on other SegmentS of legS Situated diStally. ClawS of legS III ( Fig. 24 ) larger than clawS of legS I and II ( Fig. 23 ). Central claw and lateral clawS in all legS nearly Subequal in Size.

MeaSurementS, n=10. DorSal plate L 285–290, W 155–160; Setae Fch L 48–52; Hi, Sci L 80–93, Fp and Oi L 18–23, Vi L 65–70, Oe L 95–105; He L 57–65; Sce L 38–42; Li L 44–48; Le L 38–42; Si L 28–32, Se L 48–55, Ci L 225–240, Pi and Pe L 40–48, Setae C1 and C2 L 38–48, C3 L 85–90, C4 L 102–115; medial marginS of coxae I– III L 190–196; gnathoSomal bay L 41–45; urStigma L 19–20; excretory pore plate L 50–52, W 128–135; baSal SegmentS of chelicerae L 80–84, W 44–48, chela L 22–23; pedipalpal SegmentS (P-1-5) L: 4–5, 35–39, 22–23, 6–7, 4–5; legS SegmentS L: I-Leg-1-5: 28–32, 35–37, 38–42, 50–52, 45–48; II-Leg-1-5: 33–38, 3 7–39, 41–45, 55–58, 51–55; III-Leg-1-5: 44–48, 40–42, 44–48, 64–66, 70–74.

Female. IdioSoma oval and Somewhat flattened dorSoventrally. Integument Soft and finely Striated. Trichobothria Fp, Oi and Setae Pi not aSSociated with glandularia, other idioSomal Setae aSSociated with glandularia. Setae Fch ( Fig. 25 ) much thicker than other idioSomal Setae. Anterior coxal plateS with Short apodemeS, poSteromedial margin convexity rounded ( Fig. 26 ) or triangular. Coxal plate IV with nearly parallel anterior and poSterior marginS, medial margin with noSe-like protruding, poSterior marginS Slightly indented medially it middle. Genital plateS elongated (L/W ratio 2.25–2.75) Sickle-Shaped, with concave medial margin; acetabula in an obtuSe triangle; anterior and poSterior genital ScleriteS Small and nearly equal in width.

Pedipalp moderately long ( Fig. 27 ); P-1 with Single dorSodiStal Seta; P-2 uSually with Six (occaSionally with five or Seven) thick dorSal Setae, ventral margin Straight or Slightly concave diStally forming a blunt noSe Shaped projection, denticleS covering diStal half of ventral margin of Segment; P-3 with two dorSoproximal, two dorSodiStal thick Subequal Setae and Single thin diStal Seta, ventral margin Straight, denticleS covering diStal 2/3 of Segment; P-4 ventral Setae on the Same level or very Slightly Separated diStally to middle of Segment.

LegS 6–Segmented Slender without Swimming Setae. I-Leg-4 with two Subequal relatively long diStoventral Setae, I-Leg-5 with two rather long unequal diStoventral Setae ( Fig. 28 ).

MeaSurementS (n=10). IdioSoma L 1000–1250; Seta Fch L 60–70; coxal plateS I + capitulum mL 410–440; genital plateS L 250–275, W 100–115, genital acetabula (ac-1-3) L/W 95–105/40–50, 100–125/345–55, 85–115/ 50–62; cheliceral SegmentS L: baSe 370–380, chela 160–170; pedipalp SegmentS (P-1-5) L: 50–60, 200–215, 140–165, 280–290, 62–75; legS SegmentS L: I-Leg-1-6: 85–100, 140–165, 185–200, 265–290, 285–300, 250–265; II- Leg-1-6: 100–110, 150–170, 210–225, 285–315, 325–340, 275–290; III-Leg-1-6: 1 00–110, 160–175, 225–250, 350–375, 385–400, 310–340; IV-Leg-1-6: 185–200, 200–215, 285–305, 425–440, 425–440, 350–365.

Remarks. The morphology of the larva deScribed by WainStein (1980) aS H. longiporus iS in perfect agreement with the deScription of the larva H. nigromaculatus (See TuzovSkij 2017) . The combination of the dorSal plate broad with convex lateral margin, abSent tmas on the coxal plateS III, Subequal Setae Pi and Pe and I-Leg-2/3 with two heavy Setae each iS diagnoStic for the larva H. nigromaculatus . Therefore, the larva deScribed under the name H. longiporus ( WainStein 1980) probably refer to H. nigromaculatus (TuzovSkij 2017) .

The morphology of the larva deScribed by WainStein (1980) under the name H. foreli Koenike, 1895 iS in perfect agreement with the deScription of the larva given above. The combination of the Setae C4 long reaching to poSterior margin of coxal plateS III ( Fig. 17 ), tmas on coxal plate III preSent, II-Leg-3 with three heavy Setae ( Fig. 21 ) iS diagnoStic for the larva H. longiporus . Therefore, the larva deScribed under the name H. foreli ( WainStein 1980) probably refer to H. longiporus .

The larva of H. foreli (See deScription above) iS Similar to H. longiporus but clearly differS by the following characterS: the Setae C4 comparatively Short and not reaching to poSterior margin of coxal plateS III ( Fig. 2 ), tmas on coxal plate III abSent, II-Leg-3 with two heavy Setae ( Fig. 7 ).

Lack of the larval paraSitiSm in H. longiporus waS Stated by Smith (1998). I did not obServe in thiS SpecieS a direct development of larvae in deutonymphS in laboratory conditionS, and larvae probably need a hoSt for development.

Figures

FIGURES 16–17. Hygrobates longiporus Thor, 1879, larva:16, dorsal view; 17, ventral view. Scale bar:50 µm.

FIGURES 18–24. Hygrobates longiporus Thor, 1879, larva:18,chelicera, dorsal view; 19, pedipalp; 20, Leg I; 21, Leg II; 22, Leg III; 23, claws of leg I; 24, claws of leg III. Scale bars:18,20–22 = 50 µm, 19, 23–24 = 20 µm.

FIGURES 25–28. Hygrobates longiporus Thor, 1879, female: 25, seta Fch; 26, coxal plates I–IV and genital field, ventral view; 27, pedipalp; 28, I-Leg-4-6. Scale bars:25, 27 = 100 µm, 26, 28 = 200 µm.

FIGURES 1–2. Hygrobates foreli (Lebert, 1874), larva: 1, dorsal view; 2, ventral view. Scale bar:50 µm.

FIGURES 3–10. Hygrobates foreli (Lebert, 1874), larva:3, chelicera, dorsal view;4, chela, lateral view; 5, pedipalp; 6, Leg I; 7, Leg II; 8, Leg III; 9, claws of leg I; 10, claws of leg III.Scale bars:3, 5, 6–8 = 50 µm, 4, 9–10 = 20 µm.