Paratetrahygrobatella magellanica, Tuzovskij, Petr V. & Stolbov, Vitaly A., 2016

Tuzovskij, Petr V. & Stolbov, Vitaly A., 2016, Description of a new hygrobatid genus from Chile (Acari, Hydrachnidia: Hygrobatidae), Zootaxa 4161 (4), pp. 579-585 : 580-583

Paratetrahygrobatella magellanica sp. n.

( Figs 1–20 )

Type series. Holotype male, slide 9910, South America, Chile, Provincia de Magallanes, Isla Grande de Tierra del Fuego , stream running into Lago Blanco (54º 04’14” S 68º52’ 43” W), 4.11.2015, substrates: stones and tree trunks, washout was from the submerged trunks of trees, leg. A. Prokin . Paratypes: One male and 23 females of same data and locality as holotype (both males and seven females dissected).

Additional materials. Six females (all dissected), Provincia de Magallanes, Rio de Los Ciervos (53°12'09"S 70°56'15"W) near Punta Arenas city, substrates: stones and mosses, 07.11.2014, leg. V. Stolbov ; 23 females (14 dissected), Provincia de Magallanes, stream south of Punta Arenas city (53°34'29” S 70°56'23” W), substrates: stones and mosses, 08.11.2014, leg. V. Stolbov .

Description. Female. Dorsal integument with honeycomb-like structure. Dorsal side ( Fig. 1 ) with one pair of anteromedial plates, one pair of posteromedial platelets and three pairs of dorsolateral platelets. Anterolateral plates midsized, oval and bearing trichobothria Oi, the rest of the dorsal platelets small and more or less circular. Setae Fch longer and thicker than others idiosomal setae. Lateral eyes not in capsules lying under integument, eye pigment present. All lyriform organs (i1-i5) situated along lateral edges of idiosoma.

All coxal groups well separated from each other and bearing some setae each ( Fig. 2 ). Setae Hv situated posterolaterally on coxal plates II, glandularia Pe located near anterior edge of the coxal plates IV. Setae Pe reduced but their alveoli present near medial edge of coxal plates IV. Capitulum elongate without anchoral process, with two pairs of subequal anterior ventral setae. Posterior coxal groups and genital field far from each other. Integument in interspace between posterior coxal groups and genital field striated. Gonopore and acetabular plates subequal in length. Genital plates elongated, recurved with concave inner margin and bearing three acetabula, ac-1 and ac-2 oval and ac-3 usually circular; size and shape of acetabula variable among individuals; distance between ac-2 and ac-3 usually smaller than distance between ac-1 and ac-2 ( Figs 4–5 ), but sometimes these distances are subequal ( Fig. 3 ). Acetabular plates with 8–12 genital thin setae each, three setae longer than others. Anterior and posterior genital sclerites small, subequal in size. Excretory pore free, caudally located. Surface of all coxal plates and capitulum porous.

Chelicera with large basal segment and short crescent chela ( Fig. 6 ).

Pedipalp ( Fig. 7 ) with thin, short P-1 bearing a single dorsodistal seta; P-2 and P-3 with numerous small ventral teeth; P-2 with straight ventral margin, bearing three to four subequal dorsoproximal setae and two larger dorsodistal setae; P-3 with convex ventral margin, bearing two to three dorsoproximal setae and two dorsodistal setae; P-4 slender, with a single distomedial spine and seven to eight thin setae (two long thin ventral setae, two dorsoproximal thin setae, three to four thin distal setae); P-5 with three distal claw-lets.

Legs slender, without swimming setae. Shape and arrangement of setae on legs I–IV as shown in Figs 8–11 , respectively. I–III-Leg-1 with some short, thick dorsal setae and one long distolateral seta; IV-Leg-1 a little longer than IV-Leg–II (IV-Leg-1/IV-Leg-2 L ratio 1.15–1.35), with a single short dorsoproximal seta and two unequal dorsodistal setae. All legs claws equal in shape but claws of legs IV slightly larger than others claws. Figure 12 shows a claw with two unequal pointed clawlets and a mid-sized claw lamella.

Measurements (n=10). Idiosoma L 560–850; anterior dorsal plates L 75–90, W 37–50; coxal plates III+IV L 225– 300, W 135–175; acetabular plates L 135–160, W 62–75; genital acetabula (ac-1–3) L or D 30–45, 3 0–45, 35–50; cheliceral segments: base L 160–190, chela L 70–87; pedipalp segments (P-1–5) L: 30–50, 80–100, 80–105, 100–135, 40– 50; leg segments L: I-Leg-1–6: 50–60, 60–75, 75–100, 80–135, 110–150, 110–125; II-Leg-1–6: 50–65, 50–65, 70–100, 115–140, 100–170, 110–160; III-Leg-1–6: 60–75, 50–70, 75–100, 125–175, 150–200, 125–180; IV-Leg-1–6: 100–140, 75–100, 95–125, 150–180, 165–215, 150–210.

Male. Dorsal shield ( Fig. 13 ) large bearing eight pairs of setae (Vi, Oi, Oe, Hi, Sci, Sce, Li, Le) and two pairs of slitorgans organs (i3 and i4), setae Fch long, thick, Fp thin, hair-like and located on small sclerites; three pairs of slit organs (i1, i2 and i5) situated on soft integument.

Coxal plates in four groups ( Fig.14 ). Anterior coxal groups relatively small, well separated, with short apodemes, setae Hv located posterolaterally on coxal plates II. Posterior coxal groups comparatively large, coxal plates IV elongated triangular, glandularia Pe located near anterior edge of the coxal plates IV; sclerites bearing seta and glandularium Ci fused with medial margin of coxal plates IV. Genital acetabula lying on large triangular plate incorporating as well the excretory pore. Setae Se fused the ventral sclerite laterocaudally, and Si caudally. Acetabula well separated, distance between ac-2 and ac-3 larger than diameter of ac-3, but smaller than distance between ac-1 and ac-2. Genital field with 28–33 thin setae; gonopore small, elongated and situated near anterior edge of acetabular plate, excretory pore located close to the gonopore.

Pedipalp ( Fig. 20 ) similar to female, but P-2 with ventrodistal projection, and P-3 presents obtuse proximoventral protrusion.

Legs and claws are similar to the female. Shape and arrangement of setae on legs I–IV as shown in Figs 15–18 , and claw in Fig. 19 , respectively. IV-Leg-1 longer than IV-Leg-2 (IV-Leg-1/IV-Leg-2 L ratio 1.5–1.6).

Measurements (n=2). Idiosoma L 750–815; dorsal shield L 585, W 325; seta Fch L 105; coxal plates III+IV L 400– 440, W 175–250; genital plate L 275, W 175; capitulum L 175, W 105; genital acetabula (ac-1–3) L or D 40–45, 35–40, 37–40; cheliceral segments L: base 125, chela 70; pedipalp segments (P-1–5) L: 37–50, 87–120, 125–150, 150–215, 60– 65; leg segments L: I-Leg-1–6: 60–75, 75–80, 90–100, 135–150, 150–165, 125–140; II-Leg-1–6: 60–75, 60–75, 100–105, 150–155, 150–175, 135–150; III–Leg-1–6: 75–90, 70–75, 100–105, 175–190, 200–225, 175–190; IV-Leg-16: 175–190, 110–125, 110–125, 175–190, 200–215, 185–200.

Etymology. The species is named after the Region (Magellan, from the English word for Magallanes) where it was collected.

Habitat. Running waters.

Distribution. South America ( Chile: Magellan Region).

Figures

FIGURES 1 – 2. Paratetrahygrobatella magellanica sp. n., female: 1, dorsal view; 2, ventral view. Scale bar: 200 µm.

FIGURES 3 – 7. Paratetrahygrobatella magellanica sp. n., female: 3, genital field; 4 – 5, genital plate (paratypes); 6, chelicera, lateral view; 7, pedipalp lateral view. Scale bars: 3 – 6 = 100 µm, 7 = 50 µm.

FIGURES 8 – 12. Paratetrahygrobatella magellanica sp. n., female: 8, leg I; 9, leg II; 10, leg III; 11, leg IV; 12, claws of leg IV. Scale bars: 8 – 11 = 100 µm, 12 = 50 µm.

FIGURES 13 – 14. Paratetrahygrobatella magellanica sp. n., male: 13, dorsal view (holotype); 14, ventral view (paratype). Scale bars: 13 = 100 µm, 14 = 200 µm.

FIGURES 15 – 17. Paratetrahygrobatella magellanica sp. n., male (paratype): 15, leg I; 16, leg II; 17, leg III. Scale bar: 100 µm.

FIGURES 18 – 20. Paratetrahygrobatella magellanica sp. n., male (holotype): 18, leg IV; 19, claw of leg IV; 20, pedipalp (lateral view). Scale bars: 18, 20 = 100 µm, 19 = 50 µm.