Atractides (Atractides) albaruthenicus, Cichocka, Maria & Biesiadka, Eugeniusz, 2013

Cichocka, Maria & Biesiadka, Eugeniusz, 2013, Two new species of the genus Atractides KOCH, 1837 (Acari: Hydrachnidia, Hygrobatidae) from Belarus, Zootaxa 3608 (4), pp. 253-263 : 254-258

Atractides (Atractides) albaruthenicus sp. nov.

( Figs. 1–14 )

Type material. Holotype: male dissected and slide mounted in Hoyer’s fluid. Belarus, river Svisloč, Suchaja Dolina (N: 53 0 47’459; E: 23 0 97’78), 12.06.1998, leg. E. Biesiadka. Paratypes: 5 males, 10 females, same data as holotype and other males, 10 larvae reared in the laboratory from 4 females captured 15.06.1998, same data as holotype and other males, oviposition 14.07., hatching after 16–22 days.

Diagnosis. In both sexes integument smooth without microsculpture, Ac-3 larger than Ac-1 and -2. Base of Vgl 1 fragile, Vgl 1 located close to Vgl 2. Whip-like seta located on the mediodistal margin of I-L-5 bipartite, with an additional short tip in the proximal part. Males: Genital plate similar to that of A. nodipalpis , with maximum width in the centre, number of setae 28–36 in both side, Vgl 4 at the level of Ac-2. Females: Vgl-4 posterior to genital plate, this plate narrow, with Ac- 1–3 in an arcuate line. Larvae: Broadly ovoid in shape, possessing a large plate that covers nearly the whole dorsal area; Larval small, falciform process slightly distant from the anterior edge of the organ. Anal plate nearly twice as wide as long. Excretory pore located in the anterior third of the excretory pore plate. Larvae may develop to nymphs without parasitic phase, nymphs were observed inside some larvae.

Description. Male (measurements: n = 6, holotype, 5 paratypes in parentheses). L idiosoma 660 (637–695), W 528 (510–535). L coxal field 404 (395–415), maximal W 485 (466–490), L of suture between Cx-1 123 (120–130), Cx-1 W 229 (225–232), Cx-2 W 250 (240–255), Cx-3 W 420 (418–430). Distance between Cx-3+4 47 (47–49). Posterior margin of Cx-1+2 rounded, medial apodeme not extend outside of posterior margin of Cx-1, lateral apodemes well developed. Genital field variable ( Fig. 1 ), mostly rhomboidal in shape, anterior margin with large concavity, L 120 (115–128), W 154 (150–160). Ac oval or subtriangular in shape. Ac-1–3 L 31 (31–32)-47 (47–49)-62 (62–63). Excretory pore smooth, located behind Vgl-1; Vgl-1 separated from Vgl-2. Palp ( Fig. 2 ) total dorsal L 394 (381–406), dorsal L of individual segments: P-1, 42 (39–43); P-2, 87 (84–90); P-3, 90 (87–92); P-4, 125 (124–129); P-5, 50 (47–52); relative L of individual segments for holotype (in % of total length): P-1, 10.6; P- 2, 22.1; P-3, 22.8; P-4, 31.7; P-5, 12.6; ventral margin of P-2 with a mediodistal protrusion, P-3 distinctly concave, P-4 swollen at the insertion of proximoventral hair, distance between ventral setae 25 (24–27), bases of ventral setae divide P-4 into three unequal sectors (2-1-2), sword seta inserted halfway between ventral setae, proximal seta thicker than distal.

I-L as given in Fig. 3 , I-L-5 more or less enlarged in distal part, dorsal L 210 (202–218), ventral L 149 (140–159), S-1 L 113 (112–115), ratio S-1 L/ W 11.58 (13.57–13.62), S-2 L 94 (93–96), ratio S-2 L/ W 7.52 (7.52–7.61), mediodistal whip-like seta bipartite, with an additional short tip in the proximal part ( Fig. 3 ). I-L-6 L 167 (160–170).

Female (measurements: n = 5). L idiosoma ( Fig. 4 ) 980–1350, W 480–580. L of coxal field 360–410, maximal W 637–660, L of suture between Cx-1 119–150, Cx-1 W 237–276, Cx-2 W 324–395, Cx-3 W 458–600. Distance between Cx-3+4 87–165. Posterior margin of Cx-1+2 broadly rounded, with three apodemal processes. Genital field L 390–405, W 385–395, genital plates narrow, elongate, L 285–291, Ac located in arcuate line, Ac-1-3 L (114–116)-(90–92)-(88–90). Excretory pore and Vgl as in male. Palp ( Fig. 5 ) total dorsal L 461–504, dorsal L of individual segments: P-1, 20–25; P-2, 91–98; P-3, 165–180; P-4, 140–149; P-5, 45–52; relative L of individual segments for one specimen (in % of total L): P-1, 4.9; P-2, 19.4; P-3, 35.7; P-4, 29.5; P-5, 10.3.

I-L ( Fig. 6 ) with I-L-5 less enlarged in distal part than in males, dorsal L 260–272, ventral L 194–199, S-1 L 140–142, ratio S-1 L/ W 9.1, S-2 L 118–119, ratio S-2 L/ W 6.7, distal curved seta bipartite. I-L-6 L 192–198. IV-L slender, distal end of IV-L-4 and-5 with four unequal setae—two significantly longer than others ( Fig. 7 ). Claw denticles at the same lengths.

Larva (n = 10). Idiosoma broadly oval, L 260–286, W 221–247. Dorsal plate oval ( Fig. 8 ), L 234–273, W 195–221. Anterior edge of the plate straight. Microrelief consisting of polygons, elongated in the anterior section and more regular in the medial and posterior parts. Lateropropodosomal setae Lp1 very long, Lp2 slightly shorter and mediopropodosomal Mp1 and Mp2 very short, with thick bases. Coxal plates ( Fig. 9 ) covering nearly the whole ventral area of the idiosoma, maximum L 234–262, medial L 176–195. Urstigma small, the falciform process (urstigmal blade) slightly distant from the margin of the larval organ. Posterior margins of the coxal plates rounded. Microrelief similar to that on the dorsal plate. Coxal setae C2, C3 and C4 long, C3 longer than C1-2 and - 4. C1 very short, at the same level as C3. Excretory pore plate ( Fig. 9 ) L 39–49, W 85–98, located in the posterior part of the ventral area of the idiosoma, lenticular in shape, rather large and with wavy anterior margin. Excretory pore located in the anterior third of the plate. Posterior ventral setae on thick bases, as typical from all Hygrobatidae , L 203–234. Gnathosoma cup-shaped and quite wide ( Fig. 9 ). Capitular bay rather shallow, 39–46 long and 44–57 wide. Chelicerae ( Fig. 11 ) L 57–67 and W at the base 36–41. Palps relatively short, total L 39–49. Legs in shape and setation typical for the genus, with relatively short setae ( Figs 12–14 ). The thickest stiletto-like setae on the ventral side of the distal margins of the femur, genu and tibia. Minimum, maximum and mean lengths of particular segments of the legs as given in Table 1 .

Some of the studied specimens had obviously developed to nymphs without a parasitic phase ( Fig. 10 ). Some active deutonymphs were observed 6–10 days after hatching.

Remarks. Atractides albaruthenicus sp. nov. is most similar to A. yaroslavlensis Tuzovskij, 2011 , A. nodipalpis Thor, 1899 and A. robustus Sokolow, 1940 , both characterized by a smooth or finely striate integument, a male palp with a ventrodistal protrusion on P-2 and a male genital plate indented at the anterior margin. The new species differs from others in the bipartite whip-like seta on I-L-5. Morphological differences between adults A. yaroslavlensis and A. albaruthenicus are less marked. Ventral margin of male P- 4 in new species is divided 2: 1: 2, in A. yaroslavlensis 1: 1: 2 (Tuzovskij 2011). In females sword seta of P-4 inserted more proximally, P-2 and P- 3 are more elongated than ones in second species. Larva of new species distinctly differs from A. yaroslavlensis by dorsal plate oval in shape, posterior margin of coxal plates concave, chelicerae triangular in shape, with lateral margins straight; in A. yaroslavlensis larval dorsal plate elongate, with parallel lateral margins, posterior margin of coxal fields straight, lateral margins if chelicerae curved in proximal part (Tuzovskij 2011). The new species differs from A. nodipalpis and A. robustus in the following characters: in both sexes Vg1-4 situated distinctly more posterior than in A. nodipalpis and A. robustus , similarly as in A. yaroslavlensis , larva is most similar to A. nodipalpis described by Wainstein (1980), it differs by shape of dorsal plate, in new species length/width 1.2, in second species 1.4. The female genital plates resemble more closely the ones in A. yaroslavlensis , A. cultellatus (K. Viets, 1930) , known only from Spain, and in A. montanus (Halbert, 1911) , last species by Gerecke (2003) considered as species dubia.

Interestingly, A. albaruthenicus seems to belong to the species which may have lost their parasitism, a phenomenon which is in the focus of recent ecological research (Smith 1998, Martin et al. 2011).

Etymology. The name originates from the Latin name of Belarus ( Alba Russia).

Figures

FIGURES 1 – 3. Atractides albaruthenicus sp. nov., male: 1 — idiosoma, ventral view, 2 — palp, medial view, 3 — terminal segments of leg I. Scale Bars = 100 µm.

FIGURES 4 – 7. Atractides albaruthenicus sp. nov., female: 4 — idiosoma, ventral view, 5 — palp, medial view, 6 — terminal segments of leg I, 7 — terminal segments of leg IV. Scale Bars = 100 µm.

FIGURES 8 – 14. Atractides albaruthenicus sp. nov., larvae: 8 — dorsal view, 9 — ventral view, 10 — old larvae with nymph inside, 11 — helophor, 12 — leg I. 13 — leg II, 14 — leg III. (Lp 1, Lp 2 — lateropropodosomal setae; Mp 1, Mp 2 — mediopropodosomal setae; C 1 - 4 — coxal setae; Lh 1, Lh 2, Lh 3 — latrohysterosomal setae). Scale Bars = 100 µm, Fig 11 = 50 µm.

Tables

TABLE 1. Leg measurements (in μm) of larvae Atractides albaruthenicus sp. nov.

Measurements	Leg segments				Total length
	trochanter femur	genu	tibia	tarsus
I-L min–max	18.2–31.2 26.0–39.0	31.2–39.0	41.6–46.8	49.2–59.8	169.0–202.8
mean	25.2 35.4	36.1	43.4	54.3	194.4
II–L min–max	26.0–33.8 31.2–41.6	36.4–41.6	46.8–54.6	65.0–70.2	210.6–234.0
mean	30.4 36.4	38.5	50.9	66.0	222.2
III–L min–max	31.2–39.0 36.4–41.6	41.6–46.8	52.0–57.2	67.6–78.0	233.6–260.0
mean	35.3 38.2	43.2	57.4	75.9	250.0