Amerothyasella tiunovae, Semenchenko, Ksenia A., 2010

Semenchenko, Ksenia A., 2010, Two new water mites species (Acariformes: Hydrachnidia) from interstitial waters of the Russian Far East, Zootaxa 2429, pp. 52-60 : 53-57

Amerothyasella tiunovae sp. n.

( Figs. 1–21 )

Type series. Holotype: female (407-kas– IBSS), Russia, Khabarovsk Territory, Nikolaevsky District, Cape of Lazarev, small brook on the sea coast of the Strait of Tartary, N 52o14.390’; E 141o21.749’; depth up to 50 cm; substrates: boulders, stones, pebbles, detritus, 21.06.2005, leg. K.A. Semenchenko, D.A. Sidorov. Paratype: 1 deutonymph (408-kas– IBSS) same locality and date as holotype.

Description. Female. Dorsal plates expanded, covering more than half of dorsal surface ( Fig. 1 ). Pre- and postfrontalia fused into frontal plate which narrow posteriorly and bearing setae Oi. Dorsocentralia 5 and dorsolateralia 1–4 larger than dorsocentralia 1–4. Setae Fp and Oi without glandularia, other dorsal setae associated with glandularia. Setae Fch long and smooth ( Fig. 2 ). Setae Fp longer than other idiosomal setae, surrounded by a wide sclerotized ring ( Fig. 3 ). Median eye absent. Lateral eyes in capsules. Integument with swelling papillae connected by subtle reticulum ( Fig. 4 ). Coxae of legs occupy about half of idiosomal length ( Fig. 5 ). Ventrolateralia 1 and 4 transverse; other ventrolateralia lengthwise; ventrolateralia 6 larger than rest of ventral plates. Ventrocentralia on right side of body with 2 plates, on left side—1 plate. Setae Pe situated near posterior margins of coxae IV.

Genital flaps elongated (ratio length/width = 2.9), with slightly convex lateral margins, bearing numerous setae arranged in 4–7 rows along its medial margins ( Fig. 6 ). Pregenital plate fused with anterior genital sclerite. All acetabula rounded in shape, situated on separate bases; length of bases of third acetabula longer than those of first and second acetabula. Anal opening surrounded by oval sclerotized ring tapered anteriorly.

Capitulum with relatively long rostrum, about 1/4 of capitulum length ( Fig. 7 ).

Basal segment of chelicera with convex dorsal and slightly concave ventral side ( Fig. 8 ). Cheliceral stylet large, slightly shorter than basal segment, its terminal half pointed with a row of fine dorsal teeth.

Pedipalpal trochanter with 1–2, femur with 8, genu with 2 setae ( Fig. 9 ). Tibia of pedipalp slightly tapering distally, with 2 slender setae and a blunt distodorsal extension. Pedipalpal tarsus with proximal solenidion, 5 slender setae and 4 stout distal spines ( Fig. 10 ).

All legs segments with short thick setae, except tarsus of legs I–II ( Figs. 11–12 ). Tarsus of legs III–IV bearing some thick setae. Claws simple, hook-shaped ( Fig. 13 ).

Measurements (n=1). Length of body 1190; length of eye capsule 44; length of seta Fch 100; length of frontal plate 224, width 310; length of genital flaps 270, width 92; diameter of genital acetabula (ac. 1–3): 20, 18, 19; length of bases of genital acetabula (ac. 1–3): 14, 12, 25; length of capitulum 297, length of rostrum 66; length of cheliceral basal segment 198, length of cheliceral stylet 145; length of pedipalpal segments (P-1– 5): 65, 104, 68, 110, 27; length of leg segments: I-L- 1–6—55, 132, 95, 132, 158, 140; II-L- 1–6—59, 132, 86, 125, 158, 145; III-L- 1–6—60, 112, 72, 115, 165, 185; IV-L-1–6—158, 105, 106, 172, 198, 200.

Deutonymph. Dorsal plates small, covering less than half of dorsal surface ( Fig. 14 ). Dorsocentralia 5 and dorsolateralia 1–4 larger than dorsocentralia 1–4. Setae Fp, Oi and Pi without glandularia, other idiosomal setae associated with glandularia. Setae Fch long and smooth ( Fig. 15 ). Setae Fp longer than other idiosomal setae, surrouded by wide sclerotized ring ( Fig. 16 ). Integument as in female ( Fig. 17 ). Coxae of legs occupy less than half of idiosomal length ( Fig. 18 ). Ventrolateralia 6 pairs; ventrolateralia 6 larger than rest of ventral plates. Ventrocentralia small and rounded. Setae Pe situated near posterior margins of coxae IV.

Genital flaps with 6–7 medial setae ( Fig. 19 ). All acetabula situated on separate bases; length of bases of first and second acetabula approximately subequal in size. Genital plate rounded, situated between genital flaps. Postgenital plate larger than pregenital plate. Anal opening surrounded by a rounded sclerotized ring.

Basal segment of chelicera with convex dorsal and nearly straight ventral side ( Fig. 20 ). Cheliceral stylet large, about two thirds of basal segment length, its terminal half pointed with a row of fine dorsal teeth.

Pedipalpal trochanter with 1, femur with 5, genu with 2–3 setae ( Fig. 21 ). Tibia of pedipalp slightly tapering distally, with 1 thin seta and a blunt distodorsal extension. Pedipalpal tarsus with proximal solenidion, 3 thin setae and 4 stout distal spines.

Measurements (n=1). Length of body 1080; length of eye capsule 35; length of seta Fch 25; length of frontal plate 200, width 244; length of genital flaps 95, width 53; diameter of genital acetabula (ac. 1–2): 17, 18; length of bases of genital acetabula (ac. 1–2): 19, 21; length of capitulum?, length of rostrum?; length of cheliceral basal segment 165, length of cheliceral stylet 108; length of pedipalpal segments (P-1–5): 51, 82, 48, 88, 24; length of leg segments: I-L- 1–6—55, 85, 72, 92, 118, 145; II-L- 1–6—58, 86, 66, 92, 127, 145; III- L- 1–6—59, 72, 53, 86, 120, 138; IV-L-1–6—112, 79, 74, 125, 140, 138.

Male. Unknown.

Differential diagnosis. The genus Amerothyasella contains two species described from North America: A. appalachiana Smith & Cook, 1999 and A. tracensis Smith & Cook, 1999 ( Smith & Cook 1999) . Amerothyasella tiunovae sp. n. is more closely related to A. appalachiana , which also has short blunt distodorsal extensions of pedipalpal tibia. The new species differs from the latter species in the following characters (character states of A. appalachiana are indicated in parentheses from Smith & Cook 1999): genital flaps in female bearing 3 pairs of acetabula (4 pairs), with numerous setae along its medial margins (less than 20 setae on each genital flap); setae Pe situated near posterior margins of coxae IV (near middle of coxae IV); length of sclerotized ring surrounding anal opening about twice its width (its length and width approximately subequal in size). It should be noted that the presence of ventrolateralia 1–6, pregenital and postgenital plates were not indicated in the original description of Amerothyasella , but found in A. tiunovae sp. n. According to the scheme of idiosomal plates, representatives of the family Thyadidae have 6 pairs ventrolateralia (Tuzovskij 1987, 2007). It is most probably that in the original description of Amerothyasella these features, along with the presence of pregenital and postgenital plates in adults and deutonymphs, genital plates in deutonymphs were not taken into consideration by the authors.

Etymology. The new species is named in honour of the aquatic biologist Tatiana Mikhailovna Tiunova (Institute of Biology and Soil Science, Vladivostok) in appreciation of her support in studying Far Eastern water mites.

Habitat. Interstitial waters.

Distribution. Khabarovsk Territory, Far East of Russia.

Figures

FIGURES 1 – 5. Amerothyasella tiunovae sp. n., female: 1, idiosoma, dorsal view; 2, seta Fch; 3, seta Fp; 4, fragment of integument; 5, idiosoma, ventral view. Scale bars = 100 µm for Figs. 1, 5; 50 µm for Figs. 2 – 3; 25 µm for Fig. 4.

FIGURES 6 – 13. Amerothyasella tiunovae sp. n., female: 6, genital field; 7, capitulum (lateral view); 8, chelicera; 9, pedipalp, lateral view; 10, pedipalpal tarsus; 11, tarsus of leg I; 12, leg IV; 13, claws of leg IV. Scale bars = 100 µm for Fig. 6; 50 µm for Figs. 7 – 9, 11 – 12; 25 µm for Figs. 10, 13.

FIGURES 14 – 21. Amerothyasella tiunovae sp. n., deutonymph: 14, idiosoma, dorsal view; 15, seta Fch; 16, seta Fp; 17, fragment of integument; 18, idiosoma, ventral view; 19, genital field; 20, chelicera; 21, pedipalp, lateral view. Scale bars = 100 µm for Figs. 14, 18; 50 µm for Fig. 20; 25 µm for Figs. 15 – 17, 19, 21.