Unionicola (Unionicola) xishuiensis Ding & Jin, 2019

Ding, Zhuhui, Jin, Daochao, Guo, Jianjun & Yi, Tianci, 2019, Three new species of the subgenus Unionicola Haldeman, 1842 (Acari, Hydrachnidia, Unionicolidae) from Guizhou, China, Zootaxa 4658 (1), pp. 141-154 : 146-150

Unionicola (Unionicola) xishuiensis Ding & Jin , sp. nov.

( Figs. 4 , 5 , 6 )

Material examined. Holotype: ♀, GZ-UN-2006081802, Sanchahe town , Xishui county, Guizhou province, China (28°26′27″ N, 106°24′11′′ E, 1023 m a.s.l.), collected by Tianci Yi, 18-VIII-2006 , Paratype: 3 ♂♂, 3 ♀♀, same data as holotype .

Diagnosis. Dorsum with two pairs of small unequal platelets, anterior platelets larger; laterally with five pairs of little papillae; excretory pore and L 4 at the same level; P-3 with a pair of setae, lateral one situated on medial and longer; P-4 with three distoventral projections, of which lateral one largest; ventral apodeme of infracapitulum bent distally as a hook; each genital plate with only one long, slender medial setae; I-L-6 with one dorsoproximal seta.

Description. Female. Integument soft and smooth; dorsum with two pairs of platelets in unequal size ( Figs. 4-B ); anterior platelets larger, laterally both with five little papillae in order, respectively; excretory pore not developed, and at the same level as L 4, V 1 on dorsum terminal. Coxal plates in four groups ( Figs. 4-A ), surface lightly reticulated ( Figs. 5-C ); posterior apodemes of ACG extending to anterior third of Cx-III; suture line of Cx-III/IV curved forward, and ending nearly at median of Cx-III, linked with lines of PCG and formed tree-like decoration; Cx-IV with one to five short lines in circular shape. Acetabular plates terminally located with six pairs of acetabula which occupying about three-fourths area ( Figs. 4-C ). V 4 gland much lager than those of other glandularia.

Palp slender ( Figs. 5-F ). P-2 with four setae; P-3 with a pair of unequal setae and the lateral one longer; P-4 with one long lateral and two small ventral subequal projections; P-5 curved with one proximal seta and four clawlet. Ventral apodeme of infracapitulum bent distally as a hook and longer than dorsal apodeme ( Figs. 5-D ). Chelicera with one proximal sickle-shaped projection and well-developed claw ( Figs. 5-C ).

Leg I–IV showed as Figs. 6 . I-L-1 dorsally with four setae ( Figs. 6-A ); I-L-2 ventrally with one long and one short blunt seta, dorsally with five awl-shaped setae; I-L-3 with two medioventral blunt setae and five dorsal setae, of which the distal one longest; I-L-4 with two pairs of blunt setae, anterior setae longer than posterior twos, distally with one short blunt seta and dorsally with four short awl-shaped setae; I-L-5 ventrally with five blunt setae, of which the first one longest and the second shortest, distally and also dorsally with two short awl-shaped setae; I-L-6 dorsally with one seta. II-L-1 dorsally with four awl-shaped setae ( Figs. 6-B ). II-L-2 with five dorsal awl-shaped setae and one ventral slender blunt seta; II-L-3 with seven awl-shaped setae, the distal twos longer, and one ventral swimming seta; II-L-4 with three lateral short heavy setae, five dorsal awl-shaped setae and two ventral long setae; II-L-5 with two ventral, three lateral and one dorsodistal setae. III-L-1 with three awl-shaped setae ( Figs. 6-C ); III- L-2 with two short ventral blunt setae and two pairs of dorsal awl-shaped setae; III-L-3 distally with one long seta; III-L-4 laterally with three setae, dorsally with five awl-shaped setae, and ventrally with one blunt seta and three swimming setae; III-L-5 ventrally with six blunt setae, dorsally with three awl-shaped setae, and distally with three swimming setae. IV-L-1 with three dorsal awl-shaped setae and one lateral slender seta ( Figs. 6-D ); IV-L-2 with three dorsal awl-shaped setae and one distal blunt seta; IV-L-3 with three lateral, three ventral slender long setae, distally with one dorsal short blunt seta and one long serrate swimming seta; IV-L-4 ventrally with four unequal blunt setae, laterally with two heavy setae, distally with two short and three long serrate swimming setae; IV-L-5 with three ventral blunt setae, distally with three serrate long swimming setae; IV-L-6 ventrally with two short awl-shaped setae. The sixth segment of leg II–IV distally each with one thin curved projection, claws of legs II–IV sickle-shaped and each with a short dorsal and a long ventral clawlet ( Figs. 6-F ).

Measurements (n=4). Idiosoma L/W 680/467–706/527 (ratio 1.33–1.47). Genital field L/W 98/133–123/133 (L/W ratio 0.73–0.92). LA 230–240. LP 230–240. Medial distance between Cx-IV 37–57. Chelicera L 136–147. L of P-1–5: 15–20; 93–122; 50–63; 83–108; 67–80. Lengths of I-L-1–6: 80–83; 170–193; 197–217; 263–287; 183–190; 190–207. Lengths of II-L-1–6: 64–73; 167–174; 213–227; 273–287; 297–317; 244–270. Lengths of III- L-1–6: 66–70; 133–173; 160–177; 174–200; 220–250; 197–223. Lengths of IV-L-1–6: 83–103; 134–163; 194–203; 217–247; 317–367; 307–323.

Male. Similar to female, idiosoma with prominent posterolateral protuberances ( Figs. 4-D ); genital plates crescent-shaped ( Figs. 4-F ), anteriorly and posteriorly fused by sclerotized cuticle, with seven thin setae on each side, of which two located anteriorly, two on the area between the two acetabular groups, and two laterally and one posteriorly to the second acetabular group; two anteriolateral genital setae long, of which one free from genital plates, another one located on the edge of genital plate at second acetabulum (the two setae located same in examined three specimens).

Measurements (n=3). Idiosoma L/W 527/415–580/433 (ratio 1.27–1.34). Genital field L/W 167/187–163/193 (L/W ratio 0.84–0.89). LA 217–220. LP 223–233. Medial distance between Cx-IV 27–30. Ejaculatory complex L 197–217. Chelicera L 118–123. L of P-1–5: 17–19; 80–91; 40–41; 83–87; 68–72. Lengths of I-L-1–6: 66–76; 157– 177; 173–187; 237–250; 157–177; 153–180. Lengths of II-L-1–6: 60–70; 160–174; 194–210; 254–270; 285–297; 237–240. Lengths of III-L-1–6: 60–63; 137–144; 150–164; 177–187; 177–237; 192–200. Lengths of IV-L-1–6: 96–100; 127–134; 177–180; 214–217; 317–320; 260–280.

Remarks. The new species is mostly related to U. crassipes (Müller, 1776) , However, the latter species can be distinguished by (1) The area between two acetabular groups with two inner slender setae in male ( Gerecke et al. 2016, Tuzovskij & Semenchenko 2015), while with only one in U. xishuiensis ; (2) Ventral apodeme of infracapitulum straight ( Jin 1997), while bent distally as a hook in U. xishuiensis .

The new species is also similar to U. marginata Jin, 1997 collected in a lake from Guiyang, China. From the new species, U. marginata differs in (1) Dorsum without platelets in female, while with two pairs of platelets in U. xishuiensis ; (2) Ventral apodeme of infracapitulum straight, while bent distally as a hook in U. xishuiensis ; (3) Chelicera proximally smooth, while with a sickle-shaped projection in U. xishuiensis .

Etymology. The species is named after the county (Xishui) from where it was collected.

Habitat. Pond, surrounded by Phragmites communis and Nelumbo sp..

Distribution. China (Guizhou province).

Figures

FIGURE 4. U. xishuiensis sp. nov. A–C, female (holotype): A. idiosoma ventral view; B. idiosoma dorsal view; C. genital field. D–F, male (paratype): D. genital field, E. idiosoma ventral view; F. idiosoma dorsal view. Scale bars = 100 μm

FIGURE 5. U. xishuiensis sp. nov., A–B, male (paratype): A. palp; B. ejaculatory complex. C–F, female (holotype): C. chelicera; D. infracapitulum; E. mesh pattern of Cx-I. F. palp. Scale bars = 100 μm.

FIGURE 6. U. xishuiensis sp. nov., A–D, female (holotype): A. leg I; B. leg II; C. leg III; D. leg IV; E. claws of leg I; F. claws of leg IV. Scale bars = 100 μm.