New species of genus Atractides Koch, 1837

. The paper deals with five new species of the genus Atractides Koch, 1837 (Acari: Hydrachnidiae, Hygrobatidae) collected from Qinghai Province, P.R. China, Atractides ( Atractides ) biprojectus Zhang, Li & Guo sp. nov., Atractides ( Atractides ) smiti Zhang, Li & Guo sp. nov., Atractides ( Atractides ) menyuanensis Zhang, Li & Guo sp. nov., Atractides ( Atractides ) longiprojectus Zhang, Li & Guo sp. nov. and Atractides ( Atractides ) xianmiensis Zhang, Li & Guo sp. nov. All the new species are described and illustrated in detail, and all the type specimens are deposited in the Institute of Entomology, Guizhou University, Guiyang, China (GUGC).

The Qinghai Province lies in the west of China, on the Qinghai-Tibet Plateau. The Qinghai-Tibet Plateau is the highest and largest plateau in the world, which has a wide range of geological, topographical and climatic gradients. Therefore, there is a greater biodiversity than in the surrounding lowlands and other high elevation regions (Sun et al. 2014). Through a joint investigation of water mites in Qinghai Province, five new species are found: Atractides (Atractides) biprojectus Zhang, Li & Guo sp. nov., Atractides (Atractides) smiti Zhang, Li & Guo sp. nov., Atractides (Atractides) menyuanensis Zhang, Li & Guo sp. nov., Atractides (Atractides) longiprojectus Zhang, Li & Guo sp. nov. and Atractides (Atractides) xianmiensis Zhang, Li & Guo sp. nov. All the new species are described and illustrated in detail.

Material and methods
Specimens in this study were all collected by Hai-Tao Li from Qinghai Province, P.R. China. Water mites were collected by hand netting, sorted on the spot from the living material, preserved in Koenike's fluid and dissected following Jin (1997) under a Motic SMZ-168 stereo microscope. Specimens were observed under a Nikon Ni-E microscope (with a Nikon DS-Ri2 camera). All illustrations were edited with Adobe Photoshop CC2018.

Diagnosis
Male Dorsal muscle attachment unsclerotized. I-L-5 longish, S-1 and S-2 with blunt tips and with a narrow setal interspace between them; I-L-6 curved. Ac in an obtuse triangle, V 1 separated from V 2 . P-2 and P-3 with a ventral projection respectively; P-4 divided by two long ventral hairs in sectors 2:3:1, sword seta between two ventral hair insertions and near the terminal.

Female
Similar to male. Ventral projection of P-2 not obvious, and P-3 ventral margin nearly straight.

Etymology
The Latin prefix 'bi-' means two, in the male of the new species P-2 and P-3 are with a ventral projection respectively.

Description
Male (n = 4) Idiosoma oval; dorsal muscle attachment unsclerotized, O 2 and D 1 at the same level; setae of D 1 and D 2 longer than others, setae of D 2 reaching to D 3 ; all slit organs visible, So 1 near the eye capsule and at the level of O 1 , So 2 in front of L 2 , So 3 near D 2 , So 4 at the middle of D 3 and L 4 ; So 5 behind D 4 (Fig. 1A). ACG fused together and with a suture, PCG separated; apodemes from ACG not reaching to Cx-IV. Acetabula three pairs and in an obtuse triangle; V 1 separated from V 2 ; V 3 and V 4 forming a trapezoid, V 4 at the same level as the middle of Ap (Fig. 1B). Palp five-segmented; P-2 and P-3 with a ventral projection respectively; P-4 with numerous dorsal hairs, and divided by two long ventral hairs in sectors 2:3:1, sword seta between two ventral hair insertions and near the terminal (Fig. 1E). I-L-5 longish, S-1 and S-2 both with blunt tips and with a narrow setal interspace between them; I-L-6 curved (Fig. 3A).

Diagnosis
Muscle attachments between D 3 sclerotized. I-L-5 longish, S-1 and S-2 both with blunt tips and with a narrow setal interspace between them; I-L-6 curved. Ac in an obtuse triangle; V 1 fused to V 2 , excretory pore surrounded by sclerotized ring. P-2 and P-3 ventral margin slightly straight; P-4 divided by two ventral hairs in sectors 3:3:2, sword seta at the middle of P-4.

Etymology
The species is named after Dr Harry Smit in appreciation of his contributions to the taxonomy of water mites.

Male
Idiosoma oval; O 2 and L 1 at the same level; setae of D 1 about two thirds of the distance from D 1 to D 2 ; setae of D 2 reaching to the level of D 3 ; muscle attachments between D 3 sclerotized; all setae surrounded by sclerites; So 1 in front of A 2 , So 2 at the same level as D 1 , So 3 near D 2 , So 4 at the same level as D 3 , So 5 behind D 4 (Fig. 4A). ACG fused together and with a suture, apodemes of ACG reaching to Cx-III; genital field with a development sclerotization, the anterior part of Ap with a projection, Ac in an obtuse triangle, Ac2 near Ac3 rather than Ac1, Ac3 the biggest; V 1 fused to V 2 , V 3 and V 4 forming a trapezoid, V 4 at the same level as the anterior of acetabular plate; excretory pore surrounded by sclerotized ring (Fig. 4B). Palp five-segmented; P-2 and P-3 ventral margins slightly straight; P-4 with numerous dorsal hairs, and divided by two ventral hairs in sectors 3:3:2, sword seta at the middle of P-4 (Fig. 4E). I-L-5 longish, S-1 and S-2 both with blunt tips and with a narrow setal interspace between them; I-L-6 curved (Fig. 5A).

Female
Unknown.

Diagnosis
Dorsal muscle attachment unsclerotized. I-L-5 longish, S-1 close to S-2. I-L-6 curved. Ac in an obtuse triangle; V 1 separated from V 2 . P-2 ventral margin slightly convex; P-3 ventral margin nearly straight; two long hairs on the ventral surface of P-4 near the base, sword seta near the base. Ac in a weakly curved line in female.

Etymology
The new species is named after the name of Menyuan Hui Autonomous County where the specimens were collected.

Description
Male (n = 1) Idiosoma oval, dorsal muscle attachment unsclerotized; all slit organs visible, So 1 near the eye capsule, So 2 near L 2 , So 3 at the level of D 2 , So 4 at the level of D 3 , So 5 on the outside of D 4 (Fig. 6A). ACG fused together and with a suture, PCG separated; apodemes from ACG not reaching to PCG; Ac in an obtuse triangle; V 1 separated from V 2 ; V 3 and V 4 forming a trapezoid, V 4 at the same level as the anterior of acetabular plate (Fig. 6B). Palp five-segmented; P-2 ventral margin slightly convex; P-3 ventral margin nearly straight; P-4 with numerous dorsal hairs, two long hairs on the ventral surface of P-4 near the base, sword seta near the base (Fig. 6E). I-L-5 longish, S-1 close to S-2; I-L-6 curved (Fig. 8A).

Diagnosis
Dorsal muscle attachment unsclerotized, setae of D 1 and D 2 significantly longer than others, setae of D 1 nearly reaching to D 2 , setae of D 2 extending beyond D 3 . I-L-5 longish, S-1 and S-2 with a narrow setal interspace between them, S-1 longer than S-2. I-L-6 straight. Ac in a weakly curved line; V 1 separated from V 2 . P-2 with an unobvious ventral projection; P-3 ventral margin slightly convex; the ventral edge of P-4 divided by two long hairs in 2:1:2, sword seta at two thirds of P-4.

Etymology
The Latin prefix 'longi-' means long, ACG of the female of this new species is with a particularly long hind projection.

Description
Female (n = 3) Idiosoma oval, dorsal muscle attachment unsclerotized; O 2 and D 1 at the same level; setae of D 1 and D 2 significantly longer than others, setae of D 1 nearly reaching to D 2 , setae of D 2 extending beyond D 3 ; all slit organs visible, So 1 near the eye capsule, So 2 at the same level as D 1 , So 3 near D 2 , So 4 in front of L 4 , So 5 behind of D 4 (Fig. 9A). Coxal group occupying a half of ventral surface, projections from ACG extending to Cx-IV; Ac in a weakly curved line; V 1 separated from V 2 ; V 3 and V 4 forming a rectangle, V 4 at the same level as the anterior of acetabular plate (Fig. 9B). Palp five-segmented; P-2 with an unobvious ventral projection; P-3 ventral margin slightly convex; P-4 with numerous dorsal hairs, the ventral edge of P-4 divided by two long hairs in 2:1:2, sword seta at two thirds of P-4 (Fig. 9E). I-L-5 longish, S-1 and S-2 with a narrow setal interspace, S-1 longer than S-2. I-L-6 straight (Fig. 10A).

Male
Unknown.

Remarks
The new species Atractides (Atractides) longiprojectus sp. nov. is similar to Atractides inflatipalpis K. Viets, 1950   Diagnosis Male Dorsal muscle attachment unsclerotized. I-L-5 longish, S-1 and S-2 both with blunt tips and with a setal interspace between them; I-L-6 straight. Ac in an obtuse triangle; V 1 separated from V 2 . P-2 and P-3 with a ventral projection respectively, P-4 with numerous dorsal hairs, ventral hairs long, one at the middle of the surface, and the other one at the terminal of lateral edge, sword seta at the middle of P-4.

Female
Ac in a weakly curved line. P-2 with a ventral projection, P-3 ventral margin slightly convex, P-4 divided by two ventral hairs in sectors 1:1:1.

Etymology
The new species is named after the name of the Xianmi National Nature Reserve where the specimens were collected.

Description
Male (n = 4) Idiosoma oval, dorsal muscle attachment unsclerotized; So 1 near eye capsule; So 2 at the same level as D 1 ; So 3 at the same level as D 2 ; So 4 in front of L 4 ; So 5 behind D 4 (Fig. 11A). ACG fused together and with a suture, apodemes of ACG well developed, and reaching to Cx-III; Ac in an obtuse triangle, Ac3 biggest; V 1 separated far from V 2 , V 3 and V 4 forming a rectangle, V 4 at the same level as the anterior part of acetabular plate (Fig. 11B). Palp five-segmented; P-2 and P-3 with a ventral projection respectively, P-4 with numerous dorsal hairs, ventral hairs long, one at the middle of the surface, and the other one at the terminal of lateral edge, sword seta at the middle of P-4 (Fig. 11E). I-L-5 longish, S-1 and S-2 with blunt tips and with a setal interspace between them; I-L-6 straight (Fig. 13A).

Remarks
The new species Atractides (Atractides) xianmiensis sp. nov. is similar to Atractides inflatus Walter, 1925 in the following points: (1) P-2 and P-3 of the male both with a ventral projection respectively; (2) V 1 not fused to V 2 ; (3) S-1 and S-2 both with blunt tips and with a setal interspace between them; (4) Ac in an obtuse triangle in the male and in a weakly curved line in the female. However, A. (A.) xianmiensis differs from A. inflatus in the following aspects: (1) apodemes of ACG in female well developed and reaching to Cx-III in A. (A.) xianmiensis, but not reaching to Cx-III in A. inflatus; (2) I-L-6 straight in A. (A.) xianmiensis, but curved in A. inflatus (Gerecke 2003).

Discussion
Due to the soft body wall and few specialized structures, there are only a few taxonomic features that can be used for species identification in Atractides, which might cause confusion in the taxonomy of these species. So it is of great importance to search for new taxonomic features in Atractides. Jin (1997) mentioned that the relative position of glandularia is different in various groups of water mites, and Ramírez-Sánchez et al. (2016) also mentioned that glandularia in Arrenuridae Thor, 1900 could be potential taxonomic characters. So the relative position of glandularia may be among the new taxonomic features that can be used in the taxonomy of Atractides. For example, the coxae group and palps of Atractides (Atractides) biprojectus sp. nov. and Atractides (Atractides) xianmiensis sp. nov. are similar in morphology, but the relative position of V 3 in relation to V 4 and V 4 in relation to the genital field in A. (A.) biprojectus is significantly different from that in A. (A.) xianmiensis. Therefore, it is suggested to mention the relative position of glandularia on the body wall when describing and drawing species of Atractides.