Li, Hai-Tao ¹ ; Zhan, Bao-Xiang ² ; Hu, Zhan-Yu ³ ; Gu, Xin-Yao ⁴ ; Jin, Dao-Chao ⁵ and Guo, Jian-Jun ⁶

¹Institute of Entomology, Guizhou University; Scientific Observing and Experimental Station of Crop Pests in Guiyang, Ministry of Agricultural and Rural Affairs of the P. R. China, Guiyang 550025, P. R. China.
²Institute of Entomology, Guizhou University; Scientific Observing and Experimental Station of Crop Pests in Guiyang, Ministry of Agricultural and Rural Affairs of the P. R. China, Guiyang 550025, P. R. China.
³Sanqi Medical College, Wenshan University, Wenshan 663099, P. R. China.
⁴College of Animal Sciences, Guizhou University, Guiyang 550025, P. R. China.
⁵Institute of Entomology, Guizhou University; Scientific Observing and Experimental Station of Crop Pests in Guiyang, Ministry of Agricultural and Rural Affairs of the P. R. China, Guiyang 550025, P. R. China.
⁶Institute of Entomology, Guizhou University; Scientific Observing and Experimental Station of Crop Pests in Guiyang, Ministry of Agricultural and Rural Affairs of the P. R. China, Guiyang 550025, P. R. China.

2024 - Volume: 64 Issue: 4 pages: 1149-1162

ZooBank LSID: 018678F9-54D6-4831-9C53-56FE53BB5B4D

Original research

Keywords

Abstract

Introduction

The Cyclothyadinae Lundblad, 1941 includes three species, i.e. Cyclothyas mirabilis Lundblad, 1941 (Burma), Cyclothyas heterospinus (Imamura, 1955) (Japan) and Cyclothyas siskiyouensis I.M. Smith, 1983 (North America) (Lundblad 1941, 1967; Imamura 1955; I.M. Smith 1983). This group has a unique character setting it apart from almost all hydryphantid mites and even the entire water mites, i.e. lateral glandularia surrounded by peripheral sclerites, and connected each other to form a solid ring around the edge of the body (Cook 1974). It is worth noting that the Australian genus, Cyclohydryphantes Lundblad, 1941 (with three species), from another subfamily, Pseudohydryphantinae K. Viets, 1926, also having the peripheral sclerites. But the presence of the middle eye and the number of acetabula can be used to distinguish two groups effectively (Harvey 1987; Smit 1998, 2020).

Among the total of 13 subfamilies known to Hydryphantidae Piersig, 1896, six subfamilies were reported from China (Li et al. 2024). After field surveys, two new species, Cyclothyas longipalpis Li & Jin sp. nov. from Shaanxi and Cyclothyas smiti Li & Guo sp. nov. from Tibet were discovered, which are the first records of the subfamily Cyclothyadinae Lundblad, 1941 for the Chinese fauna. Meanwhile, peripheral sclerites of every specimen were observed in detail.

Material and methods

The collection, preservation of water mites and preparation of slides followed Gu et al. (2021). Specimens were examined and illustrated under a Leica DM3000 microscope. All photographs and illustrations were edited with Adobe Photoshop CS6. All measurements (given in μm) were made with a Nikon Ni-E (with Nikon DS-Ri2 camera). The measurement methods followed Li et al. (2024).

The terminology and abbreviations used were updated from Jin (1997): a.s.l. = above sea level, A₁ = preantennal glandularia, A₂ = postantennal glandularia, ACG = anterior coxal group (Cx-I+Cx-II), C₂ & C₄ = coxoglandularia 2 & 4, Cx-I–IV = coxae I–IV, D₁ –D₄ = dorsoglandularia 1–4, I-L-1–6, etc. = the first–sixth segment of the first leg, etc., L = length, L₁ –L₄ = lateroglandularia 1–4, O₁ = preocularia, O₂ = postocularia, P-1–5 = the first–fifth segments of the palp (from most proximal to most distal), PCG = posterior coxal group (Cx-III+Cx-IV), V₁–V₄ = ventroglandularia 1–4, W = width.

The type series were deposited in the Institute of Entomology, Guizhou University, Guiyang, P. R. China (GUGC).

Systematics

Family Hydryphantidae Piersig, 1896

Subfamily Cyclothyadinae Lundblad, 1941

Genus Cyclothyas Lundblad, 1941

Cyclothyas longipalpis Li & Jin sp. nov. (Figures 1–6)

ZOOBANK: 3A438B37-7CC9-483D-BA9A-FA885A7568CC

Habitat

Brook with organic detritus, gravels and cobblestones.

Material examined

Holotype: adult male, Mount Tai bai, Shaanxi Province, P. R. China (34°05′27″ N, 107°49′54″ E, 1353 m a.s.l.), collected by Ze-Yu Wang, 18-VII-2012. Slide No. SX-HY-2012071801. Paratype: one female, same data as holotype, Slide No. SX-HY-2012071802.

Etymology

The new species is named due to its palp being relatively longer than in other species of the genus.

Diagnosis

Coxal groups with numerous setae; genital field partially enveloped in PCG; acetabula evenly distributed on the lateral side of the acetabular plate; C₄ between PCG and genital field; A₁ close to the first pair of peripheral sclerites but not fused; rostrum thick and short; palp slender.

Male — Genital plate with 24 acetabula and 13 setae on the left, 23 acetabula and 12 setae on the right.

Female — Genital plate with 16 acetabula and 12 setae on the left, 21 acetabula and 11 setae on the right.

Description

Male (n=1) — Membranous integument covered with papillae. In dorsal view: arrangement of D₁ –D₄ arc-shaped; peripheral sclerites connected to form a solid ring around the edge of the idiosoma (Figures 1A, 2A). In ventral view: coxal groups with numerous setae; genital field partially enveloped in PCG, with 24 acetabula and 13 setae on the left, and 23 acetabula and 12 setae on the right, acetabula evenly distributed on the lateral side of the genital plate; C₄ between PCG and genital field; V₁ in front of V₃ (Figures 1B, 2B, 3C). In lateral view: five pairs of peripheral sclerites (beneath integument) tightly connected, each of these sclerites variable in shape; L₂ –L₄ fused with peripheral sclerites but L₁ not (Figures 1E, 2D–J). In frontal view: A₁ close to the first pair of peripheral sclerites but not fused, eye capsules, O₁ and A₂ fused with the first pair of peripheral sclerites (Figures 1C, 2C). In rear view: V₄ fused with the fifth pair of peripheral sclerites (Figures 1D, 2K–L).

Gnathosomal base inverted trapezoidal in ventral view, rostrum thick and short (Figure 1F–G). Chelicera two-segmented, chela with teeth on one side (Figure 1I). Slender palp five-segmented: P-1 long and with a seta near the middle of dorsal margin; P-2 with three setae on dorsal margin and five feathered setae near anterior margin; P-3 with three setae, two on dorsal margin and another on medial side; P-4 terminal with a stout seta on dorsal margin and a seta on ventral margin; P-5 with three fine setae (Figures 1H, 3D).

Legs without swimming setae, first and second pairs stout, fourth pair longer than others; claws of all legs simple (Figure 4).

Female (n=1) — Similar to the male, but genital field larger, left genital plate with 16 acetabula and 12 setae, right with 21 acetabula and 11 setae, acetabula evenly distributed on the lateral side of the genital plate (Figures 3E–F, 5–6).

Measurements

Male (n=1) — Idiosoma L/W 838/582; ACG L 233; PCG L 213; genital plate L 209, gonopore L 158; excretory pore L 20, excretory plate L 56. Gnathosoma L 177, rostrum L 77; chelicera base L 168, chelicera claw L 58; palp segments L/W: P-1–5 43/32, 72/41, 63/36, 122/31, 37/11. Leg segments L: Ⅰ-L-1 52, Ⅰ-L-2 133, Ⅰ-L-3 79, Ⅰ-L-4 102, Ⅰ-L-5 113, Ⅰ-L-6 148; II-L-1 46, II-L-2 151, II-L-3 84, II-L-4 118, II-L-5 133, II-L-6 162; III-L-1 49, III-L-2 114, III-L-3 76, III-L-4 124, III-L-5 146, III-L-6 154; IV-L-1 90, IV-L-2 116, IV-L-3 121, IV-L-4 200, IV-L-5 202, IV-L-6 185.

Female (n=1) — Idiosoma L/W 888/623; ACG L 240; PCG L 228; genital plate L 249, gonopore L 188; excretory pore L 22, excretory plate L 69. Gnathosoma L 197, rostrum L 93; chelicera base L 172, chelicera claw L 64; palp segments L/W: P-1–5 43/36, 72/46, 66/38, 134/30, 45/14. Leg segments L: Ⅰ-L-1 61, Ⅰ-L-2 139, Ⅰ-L-3 86, Ⅰ-L-4 104, Ⅰ-L-5 120, Ⅰ-L-6 140; II-L-1 60, II-L-2 152, II-L-3 87, II-L-4 126, II-L-5 141, II-L-6 159; III-L-1 58, III-L-2 132, III-L-3 81, III-L-4 136, III-L-5 149, III-L-6 165; IV-L-1 100, IV-L-2 131, IV-L-3 131, IV-L-4 213, IV-L-5 209, IV-L-6 184.

Remarks

The female of Cyclothyas longipalpis Li & Jin sp. nov. is similar to C. mirabilis Lundblad, 1941 (male unknown) in two points: (1) genital field partially enveloped in PCG; (2) numerous acetabula evenly distributed on the lateral side of the acetabular plate. However, the present new species differs from C. mirabilis in following aspects: (1) the number of acetabula of Cyclothyas longipalpis Li & Jin sp. nov. is much less than in C. mirabilis; (2) P-4 terminal with a stout seta on dorsal margin in Cyclothyas longipalpis Li & Jin sp. nov., but the terminal of P-4 with a dorsal protrusion in C. mirabilis; (3) gnathosomal base of Cyclothyas longipalpis Li & Jin sp. nov. inverted trapezoidal in ventral view, but rectangular in C. mirabilis (Lundblad 1941, 1967).

Distribution

China (Shaanxi); only known from the locus typicus.

Cyclothyas smiti Li & Guo sp. nov. (Figures 7–10)

ZOOBANK: B475F795-A1C2-40E7-A968-329AC07B5152

Habitat

Brook with organic detritus, gravels and cobblestones (Figure 7).

Material examined

Holotype: adult male, Yigong Town, Bomi County, Xizang Autonomous Region, P. R. China (30°15′06″ N, 94°99′04″ E, 2034 m a.s.l.), collected by Hai-Tao Li and Yu-Lin Zheng, 28-VI-2022. Slide No. XZ-HY-2022062801.

Etymology

This new species is named after Dr Harry Smit (the Netherlands) in appreciation to his brilliant contribution to water mite taxonomy

Diagnosis

Male — Coxal groups with dense setae; genital field completely enveloped in PCG, anterior centre of genital plate not occupied by acetabula, with 17 acetabula and 10 setae on the left, and with 15 acetabula and 10 setae on the right; C₄ fused with acetabular plate; eye capsules, A₁ , O₁ and A₂ fused with the first pair of peripheral sclerites together; rostrum long; palp stocky.

Description

Male (n=1) — Papillae scattered on the membranous integument. In dorsal view: arrangement of D₁ –D₄ arc-shaped; peripheral sclerites connected each other, and forming a solid ring around the edge of the body (Figures 8A, 9A). In ventral view: coxal groups with dense setae; genital field completely enveloped in PCG, anterior centre of acetabular plate not occupied by acetabula, with 17 acetabula and 10 setae on the left, and with 15 acetabula and 10 setae on the right; C₄ fused with genital plate on one side but free on the other side (Figures 3A, 8B, 9B). In lateral view: five pairs of peripheral sclerites (beneath integument) tightly connected, each of these sclerites variable in shape; all lateroglandularia fused with peripheral sclerites except L₁ (Figures 8E, 9D–J). In frontal view: eye capsules, A₁ , O₁ and A₂ fused with the first pair of peripheral sclerites (Figures 8C, 9C). In rear view: V₄ fused with the fifth pair of peripheral sclerites (Figures 8D, 9K–L).

Anterior portion of gnathosomal base slightly wider than posterior in ventral view, rostrum long (Figure 8F–G). Chelicera base slender, chela with teeth on one side (Figure 8I). Palp stocky: P-1 with a seta at the middle portion of dorsal margin; P-2 with three setae on dorsal margin and five feathered setae near anterior margin; P-3 with three feathered setae, two on dorsal margin and another on inner medial surface; P-4 short, terminal with a stout seta on dorsal margin and a long seta on ventral margin (Figures 3B, 8H).

Legs without swimming setae, the fourth pair longer than others; claws of all legs simple (Figure 10).

Female — Not collected.

Measurements

Male (n=1) — Idiosoma L/W 615/453; ACG L 206; PCG L 174; genital plate L 160, gonopore L 88; excretory pore L 10, excretory plate L 42. Gnathosoma L 189, rostrum L 79; chelicera base L 147, chelicera claw L 45; palp segments L/W: P-1–5 22/37, 73/50, 61/51, 91/32, 36/13. Leg segments L: Ⅰ-L-1 44, Ⅰ-L-2 101, Ⅰ-L-3 57, Ⅰ-L-4 80, Ⅰ-L-5 92, Ⅰ-L-6 108; II-L-1 41, II-L-2 107, II-L-3 64, II-L-4 97, II-L-5 104, II-L-6 125; III-L-1 44, III-L-2 93, III-L-3 56, III-L-4 98, III-L-5 106, III-L-6 120; IV-L-1 96, IV-L-2 105, IV-L-3 92, IV-L-4 132, IV-L-5 129, IV-L-6 118.

Remarks

Cyclothyas smiti Li & Guo sp. nov. differs from all other species by following characteristics, i.e. the setae on coxal groups extremely dense, genital field completely enveloped in PCG, and C₄ fused with acetabular plate (Imamura 1955; Lundblad 1967; I.M. Smith 1983).

Distribution

China (Xizang); only known from the locus typicus.

Discussion

After comparing all species in Cyclothyadinae, high similarities were found in some important characters, e.g. overall dorsal characters, chaetotaxy of palp, which brought certain difficulties to the species identification. In order to obtain more information to make the identified results more objective, our sight was focused on the peripheral sclerites, whose characters are very rare in the hydryphantid mites. It is regrettable that less attention was received before. Through a detailed examination of the two new species involved in this article, we had found the following points: (1) both species with five pairs of peripheral sclerites; (2) all shapes of peripheral sclerites variable, not only manifested between different individuals, but also on the left and right sides of the same individual; (3) A₁ separated with the first pair of peripheral sclerites in Cyclothyas longipalpis Li & Jin sp. nov., but fused in Cyclothyas smiti Li & Guo sp. nov. Therefore, we could make a judgment that the shape of each peripheral sclerites cannot be used for species identification, but the fused situation of the first pair of peripheral sclerites and glandularia could provide a basis.

Acknowledgements

We are indebted to Ze-Yu Wang (P. R. China) & Yu-Lin Zheng (College of Pharmacy, Dali University, P. R. China) for specimen collection. Furthermore, we all appreciate deeply Dr. Harry Smit (Naturalis Biodiversity Center, Leiden, the Netherlands) for providing literature, and Yu-Hao Zhang (Institute of Entomology, Guizhou University, P. R. China) & Lan Jia (Institute of Entomology, Guizhou University, P. R. China) for providing technical assistance. This research was supported by National Natural Science Foundation of China (32260125), and Guizhou Provincial Science and Technology Projects (Qiankehe Pingtai Rencai-GCC [2022]029-1).

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