# Two species representing a rare genus Sinaxonopsis (Acari, Hydrachnidiae, Aturidae) from China, with discussion of some taxonomic features

Lan Jia, Hai-Tao Li, Jian-Jun Guo

► To cite this version:

Lan Jia, Hai-Tao Li, Jian-Jun Guo. Two species representing a rare genus Sinaxonopsis (Acari, Hydrachnidiae, Aturidae) from China, with discussion of some taxonomic features. Acarologia, 2024, 64 (2), pp.554-574. 10.24349/orqe-mqh. hal-04582869

HAL Id: hal-04582869

https://hal.science/hal-04582869

Submitted on 22 May 2024

HAL is a multi-disciplinary open access
archive for the deposit and dissemination of sci-
entific research documents, whether they are pub-
lished or not. The documents may come from
teaching and research institutions in France or
abroad, or from public or private research centers.

L'archive ouverte pluridisciplinaire HAL, est
destinée au dépôt et à la diffusion de documents
scientifiques de niveau recherche, publiés ou non,
émanant des établissements d'enseignement et de
recherche français ou étrangers, des laboratoires
publics ou privés.

<figure><img src="image_1.png" /></figure>

Distributed under a Creative Commons Attribution 4.0 International License
Acarologia

Open Science
in Acarology

# Two species representing a rare genus *Sinaxonopsis* (Acari, Hydrachnidiae, Aturidae) from China, with discussion of some taxonomic features

Lan Jia IDª, Hai-Tao Li IDª, Jian-Jun Guo IDª

## Original research

### ABSTRACT

*Sinaxonopsis* Yi & Jin, 2012 was erected based on *S. unicrus* from China. In this paper, one more species new to science, *Sinaxonopsis hainanensis* sp. nov. is described from China. *Sinaxonopsis unicrus* Yi & Jin, 2012, is redescribed with more details, including information on the glandularia and patches of the large posterior dorsal plate, among others. Using scanning electron microscope (SEM) images, this work has clarified that the dorsoglandularia $D_4$ do indeed have glands, and that the phenomenon of missing glands is absent on the dorsal plate of *Sinaxonopsis*, which occurs in some genera of Aturidae. Sixteen pairs of glandularia and two pairs of ocularia of *Sinaxonopsis* are consistent with the common patterns in water mites.

**Keywords** Axonopsinae; Chinese fauna; glandularia; ultrastructure; water mites

**Zoobank** http://zoobank.org/27F5A3C9-FC58-47CA-AE05-6309DF752E46

### Introduction

Aturidae Thor, 1900 is a family of water mites that is widely distributed and species-diverse. Members of this family have small, heavily sclerotized, and dorsoventrally flattened bodies (Gerecke 2014; Smit 2020). A rare genus, *Sinaxonopsis* Yi & Jin, 2012, was established on the following features: (1) dorsal shields formed by a large posterior plate and a pair of anterior platelets; (2) a relatively bigger and plumper body than other aturid mites (Yi and Jin 2012). Until now, only three species, *Sinaxonopsis unicrus* Yi & Jin, 2012 (from China), *Sinaxonopsis laosensis* Pešić & Smit, 2016 (from Laos), *Sinaxonopsis siamicus* Smit, 2016 (from Thailand), have been recorded worldwide (Yi and Jin 2012; Pešić and Smit 2016; Smit 2016).

Both presence and position of glandularia are important and highly variable features in water mites (Wiles 1997; Jin 1997; Shatrov 2008); this variation is remarkable in Aturidae since, for example, some species of *Aturus* Kramer, 1875 lack the gland of $D_4$, and the genus *Albia* Thon, 1899 lacks of $V_1$ (Wiles 1991; Kim and Chung 1993, 1995; Smit 2017). However, glandularia has received poor attention in *Sinaxonopsis*, and clarification of glandularia including their quantity, distribution and condition is significant in order to establish the taxonomic status of this group. In addition, as Aturidae species are small in size, distinguishing features are difficult to observe unless specimens are properly mounted, especially in this rare group of *Sinaxonopsis*, which make species identification much difficult.

In this paper, a Chinese species new to science, *Sinaxonopsis hainanensis* sp. nov., is described and illustrated in detail, focusing on the quantity, position, and condition of

Received 03 February 2024

Accepted 05 April 2024

Published 23 April 2024

Corresponding author

Jian-Jun Guo ID: jjguo@gzu.edu.cn

Academic editor

Auger, Philippe

https://doi.org/10.24349/orqe-mqh

ISSN 0044-586X (print)

ISSN 2107-7207 (electronic)

<figure><img src="image_1.png" /></figure>

Jia L. et al.

Licensed under
Creative Commons CC-BY 4.0

OPEN ACCESS

<footnote>ªInstitute 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.</footnote>
Acarologia

Open Science
in Acarology

# Two species representing a rare genus *Sinaxonopsis* (Acari, Hydrachnidiae, Aturidae) from China, with discussion of some taxonomic features

Lan Jia IDª, Hai-Tao Li IDª, Jian-Jun Guo IDª

## Original research

### ABSTRACT

*Sinaxonopsis* Yi & Jin, 2012 was erected based on *S. unicrus* from China. In this paper, one more species new to science, *Sinaxonopsis hainanensis* sp. nov. is described from China. *Sinaxonopsis unicrus* Yi & Jin, 2012, is redescribed with more details, including information on the glandularia and patches of the large posterior dorsal plate, among others. Using scanning electron microscope (SEM) images, this work has clarified that the dorsoglandularia $D_4$ do indeed have glands, and that the phenomenon of missing glands is absent on the dorsal plate of *Sinaxonopsis*, which occurs in some genera of Aturidae. Sixteen pairs of glandularia and two pairs of ocularia of *Sinaxonopsis* are consistent with the common patterns in water mites.

**Keywords** Axonopsinae; Chinese fauna; glandularia; ultrastructure; water mites

**Zoobank** http://zoobank.org/27F5A3C9-FC58-47CA-AE05-6309DF752E46

## Introduction

Aturidae Thor, 1900 is a family of water mites that is widely distributed and species-diverse. Members of this family have small, heavily sclerotized, and dorsoventrally flattened bodies (Gerecke 2014; Smit 2020). A rare genus, *Sinaxonopsis* Yi & Jin, 2012, was established on the following features: (1) dorsal shields formed by a large posterior plate and a pair of anterior platelets; (2) a relatively bigger and plumper body than other aturid mites (Yi and Jin 2012). Until now, only three species, *Sinaxonopsis unicrus* Yi & Jin, 2012 (from China), *Sinaxonopsis laosensis* Pešić & Smit, 2016 (from Laos), *Sinaxonopsis siamicus* Smit, 2016 (from Thailand), have been recorded worldwide (Yi and Jin 2012; Pešić and Smit 2016; Smit 2016).

Both presence and position of glandularia are important and highly variable features in water mites (Wiles 1997; Jin 1997; Shatrov 2008); this variation is remarkable in Aturidae since, for example, some species of *Aturus* Kramer, 1875 lack the gland of $D_4$, and the genus *Albia* Thon, 1899 lacks of $V_1$ (Wiles 1991; Kim and Chung 1993, 1995; Smit 2017). However, glandularia has received poor attention in *Sinaxonopsis*, and clarification of glandularia including their quantity, distribution and condition is significant in order to establish the taxonomic status of this group. In addition, as Aturidae species are small in size, distinguishing features are difficult to observe unless specimens are properly mounted, especially in this rare group of *Sinaxonopsis*, which make species identification much difficult.

In this paper, a Chinese species new to science, *Sinaxonopsis hainanensis* sp. nov., is described and illustrated in detail, focusing on the quantity, position, and condition of

Received 03 February 2024

Accepted 05 April 2024

Published 23 April 2024

Corresponding author

Jian-Jun Guo ID: jjguo@gzu.edu.cn

Academic editor

Auger, Philippe

https://doi.org/10.24349/orqe-mqh

ISSN 0044-586X (print)

ISSN 2107-7207 (electronic)

<figure><img src="image_2.png" /></figure>

Jia L. et al.

Licensed under
Creative Commons CC-BY 4.0

OPEN ACCESS

<footnote>ªInstitute 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.</footnote>
glandularia. We achieved this through the images of camera, optical microscope, and scanning electron microscope (SEM). Finally, the shape and color of the patches on the large posterior plate of species in *Sinaxonopsis* were compared between *S. unicucrus* and *S. hainanensis* sp. nov., and examined whether they are stable within species, or obviously different between species, and whether they can be used, besides glandularia information, as diagnostic features at the species level in this genus.

## Material and methods

The collection, preservation of specimens and slide mounting follow Gu *et al.* (2020). Canon 5D Mark IV digital camera (Canon, Japan) in conjunction with a Mitutoyo Plan NIR 10x lens (Mitutoyo, Japan) and a Godox MF12 flash as the light source (Godox, China) were used to generate the images of water mites. Leica DM3000 microscope (Leica, Germany) was used to identify and illustrate the specimens. Scanning Electron Microscope (SEM, Nikon, Japan) processing and photography follow Li *et al.* (2022). All photographs and illustrations were edited with Adobe Photoshop CS6. Measurements were taken using a Nikon Ni-E microscope with a Nikon DS-Ri2 camera (Nikon, Japan) and are given in micrometers (μm).

All terminology and abbreviations in this article were taken and updated from Jin (1997): a.s.l. = above sea level, $A_1$ = preantennal glandularia, $A_2$ = postantennal glandularia, $A_2g$ = glands of the $A_2$, $A_2s$ = seta of the $A_2$, $C_2$ and $C_4$ = coxoglandularia 2 and 4, Cx-I-Cx-IV = coxe I-IV, $D_1-D_4$ = dorsoglandularia 1-4, $D_1g-D_4g$ = glands of the $D_1-D_4$, $D_1s-D_4s$ = setae of the $D_1-D_4$, dL = dorsal length, I-L-1-6, so forth. = first to sixth segment of the first leg, so forth., L = length, $L_1-L_4$ = latero-glandularia 1-4, $L_1g-L_4g$ = glands of the $L_1-L_4$, $L_1s-L_4s$ = setae of the $L_1-L_4$, $O_1$ = preocularia, $O_2$ = postocularia, P-1-5 = first to fifth segments of the palp (from proximal to distal), $V_1-V_4$ = ventroglandularia 1-4, vL = ventral length, W = width.

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

## Systematics

**Family Aturidae Thor, 1900**

**Subfamily Axonopsinae K. Viets, 1929**

**Genus Sinaxonopsis Yi & Jin, 2012**

**Sinaxonopsis unicucrus Yi & Jin, 2012**

(Figures 1–12)

**Habitat** — Slow flow of stream, many pebbles covered by mosses at the bottom.

**Material examined** — 3♂, 9♀, Baotianman National Nature Reserve, Nanyang City, Henan Province, P.R. China (33°46′73″ N, 111°89′98″ E, 555 m a.s.l.), collected by Hai-Tao Li, 11-VI-2021. Slides No. HN-AT-2021061101–2021061112.

**Description** — *Male* (n=3). Idiosoma oval, slightly truncate at anterior end; dorsal and ventral shield present and this last with a conspicuous concavity (Figures 1 and 2). In dorsal view (Figures 1A and 2A): dorsal shield formed by one pair of anterior platelets and a large posterior plate; anterior platelets bearing the lateral eyes, $O_2$, $A_2$ and $D_1$; posterior plate bearing six pairs of glandularia ($D_2-D_4$, $L_2-L_3$ and $V_4$), setae of $A_2$, $D_1-D_3$, $L_2-L_3$ all far away from glands, numerous longitudinal stripes, and two eyepatch-like violet spots, of which the anterior one is larger and covering almost 1/3 of the entire dorsal shield, and the posterior one situated at the end of the body; excretory pore protruding, located at the posterior end of the dorsal shield. In ventral view (Figures 1B and 2B): coxal plate single; tips of Cx-I not extending beyond the frontal margin; Cx-IV with distinct suture lines; suture line of Cx-III/IV ending medially to IV-L insertions and not reaching the medial line; $C_2$ located at the posterior margin of Cx-II
glandularia. We achieved this through the images of camera, optical microscope, and scanning electron microscope (SEM). Finally, the shape and color of the patches on the large posterior plate of species in *Sinaxonopsis* were compared between *S. unicucrus* and *S. hainanensis* sp. nov., and examined whether they are stable within species, or obviously different between species, and whether they can be used, besides glandularia information, as diagnostic features at the species level in this genus.

## Material and methods

The collection, preservation of specimens and slide mounting follow Gu *et al.* (2020). Canon 5D Mark IV digital camera (Canon, Japan) in conjunction with a Mitutoyo Plan NIR 10x lens (Mitutoyo, Japan) and a Godox MF12 flash as the light source (Godox, China) were used to generate the images of water mites. Leica DM3000 microscope (Leica, Germany) was used to identify and illustrate the specimens. Scanning Electron Microscope (SEM, Nikon, Japan) processing and photography follow Li *et al.* (2022). All photographs and illustrations were edited with Adobe Photoshop CS6. Measurements were taken using a Nikon Ni-E microscope with a Nikon DS-Ri2 camera (Nikon, Japan) and are given in micrometers (μm).

All terminology and abbreviations in this article were taken and updated from Jin (1997): a.s.l. = above sea level, $A_1$ = preantennal glandularia, $A_2$ = postantennal glandularia, $A_2g$ = glands of the $A_2$, $A_2s$ = seta of the $A_2$, $C_2$ and $C_4$ = coxoglandularia 2 and 4, Cx-I-Cx-IV = coxe I-IV, $D_1-D_4$ = dorsoglandularia 1-4, $D_1g-D_4g$ = glands of the $D_1-D_4$, $D_1s-D_4s$ = setae of the $D_1-D_4$, dL = dorsal length, I-L-1-6, so forth. = first to sixth segment of the first leg, so forth., L = length, $L_1-L_4$ = latero-glandularia 1-4, $L_1g-L_4g$ = glands of the $L_1-L_4$, $L_1s-L_4s$ = setae of the $L_1-L_4$, $O_1$ = preocularia, $O_2$ = postocularia, P-1-5 = first to fifth segments of the palp (from proximal to distal), $V_1-V_4$ = ventroglandularia 1-4, vL = ventral length, W = width.

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

## Systematics

**Family Aturidae Thor, 1900**

**Subfamily Axonopsinae K. Viets, 1929**

**Genus Sinaxonopsis Yi & Jin, 2012**

**Sinaxonopsis unicucrus Yi & Jin, 2012**

(Figures 1–12)

**Habitat** — Slow flow of stream, many pebbles covered by mosses at the bottom.

**Material examined** — 3♂, 9♀, Baotianman National Nature Reserve, Nanyang City, Henan Province, P.R. China (33°46′73″ N, 111°89′98″ E, 555 m a.s.l.), collected by Hai-Tao Li, 11-VI-2021. Slides No. HN-AT-2021061101-2021061112.

**Description** — *Male* (n=3). Idiosoma oval, slightly truncate at anterior end; dorsal and ventral shield present and this last with a conspicuous concavity (Figures 1 and 2). In dorsal view (Figures 1A and 2A): dorsal shield formed by one pair of anterior platelets and a large posterior plate; anterior platelets bearing the lateral eyes, $O_2$, $A_2$ and $D_1$; posterior plate bearing six pairs of glandularia ($D_2-D_4$, $L_2-L_3$ and $V_4$), setae of $A_2$, $D_1-D_3$, $L_2-L_3$ all far away from glands, numerous longitudinal stripes, and two eyepatch-like violet spots, of which the anterior one is larger and covering almost 1/3 of the entire dorsal shield, and the posterior one situated at the end of the body; excretory pore protruding, located at the posterior end of the dorsal shield. In ventral view (Figures 1B and 2B): coxal plate single; tips of Cx-I not extending beyond the frontal margin; Cx-IV with distinct suture lines; suture line of Cx-III/IV ending medially to IV-L insertions and not reaching the medial line; $C_2$ located at the posterior margin of Cx-II
<figure><img src="image_2.png" /><figcaption>**Figure 1** *Sinaxonopsis unicucrus* Yi & Jin, 2012, A–C, G, ♂, (HN-AT-202106110501); D–F, ♀, (HN-AT-202106110503). Optical microscope photographs: A – Dorsal view; B – Ventral view; C – Lateral view; D – Dorsal view; E– Ventral view; F – Lateral view; G – Chelicerae. Scale bars = 100 µm.</figcaption></figure>
<figure><img src="image_3.png" /><figcaption>**Figure 1** *Sinaxonopsis unicucrus* Yi & Jin, 2012, A–C, G, ♂, (HN-AT-202106110501); D–F, ♀, (HN-AT-202106110503). Optical microscope photographs: A – Dorsal view; B – Ventral view; C – Lateral view; D – Dorsal view; E– Ventral view; F – Lateral view; G – Chelicerae. Scale bars = 100 µm.</figcaption></figure>
<figure><img src="image_3.png" /><figcaption>**Figure 2** *Sinaxonopsis unicucrus* Yi & Jin, 2012, A–C, ♂, (HN-AT-202106110502); D–E, ♀, (HN-AT-202106110504). A – Dorsal view; B – Ventral view; C – Lateral view; D – Dorsal view; E– Ventral view. Scale bars = 100 µm.</figcaption></figure>
<figure><img src="image_4.png" /><figcaption>**Figure 2** *Sinaxonopsis unicucrus* Yi & Jin, 2012, A–C, ♂, (HN-AT-202106110502); D–E, ♀, (HN-AT-202106110504). A – Dorsal view; B – Ventral view; C – Lateral view; D – Dorsal view; E– Ventral view. Scale bars = 100 µm.</figcaption></figure>
<figure><img src="image_4.png" /><figcaption>**Figure 3** *Sinaxonopsis unicrus* Yi & Jin, 2012, ♂ (HN-AT-202106110511), SEM photographs: A –Genital field; B – Gnathosoma; C – Coxoglandularia 2 (*C*₂); D – Ventroglandularia 3 (*V*₃); E – Coxoglandularia 4 (*C*₄).</figcaption></figure>

where suture line of Cx-II/III convex latero-posteriorly (Figure 3C); Cx-IV well extended posteriorly with round posterior margin and laterally with a ridge; IV-L basal segmental fossa without ankles. Genital field (Figure 3A) triangular and slightly depressed, fused to ventral shield; gonopore elongated and somewhat projecting, anteriorly with several genital hairs; with multiple acetabula located on both sides of gonopore to the posterolateral area of idiosoma; *C*₄ located at either side of posterior part of genital pore (Figure 3E).

Gnathosoma with pointed dorsal apodemed, ventral apodeme blunt and almost equal in length, with two pairs of setae at the tip of the rostrum (Figure 3B). Cheliceral two-segmented, chelicera claw curved knife in shape (Figure 1G).

Palp five-segmented (Figure 4); P-1 with one dorsal seta on the inner side; P-2 with two dorsal setae on the outer side, three dorsal setae on the inner side; P-3 short, with three dorsal
<figure><img src="image_5.png" /><figcaption>**Figure 3** *Sinaxonopsis unicrus* Yi & Jin, 2012, ♂ (HN-AT-202106110511), SEM photographs: A –Genital field; B – Gnathosoma; C – Coxoglandularia 2 (*C*₂); D – Ventroglandularia 3 (*V*₃); E – Coxoglandularia 4 (*C*₄).</figcaption></figure>

where suture line of Cx-II/III convex latero-posteriorly (Figure 3C); Cx-IV well extended posteriorly with round posterior margin and laterally with a ridge; IV-L basal segmental fossa without ankles. Genital field (Figure 3A) triangular and slightly depressed, fused to ventral shield; gonopore elongated and somewhat projecting, anteriorly with several genital hairs; with multiple acetabula located on both sides of gonopore to the posterolateral area of idiosoma; C₄ located at either side of posterior part of genital pore (Figure 3E).

Gnathosoma with pointed dorsal apodemed, ventral apodeme blunt and almost equal in length, with two pairs of setae at the tip of the rostrum (Figure 3B). Cheliceral two-segmented, chelicera claw curved knife in shape (Figure 1G).

Palp five-segmented (Figure 4); P-1 with one dorsal seta on the inner side; P-2 with two dorsal setae on the outer side, three dorsal setae on the inner side; P-3 short, with three dorsal
<figure><img src="image_5.png" /><figcaption>**Figure 4** *Sinaxonopsis unicucrus* Yi & Jin, 2012, ♂ (HN-AT-202106110511), SEM photographs: A – Outer side of Palp; B – Detail of outer side of Palp-4–5; C – Inner side of Palp; D – Detail of inner side of Palp-4–5.</figcaption></figure>

<figure><img src="image_6.png" /><figcaption>**Figure 5** *Sinaxonopsis unicucrus* Yi & Jin, 2012, ♂ (HN-AT-202106110511), SEM photographs: A – Outer side of I-Leg-1–6; B – Inner side of I-Leg-1–6; C – Outer side of II-Leg-3–6; D – Inner side of II-Leg-1–6.</figcaption></figure>
<figure><img src="image_6.png" /><figcaption>**Figure 4** *Sinaxonopsis unicucrus* Yi & Jin, 2012, ♂ (HN-AT-202106110511), SEM photographs: A – Outer side of Palp; B – Detail of outer side of Palp-4–5; C – Inner side of Palp; D – Detail of inner side of Palp-4–5.</figcaption></figure>

<figure><img src="image_7.png" /><figcaption>**Figure 5** *Sinaxonopsis unicucrus* Yi & Jin, 2012, ♂ (HN-AT-202106110511), SEM photographs: A – Outer side of I-Leg-1–6; B – Inner side of I-Leg-1–6; C – Outer side of II-Leg-3–6; D – Inner side of II-Leg-1–6.</figcaption></figure>
<figure><img src="image_7.png" /><figcaption>**Figure 6** *Sinaxonopsis unicucrus* Yi & Jin, 2012, ♂ (HN-AT-202106110511), SEM photographs: A – Outer side of III-Leg-1-6; B – Detail of outer side of III-Leg-5; C – Inner side of III-Leg-1-6; D – Detail of inner side of III-Leg-5.</figcaption></figure>

<figure><img src="image_8.png" /><figcaption>**Figure 7** *Sinaxonopsis unicucrus* Yi & Jin, 2012, ♂ (HN-AT-202106110511), SEM photographs: A – Outer side of IV-Leg-2-6; B – Detail of outer side of IV-Leg-5; C – Inner side of IV-Leg-1-6; D – Detail of inner side of IV-Leg-5.</figcaption></figure>

setae on the outer side; P-4 longest, basally and distally concave on venter, medially convex with a pair of long setae.
<figure><img src="image_8.png" /><figcaption>**Figure 6** *Sinaxonopsis unicucrus* Yi & Jin, 2012, ♂ (HN-AT-202106110511), SEM photographs: A – Outer side of III-Leg-1-6; B – Detail of outer side of III-Leg-5; C – Inner side of III-Leg-1-6; D – Detail of inner side of III-Leg-5.</figcaption></figure>

<figure><img src="image_9.png" /><figcaption>**Figure 7** *Sinaxonopsis unicucrus* Yi & Jin, 2012, ♂ (HN-AT-202106110511), SEM photographs: A – Outer side of IV-Leg-2-6; B – Detail of outer side of IV-Leg-5; C – Inner side of IV-Leg-1-6; D – Detail of inner side of IV-Leg-5.</figcaption></figure>

setae on the outer side; P-4 longest, basally and distally concave on venter, medially convex with a pair of long setae.
<figure><img src="image_9.png" /><figcaption>**Figure 8** *Sinaxonopsis unicucrus* Yi & Jin, 2012, ♂ (HN-AT-202106110511), SEM photographs: A - Claw of I-Leg; B - Claw of II-Leg; C - Claw of III-Leg; D - Claw of IV-Leg.</figcaption></figure>

Legs six-segmented; ventral margin of I-L-6 and II-L-6 with dense small setae; claws with one dorsal and one ventral clawlet (Figures 5, 8A and 8B); III-L and IV-L exhibiting significant sexual dimorphism; III-L-4 with four large setae at the end of the outer side, two of which are blunt and cylindrical; III-L-5 ending in one large cylindrical seta curved towards the ventral surface on the outer side; III-L-6 ventrally curved, with a pair of heteromorphic claws (Figures 6 and 8C). IV-L-4 with a developed irregular protrusion and four large setae at the end of the outer side, the two last of which are blunt and cylindrical; IV-L-5 with one cylindrical seta at the end; lateral margin with a row of setae neatly arranged; IV-L-6 terminally enlarged, with a particularly well-developed dorsal process; features of the claws the same as I-L and II-L (Figures 7 and 8A).

*Female* (n=9). Characteristics almost similar to male, except for the following: from the lateral view, the ventral margin of idiosoma straight, without concavity (Figure 1F); genital field well developed and situated at the ventral end of the body (Figures 1E, 2E and 10A); gonopore large and terminally located (Figure 10B); $V_3$ more anteriorly located, and lateral to the genital field (Figures 10A and 10E), and $C_4$ located anteriorly on both sides of the gonopore (Figure 10C). III-L-4 terminally with one long swimming seta and several additional setae; III-L-5 with two long swimming setae and two short pointed setae (Figures 12A and 12B); IV-L-4 terminally with one long swimming seta and six large additional setae; IV-L-5 terminally with two long swimming setae and five large additional setae, and with a row of setae inserted on lateral margins (Figures 12C and 12D).

**Measurements** — *Male* (n=3). Idiosoma L/W 521 (521–566)/442 (442–497); anterior platelets L/W 221 (221–222)/78 (78–89), posterior plate L/W 407 (407–444)/411 (411–446); gnathosomal bay L 136 (136–152); gonopore L/W 71 (71–72)/21 (21–24), ratio 3.36 (3.0–3.36). gnathosoma vL 127 (127–139), dL 145 (145–146); chelicera total L 141 (141–168), claw L 50 (50–52), basal segment L 107 (107–123), L basal segment/claw ratio 2.14 (2.14–2.45). Palp: dL/H, dL/H ratio: P-1, 42 (42–43)/27 (27–29), 1.44 (1.44–1.59); P-2, 83 (83–84)/29 (29–30),
<figure><img src="image_10.png" /><figcaption>**Figure 8** *Sinaxonopsis unicucrus* Yi & Jin, 2012, ♂ (HN-AT-202106110511), SEM photographs: A - Claw of I-Leg; B - Claw of II-Leg; C - Claw of III-Leg; D - Claw of IV-Leg.</figcaption></figure>

Legs six-segmented; ventral margin of I-L-6 and II-L-6 with dense small setae; claws with one dorsal and one ventral clawlet (Figures 5, 8A and 8B); III-L and IV-L exhibiting significant sexual dimorphism; III-L-4 with four large setae at the end of the outer side, two of which are blunt and cylindrical; III-L-5 ending in one large cylindrical seta curved towards the ventral surface on the outer side; III-L-6 ventrally curved, with a pair of heteromorphic claws (Figures 6 and 8C). IV-L-4 with a developed irregular protrusion and four large setae at the end of the outer side, the two last of which are blunt and cylindrical; IV-L-5 with one cylindrical seta at the end; lateral margin with a row of setae neatly arranged; IV-L-6 terminally enlarged, with a particularly well-developed dorsal process; features of the claws the same as I-L and II-L (Figures 7 and 8A).

*Female* (n=9). Characteristics almost similar to male, except for the following: from the lateral view, the ventral margin of idiosoma straight, without concavity (Figure 1F); genital field well developed and situated at the ventral end of the body (Figures 1E, 2E and 10A); gonopore large and terminally located (Figure 10B); $V_3$ more anteriorly located, and lateral to the genital field (Figures 10A and 10E), and $C_4$ located anteriorly on both sides of the gonopore (Figure 10C). III-L-4 terminally with one long swimming seta and several additional setae; III-L-5 with two long swimming setae and two short pointed setae (Figures 12A and 12B); IV-L-4 terminally with one long swimming seta and six large additional setae; IV-L-5 terminally with two long swimming setae and five large additional setae, and with a row of setae inserted on lateral margins (Figures 12C and 12D).

**Measurements** — *Male* (n=3). Idiosoma L/W 521 (521–566)/442 (442–497); anterior platelets L/W 221 (221–222)/78 (78–89), posterior plate L/W 407 (407–444)/411 (411–446); gnathosomal bay L 136 (136–152); gonopore L/W 71 (71–72)/21 (21–24), ratio 3.36 (3.0–3.36). gnathosoma vL 127 (127–139), dL 145 (145–146); chelicera total L 141 (141–168), claw L 50 (50–52), basal segment L 107 (107–123), L basal segment/claw ratio 2.14 (2.14–2.45). Palp: dL/H, dL/H ratio: P-1, 42 (42–43)/27 (27–29), 1.44 (1.44–1.59); P-2, 83 (83–84)/29 (29–30),
<figure><img src="image_10.png" /><figcaption>**Figure 9** *Sinaxonopsis unicrus* Yi & Jin, 2012, ♀ (HN-AT-202106110512), SEM photographs: A – Dorsal view; B – Preantennal glandularia (*A*₁), Preocularia (*O*₁); C – Postantennal glandularia (*A*₂), Postocularia (*O*₂), Dorsoglandularia 1 (*D*₁); D – Dorso-glandularia 2 (*D*₂); E – Dorsoglandularia 3 (*D*₃), Dorsoglandularia 4 (*D*₄); F – Ventro-glandularia 4 (*V*₄); G – Lateroglandularia 1 (*L*₁); H – Lateroglandularia 2 (*L*₂); I – Lateroglandularia 3 (*L*₃).</figcaption></figure>

2.88 (2.80–2.88); P-3, 45 (42–45)/25 (25–26), 1.79 (1.61–1.79); P-4, 120 (120–124)/23 (21–23), 5.32 (5.32–5.83); P-5, 46 (46–47)/17 (17–18), 2.61 (2.61–2.79); Legs: dL of I-L-1-6: 57 (57–58), 59 (55–59), 78 (78–83), 116 (116–119), 143 (143–144), 149 (149–156); dL of II-L-1-6: 56 (56–59), 60 (60–62), 88 (88–91), 131 (131–133), 164 (161–164), 170 (166–170); dL of III-L-1-6: 78 (78–80), 61 (56–61), 94 (94–106), 102 (99–102), 195 (195–198), 182 (177–182); dL of IV-L-1-6: 98 (98–123), 134 (122–134), 192 (192–207), 103 (103–113), 230 (225–230), 198 (198–206).

*Female* (n=9). Idiosoma L/W 572–654/463–525; anterior platelets L/W 217–238/76–84, posterior plate L/W 455–507/430–489; gnathosomal bay L 159–171, gnathosoma vL 122–146, dL 146–158. Palp: dL of P-1-5, 47–51, 82–94, 41–45, 114–125, 44–45. Legs: dL of I-L-1-6: 47–56, 50–56, 63–70, 94–105, 113–122, 118–134; dL of II-L-1-6: 51–53, 52–57, 69–73,108–111, 131–144, 138–146; dL of III-L-1-6: 56–63, 54–55, 72–74, 107–116, 138–141, 143–145;
<figure><img src="image_11.png" /><figcaption>**Figure 9** *Sinaxonopsis unicrus* Yi & Jin, 2012, ♀ (HN-AT-202106110512), SEM photographs: A – Dorsal view; B – Preantennal glandularia (*A*₁), Preocularia (*O*₁); C – Postantennal glandularia (*A*₂), Postocularia (*O*₂), Dorsoglandularia 1 (*D*₁); D – Dorso-glandularia 2 (*D*₂); E – Dorsoglandularia 3 (*D*₃), Dorsoglandularia 4 (*D*₄); F – Ventro-glandularia 4 (*V*₄); G – Lateroglandularia 1 (*L*₁); H – Lateroglandularia 2 (*L*₂); I – Lateroglandularia 3 (*L*₃).</figcaption></figure>

2.88 (2.80–2.88); P-3, 45 (42–45)/25 (25–26), 1.79 (1.61–1.79); P-4, 120 (120–124)/23 (21–23), 5.32 (5.32–5.83); P-5, 46 (46–47)/17 (17–18), 2.61 (2.61–2.79); Legs: dL of I-L-1-6: 57 (57–58), 59 (55–59), 78 (78–83), 116 (116–119), 143 (143–144), 149 (149–156); dL of II-L-1-6: 56 (56–59), 60 (60–62), 88 (88–91), 131 (131–133), 164 (161–164), 170 (166–170); dL of III-L-1-6: 78 (78–80), 61 (56–61), 94 (94–106), 102 (99–102), 195 (195–198), 182 (177–182); dL of IV-L-1-6: 98 (98–123), 134 (122–134), 192 (192–207), 103 (103–113), 230 (225–230), 198 (198–206).

*Female* (n=9). Idiosoma L/W 572–654/463–525; anterior platelets L/W 217–238/76–84, posterior plate L/W 455–507/430–489; gnathosomal bay L 159–171, gnathosoma vL 122–146, dL 146–158. Palp: dL of P-1-5, 47–51, 82–94, 41–45, 114–125, 44–45. Legs: dL of I-L-1-6: 47–56, 50–56, 63–70, 94–105, 113–122, 118–134; dL of II-L-1-6: 51–53, 52–57, 69–73,108–111, 131–144, 138–146; dL of III-L-1-6: 56–63, 54–55, 72–74, 107–116, 138–141, 143–145;
<figure><img src="image_11.png" /><figcaption>**Figure 10** *Sinaxonopsis unicrus* Yi & Jin, 2012, ♀ (HN-AT-202106110512), SEM photographs: A – Ventral view; B – Gonopore; C – Coxoglandularia 4 (*C*₄); D – Coxoglandula-ria 2 (*C*₂); E – Ventroglandularia 3 (*V*₃); F – Ventroglandularia 1 (*V*₁), Ventroglandula-ria 2 (*V*₂).</figcaption></figure>
<figure><img src="image_12.png" /><figcaption>**Figure 10** *Sinaxonopsis unicrus* Yi & Jin, 2012, ♀ (HN-AT-202106110512), SEM photographs: A – Ventral view; B – Gonopore; C – Coxoglandularia 4 (*C*₄); D – Coxoglandula-ria 2 (*C*₂); E – Ventroglandularia 3 (*V*₃); F – Ventroglandularia 1 (*V*₁), Ventroglandula-ria 2 (*V*₂).</figcaption></figure>
<figure><img src="image_12.png" /><figcaption>**Figure 11** *Sinaxonopsis unicucrus* Yi & Jin, 2012, ♀ (HN-AT-202106110512), SEM photographs: A – Outer side of Palp; B – Detail of outer side of Palp-5; C – Inner side of Palp; D – Detail of inner side of Palp-5.</figcaption></figure>

<figure><img src="image_13.png" /><figcaption>**Figure 12** *Sinaxonopsis unicucrus* Yi & Jin, 2012, ♂ (HN-AT-202106110512), SEM photographs: A – Outer side of III-Leg-1-6; B – Inner side of III-Leg-1-6; C – Outer side of IV-Leg-1-6; D – Inner side of IV-Leg-1-6.</figcaption></figure>

dL of IV-L-1-6: 94–109, 76–85, 109–119, 112–124, 148–164, 136–155.

**Remarks** — The specimens from Henan Province were identified as *S. unicucrus* Yi &
<figure><img src="image_13.png" /><figcaption>**Figure 11** *Sinaxonopsis unicucrus* Yi & Jin, 2012, ♀ (HN-AT-202106110512), SEM photographs: A – Outer side of Palp; B – Detail of outer side of Palp-5; C – Inner side of Palp; D – Detail of inner side of Palp-5.</figcaption></figure>

<figure><img src="image_14.png" /><figcaption>**Figure 12** *Sinaxonopsis unicucrus* Yi & Jin, 2012, ♂ (HN-AT-202106110512), SEM photographs: A – Outer side of III-Leg-1-6; B – Inner side of III-Leg-1-6; C – Outer side of IV-Leg-1-6; D – Inner side of IV-Leg-1-6.</figcaption></figure>

dL of IV-L-1-6: 94–109, 76–85, 109–119, 112–124, 148–164, 136–155.

**Remarks** — The specimens from Henan Province were identified as *S. unicucrus* Yi &
<figure><img src="image_14.png" /><figcaption>**Figure 13** *Sinaxonopsis hainanensis* sp. nov., ♂ holotype (HN-AT-202304130201), habitat photographs.</figcaption></figure>

Jin, 2012 due to the following characteristics: (1) dorsal shield formed by one pair of anterior platelets and a large posterior plate; (2) III-L-4 with two blunt and cylindrical setae at the end; (3) III-L-5 terminally with one large cylindrical seta curving toward the ventral surface; (4) III-L-6 with a pair of heteromorphic claws; (5) IV-L-4 with a developed irregular protrusion and four large setae at the end; (6) IV-L-5 with well-developed protrude collar and three heteromorphic setae at the end, the nearest to the back is cylindrical and much thicker than the other two; (7) IV-L-6 with a particularly well-developed dorsal process (Yi and Jin 2012).

The species was firstly discovered in Anhui Province, which is the neighbor of Henan Province. Meanwhile, the species was redescribed in this paper, due to the lack of some important characteristic information, e.g. the glandularia, the patches of the large posterior dorsal plate, etc.

**Distribution** — China (Anhui, Henan).

**Sinaxonopsis hainanensis** sp. nov.

Zoobank: 4AB02675-9B86-42FF-87EE-203ABED00AC4

(Figures 13–21)

**Habitat** — Stream with numerous rocks and aquatic plants at the bottom (Figure 13).

**Material examined** — Holotype: male, Diaoluoshan Nature Reserve, Benhao Town, Lingshui Li Autonomous County, Hainan Province, P.R. China (18°67′08″ N, 109°89′43″ E, 270 m a.s.l.), collected by Hai-Tao Li, Yu-Lin Zheng, and Yu-Hao Zhang, 13-IV-2023. Slides No. HN-AT-2023041301. Paratypes: 3♂, the same data as the holotype, Slide No. HN-AT-2023041302–2023041304; 2♂, 1♀, Qinglv waterfall, Yaga Scenic Area, Bawangling National Nature Reserve, Qicha Town, Changjiang Li Autonomous County, Hainan Province, P.R. China (19°08′48″ N, 109°12′39″ E, 463 m a.s.l.), collected by Hai-Tao Li, Yu-Lin Zheng, and Yu-Hao Zhang, 23-IV-2023. Slides No. HN-AT-2023042301–2023042303.

**Diagnosis** — Dorsal shield formed by one pair of anterior platelets and a large posterior plate; anterior platelets bearing the lateral eyes, *O*₂, *A*₂ and *D*₁; posterior plate bearing six pairs of glandularia, *D*₂–*D*₄, *L*₂–*L*₃ and *V*₄. *Male*. Idiosoma blue to purple in color, with an irregular bluish-purple pattern, genital field triangular; genital pore L/W 2.86–3.07; IV-L-5 ventrally with a row of plumose setae; IV-L-6 without distinct processes. *Female*. Idiosoma brownish
<figure><img src="image_15.png" /><figcaption>**Figure 13** *Sinaxonopsis hainanensis* sp. nov., ♂ holotype (HN-AT-202304130201), habitat photographs.</figcaption></figure>

Jin, 2012 due to the following characteristics: (1) dorsal shield formed by one pair of anterior platelets and a large posterior plate; (2) III-L-4 with two blunt and cylindrical setae at the end; (3) III-L-5 terminally with one large cylindrical seta curving toward the ventral surface; (4) III-L-6 with a pair of heteromorphic claws; (5) IV-L-4 with a developed irregular protrusion and four large setae at the end; (6) IV-L-5 with well-developed protrude collar and three heteromorphic setae at the end, the nearest to the back is cylindrical and much thicker than the other two; (7) IV-L-6 with a particularly well-developed dorsal process (Yi and Jin 2012).

The species was firstly discovered in Anhui Province, which is the neighbor of Henan Province. Meanwhile, the species was redescribed in this paper, due to the lack of some important characteristic information, e.g. the glandularia, the patches of the large posterior dorsal plate, etc.

**Distribution** — China (Anhui, Henan).

**Sinaxonopsis hainanensis** sp. nov.

Zoobank: 4AB02675-9B86-42FF-87EE-203ABED00AC4

(Figures 13–21)

**Habitat** — Stream with numerous rocks and aquatic plants at the bottom (Figure 13).

**Material examined** — Holotype: male, Diaoluoshan Nature Reserve, Benhao Town, Lingshui Li Autonomous County, Hainan Province, P.R. China (18°67′08″ N, 109°89′43″ E, 270 m a.s.l.), collected by Hai-Tao Li, Yu-Lin Zheng, and Yu-Hao Zhang, 13-IV-2023. Slides No. HN-AT-2023041301. Paratypes: 3♂, the same data as the holotype, Slide No. HN-AT-2023041302–2023041304; 2♂, 1♀, Qinglv waterfall, Yaga Scenic Area, Bawangling National Nature Reserve, Qicha Town, Changjiang Li Autonomous County, Hainan Province, P.R. China (19°08′48″ N, 109°12′39″ E, 463 m a.s.l.), collected by Hai-Tao Li, Yu-Lin Zheng, and Yu-Hao Zhang, 23-IV-2023. Slides No. HN-AT-2023042301–2023042303.

**Diagnosis** — Dorsal shield formed by one pair of anterior platelets and a large posterior plate; anterior platelets bearing the lateral eyes, *O*₂, *A*₂ and *D*₁; posterior plate bearing six pairs of glandularia, *D*₂–*D*₄, *L*₂–*L*₃ and *V*₄. *Male*. Idiosoma blue to purple in color, with an irregular bluish-purple pattern, genital field triangular; genital pore L/W 2.86–3.07; IV-L-5 ventrally with a row of plumose setae; IV-L-6 without distinct processes. *Female*. Idiosoma brownish
<figure><img src="image_15.png" /><figcaption>**Figure 14** *Sinaxonopsis hainanensis* sp. nov., habitus taken by the camera, A–B, ♂ (HN-AT-202304230301); C–D, ♀ (HN-AT-202304230303). A – Dorsal view; B – Ventral view C – Dorsal view; D– Ventral view. Scale bars = 250 µm.</figcaption></figure>

to yellow, with an irregular brownish-yellow pattern on the posterior dorsal plate; genital field well developed and placed at the ventral end of the body.

**Description** — *Male* (n=6). Idiosoma oval, blue-purple color, slightly truncate at anterior end; dorsal and ventral shields present (Figures 14 and 15). In dorsal view (Figures 14A, 15A and 16A): dorsal shield formed by one pair of anterior platelets and a large posterior plate; anterior platelets bearing the lateral eyes, *O*₂, *A*₂ and *D*₁; posterior plate bearing six pairs of glandularia, *D*₂–*D*₄, *L*₂–*L*₃ and *V*₄ (Figure 16A), setae of *A*₂, *D*₁–*D*₃, *L*₂–*L*₃ all far away from
<figure><img src="image_16.png" /><figcaption>**Figure 14** *Sinaxonopsis hainanensis* sp. nov., habitus taken by the camera, A–B, ♂ (HN-AT-202304230301); C–D, ♀ (HN-AT-202304230303). A – Dorsal view; B – Ventral view C – Dorsal view; D– Ventral view. Scale bars = 250 µm.</figcaption></figure>

to yellow, with an irregular brownish-yellow pattern on the posterior dorsal plate; genital field well developed and placed at the ventral end of the body.

**Description** — *Male* (n=6). Idiosoma oval, blue-purple color, slightly truncate at anterior end; dorsal and ventral shields present (Figures 14 and 15). In dorsal view (Figures 14A, 15A and 16A): dorsal shield formed by one pair of anterior platelets and a large posterior plate; anterior platelets bearing the lateral eyes, *O*₂, *A*₂ and *D*₁; posterior plate bearing six pairs of glandularia, *D*₂–*D*₄, *L*₂–*L*₃ and *V*₄ (Figure 16A), setae of *A*₂, *D*₁–*D*₃, *L*₂–*L*₃ all far away from
<figure><img src="image_16.png" /><figcaption>**Figure 15** *Sinaxonopsis hainanensis* sp. nov., A–C, ♂, holotype, (HN-AT-202304130201); D–F, ♀, (HN-AT-202304230303), optical microscope photographs: A – Dorsal view; B – Ventral view; C – Lateral view, D – Dorsal view; E – Ventral view; F – Lateral view. Scale bars = 100 µm.</figcaption></figure>
<figure><img src="image_17.png" /><figcaption>**Figure 15** *Sinaxonopsis hainanensis* sp. nov., A–C, ♂, holotype, (HN-AT-202304130201); D–F, ♀, (HN-AT-202304230303), optical microscope photographs: A – Dorsal view; B – Ventral view; C – Lateral view, D – Dorsal view; E – Ventral view; F – Lateral view. Scale bars = 100 µm.</figcaption></figure>
<figure><img src="image_17.png" /><figcaption>**Figure 16** *Sinaxonopsis hainanensis* sp. nov., ♀ (HN-AT-202304230301): A – Dorsal view; B – Ventral view; C – Lateral view; D – Chelicerae; E – III-Leg-4–6; F – IV-Leg-4–6. Scale bars = 100 µm.</figcaption></figure>
<figure><img src="image_18.png" /><figcaption>**Figure 16** *Sinaxonopsis hainanensis* sp. nov., ♀ (HN-AT-202304230301): A – Dorsal view; B – Ventral view; C – Lateral view; D – Chelicerae; E – III-Leg-4–6; F – IV-Leg-4–6. Scale bars = 100 µm.</figcaption></figure>
<figure><img src="image_18.png" /><figcaption>**Figure 17** *Sinaxonopsis hainanensis* sp. nov., ♀ (HN-AT-202304230303): A – Dorsal view; B – Ventral view; C–III-Leg-4–6; D – IV-Leg-4–6. Scale bars = 100 µm.</figcaption></figure>

glands, numerous longitudinal stripes, and with an irregular bluish-purple pattern, almost 2/3 of the entire large posterior plate (Figure 15A); excretory pore protruding, located at the posterior end of dorsal shield. In ventral view (Figures 14B, 15B and 16B): coxal plate single; tips of Cx-I not extending beyond frontal margin; Cx-IV with distinct suture lines, suture line of Cx-III/IV ending medially to IV-L insertions and not reaching the medial line; C₂ located at the posterior margin of Cx-II where suture line of Cx-II/III slightly curved; Cx-IV well extended posteriorly with round posterior margin and laterally with a ridge; basal segmental fossa of IV-L without ankles (Figure 18A). Genital field triangular and slightly depressed, fused to ventral shield; gonopore elongated and somewhat projecting, anteriorly with several genital hairs; multiple acetabula located on both sides of gonopore in the posterolateral area of idiosoma (Figure 18B); C₄ located at either side of posterior part of genital pore.

Gnathosoma with pointed dorsal apodeme, ventral apodeme blunt and almost equal in length; two pairs of setae at the peak of the rostrum (Figure 18C). Chelicera two-segmented;
<figure><img src="image_19.png" /><figcaption>**Figure 17** *Sinaxonopsis hainanensis* sp. nov., ♀ (HN-AT-202304230303): A – Dorsal view; B – Ventral view; C–III-Leg-4–6; D – IV-Leg-4–6. Scale bars = 100 µm.</figcaption></figure>

glands, numerous longitudinal stripes, and with an irregular bluish-purple pattern, almost 2/3 of the entire large posterior plate (Figure 15A); excretory pore protruding, located at the posterior end of dorsal shield. In ventral view (Figures 14B, 15B and 16B): coxal plate single; tips of Cx-I not extending beyond frontal margin; Cx-IV with distinct suture lines, suture line of Cx-III/IV ending medially to IV-L insertions and not reaching the medial line; C₂ located at the posterior margin of Cx-II where suture line of Cx-II/III slightly curved; Cx-IV well extended posteriorly with round posterior margin and laterally with a ridge; basal segmental fossa of IV-L without ankles (Figure 18A). Genital field triangular and slightly depressed, fused to ventral shield; gonopore elongated and somewhat projecting, anteriorly with several genital hairs; multiple acetabula located on both sides of gonopore in the posterolateral area of idiosoma (Figure 18B); C₄ located at either side of posterior part of genital pore.

Gnathosoma with pointed dorsal apodeme, ventral apodeme blunt and almost equal in length; two pairs of setae at the peak of the rostrum (Figure 18C). Chelicera two-segmented;
<figure><img src="image_19.png" /><figcaption>**Figure 18** *Sinaxonopsis hainanensis* sp. nov., ♂ (HN-AT-202304230302), SEM photographs: A – Ventral view; B – Genital field; C – Gnathosoma; D – IV-Leg-1–6; E – Detail of IV-Leg-5.</figcaption></figure>

cheliceral claw curved knife shaped (Figure 1D).

Palp five-segmented (Figures 19A and 19B); P-1 dorsally with one seta socket on the outer side, without seta; P-2 with three dorsal setae on the outer, two setae on the inner sides; P-3 short, with two dorsal setae on the outer side; P-4, basally and distally concave on venter, medially convex with a pair of long setae.

Legs six-segmented; ventral margin and dorsal margin of I-L-6 and II-L-6 with a dense patch of small setae (Figures 20B and 20D), claws with one dorsal and one ventral clawlet (Figures 19C, 19D and 20); III-L and IV-L exhibiting significant sexual dimorphism; III-L-4 with three large setae on the end of the inner side, two of which are cylindrical; III-L-5 terminally with one ventrally curved large seta on the outer side; III-L-6 without distinct specific setae, with a pair of heteromorphic claws (Figures 16E and 21); IV-L-4 with a well-developed projection bearing three large setae on the inner side (Figure 18E), the two last of which are blunt and slightly curved; IV-L-5 ending with one angular projection, ventrally with a row of plumose setae and one large cylindrical seta at the end; IV-L-6 without distinct processes, with a claw same as that of I-L and II-L (Figures 16F and 18D).

*Female* (n=1). Characteristics almost similar to male, except for the following: idiosoma brownish to yellow; from the lateral view, the ventral margin of idiosoma slightly projecting (Figures 14C and 15D); genital field well developed at the ventral end of the body; gonopore large and terminally located (Figure 15E); *V*₃ positioned further anterior to the genital field; *C*₄
<figure><img src="image_20.png" /><figcaption>**Figure 18** *Sinaxonopsis hainanensis* sp. nov., ♂ (HN-AT-202304230302), SEM photographs: A – Ventral view; B – Genital field; C – Gnathosoma; D – IV-Leg-1–6; E – Detail of IV-Leg-5.</figcaption></figure>

cheliceral claw curved knife shaped (Figure 1D).

Palp five-segmented (Figures 19A and 19B); P-1 dorsally with one seta socket on the outer side, without seta; P-2 with three dorsal setae on the outer, two setae on the inner sides; P-3 short, with two dorsal setae on the outer side; P-4, basally and distally concave on venter, medially convex with a pair of long setae.

Legs six-segmented; ventral margin and dorsal margin of I-L-6 and II-L-6 with a dense patch of small setae (Figures 20B and 20D), claws with one dorsal and one ventral clawlet (Figures 19C, 19D and 20); III-L and IV-L exhibiting significant sexual dimorphism; III-L-4 with three large setae on the end of the inner side, two of which are cylindrical; III-L-5 terminally with one ventrally curved large seta on the outer side; III-L-6 without distinct specific setae, with a pair of heteromorphic claws (Figures 16E and 21); IV-L-4 with a well-developed projection bearing three large setae on the inner side (Figure 18E), the two last of which are blunt and slightly curved; IV-L-5 ending with one angular projection, ventrally with a row of plumose setae and one large cylindrical seta at the end; IV-L-6 without distinct processes, with a claw same as that of I-L and II-L (Figures 16F and 18D).

*Female* (n=1). Characteristics almost similar to male, except for the following: idiosoma brownish to yellow; from the lateral view, the ventral margin of idiosoma slightly projecting (Figures 14C and 15D); genital field well developed at the ventral end of the body; gonopore large and terminally located (Figure 15E); *V*₃ positioned further anterior to the genital field; *C*₄
<figure><img src="image_20.png" /><figcaption>**Figure 19** *Sinaxonopsis hainanensis* sp. nov., ♂ (HN-AT-202304230302), SEM photographs: A – Outer side of Palp; B – Inner side of Palp; C – Outer side of I-Leg-1-6; D – Inner side of I-Leg-1-6.</figcaption></figure>

<figure><img src="image_21.png" /><figcaption>**Figure 20** *Sinaxonopsis hainanensis* sp. nov., ♂ (HN-AT-202304230302), SEM photographs: A – Outer side of II-Leg-1-6; B – Detail of outer side of II-Leg-4; C – Inner side of II-Leg-1-6; D – Detail of inner side of II-Leg-4.</figcaption></figure>
<figure><img src="image_21.png" /><figcaption>**Figure 19** *Sinaxonopsis hainanensis* sp. nov., ♂ (HN-AT-202304230302), SEM photographs: A – Outer side of Palp; B – Inner side of Palp; C – Outer side of I-Leg-1-6; D – Inner side of I-Leg-1-6.</figcaption></figure>

<figure><img src="image_22.png" /><figcaption>**Figure 20** *Sinaxonopsis hainanensis* sp. nov., ♂ (HN-AT-202304230302), SEM photographs: A – Outer side of II-Leg-1-6; B – Detail of outer side of II-Leg-4; C – Inner side of II-Leg-1-6; D – Detail of inner side of II-Leg-4.</figcaption></figure>
<figure><img src="image_22.png" /><figcaption>**Figure 21** *Sinaxonopsis hainanensis* sp. nov., ♂ (HN-AT-202304230302), SEM photographs: A – Outer side of III-Leg-1-6; B – Detail of outer side of III-Leg-5; C – Inner side of III-Leg-1-6; D – Detail of inner side of III-Leg-5.</figcaption></figure>

located anterolateral to the tip of the gonopore (Figure 17B). III-L without heteromorphic setae; claws same as in I-L and II-L (Figure 17C); IV-L-4 ending without prominence, with one long swimming hair; IV-L-5 with one angular prominence at the end, two long swimming setae and one ventrally curved large seta, and one row of tiny setae on venter (Figure 17D).

**Measurements** — *Male* (n=6). Idiosoma L/W 508 (478–534)/424 (408–442); anterior platelets L/W 198 (193–214)/73 (70–73), posterior plate L/W 405 (384–425)/388 (384–419); gnathosomal bay L 142 (137–144); gonopore L/W 71 (68–74)/25 (22–25), ratio 2.86 (2.86–3.22). gnathosoma vL 129 (125–129), dL 142 (1431–144); chelicera total L 171 (148–171), claw L 52 (42–52), basal segment L 114 (106–130), L basal segment/claw ratio 2.19 (2.19–3.09). Palp: dL/H, dL/H ratio: P-1, 44 (43–45)/23 (23–24), 1.91 (1.76–1.91); P-2, 79 (76–79)/28 (26–28), 2.73 (2.73–2.99); P-3, 37 (37–46)/23 (23–31), 1.61 (1.30–1.61); P-4, 106 (106–109), 5.91 (5.91–6.02); P-5, 42 (41–42)/11 (11–16), 3.63 (2.70–3.63); Legs: dL of I-L-1-6: 47 (44–47), 43 (43–53), 67 (67–72), 111 (105–114), 116 (116–140), 128 (128–144); dL of II-L-1-6: 54 (47–55), 62 (49–62), 79 (72–82), 113 (108–125), 144 (135–145), 139 (139–153); dL of III-L-1-6: 72 (72–82), 53 (53–60), 82 (78–89), 99 (83–99), 151 (151–171), 147 (142–149); dL of IV-L-1-6: 108 (107–118), 115 (113–118), 185 (179–190), 89 (89–108), 178 (175–191), 145 (134–159).

*Female* (n=1). Idiosoma L/W 513/422; anterior platelets L/W 204/58, posterior plate L/W 443/394; gnathosomal bay L 151. gnathosoma vL 134, dL 148. Palp: dL of P-1-5, 45, 81, 43, 105, 44; Legs: dL of I-L-1-6: 48, 43, 61, 90, 111, 118; dL of II-L-1-6: 59, 52, 67, 103, 131, 137; dL of III-L-1-6: 55, 56, 69, 109, 124, 129; dL of IV-L-1-6: 93, 73, 97, 103, 137, 121.

**Remarks** — Due to the morphology of the dorsum (formed by one pair of anterior platelets and a large posterior plate), genital field (with multiple acetabula) and palp (P-4 with a pair of long setae) of the specimens from Hainan, China, the new species, *S. hainanensis* sp. nov., resembles *S. laosensis* Pešić & Smit, 2016 from Laos. However, the new species differs from *S. laosensis* in the following aspects: (1) *S. hainanensis* sp. nov. (L/W 508 (478–534)/424 (408–442)) smaller than *S. laosensis* (L/W 581/443); (2) *S. hainanensis* sp. nov. body bluish-purple,
<figure><img src="image_23.png" /><figcaption>**Figure 21** *Sinaxonopsis hainanensis* sp. nov., ♂ (HN-AT-202304230302), SEM photographs: A – Outer side of III-Leg-1-6; B – Detail of outer side of III-Leg-5; C – Inner side of III-Leg-1-6; D – Detail of inner side of III-Leg-5.</figcaption></figure>

located anterolateral to the tip of the gonopore (Figure 17B). III-L without heteromorphic setae; claws same as in I-L and II-L (Figure 17C); IV-L-4 ending without prominence, with one long swimming hair; IV-L-5 with one angular prominence at the end, two long swimming setae and one ventrally curved large seta, and one row of tiny setae on venter (Figure 17D).

**Measurements** — *Male* (n=6). Idiosoma L/W 508 (478–534)/424 (408–442); anterior platelets L/W 198 (193–214)/73 (70–73), posterior plate L/W 405 (384–425)/388 (384–419); gnathosomal bay L 142 (137–144); gonopore L/W 71 (68–74)/25 (22–25), ratio 2.86 (2.86–3.22). gnathosoma vL 129 (125–129), dL 142 (1431–144); chelicera total L 171 (148–171), claw L 52 (42–52), basal segment L 114 (106–130), L basal segment/claw ratio 2.19 (2.19–3.09). Palp: dL/H, dL/H ratio: P-1, 44 (43–45)/23 (23–24), 1.91 (1.76–1.91); P-2, 79 (76–79)/28 (26–28), 2.73 (2.73–2.99); P-3, 37 (37–46)/23 (23–31), 1.61 (1.30–1.61); P-4, 106 (106–109), 5.91 (5.91–6.02); P-5, 42 (41–42)/11 (11–16), 3.63 (2.70–3.63); Legs: dL of I-L-1-6: 47 (44–47), 43 (43–53), 67 (67–72), 111 (105–114), 116 (116–140), 128 (128–144); dL of II-L-1-6: 54 (47–55), 62 (49–62), 79 (72–82), 113 (108–125), 144 (135–145), 139 (139–153); dL of III-L-1-6: 72 (72–82), 53 (53–60), 82 (78–89), 99 (83–99), 151 (151–171), 147 (142–149); dL of IV-L-1-6: 108 (107–118), 115 (113–118), 185 (179–190), 89 (89–108), 178 (175–191), 145 (134–159).

*Female* (n=1). Idiosoma L/W 513/422; anterior platelets L/W 204/58, posterior plate L/W 443/394; gnathosomal bay L 151. gnathosoma vL 134, dL 148. Palp: dL of P-1-5, 45, 81, 43, 105, 44; Legs: dL of I-L-1-6: 48, 43, 61, 90, 111, 118; dL of II-L-1-6: 59, 52, 67, 103, 131, 137; dL of III-L-1-6: 55, 56, 69, 109, 124, 129; dL of IV-L-1-6: 93, 73, 97, 103, 137, 121.

**Remarks** — Due to the morphology of the dorsum (formed by one pair of anterior platelets and a large posterior plate), genital field (with multiple acetabula) and palp (P-4 with a pair of long setae) of the specimens from Hainan, China, the new species, *S. hainanensis* sp. nov., resembles *S. laosensis* Pešić & Smit, 2016 from Laos. However, the new species differs from *S. laosensis* in the following aspects: (1) *S. hainanensis* sp. nov. (L/W 508 (478–534)/424 (408–442)) smaller than *S. laosensis* (L/W 581/443); (2) *S. hainanensis* sp. nov. body bluish-purple,
but colourless in *S. laosensis*; (3) IV-L-5 venter with a row of plumose setae in *S. hainanensis*
*sp. nov.*, but only one large pennate seta and two slender setae in *S. laosensis*.

**Etymology** — The name “hainanensis” refers to the type location, where the specimens were collected.

**Distribution** — China (Hainan).

Discussion

Glandularia arrangement on the mites body surface is a peculiar feature of each species
(Lundblad 1930; Jin and Li 1997; Wiles 1997) and it is considered to indicate a possible way of
evolution in this phylogenetic lineage (Shatrov et al. 2019). However, some species of Aturidae
lack the glandularia $V_1$, the gland of $D_4$, therefore, this study revealed that *S. unicucrus* and *S.
hainanensis* sp. nov. had the glandularia $V_1$ and the gland $D_4g$. Besides, this study confirms
that this genus has 16 pairs of glandularia, i.e. $A_1, A_2, C_2, C_4, D_1-D_4, L_1-L_4, V_1-V_4$, and two
pairs of ocularia ($O_1, O_2$), which is consistent with the common patterns in water mites.

It is important to acknowledge that previous studies on Aturidae may have overlooked
certain features due to the small size of the specimens and outdated experimental equipment
and techniques. Therefore, future studies should focus on glandulars, particularly $D_4$ and $V_1$, to
clarify their presence, absence, and position. This will provide a basis for further exploration
in phylogenetic research of Aturidae.

Patterns (presence or absence, shape, color and size) of large posterior dorsal plate is an
important characteristic in species identification of Aturidae, and has been widely used, e.g.
the genus of *Axonopsis*, *Hexazonopsis*, *Kongsbergia*, *Vicinaxonopsis*, etc. (Asadi *et al.* 2010;
Pešić *et al.* 2010; Radwell and Smith 2012; Pešić and Gerecke 2014; Pešić and Smit 2016;
Smit 2016). Among the two species illustrated in this paper, eyepatch-like violet spots of
the lager posterior plate in *S. unicucrus* and irregular bluish-purple pattern in *S. hainanensis*
sp. nov. are embedding into the chitin exoskeletons and maintain intraspecific stability and
interspecies differences. Therefore, the patterns (presence or absence, shape, color and size)
of the large posterior plate could be used as discriminative features for species identification
of *Sinaxonopsis*. At the same time, we should pay more attention to illustrate it in detail, to
provide enough materials for future taxonomic studies of Aturidae. The present results have
not only provided potentially effective characters for species identification in *Sinaxonopsis*, but
also materials for phylogenetic analysis based on glandularia.

Acknowledgements

We are indebted to Yu-Lin Zheng (College of Pharmacy, Dali University) and Yu-Hao Zhang
(Institute of Entomology, Guizhou University) for providing the specimens. This research
was supported by Guizhou Provincial Science and Technology Projects (Qiankehe Pingtai
Rencai-GCC [2022] 029-1) and the National Nature Science Foundation of China (32260125).

ORCID

Lan Jia https://orcid.org/0000-0001-5718-0063

Hai-Tao Li https://orcid.org/0009-0002-4639-7843

Jian-Jun Guo https://orcid.org/0000-0002-0523-6704

References

Asadi M., Pešić V., Etemadi I. 2010. A revised survey of water mites (Acari: Hydrachnidia) from Iran: new synonyms and descriptions of three new species. Zootaxa, 2628(1): 43-55. https://doi.org/10.11646/zootaxa.2628.1.3
but colourless in *S. laosensis*; (3) IV-L-5 venter with a row of plumose setae in *S. hainanensis*
*sp. nov.*, but only one large pennate seta and two slender setae in *S. laosensis*.

**Etymology** — The name “hainanensis” refers to the type location, where the specimens were collected.

**Distribution** — China (Hainan).

Discussion

Glandularia arrangement on the mites body surface is a peculiar feature of each species
(Lundblad 1930; Jin and Li 1997; Wiles 1997) and it is considered to indicate a possible way of
evolution in this phylogenetic lineage (Shatrov et al. 2019). However, some species of Aturidae
lack the glandularia $V_1$, the gland of $D_4$, therefore, this study revealed that *S. unicucrus* and *S.
hainanensis* sp. nov. had the glandularia $V_1$ and the gland $D_4g$. Besides, this study confirms
that this genus has 16 pairs of glandularia, i.e. $A_1, A_2, C_2, C_4, D_1-D_4, L_1-L_4, V_1-V_4$, and two
pairs of ocularia ($O_1, O_2$), which is consistent with the common patterns in water mites.

It is important to acknowledge that previous studies on Aturidae may have overlooked
certain features due to the small size of the specimens and outdated experimental equipment
and techniques. Therefore, future studies should focus on glandulars, particularly $D_4$ and $V_1$, to
clarify their presence, absence, and position. This will provide a basis for further exploration
in phylogenetic research of Aturidae.

Patterns (presence or absence, shape, color and size) of large posterior dorsal plate is an
important characteristic in species identification of Aturidae, and has been widely used, e.g.
the genus of *Axonopsis*, *Hexazonopsis*, *Kongsbergia*, *Vicinaxonopsis*, etc. (Asadi *et al.* 2010;
Pešić *et al.* 2010; Radwell and Smith 2012; Pešić and Gerecke 2014; Pešić and Smit 2016;
Smit 2016). Among the two species illustrated in this paper, eyepatch-like violet spots of
the lager posterior plate in *S. unicucrus* and irregular bluish-purple pattern in *S. hainanensis*
sp. nov. are embedding into the chitin exoskeletons and maintain intraspecific stability and
interspecies differences. Therefore, the patterns (presence or absence, shape, color and size)
of the large posterior plate could be used as discriminative features for species identification
of *Sinaxonopsis*. At the same time, we should pay more attention to illustrate it in detail, to
provide enough materials for future taxonomic studies of Aturidae. The present results have
not only provided potentially effective characters for species identification in *Sinaxonopsis*, but
also materials for phylogenetic analysis based on glandularia.

Acknowledgements

We are indebted to Yu-Lin Zheng (College of Pharmacy, Dali University) and Yu-Hao Zhang
(Institute of Entomology, Guizhou University) for providing the specimens. This research
was supported by Guizhou Provincial Science and Technology Projects (Qiankehe Pingtai
Rencai-GCC [2022] 029-1) and the National Nature Science Foundation of China (32260125).

ORCID

Lan Jia https://orcid.org/0000-0001-5718-0063

Hai-Tao Li https://orcid.org/0009-0002-4639-7843

Jian-Jun Guo https://orcid.org/0000-0002-0523-6704

References

Asadi M., Pešić V., Etemadi I. 2010. A revised survey of water mites (Acari: Hydrachnidia) from Iran: new synonyms and descriptions of three new species. Zootaxa, 2628(1): 43-55. https://doi.org/10.11646/zootaxa.2628.1.3
Gerecke R. 2014. Studies on European species of the water mite family Aturidae Thor (Acari: Hydrachnidia). Zootaxa, 3841(1): 1-46. https://doi.org/10.11646/zootaxa.3841.1.1

Gu X.-Y., Jia L., Jin D.-C., Guo J.-J. 2020. Four new species of *Torrenticola* (Acari, Hydrachnidia, Torrenticolidae) from Northeastern China. Zootaxa, 4779(2): 245-259. https://doi.org/10.11646/zootaxa.4779.2.6

Jin D.-C. 1997. Hydrachnellae-morphology systematics a primary study of Chinese fauna. Guiyang: Guizhou Science and Technology Publishing House, pp. 356. (in Chinese)

Jin D.-C., Li L.-S. 1997. On glandularia morphology of water mites (Acari, Actinedida, Hydrachnellae) and evolutionary theory of the mite soma. Acta Entomologica Sinica, 43(3): 231-246.

Kim I.-H., Chung, K. -S. 1993. Water Mites of the Genus *Aturus* (Acarina: Aturidae) in Korea. The Korean Journal of Zoology, 36: 329-341.

Kim I.-H., Chung, K. -S. 1995. Water mites of the genus *Aturus* (Acarina: Aturidae) from the eastern side of Korea, including five new species. The Korean Journal of Zoology, 38: 269-285.

Li H.-T., Jin D.-C., Guo J.-J. 2022. *Acucapito hainanensis* sp. nov., the first record of the family Acucapitidae Wiles, 1996 (Acari, Hydrachnidia) from China. Acarologia, 62(1): 250-261. https://doi.org/10.24349/h7mp-06fx

Lundblad O. 1930. Über die Anatomie von Arrhenurus mediorotundatus und die Hautdrüsen der Arrhenurus-Arten. Zeitschrift für Morphologie und Ökologie der Tiere, 17(1/2): 302-338. https://doi.org/10.1007/BF00406261

Pešić V., Gerecke R. 2014. Water mites from caves of the Ha Giang province, northern Vietnam (Acari: Hydrachnidia). Zootaxa, 3774(4): 367-380. https://doi.org/10.11646/zootaxa.3774.4.5

Pešić V., Smit H. 2016. New records of water mites from Southeast Asia (Acari: Hydrachnidia) with the description of two new genera and 12 new species. Acarologia, 56(3): 393-433. https://doi.org/10.1051/acarologia/20162251

Pešić V., Smit H., Gerecke R., Di S. -A. 2010. The water mites (Acari: Hydrachnidia) of the Balkan peninsula, a revised survey with new records and descriptions of five new taxa. Zootaxa, 2586(1): 1-100. https://doi.org/10.11646/zootaxa.2586.1.1

Radwell A. -J., Smith I. -M. 2012. North American members of the reticulata-like species group of the water mite genus *Kongsbergia* (Acari: Hydrachnidiae: Aturidae). Zootaxa, 3540(1): 1-49. https://doi.org/10.11646/zootaxa.3540.1.1

Shatrov A. -B. 2008. Organization of unusual idiosomal glands in a water mite, *Teutonia cometes* (Teutoniidae). Experimental and Applied Acarology, 44: 249-263. https://doi.org/10.1007/s10493-008-9148-8

Shatrov A. -B., Soldatenko E. -V., Stolbov V. -A., Smirnov P. -A., Petukhova, O. -A. 2019. Ultrastruc- ture and functional morphology of dermal glands in the freshwater mite *Limnochores aquatica* (L., 1758) (Acariformes, Limnocharidae). Arthropod structure & development, 49: 85-102. https://doi.org/10.1016/j.asd.2018.11.010

Smit H. 2016. The water mite family Aturidae Thor, 1900 from Southeast Asia (Acari: Hydrachnidia) with the description of one new genus and 14 new species. Acarologia, 56(3): 341-365. https://doi.org/10.1051/acarologia/20162248

Smit H. 2017. New species of aturid water mites from southern Africa (Acari: Hydrachnidia: Aturidae). Zootaxa, 4273(2): 287-295. https://doi.org/10.11646/zootaxa.4273.2.9

Smit H. 2020. Water mites of the world, with keys to the families, subfamilies, genera and subgenera (Acari: Hydrachnidia). Leiden, Monografieën van de Nederlandse Entomologische Vereniging, pp. 774.

Wiles P.-R. 1991. Watermites (Hydrachnidia: Aturidae) of the genus *Albia* Thon from Asia and Australasia with descriptions of eleven new species. Insect Systematics & Evolution, 22(4): 465-487. https://doi.org/10.1163/187631291X00264

Wiles P.-R. 1997. The homology of glands and glandularia in the water mites (Acari: Hydrachnidia). Journal of Natural History, 31(8): 1237-1251. https://doi.org/10.1080/00222939700770671

Yi T.-C., Jin D.-C. 2012. Description of *Sinaxonopsis unicucrus* sp. nov. et gen. nov. (Acari: Hydrachnidia: Aturidae) from Anhui Province, China. International Journal of Acarology, 38(5): 402-409. https://doi.org/10.1080/01647954.2012.657802
Gerecke R. 2014. Studies on European species of the water mite family Aturidae Thor (Acari: Hydrachnidia). Zootaxa, 3841(1): 1-46. https://doi.org/10.11646/zootaxa.3841.1.1

Gu X.-Y., Jia L., Jin D.-C., Guo J.-J. 2020. Four new species of *Torrenticola* (Acari, Hydrachnidia, Torrenticolidae) from Northeastern China. Zootaxa, 4779(2): 245-259. https://doi.org/10.11646/zootaxa.4779.2.6

Jin D.-C. 1997. Hydrachnellae-morphology systematics a primary study of Chinese fauna. Guiyang: Guizhou Science and Technology Publishing House, pp. 356. (in Chinese)

Jin D.-C., Li L.-S. 1997. On glandularia morphology of water mites (Acari, Actinedida, Hydrachnellae) and evolutionary theory of the mite soma. Acta Entomologica Sinica, 43(3): 231-246.

Kim I.-H., Chung, K. -S. 1993. Water Mites of the Genus *Aturus* (Acarina: Aturidae) in Korea. The Korean Journal of Zoology, 36: 329-341.

Kim I.-H., Chung, K. -S. 1995. Water mites of the genus *Aturus* (Acarina: Aturidae) from the eastern side of Korea, including five new species. The Korean Journal of Zoology, 38: 269-285.

Li H.-T., Jin D.-C., Guo J.-J. 2022. *Acucapito hainanensis* sp. nov., the first record of the family Acucapitidae Wiles, 1996 (Acari, Hydrachnidia) from China. Acarologia, 62(1): 250-261. https://doi.org/10.24349/h7mp-06fx

Lundblad O. 1930. Über die Anatomie von Arrhenurus mediorotundatus und die Hautdrüsen der Arrhenurus-Arten. Zeitschrift für Morphologie und Ökologie der Tiere, 17(1/2): 302-338. https://doi.org/10.1007/BF00406261

Pešić V., Gerecke R. 2014. Water mites from caves of the Ha Giang province, northern Vietnam (Acari: Hydrachnidia). Zootaxa, 3774(4): 367-380. https://doi.org/10.11646/zootaxa.3774.4.5

Pešić V., Smit H. 2016. New records of water mites from Southeast Asia (Acari: Hydrachnidia) with the description of two new genera and 12 new species. Acarologia, 56(3): 393-433. https://doi.org/10.1051/acarologia/20162251

Pešić V., Smit H., Gerecke R., Di S. -A. 2010. The water mites (Acari: Hydrachnidia) of the Balkan peninsula, a revised survey with new records and descriptions of five new taxa. Zootaxa, 2586(1): 1-100. https://doi.org/10.11646/zootaxa.2586.1.1

Radwell A. -J., Smith I. -M. 2012. North American members of the reticulata-like species group of the water mite genus *Kongsbergia* (Acari: Hydrachnidiae: Aturidae). Zootaxa, 3540(1): 1-49. https://doi.org/10.11646/zootaxa.3540.1.1

Shatrov A. -B. 2008. Organization of unusual idiosomal glands in a water mite, *Teutonia cometes* (Teutoniidae). Experimental and Applied Acarology, 44: 249-263. https://doi.org/10.1007/s10493-008-9148-8

Shatrov A. -B., Soldatenko E. -V., Stolbov V. -A., Smirnov P. -A., Petukhova, O. -A. 2019. Ultrastruc- ture and functional morphology of dermal glands in the freshwater mite *Limnochores aquatica* (L., 1758) (Acariformes, Limnocharidae). Arthropod structure & development, 49: 85-102. https://doi.org/10.1016/j.asd.2018.11.010

Smit H. 2016. The water mite family Aturidae Thor, 1900 from Southeast Asia (Acari: Hydrachnidia) with the description of one new genus and 14 new species. Acarologia, 56(3): 341-365. https://doi.org/10.1051/acarologia/20162248

Smit H. 2017. New species of aturid water mites from southern Africa (Acari: Hydrachnidia: Aturidae). Zootaxa, 4273(2): 287-295. https://doi.org/10.11646/zootaxa.4273.2.9

Smit H. 2020. Water mites of the world, with keys to the families, subfamilies, genera and subgenera (Acari: Hydrachnidia). Leiden, Monografieën van de Nederlandse Entomologische Vereniging, pp. 774.

Wiles P.-R. 1991. Watermites (Hydrachnidia: Aturidae) of the genus *Albia* Thon from Asia and Australasia with descriptions of eleven new species. Insect Systematics & Evolution, 22(4): 465-487. https://doi.org/10.1163/187631291X00264

Wiles P.-R. 1997. The homology of glands and glandularia in the water mites (Acari: Hydrachnidia). Journal of Natural History, 31(8): 1237-1251. https://doi.org/10.1080/00222939700770671

Yi T.-C., Jin D.-C. 2012. Description of *Sinaxonopsis unicucrus* sp. nov. et gen. nov. (Acari: Hydrachnidia: Aturidae) from Anhui Province, China. International Journal of Acarology, 38(5): 402-409. https://doi.org/10.1080/01647954.2012.657802