Torrenticola eurytopica n. sp. (Acari: Hydrachnidia: Torrenticolidae), the only European member of the genus inhabiting both running and standing waters

Vladimir Pešić, Andrej Zawal, Tom Goldschmidt

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Vladimir Pešić, Andrej Zawal, Tom Goldschmidt. Torrenticola eurytopica n. sp. (Acari: Hydrachnidia: Torrenticolidae), the only European member of the genus inhabiting both running and standing waters. Acarologia, 2025, 65 (4), pp.1173-1187. 10.24349/n9hh-29w1. hal-05387151

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# *Torrenticola eurytopica* n. sp. (Acari: *Hydrachnidia: Torrenticolidae*), the only European member of the genus inhabiting both running and standing waters

Vladimir Pešić IDª, Andrej Zawal IDᵇ, Tom Goldschmidt IDᶜ

## Original research

### ABSTRACT

In this study, morphological data and DNA barcoding were used to re-examine voucher specimens of *Torrenticola meridionalis* Di Sabatino & Cicolani, 1990, from southern Italy and the Balkans. Populations from the Balkans previously attributed to *T. meridionalis* are herein described as a new species, *T. eurytopica n. sp.* This new species appears to be the only member of the genus in the Palaearctic known to inhabit both running waters (streams and rivers) and standing waters, such as the ancient Prespa Lake.

**Keywords** Balkan peninsula; water mites; DNA barcoding; cytochrome c oxidase subunit I; COI; integrative taxonomy; systematics

**Zoobank** http://zoobank.org/9430B9A0-0A50-4EC4-9A5C-B04B6CCD69BB

### Introduction

The water mite genus *Torrenticola* Piersig, 1896, is one of the most diverse and abundant groups of water mites in running waters on all continents except Antarctica, with the highest diversity in the Northern Temperate and Tropical regions (Goldschmidt 2009). Over the last decade, the application of integrative taxonomical approaches has revealed a high degree of cryptic and pseudo-cryptic diversity among European torrenticolids, leading to the discovery of previously unrecognized species and the identification of several species complexes composed of genetically distinct lineages (e.g., Pešić *et al.* 2012; Pešić and Smit 2022; Pešić *et al.* 2021, 2023, 2024a, 2025a,d). Notable examples include the *T. laskai* complex (e.g., Pešić and Smit 2022; Pešić *et al.* 2020, 2023), the *T. barsica* complex (e.g., Pešić and Smit 2022), and the *T. meridionalis* complex (e.g., Pešić *et al.* 2021).

*Torrenticola meridionalis* Di Sabatino & Cicolani, 1990, was originally described from Calabria, southern Italy (Di Sabatino & Cicolani, 1990). In the original description, the species was compared with *T. elliptica* Maglio, 1909, a species widely distributed in Central Europe and typically associated with montane, low-order streams (Di Sabatino *et al.* 2009). *Torrenticola meridionalis* was distinguished from *T. elliptica* by its less slender idiosoma and, in males, by a relatively shorter medial suture of Cx-II+III and a stouter genital field. Subsequently, *T. meridionalis* was reported from the Balkans (Di Sabatino *et al.* 2003) and France (Di Sabatino *et al.* 2009). However, some of these populations exhibit a wide variability in the first two

Received 19 September 2025
Accepted 15 November 2025
Published 20 November 2025

Corresponding author
Vladimir Pešić ID:
vladopesic@gmail.com

Academic editor
Mąkol, Joanna

https://doi.org/10.24349/n9hh-29w1

ISSN 0044-586X (print)
ISSN 2107-7207 (electronic)

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

Pešić V. *et al.*

Licensed under
Creative Commons CC-BY 4.0

OPEN ACCESS

<footnote>ªDepartment of Biology, University of Montenegro, Cetinjski put b.b., 81000 Podgorica, Montenegro.</footnote>

<footnote>ᵇInstitute of Marine and Environmental Sciences, Center of Molecular Biology and Biotechnology, University of Szczecin, Wąska 13, 71-415 Szczecin, Poland.</footnote>

<footnote>ᶜBavarian State Collection of Zoology, Section Arthropoda varia, Münchhausenstraße 21, 81247 Munich, Germany.</footnote>
diagnostic characters, overlapping with the variation observed in *T. elliptica*, thereby blurring
the morphological distinction between the two species.

For example, Di Sabatino *et al.* (2009) reported that specimens from France (Auvergne) possess a genital field consistent with *T. elliptica* (L/W ratio > 1.25), intermediate proportions of Cx-I/II+III (L Cx-I/Cx-II+III ratio 3.0-3.5), and a dorsal shield (L/W ratio < 1.5) resembling that of *T. meridionalis*. This suggests that the high morphometric variability observed across the distribution ranges of both morphospecies may indicate that they represent species complexes composed of genetically distinct lineages, often with geographically restricted distributions.

Recently, Pešić *et al.* (2021) demonstrated that populations previously identified as *T. meridionalis* include at least three divergent barcode clusters. One of these (BOLD:AEK9662) is restricted to populations from Italy, while the other two, i.e., BOLD:AED7519 and BOLD:AEI3402, represent widely distributed haplogroups comprising populations from the Balkans. A re-examination of the specimens assigned to BOLD:AEI3402, previously published by Pešić *et al.* (2021) under the name *T. meridionalis* Clade 3 (=TorrM-III Clade), revealed that these specimens, due to their elongated idiosoma and the excretory pore being distinctly embedded within the area of primary sclerotization, correspond morphologically to *T. similis* (see Pešić *et al.* 2025d for further discussion).

In the present study, we used morphological data and DNA barcoding to re-examine voucher
material of *T. meridionalis* from Italy and the Balkans. As a result, we describe one species
new to science.

**Material and methods**

Water mites were collected with kick nets and immediately preserved in 96% ethanol for the
purpose of molecular analyses. Water mite specimens used for the molecular study are listed
in Table 1. After non-destructive, whole-body DNA extraction, the specimen vouchers were
stored in 96% ethanol and morphologically examined. Some of these vouchers were dissected
and slide mounted in Faure's medium, while the rest was transferred to Koenike's fluid.

Morphological nomenclature follows Gerecke *et al.* (2016). The dorsal platelets of *Torrenticola* spp. were measured on both sides, therefore their dimensions are given as a range of values, rather than a single number. The holotype and paratypes of the new species are deposited in Naturalis Biodiversity Center in Leiden (RMNH).

All measurements are given in µm. The photographs of selected structures were made
using a camera on a Samsung Galaxy smartphone. The following abbreviations are used: Al
pl = antero-lateral platelets, Am pl = antero-medial platelets, Cx-I = first coxae, Cxgl-4 =
coxoglandularia of first coxae, dL = dorsal length, dp = dorsal plate, ds = dorsal shield, expo
= excretory pore, gf = genital field, H = height, ec = ejaculatory complex, I-L-4 = first leg,
fourth segment, L = length, mL = medial length, P-1 = palp, first segment, RMNH = Naturalis
Biodiversity Center in Leiden, Vgl = ventroglandularia, vL = ventral length, W = width.

**Molecular and DNA barcode analyses**

The molecular analysis was conducted at the Institute of Biology, University of Szczecin
(IoB-UoS), and at the University of Lodz (UniLodz), Lodz, Poland. DNA was extracted using
a non-destructive protocol as described in Pešić *et al.* (2025b). At UniLodz amplification and
DNA sequencing using Oxford Nanopore Technology was done according to the protocol in
Pešić *et al.* (2025b). Raw reads were demultiplexed using the Pacific Biosciences SMRT Link
software. Consensus sequences were generated with the PacBio Amplicon Analysis (pbaa) tool.
Primer trimming, translation and stop codon checking were performed using Geneious Prime
2024.0.1. Consensus sequences were made available in the BOLD database (Ratnasingham
& Hebert 2007). Relevant voucher information, photos, and DNA barcodes of the new
species are publicly accessible through the Dataset “DS-BALHYD DNA barcode reference
library of Balkan water mites» (https://portal.boldsystems.org/recordset/DS-BALHYD; doi.org/10.5883/DS-BALHYD).

Sequence alignments were performed using MUSCLE (Edgar 2004). Intra- and interspecific genetic distances were calculated based on the *p*-distance using MEGA11 (Tamura *et al.* 2021). The latter software was used to calculate Neighbor-Joining (NJ) trees based on K2P distances (standard for barcoding studies) using pairwise deletion for missing data. Branch support was calculated using nonparametric bootstrap (Felsenstein 1985) with 1000 replicates and shown next to the branches.

## Systematics

**Family Torrenticolidae Piersig, 1902**

**Genus Torrenticola Piersig, 1896**

**Torrenticola meridionalis Di Sabatino & Cicolani, 1990**

Figures 1, 5A

**Material examined** — Italy, Calabria, Fossiata, stream, 39.4011°N, 16.5884°E, 23 August 2018, leg. Goldschmidt, 2♂, 1♀ (sequenced; DCBDJ062-21, DCBDJ041-21, DCBDJ067-21), 1♂ (Voucher Id: CCDB 38392 F02) dissected and slide mounted (RMNH).

**Remarks** — Examination of specimens from Calabria, southern Italy, assigned to BOLD:AEI3403 showed that they morphologically match the original description of *T. meridionalis*, a species described from the River Alli at the locality Belladona in Calabria (Di Sabatino and Cicolani, 1990). In the original description, *T. meridionalis* was compared with *T. elliptica*, from which it differs by a less slender idiosoma (L/W ratio of dorsal shield < 1.5 vs. > 1.5 in *T. elliptica*), and in males, by a relatively shorter medial suture of Cx-II+III (length ratio Cx-I/Cx-II+III > 3.5 vs. < 3.0), and a stouter genital field (L/W ratio ~1.2 vs. ~1.3).

Additionally, Di Sabatino and Cicolani (1990) noted differences in the ecological preferences of the two species. *Torrenticola elliptica* is considered the most stenothermic species of the genus and, in the Mediterranean region, is confined to high-elevation habitats. In contrast, *T. meridionalis* is eurythermic and inhabits lowland streams (Figure 2) and rivers at lower elevations, often in watercourses affected by thermal fluctuations and seasonal changes in discharge.

Measurements of the examined male are provided in Table 1.

**Genetic data** — All examined specimens belong to a unique BIN (BOLD:AEK9662).

**Distribution** — Southern Italy.

**Torrenticola (Torrenticola) eurytopica n. sp.**

Zoobank: D4B72B56-529A-493B-98A1-40739C2398E2

Figures 3-4, 5B-F

*Torrenticola meridionalis* Di Sabatino & Cicolani, 1990 [in part] – Di Sabatino *et al.* (2003), Pešić *et al.* (2018, 2021, 2024b, 2025c).

**Material examined**

Holotype ♂ (sequenced; DNCBD049-20), Montenegro, Bar, Rikavac stream near Old Bar, 42.1001°N, 19.1432°E, 3 June 2020, leg. Pešić, dissected and slide mounted (voucher Id: CCDB_3867_E03; RMNH). Paratypes: 1♀ (sequenced; DNCBD049-20), same data as holotype, dissected and slide mounted (voucher Id: CCDB_3867_E01; RMNH); 2♂ (sequenced; DNCBD073-20, DNCBD074-20), Montenegro, Virpazar, Orahovštica river, 42.2476°N, 19.0798°E, 10 June 2020, leg. Pešić; 3♂, 1♀ (2♂ sequenced; DNAEC022-20, DNAEC023-20); North Macedonia, Prespa Lake near Oteševo, 40.979°N, 20.917°E, 15 September 2019 leg. Pešić, Jovanović & Manović, 2♂, 1♀ dissected and slide mounted (all RMNH).
<figure><img src="image_3.png" /><figcaption>**Figure 1** *Torrenticola meridionalis*, ♂, Calabria, Fossiata [CCDB 38392 F02]: A – dorsal shield; B – ventral shield; C – palp, medial view (P-1 lacking); D – capitulum; E – ejaculatory complex. Scale bars = 100 µm.</figcaption></figure>
<figure><img src="image_4.png" /><figcaption>**Figure 2** Photograph of sampling site of *Torrenticola meridionalis* (Italy, Calabria, Fossiata, stream). Photo by T. Goldschmidt.</figcaption></figure>

**Diagnosis**

**Morphological** — Colour pattern of dorsal shield as given in Figures. 5B-F; male medial suture Cx-II+III short (L 90-100); male genital field subrectangular in shape L/W ratio 1.3, posterior margins of genital flaps with a few short setae in both sexes; male ejaculatory complex with large proximal chamber, P-2 slightly longer than P-4.

**Molecular** — this lineage is represented by a unique BIN (BOLD:AED7519) which differs from *T. meridionalis* clade (BOLD:AEK9662) from South Italy by 7.18% p-distance for COI.

**Description**

**General features** — Idiosoma longish in shape; dorsal shield with a colour pattern as given in Figures 5B-F; area of primary sclerotization of the dorsal plate with two dorsoglandularia (Figures 3A, 4A); gnathosomal bay U-shaped, proximally rounded; Cxgl-4 subapical; postgenital area extended, L > 200 µm; excretory pore and Vgl-2 near the line of primary sclerotization. Gnathosoma ventral margin strongly curved, gnathosomal rostrum well developed (Figure 3D); P-2 ventral margin nearly straight or slightly convex, P-2 and P-3 ventrodistal protrusions bluntly pointed, P-4 with a ventral tubercle bearing one long and three shorter setae (Figures 3C, 4C). *Male* — Medial suture Cx-II+III short, suture line of Cx-IV slightly evident; genital field
<figure><img src="image_5.png" /><figcaption>**Figure 3** ***Tarreaticola eurytopica n. sp.**, ♂ (A-C holotype, Bar, Rikavac [CCDB_3867_E03]; D-E paratype, Prespa Lake, Oteševo [15. CG2019_7 B12]): A – dorsal shield; B – ventral shield; C – palp, lateral view; D – capitulum; E – ejaculatory complex. Scale bars = 100 µm.*</figcaption></figure>
large, subrectangular; ejaculatory complex with large proximal chamber (Figure 3E). *Female* — Genital field large (Figure 4B).

**Measurements** — *Male* (holotype [CCDB_3867_E03]) — Idiosoma L 859, W 663; dorsal shield L 718, W 514, L/W ratio 1.4; dorsal plate L 673; antero-lateral platelets L 213-220, W 78-79, L/W ratio 2.7-2.8; antero-medial platelet L 138, W 60-61, L/W ratio 2.25-2.3; antero-

<table><caption>**Table 1** Measurements of selected specimens of *Torrenticola meridionalis* and *T. eurytopica* n. sp.</caption><thead><tr><th></th><th><em>Torrenticola meridionalis</em></th><th><em>Torrenticola eurytopica</em> n. sp.</th><th></th><th></th></tr><tr><th></th><th>Italy, Fossiata<br>CCDB 38392 F02, ♂</th><th>North Macedonia, Prespa Lake<br>15. CG2019_7 B12, ♂</th><th>♂</th><th>♀</th></tr></thead><tbody><tr><td>Idiosoma L</td><td>825</td><td>806</td><td>791</td><td>938</td></tr><tr><td>Idiosoma W</td><td>602</td><td>606</td><td>575</td><td>700</td></tr><tr><td>Ds L</td><td>696</td><td>700</td><td>681</td><td>819</td></tr><tr><td>Ds W</td><td>500</td><td>473</td><td>453</td><td>561</td></tr><tr><td>Ds L/W ratio</td><td>1.39</td><td>1.48</td><td>1.5</td><td>1.46</td></tr><tr><td>Dp L</td><td>650</td><td>652</td><td>633</td><td>766</td></tr><tr><td>Al plate L</td><td>206-209</td><td>218-219</td><td>213-216</td><td>225</td></tr><tr><td>Al plate W</td><td>75-78</td><td>84-88</td><td>78-84</td><td>83-91</td></tr><tr><td>Al plate L/W</td><td>2.68-2.75</td><td>2.5-2.6</td><td>2.6-2.7</td><td>2.5-2.7</td></tr><tr><td>Am plate L</td><td>141</td><td>142-144</td><td>136-139</td><td>148-156</td></tr><tr><td>Am plate W</td><td>63</td><td>68-69</td><td>68</td><td>69-72</td></tr><tr><td>Am plate L/W ratio</td><td>2.24</td><td>2.06-2.12</td><td>2.0-2.04</td><td>2.1-2.3</td></tr><tr><td>Al pl L/Am pl L ratio</td><td>1.46-1.48</td><td>1.51-1.54</td><td>1.55-1.56</td><td>1.4-1.5</td></tr><tr><td>Gnathosomal bay L</td><td>166</td><td>147</td><td>156</td><td>178</td></tr><tr><td>Cx-I L</td><td>327</td><td>303</td><td>317</td><td>347</td></tr><tr><td>Cx-I mL</td><td>161</td><td>156</td><td>159</td><td>169</td></tr><tr><td>Cx-II+III mL</td><td>83</td><td>91</td><td>91</td><td>31</td></tr><tr><td>Cx-1 L/Cx-II+III mL</td><td>3.9</td><td>3.3</td><td>3.48</td><td>11.2</td></tr><tr><td>Cx-I mL/Cx-II+III mL ratio</td><td>1.94</td><td>1.71</td><td>1.75</td><td>5.45</td></tr><tr><td>Genital field L</td><td>163</td><td>170</td><td>166</td><td>200</td></tr><tr><td>Genital field W</td><td>141</td><td>130</td><td>131</td><td>165</td></tr><tr><td>Gf L/W ratio</td><td>1.16</td><td>1.3</td><td>1.26</td><td>1.21</td></tr><tr><td>Distance gf—expo</td><td>180</td><td>181</td><td>172</td><td>237</td></tr><tr><td>Distance gf—cauda</td><td>241</td><td>244</td><td>219</td><td>331</td></tr><tr><td>Ec L</td><td>250</td><td>-</td><td>259</td><td>-</td></tr><tr><td>Gnathosoma vL</td><td>316</td><td>312</td><td>305</td><td>348</td></tr><tr><td>Chelicera L</td><td>353</td><td>344</td><td>350</td><td>406</td></tr><tr><td>Palp, total L</td><td>331</td><td>332</td><td>323</td><td>366</td></tr><tr><td>P-1 dL/H</td><td>42/35</td><td>38/34</td><td>34/34</td><td>41/41</td></tr><tr><td>P-2 dL/H</td><td>103/57</td><td>106/56</td><td>105/53</td><td>119/69</td></tr><tr><td>P-3 dL/H</td><td>63/53</td><td>63/52</td><td>61/48</td><td>70/61</td></tr><tr><td>P-4 dL/H</td><td>103/31</td><td>105/33</td><td>103/31</td><td>114/38</td></tr><tr><td>P-5 dL/H</td><td>20/11</td><td>20/16</td><td>20/13</td><td>22/14</td></tr><tr><td>dL P-2/P-4 ratio</td><td>1</td><td>1.01</td><td>1.02</td><td>1.04</td></tr><tr><td>dL I-L-4</td><td>105</td><td>111</td><td>109</td><td>119</td></tr><tr><td>dL I-L-5</td><td>115</td><td>115</td><td>116</td><td>119</td></tr><tr><td>dL I-L-6</td><td>116</td><td>114</td><td>113</td><td>116</td></tr><tr><td>H I-L-6</td><td>44</td><td>42</td><td>40</td><td>44</td></tr><tr><td>dL/H I-L-6 ratio</td><td>2.64</td><td>2.7</td><td>2.9</td><td>2.6</td></tr></tbody></table>
<figure><img src="image_6.png" /><figcaption>**Figure 4** *Tarrenticola eurytopica n. sp.*, ♀, Prespa Lake: A – dorsal shield; B – ventral shield; C – palp, medial view. Scale bars = 100 µm.</figcaption></figure>
lateral/antero-medial platelets L 1.55-1.6. Gnathosomal bay L 158, Cx-I total L 330, Cx-I mL 172, Cx-II+III mL 97; ratio Cx-I L/Cx-II+III mL 3.4; Cx-I mL/Cx-II+III mL 1.77. Genital field L/W 178/141, ratio 1.27; distance genital field-excretory pore 172, genital field-caudal idiosoma margin 239. Ejaculatory complex L 312.

Capitulum vL 323, chelicera L 370; palp total L 326, dL/H: P-1, 36/36; P-2, 107/59; P-3, 61/52; P-4, 102/33; P-5, 20/11; L ratio P-2/P-4, 1.05. dL of I-L-4-6: 111, 116, 114; I-L-6 H 42; dL/H I-L-6 ratio 2.7.

*Female* (paratype, CCDB_3867_E01) — Idiosoma L 978, W 759; dorsal shield L 850, W 619, L/W ratio 1.37; dorsal plate L 789; antero-lateral platelets L 234-247, W 94-97, L/W ratio 2.5-2-55; antero-medial platelets L 169-170, W 80, L/W ratio 2.11-2.14; antero-lateral/antero-medial platelets L 1.37-1.46. Gnathosomal bay L 184, Cx-I total L 363, Cx-I mL 178, Cx-II+III mL 31; ratio Cx-I L/Cx-II+III mL 11.7; Cx-I mL/Cx-II+III mL 5.7. Genital field L/W 191/174, ratio 1.09; distance genital field-excretory pore 275, genital field-caudal idiosoma margin 369.

Capitulum vL 364, chelicera L 423; palp total L 387, dL/H: P-1, 41/45; P-2, 126/70; P-3, 75/61; P-4, 120/38; P-5, 25/14; L ratio P-2/P-4, 1.05. dL of I-L-4-6: 123, 129, 127; I-L-6 H 44; dL/H ratio I-L-6 2.9.

## Etymology

The name of new species refers to diversity of habitats where the new species was collected and combines two Greek words: *eurys* (“wide”) and *topos* (“place”).

## Species delimitation using DNA barcodes

The final alignment for species delimitation using COI sequence data comprised 669 nucleotide positions (nps) of the 134 *Torrenticola* specimens listed in Supplementary material and one outgroup, *Monatractides madritensis* (K. Viets, 1930) from Serbia to root the tree. Genetic data indicate that all examined specimens of the new species form a unique BIN (BOLD:AED7519). The closest neighboring BIN is that of the *T. similis* group (BOLD:AEI3402), comprising specimens from Montenegro, Austria, and Romania. The *p*-distance between these two BINs was estimated at 5.69%.

The NJ tree is presented in Figure 6. In the phylogenetic tree, *T. meridionalis* from southern Italy was recovered as a sister clade to the *T. similis* group (BOLD:AEI3402). The COI sequences obtained from specimens of *T. eurytopica n. sp.* form a strongly supported clade, which is placed as sister to the *T. meridionalis* (southern Italy) + *T. similis* group clade.

The genetic distance between the BIN of the new species (BOLD:AED7519) and the BIN grouping *T. meridionalis* sequences from southern Italy (BOLD:AEK9662) was estimated at 7.18% *p*-distance. The mean intraspecific *p*-distance within the cluster of the new species was 1.35%.

## Discussion

The new species morphologically closely resembles *T. meridionalis*, with which it was previously confused in the Balkans. However, *T. meridionalis* can be distinguished from the new species by the absence of a characteristic dorsal shield colour pattern (Figure 5A), nearly equal lengths of P-2 and P-4 (P-2 slightly longer than P-4 in *T. eurytopica n. sp.*), and in males, by a stouter genital field (L/W ratio ~1.2, vs. >1.25 in *T. eurytopica n. sp.*).

Phylogenetic analysis based on COI data supports the distinction between the two species, revealing a high genetic divergence (COI: 7.18% *p*-distance) between the new species and *T. meridionalis* from southern Italy. This suggests a long independent evolutionary history.

## Biology

The new species appears to be eurytopic, inhabiting springs and running waters at low to medium elevations (Figures 7A-C). But it has also been found in a lacustrine environment (Prespa Lake in North Macedonia; Figure 7D).
<figure><img src="image_7.png" /><figcaption>**Figure 5** Photographs of dorsal shields (vouchered material). A: *Torrenticola meridionalis*, ♂, [CCDB 38392 F02] Calabria, Fossiata. B–F: *T. eurytopica* n. sp.: B – ♂ [CCDB_3867_E03], Rikavac, Bar; C – ♀ [CCDB_3867_E01], Rikavac, Bar; D – ♂ [15. CG2019_7 B12], Oteševo, Prespa Lake; E – ♂, Oteševo, Prespa Lake; F – ♀, Oteševo, Prespa Lake.</figcaption></figure>

**Distribution**

The exact distribution of the new species remains unclear due to historical confusion with *T. meridionalis*. However, it is likely widespread across the Balkans. Previous records of *T. meridionalis* from this region (e.g., Di Sabatino *et al.* 2003; Pešić *et al.* 2018, 2021, 2024b, 2025c), belonging to BOLD:AED7519, likely refer to the new species. Recently, this lineage was reported from a stream in the Babia Góra Mountain in Poland (Szenejko *et al.* 2023).
<figure><img src="image_8.png" /><figcaption>**Figure 6** Neighbour-Joining tree of the genus *Torrenticola*, obtained from 134 nucleotide COI sequences listed in Supplementary material. Sequences of *T. eurytopica* *n. sp.* are marked in red. Bootstrap values >50% from 1000 bootstrap replicates on branches.</figcaption></figure>
<figure><img src="image_9.png" /><figcaption>**Figure 7** Photographs of the sampling sites of *Torrenticola eurytopica* n. sp. A – Montenegro, Bar, the canyon of Rikavac stream (inset: sampling site), the type locality of the new species; B – Biljana's Springs in Ohrid, North Macedonia; C – Bregava River near Stolac, Bosnia and Herzegovina; D – Prespa Lake near Oteševo, North Macedonia. Photos by V. Pešić.</figcaption></figure>
**Key to the European species of the *Torrenticola elliptica* - species group**

This group is characterized by the relatively slender rostrum and palp, longish idiosoma, and in male a short median suture of Cx-II+III and extended postgenital area.

1. Excretory pore embedded in the area of primary sclerotization. *Torrenticola similis*
   — Excretory pore not embedded in the area of primary sclerotization. 2

2. Idiosoma slender (dorsal shield L/W ratio > 1.5). *Torrenticola elliptica*
   — Idiosoma less slender (dorsal shield L/W ratio < 1.5). 3

3. Male genital field enlarged, L/W ratio ~1.20; dorsal shield without a colour pattern. *Torrenticola meridionalis*
   — Male genital field more slender, L/W ratio >1.25; dorsal shield with a colour pattern. *Torrenticola eurytopica n. sp*

**Discussion**

Most species of the water mite genus *Torrenticola* Piersig, 1896 in the Palaearctic region inhabit lotic environments, although some have also been reported from interstitial waters (Di Sabatino *et al.* 2010). Exceptionally, certain *Torrenticola* species have been found to colonize lentic habitats, such as pools (e.g., *T. anomala*; see Di Sabatino *et al.* 2010) or even lakes. For example, Pešić *et al.* (2021) reported that Balkan populations of *T. meridionalis* Di Sabatino & Cicolani, 1990, herein described as *T. eurytopica n. sp.*, inhabit streams and rivers at low to medium altitudes (see also Pešić *et al.* 2018, 2025c), but also colonize Prespa Lake (Figure 7D), one of the oldest permanent lake systems in Europe, situated on the North Macedonia–Albania–Greece border.

Based on our current knowledge, *T. eurytopica n. sp.* appears to be the only member of the genus *Torrenticola* in the Palaearctic known to occur in both standing (lakes) and running (streams and rivers) waters. This kind of bipolar habitat preference is much more commonly observed in other water mite genera, such as *Hygrobates*. For example, *H. nigromaculatus* Lebert, 1879 and *H. longipalpis* (Hermann, 1804) are both widely reported as common European species inhabiting both lakes and streams. However, the status of these *Hygrobates* species has recently been re-evaluated using DNA barcoding, which revealed that lake and stream populations represent morphologically and genetically distinct lineages (see Martin *et al.* 2010 for *H. nigromaculatus*; Pešić *et al.* 2019 for *H. longipalpis*). All these studies, as well as our study, emphasize the importance of using molecular methods in the ecological characterization of water mite species, improving their potential for ecological quality assessment.

**Acknowledgements**

We thank Joanna Mąkol (Wrocław), Harry Smit (Alkmaar) and Mirela Cîmpean (Cluj-Napoca), whose constructive comments greatly improved this work.

**Supplementary material**

List of *Torrenticola* specimens used for building the Neighbour-Joining (NJ) tree (Fig. 6). BINs are based on the barcode analysis from 1 September 2025.
ORCID

Vladimir Pešić https://orcid.org/0000-0002-9724-345X

Andrej Zawal https://orcid.org/0000-0002-5838-6060

Tom Goldschmidt https://orcid.org/0000-0002-5527-1719

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