Sperchon denticulatus Koenike, 1895

Pešić, Vladimir, Bankowska, Aleksandra, Goldschmidt, Tom, Hårsaker, Karstein, Jovanović, Milica, Kaitetzidou, Elisavet, Krakowiak, Maja, Kozłowska, Aleksandra, Michaloudi, Evangelia, Michoński, Grzegorz, Miliša, Marko, Pozojević, Ivana, Rewicz, Tomasz, Rusiniak, Oliwia, Sobolak, Karolina, Szućko, Izabela, Stryjecki, Robert, Stur, Elisabeth, Szlauer-Łukaszewska, Agnieszka, Szenejko, Magdalena & Zawal, Andrzej, 2025, Checklist of water mites from the Balkan Peninsula: second supplement, new DNA barcodes and description of a new species, Zootaxa 5676 (1), pp. 1-74 : 27-32

Sperchon denticulatus Koenike, 1895 - Pešić et al. (2021a, 2024a).

Material examined. Holotype ♂ ( RMNH), dissected and slide mounted, Bosnia and Herzegovina, Republic of Srpska , Ribnik, spring Ribnik, 44.40379º N, 16.798382º E, 1 Sept. 2012, leg. Pešić. Paratypes: 2♂, 6♀, same data as holotype , one ♀ dissected and slide mounted ( RMNH); same site as holotype, 19 Jun. 2024 leg. Pešić & Zawal , 1♂ [CCDB-48501-D10], 1♀ [ CCDB 48501 D06] (sequenced) , 1♂ dissected and slide mounted (stored in the collection of the first author).

Other material. Bosnia and Herzegovina, Republic of Srpska: Mrkonjić Grad, Sokočnica River , 1 Sept. 2012, leg. Pešić, 1♂, dissected and slide mounted ( RMNH); Trebinje, Trebišnjica river near mouth of Jazine stream, 24 Jun. 2023 leg. Zawal & Pešić 1♀ (sequenced) . Montenegro: Berane, spring near Monastery Djurdjevi Stupovi , 42.8527º N, 19.862º E, 12 Dec. 2019 leg. Pešić, Jovanović & Manović, 1♀ (sequenced); Durmitor, Glava Bukovice, limnocrene spring, 43.058611º N, 19.110556º E, 23 Jun. 2018 leg. Pešić & Zawal, 2♀ (sequenced) .

Diagnosis. Morphological: Integument dorsally and ventrally reticulate. Male postgenital plate relatively large and elongated in longitudinally, L/W ratio>1.5; tip of anterior ramus of ejaculatory complex shallowly indented with laterally rounded, posteriorly slightly pointed extensions; distolateral extension of male IV-leg-5 present but short. Molecular: this lineage represented by a unique BIN (BOLD:AED8428) differs from S. denticulatus clade by 14.8% K2P for COI.

Description. Male (holotype; in parentheses measurements of specimen from Sokočnica River, n=1): Idiosoma ventrally L 900 (800), W 700. Dorsal shield present ( Fig. 2B ), L 894 (769), W 606 (506). Cx-I+II medially close to each other but not fused; Cx-III with a glandularium (Cxgl-4); Cx-field L 453 (397); Cx-III W 450 (403). Genital field with three pairs of acetabula, anterior and middle acetabula elongated, individual genital flaps L 234 (197), L Ac-1-3: 91 (69), 88 (72), 73 (50). Postgenital plate relatively large and elongated in longitudinally, distinctly longer than wide, length/width ratio 2.7 (1.9), may include excretory pore within posterior boundary.

Ejaculatory complex L 484 (450), with an elongate, rod-shaped anterior ramus, the tip shallowly indented with laterally rounded, posteriorly slightly pointed extensions ( Figs. 3 D-E).

Gnathosoma ( Fig. 3B ) ventrally L 266 (231); chelicera L 331 (275), basal segment L 234 (194), claw L 97 (81), L chelicera basal segment/claw ratio 2.4 (2.4). Palp stout; dL/H of palpal segments: P-1, 44/78 (34/81); P-2, 166/120 (159/128); P-3, 141/89 (141/101); P-4, 191/59 (183/59); P-5, 48/25 (42/19); P-2 anterior projection anterior length 38 (28) µm, P-2 dorsally longer than P-3, P-3 ventrally slightly concave, P-4 ventral setae close together (distance 22 µm), P-4 proximoventrally slightly concave forming a slight constriction. dL of I-leg-2-6: 97 (84), 106 (94), 147 (142), 161 (156), 181 (181); dL of IV-leg: 119 (115), 125 (115), 119 (111), 228 (213), 253 (222), 242 (225); distolateral extension of IV-leg-5 present but short ( Fig. 3A ).

Female (paratype): Similar to male except in the lack of a dorsal plate ( Fig. 4B ), postgenital area ( Fig. 4A ) and palp ( Fig. 4C ). Idiosoma ventrally L 810, W 620. Dorsum with two platelets without glandularia, postfrontalia on a relatively large platelet, postocularia free in integument; centrally with a large, paired platelet (Dc-4). Cx-field L 516; Cx-III W 516. Venter without platelets, excretory pore smooth. Genital flaps L 230-237, L Ac-1-3: 97-104, 98, 75.

Gnathosoma ventrally L 316; chelicera L 375, basal segment L 288, claw L 100, L chelicera basal segment/claw ratio 2.9. Palp slender; dL/H of palpal segments: P-1, 38/89; P-2, 209/159; P-3, 265/41; P-4, 276/59; P-5, 53/28; ventral margin of P-3 covered by fine denticulation ( Fig. 4C ). dL of I-leg: 78, 113, 141, 215, 206, 206; dL of IV-leg: 150, 178, 190, 364, 353, 297.

Etymology. The name refers to the geographical provenance (from Latin balcanicus ) from where the new species is described.

Species delimitation using DNA-barcodes. The final alignment for species delimitation using COI sequence data comprised 669 nucleotide positions (nps) for 48 specimens of Sperchon denticulatus -complex ( Table 2); S. glandulosus from Norway was used as outgroup to root the tree. Maximum Likelihood (ML) analysis clustered the COI sequences of the Sperchon balcanicus sp. nov. a sister clade (albeit with a low support of only 19% ML support) to all other species of denticulatus- complex from Europe.

The genetic distance between the COI sequences of S. balcanicus sp. nov. and its closest relative, S. denticulatus , was estimated at 14.8% K2P ( Table 3). The mean K2P intraspecific distance within the clade, herein described as S. balcanicus sp. nov. was estimated at 0.35%.

The ASAP (assemble species by automatic partitioning) method observed a barcode gap of about 4-8% K2P distances ( Fig. 6 ). The applied ASAP procedure identified seven MOTUs (hypothetical species) within the selected Sperchon denticulatus- complex dataset: (1) S. violaceus , (2) S. denticulatus , (3) S. serapae from Türkiye, (4), S. vaginosus , (5) S. gr. denticulatus from Corsica, France, (6) S. hibernicus , and (7) S. balcanicus sp. nov.

Remarks. In regard to the shape of male ejaculatory complex (tip of anterior ramus indented with laterally rounded, posteriorly slightly pointed extensions), morphologically the new species closely resembles Sperchon denticulatus Koenike, 1895 , a species with which it was previously probably confused. The latter species can easily be separate from S. balcanicus sp. nov. by differently shaped male postgenital plate (anteriorly rounded, posteriorly more-or-less straight, longitudinally distinctly wider than long, length/width <1, see Di Sabatino et al. 2010 fig. 8-59b) and IV-leg-5 with prominent distolateral extension (see Lundblad 1956, fig. 39D). The phylogenetic analysis based on COI data proved the high genetic distance (COI 14.8% K2P) between the new species and S. denticulatus suggests a long independent history of these two species.

Habitat. The new species prefers strong karstic springs (such as Glava Bukovice in Montenegro and Ribnik spring in Bosnia and Herzegovina, Fig. 5 ).

Distribution: Bosnia and Herzegovina, Montenegro. Details of distribution are unknown due to the previous confusion with S. denticulatus , but the species is probably widespread in the Balkans. The former records of S. denticulatus from Bosnia and Herzegovina ( Pešić et al. 2024a) and Montenegro ( Pešić et al. 2021a) likely should be assigned to the new species.

Figures

FIGURE 2. Sperchon balcanicus sp. nov., ♂ (A–B, C holotype, Ribnik spring, Bosnia and Herzegovina; C specimen from Sokočnica river, Bosnia and Herzegovina):A—venter; B—dorsal shield; C—posterior part of the venter; D—palp, lateral view. Scale bars = 100 μm.

FIGURE 3. Sperchon balcanicus sp. nov., ♂ (A–E, C holotype, Ribnik spring, Bosnia and Herzegovina; F specimen from Sokočnica river, Bosnia and Herzegovina): A—IV-leg-4-6; B—capitulum; C—chelicera; D—ejaculatory complex; E–F—tip of ejaculatory complex. Scale bars = 100 μm.

FIGURE 4. Sperchon balcanicus sp. nov., ♀, Ribnik spring, Bosnia and Herzegovina: A—venter; B—dorsum (partially damaged); C—palp, lateral view. Scale bars = 100 μm.

FIGURE 5. Photograph of the type locality (Ribnik spring, Republic of Srpska, Bosnia and Herzegovina) of Sperchon balcanicus sp. nov. Photograph by V. Pešić (19 June 2024).

FIGURE 6. Neighbor-Joining tree of Sperchon denticulatus complex obtained from 49 nucleotide COI sequences listed in Table 2. There was a total of 669 positions in the final dataset.The results of species delimitation by ASAP procedure are indicated by vertical bars. Sequences of S. balcanicus sp. nov. are marked in red. BINs are based on the barcode analysis from 1 June 2025.