Hygrobates (Hygrobates) ponticus yildirimi, Pešić & Zawal & Gülle & Cakmak & Saboori, 2023

Pešić, Vladimir, Zawal, Andrzej, Gülle, Pinar, Cakmak, Ibrahim & Saboori, Alireza, 2023, Integrative description of a new subspecies of the water mite genus Hygrobates Koch, 1837 from southwestern Türkiye (Acariformes, Hydrachnidia, Hygrobatidae), Ecologica Montenegrina 70, pp. 14-23 : 17-22

Hygrobates (Hygrobates) ponticus yildirimi subsp. nov.

https://zoobank.org/ urn:lsid:zoobank.org:act:B5642966-444E-4257-933F-72DCCB40D589

Figs. 1-2

Material examined — Holotype ♀, sequenced ( HYDOC057-22 ), dissected and slide mounted ( RMNH), TÜRKIYE, Isparta Province, Aksu, Pazarköy, Aksu Stream-Köprüçay River , 37.7454° N, 31.0275° E, 1187 m asl., 21. August 2022 leg. Gülle. Paratypes: 1♀, same place and data as the holotype, sequenced ( HYDOC059-22 ) ; 1♂, sequenced ( HYDIR016-23 ) , Aydin Province, TR6-2023 stream near Şirindere , 37.9297° N, 27.7775° E, 14. March 2023, leg. Pešić, dissected and slide mounted ; 1♀, sequenced ( HYDIR030-23 ) , Aydin Province, TR12-2023 Tabakhane stream near Kalfaköy , 37.8744° N, 27.8459° E, 18. March 2023, leg. Pešić (all RMNH) .

Diagnosis — Morphological: P-2 with a triangular, bluntly pointed, moderately elongated (L/W ratio about 1.2) ventrodistal projection. Anterior margin of the male genital field with a shallow indentation and a small knob-shaped medial projection in the centre of the indentation; Ac-2 and Ac-3 placed next to each other; female gonopore longer than the genital plates. Molecular: this lineage differs from H. ponticus ponticus clade from Georgia and Eastern Türkiye by 10.2% K2P for COI.

Description. General features — Colour yellow to brown, integument soft, strongly lineated. Posteromedial margin of Cx-I+II obtuse-triangular, caudo-lateral apodemes of Cx-I+II moderately developed; Cx-IV subtriangular, with a distinct nose-like protruding medial margin ( Figure 1A ). Acetabula in triangular arrangement. P-2 ventral margin distally forming a triangular, bluntly pointed projection covered by small, scattered denticles; P-3 with denticles covering distal two-thirds of ventral margin; P-4 ventral setae separated ( Figures 2 A-B, D). Male — Anterior margin of genital field with a shallow indentation and a small knob-shaped medial projection in the centre of indentation, genital plate typically with an irregular margin of secondary sclerotization, posterior margin of genital field deeply indented with a small protrusion in the centre of the indentation, not extending beyond the posterior margin, Ac-3 subtriangular but not strongly elongated ( Figure 1B ). Female — Genital plates with a narrow border of porose secondary sclerotization, gonopore longer than genital plates ( Figure 1A ).

Measurements. Female (holotype, CCDB_44300_E09) — Idiosoma L 700; coxal field: L 338; CxIII 400; mL of Cx-I + gnathosoma L 286; distance between lateralmost ends of caudo-lateral Cx-II apodemes, 111; genital field L/W 194/222; genital plates L 113-116; pregenital sclerite W 92; gonopore L 167; L Ac 1-3: 44-46, 50-55, 56.

Palp — Total L 404; dL/H, dL/H ratio: P-1, 30/35, 0.85; P-2, 106/70, 1.51; P-3, 86/59, 1.45; P-4, 134/33, 4.1; P-5, 48/17, 2.77; P-2/P-4 ratio 0.79.

Legs — dL of I-L: 66, 80, 92, 134, 144, 141. dL of IV-L-2-6: 109, 156, 220, 238, 202.

Male (paratype, CCDB_39399_B04) — Idiosoma L 594, W 488; coxal field: L 291; Cx-III W 319; mL of Cx-I + gnathosoma L 188; distance between lateralmost ends of caudo-lateral Cx-II apodemes, 101; genital field L/W 111/150, ratio 0.74; L Ac 1-3: 34-38, 48, 38-41. Ejaculatory complex L 134.

Palp — Total L 351; dL/H, dL/H ratio: P-1, 25/31, 0.8; P-2, 86/60, 1.43; P-3, 73/53, 1.38; P-4, 123/28, 4.39; P-5, 44/17, 2.55; P-2/P-4 ratio 0.7. Chelicera total L 239, L basal segment 159, claw 80, L basal segment/claw ratio 2.0.

Legs — dL of I-L: 55, 66, 81, 124, 131, 134. dL of IV-L-1-6: 106, 91, 130, 194, 216, 187.

Etymology — The new subspecies is named after Prof. dr. Mehmet Zeki Yıldırım (Mehmet Akif Ersoy University, Burdur, Türkiye) in appreciation of his contribution to hydrobiological research of Türkiye.

Species delimitation using DNA-barcodes — The final alignment for the species delimitation using COI sequence data comprised 1774 nucleotide positions (nps) for 36 specimens of the Hygrobates calliger - complex taken from Pešić et al. (2022) and 10 specimens from this study ( Table 2). One specimen of H. corsicus Pešić & Smit, 2017 (NOVMB011-21) from Corsica was used as an outgroup. The Neighbour-Joining analyses clustered COI sequences of the analysed specimens into seven maximally supported clades, six of them corresponded to the previously known clades of the H. calliger -complex in Pešić et al. (2022). The clade containing sequences of specimens from southwestern Türkiye used in this study was placed with high support as a sister to clade grouping sequences of H. ponticus from Georgia and Eastern Türkiye ( Fig. 3 ). The COI sequences form a unique cluster (BOLD:AEY7516), with the nearest neighbouring BIN being that of H. ponticus (BOLD:AEO0649). The genetic distance between these two clades was estimated at 10.2±1.4% K2P (see Table 3).

The ASAP delimitation method identified MOTU (molecular operational taxonomic units) which matched the clades in Pešić et al. (2022). The best ASAP score had 3.50 at a threshold distance of 12.106% K2P identified H. ponticus clade from Georgia and Eastern Türkiye and the clade from southwestern Türkiye as a single MOTU. On the other hand, the second best score of ASAP (6.0) a threshold distance of 6.885% K2P separated the latter two clades into different MOTUs.

Discussion — The molecular analysis based on COI data placed the specimens of H. calliger complex from southwestern Türkiye used in this study for molecular analysis as sister to a clade containing specimens of H. ponticus Pešić, Esen & Mumladze, 2022 from Georgia and Eastern Türkiye. Morphologically, specimens of the latter clade resemble specimens from southwestern Türkiye by relatively long gonopore in females, which exceed the length of the genital plate. However, in the new subspecies, the ventrodistal projection of P-2 tends to be somewhat longer in comparison to the H. ponticus clade from Georgia and Eastern Türkiye (L/W ratio: 1.2 vs. 1.0 in H. p. ponticus Clade).

Based on the molecular and morphological evidence and the geographical isolation of the clades (allopatric populations), we propose the presence of two subspecies: H. ponticus ponticus Pešić, Esen & Mumladze, 2022 ( Georgia, Eastern Türkiye) and H. ponticus yildirimi ssp. nov. (southwestern Türkiye). A possible future discovery of the co-occurrence of these clades/morphotypes could indicate their reproductive isolation and would potentially justify their subsequent elevation to the status of distinct species.

Distribution — Southwestern Türkiye (Aydin and Isparta Provinces).

Figures

Figure 1. Hygrobates ponticus yildirimi ssp. nov. (A – ♀ holotype CCDB_44300_E09; B – ♂ paratype CCDB_39399_B04). A – coxal and genital field; B – genital field. Scale bars = 100 μm.

Figure 2. Hygrobates ponticus yildirimi subsp. nov. (A-C – ♂ paratype CCDB_39399_B04; B – ♀ holotype CCDB_44300_E09). A – palp, medial view; B – palp, lateral view (P-1 lacking); C – I-L-5 and -6; D – palp, lateral view. Scale bar = 100 μm.

Figure 3. Neighbour-joining tree of the Hygrobates calliger-complex obtained from 47 nucleotide COI sequences.