Sónia Ferreira water mite (Torrenticola soniae) and Elisabeth Stur water mite (Torrenticola elisabethae) as new to science

NEWS - The research team reports Sónia Ferreira water mite (Torrenticola soniae Pešić, sp. nov.) and Elisabeth Stur water mite (Torrenticola elisabethae Pešić, sp. nov.) as new to science and the first results of the analysis of water mites collected in Portugal as part of the Biodiversity Genomics Europe project.

Knowledge about water mites in Portugal is still inadequate. The checklist includes 93 species from 34 genera and 16 families for Portugal and summarizes all previous studies on water mites in Portugal and its islands. Recently, Vladimir Pešić from the University of Montenegro, added 7 new species to the Portuguese water mite fauna.

T. soniae has a relatively short, anteriorly broad Cx-I; suture lines of Cx-IV prominent, starting at right angle from genital field; ejaculatory complex with well-developed anterior keel and proximal arms; gnathosomal rostrum short, less than width of gnathosoma; P-3 with a subrectangular, apically serrated ventrodistal projection. This lineage is represented by a unique BIN that differs from the T. brevirostris clade by 12.27% K2P for COI.

Idiosoma roundish; dorsal shield without a color pattern; area of primary sclerotization of the dorsal plate with two dorsoglandularia; frontal platelets broad, relatively short; Cx-I relatively short, anteriorly broad; gnathosomal bay U-shaped, proximally rounded; Cxgl-4 subapical; medial suture line of Cx-II+III relatively short.

Postgenital area extended; excretory pore and Vgl-2 away from the line of primary sclerotization, excretory pore on the level of Vgl-2; gnathosomal rostrum short, less than depth of gnathosoma; P-2 ventral margin nearly straight or slightly convex, P-2 ventrodistal protrusion bluntly pointed, apically serrated, P-3 with a subrectangular, apically serrated ventrodistal projection, P-4 with a ventral tubercle bearing one long and three shorter setae.

Male: Suture line of Cx-IV evident, medially starting from posterior margin of genital field in a right angle to the main idiosoma axis; genital fields large, subrectangular; ejaculatory complex conventional in shape, anterior keel, proximal and distal arms well developed. Female: Genital field large and pentagonal in shape, suture lines of Cx-IV extending posteriorly beyond posterior margin of genital field, laterally curved.

Male (holotype): Idiosoma (ventral view: Fig. 1B) L 912, W 669; dorsal shield L 756, W 581, L/W ratio 1.3; dorsal plate L 700; shoulder plate L 220–222, W 97, L/W ratio 2.27–2.29; frontal plate L 150–156, W 78–88, L/W ratio 1.8–1.9; shoulder/frontal plate L 1.42–1.47.

Gnathosomal bay L 171, Cx-I total L 359, Cx-I mL 188, Cx-II+III mL 137; ratio Cx-I L/Cx-II+III mL 2.63; Cx-I mL/Cx-II+III mL 1.37. Genital field L/W 191/163, ratio 1.17; distance genital field-excretory pore 116, genital field-caudal idiosoma margin 209. Ejaculatory complex L 291. Gnathosoma vL 331, chelicera L 375; palp total L 398, dL/H, dL/H ratio: P-1, 39/39, 1.0; P-2, 117/73, 1.59; P-3, 84/63, 1.35; P-4, 120/42, 2.86; P-5, 38/17, 2.18; L ratio P-2/P-4, 0.98. dL of I-L-4–6: 134, 150, 136; I-L-6 H 100; dL/H I-L-6 ratio 1.36.

Female (paratype): Idiosoma (ventral view: Fig. 2C) L 1033, W 828; dorsal shield L 844, W 725, L/W ratio 1.16; dorsal plate L 781; shoulder plate L 222–235, W 100–102, L/W ratio 2.2–2.3; frontal plate L 173–175, W 97–98, L/W ratio 1.79; shoulder/frontal plate L 1.28–1.34.

Gnathosomal bay L 200, Cx-I total L 384, Cx-I mL 184, Cx-II+III mL 18; ratio Cx-I L/Cx-II+III mL 21.3; Cx-I mL/Cx-II+III mL 10.2. Genital field L/W 221/198, ratio 1.12; distance genital field-excretory pore 250, genital field-caudal idiosoma margin 391. Gnathosoma vL 350, chelicera L 409; palp total L 435, dL/H, dL/H ratio: P-1, 44/41, 1.08; P-2, 127/76, 1.67; P-3, 93/65, 1.44; P-4, 134/42, 3.18; P-5, 37/18, 2.0; L ratio P-2/P-4, 0.94.

The COI tree sequences derived from the specimens appear as a sister group to the sequence cluster belonging to T. brevirostris (Halbert, 1911), a rhitrobiont species widely distributed in Europe. The average genetic distance between the COI sequences of these two clusters was estimated to be 12.27 ± 1.42% K2P.

This genetic distance is much higher than the estimated barcoding gap found by ASAP analysis (3–5%) of all Torrenticola studied supporting the species status of the new taxon. The average intraspecific K2P divergence within the new species cluster was 0.63 ± 0.19%.

With respect to the presence of a wide and short Cx-I anteriorly, strong and compact palps, and a deep gnathosoma with a short rostrum, the new species resembles T. brevirostris, but can be distinguished by the slightly prominent ventrodistal projection of P-2 and especially P-3.

T. elisabethae has shoulder platelets fused with dorsal plate; dorsal shield with color pattern; Cxgl–4 subapical; medial suture line of Cx-II+III in male relatively long; ejaculatory complex with poorly developed anterior keel and a relatively large proximal chamber. This lineage represents a unique BIN differing from T. lundbladi clade by 9.8% K2P for COI.

Idiosoma oval; shoulder platelets fused to dorsal plate, but suture line visible; dorsal shield with a color pattern; area of primary sclerotization of the dorsal plate with four dorsoglandularia; gnathosomal bay U-shaped, proximally rounded; Cxgl–4 subapical.

Excretory pore and Vgl-2 at the line of primary sclerotization, excretory pore at the level of Vgl-2; gnathosomal ventral margin curved, rostrum elongated; P-2 ventral margin nearly straight or slightly concave, P-2 and P-3 ventrodistal protrusions bluntly pointed, P-4 with a ventral tubercle bearing one long and three shorter setae.

Male - Medial suture line of Cx-II+III relatively long; subrectangular genital fields; ejaculatory complex with poorly developed anterior keel, proximal chamber relatively large. Female - Genital field large and pentagonal in shape.

Male (holotype): Idiosoma (ventral view) L 856, W 691; dorsal shield L 731, W 619, L/W ratio 1.18; dorsal plate L 681; frontal plate L 173–183, W 64–66, L/W ratio 2.7–2.8. Gnathosomal bay L 194, Cx-I total L 383, Cx-I mL 188, Cx-II+III mL 131; ratio Cx-I L/Cx-II+III mL 2.92; Cx-I mL/Cx-II+III mL 1.43.

Genital field L/W 183/150, ratio 1.22; distance genital field-excretory pore 103, genital field-caudal idiosoma margin 127. Ejaculatory complex L 275. Gnathosoma vL 367, chelicera L 448; palp total L 390, dL/H, dL/H ratio: P-1, 44/38, 1.17; P-2, 133/64, 2.08; P-3, 79/58, 1.36; P-4, 112/38, 2.98; P-5, 14/22, 1.55; L ratio P-2/P-4, 1.19. dL of I-L-4–6: 145, 160, 131; I-L-6 H 46; dL/H I-L-6 ratio 2.85.

Female (paratype): Idiosoma (ventral view) L 975, W 794; dorsal shield L 806, W 663, L/W ratio 1.22; dorsal plate L 766; frontal plate L 172–175, W 63–68, L/W ratio 2.6–2.75. Gnathosomal bay L 203, Cx-I total L 391, Cx-I mL 188, Cx-II+III mL 0. Genital field L/W 214/204, ratio 1.05; distance genital field-excretory pore 256, genital field-caudal idiosoma margin 347. Egg (n = 1) maximum diameter 227.

Gnathosoma vL 379, chelicera L 478; palp total L 389, dL/H, dL/H ratio: P- 1, 41/36, 1.15; P-2, 130/64, 2.0; P-3, 80/59, 1.35; P-4, 116/40, 2.87; P-5, 22/14, 1.55; L ratio P-2/P-4, 1.13.

The sequences taken from the specimen appear to be a sister group to the cluster containing sequences of T. lundbladi (K. Viets, 1930), a rhitrobiont species known from Spain. The average K2P genetic distance COI sequences was estimated to be 9.8 ± 1.25%. This is higher than the barcode gap found for Torrenticola in the ASAP analysis. The average intraspecific divergence within the barcode group T. elisabethae is relatively low (0.2 ± 0.14% K2P).

The new species is most similar to T. lundbladi K. Viets 1930 originally described from central Spain. Both species have a dorsal shield with partially fused shoulder plates with dorsal plate, similar dorsal shield color pattern, subapically located Cxgl-4 and relatively long median suture line Cx-II-III in males. However, T. lundbladi differs with the typical shape of the ejaculatory complex (short proximal and distal arms, large proximal chamber, reduced proximal horn).

T. soniae is dedicated to Sónia Ferreira for her collection of numerous specimens and her enthusiastic support in the research of Portuguese water mites. T. elisabethae is dedicated to Elisabeth Stur who facilitated a number of barcoding projects on water mites in Europe.

Original research

Pešić V, Zawal A, Ferreira S, Benitez-Bosco L, Cruz-Oliveira A, Girão D, Padilha A, Turaccio P, Rossini S, Ballini L, Staffoni G, Fratini S, Ciofi C, Iannucci A, Ekrem T, Stur E (2024). DNA barcode library of Portuguese water mites, with the descriptions of two new species (Acari, Hydrachnidia). ZooKeys 1217: 119-171, DOI:10.3897/zookeys.1217.131730

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