Atractides disabatinoi, Pešić & Goldschmidt, 2023

Pešić, Vladimir & Goldschmidt, Tom, 2023, New DNA-assisted records of water mites from Sardinia, with the description of a new species (Acari, Hydrachnidia), Ecologica Montenegrina 69, pp. 24-44 : 36-39

Atractides disabatinoi sp. nov.

https://zoobank.org/ urn:lsid:zoobank.org:act:D10BCD8C-EC34-412A-A405-5D505191AC9C

Figs. 6 A-E, 7A-C

Type material — Holotype ♂, (sequenced; voucher ID: CCDB-44301-H09), ITALY, Sardinia, Comune di Fluminimaggiore, It 2022-2a, outflow of Sorgente Pubusinu , S of Fluminimaggiore, approx. 5km gravel road from the junction of the SS 126 to the E, small stream, moss, 39.4101° N, 8.5272° E, 198 m asl., 7. Aug. 2022, leg. Goldschmidt, dissected and slide mounted ( RMNH) . Paratypes: It 2022-2b, outflow of Sorgente Pubusinu, S of Fluminimaggiore, approx. 5km gravel road from the junction of the SS 126 to the E, small stream, stones, gravel, sand, 39.4101° N, 8.5272° E, 198 m asl., 7. Aug. 2022, leg. Goldschmidt, 1♂ (sequenced; voucher ID: CCDB-44301-H07); It 2022-1c, Sorgente Pubusinu, S of Fluminimaggiore, approx. 5km gravel road from the junction of the SS 126 to the E, strong karst spring, moss carpet on broken dam, 39.4099° N, 8.5275° E, 206 m asl., 7. Aug. 2022, leg. Goldschmidt 1♀ (sequenced; voucher ID: CCDB- 44301-H06), dissected and slide mounted ( RMNH) .

Diagnosis — Characters of the A. nodipalpis -complex (integument finely striated, muscle insertions unsclerotized; males with anteriorly indented genital field, P-2 with disto-ventral projection and ventral margin of P-4 projecting); genital field with relatively small acetabula, in a weakly curved line, antero-medial margin of male genital plate weakly indented; IV-L-4/5 with pointed lateral sheets covering the articulation of the next segments.

Description. General features — Integument striated, muscle insertions unsclerotized. Medio-caudal margin of Cx-I convex, apodemes of Cx-II in an obtuse angle ( Fig. 7A ). Genital field with relatively small acetabula, in a weakly curved line. Excretory pore smooth; Vgl-1 not fused with Vgl-2. Palp with strong sexual dimorphism, P-4 ventral seta long, near proximo-ventral seta. I-L-5 long, with diverging ventral and dorsal margins, S-1/-2 with blunt tips, S-1 longish and slender, S-2 shorter and proximally thickened; I-L-6 curved and slender, maximum height proximally, equally curved and narrowed from base to tip ( Figs. 6C , 7C ). Male — Antero-medial margin of genital field weakly indented, posterior margin indented; Ac-3 not elongated, with anterior tips distant from the posterior tips of Ac-1 ( Fig. 6B ). Ventral margin of P-2 with strong disto-ventral protrusion consisting of a bluntly pointed medial hump and an equally convex lateral thickening; P-4 stout, with a dense cover of fine dorsal setae, maximum height on the level of the proximo-ventral seta; sword seta inserting posterior to proximo-ventral seta ( Figs. 6 D-E); IV-L-4/5 with pointed lateral sheets covering the base of subsequent segments ( Fig. 6A ). Female — Ventral margin of P-2 straight with rounded distal margin, ventral margin of P-3 slightly concave, P-4 slender, slightly protruding near proximo-ventral seta ( Fig. 7B ).

Measurements. Male (holotype CCDB-44301-H09) — Idiosoma L 825. Coxal shield L 458; Cx-III W 547; Cx-I+II mL 144, Cx-I+II lL 306. Genital field L/W 134/155, ratio 0.87, L Ac-1-3: 39, 37-39, 42-44.

Palp — total L 416; dL/H, ratio dL/H: P-1 42/41, 1.04; P-2 100/86, 1.16; P-3 107/59, 1.80; P-4 120/45, 2.64; P-5 47/18, 2.63; length ratio P-2/P-4 0.84. Gnathosoma (with apodemes included) L 223; chelicera total L 297. Ejaculatory complex L 139.

Legs — I-L-5 dL 284, vL 188, dL/vL ratio 1.51, HB 77, dL/HB 3.71, S-1 L 132, L/W ratio 10.6, S-2 100, L/W ratio 5.3, distance S-1-2, 29, dL ratio S-1/2 1.32; I-L-6 dL 188, HB 24, dL/HB ratio 7.75; L I-L-5/6 ratio 1.52. dL of IV-L-1 to -6: 170, 134, 222, 313, 325, 263.

Female (paratype CCDB-44301-H06) — Idiosoma L 1030. Coxal shield L 525; Cx-III W 630; CxI+II mL 147, Cx-I+II lL 313. Genital field L/W 197/202, genital plate L 145-147, pregen W 108, L Ac-1-3: 42-43, 39, 40-42.

Palp — total L 520; dL/H, ratio dL/H: P-1 47/44, 1.07; P-2 113/81, 1.38; P-3 144/58, 2.49; P-4 163/39, 4.16; P-5 53/19, 18.8; length ratio P-2/P-4 0.69. Gnathosoma (with apodemes included) L 234; chelicera total L 331.

Legs — I-L-5 dL 361, vL 237, dL/vL ratio 1.52, HB 93, dL/HB 3.879, S-1 L 159, L/W ratio 9.3, S-2 114, L/W ratio 4.56, distance S-1-2, 40, dL ratio S-1/2 1.4; I-L-6 dL 235, HB 25, dL/HB ratio 9.4; L I-L-5/6 ratio 1.54.

Etymology — The new species is named after our colleague Antonio Di Sabatino (L'Aquila, Italy) in recognition of his enthusiasm and work on water mites of Italy.

Species delimitation using DNA-barcodes — The final alignment for species delimitation using COI sequence data comprised 678 nucleotide positions (nps) of the 63 specimens of the Atractides nodipalpis species group with A. acutirostris (Koenike, 1908) (HYDIR025-23) of the subgenus Tympanomegapus Thor, 1923 from Turkey and Mixobates processifer (Thor, 1905) from Norway used as outgroups ( Fig. 8 ). The sequences of specimens from Sardinia form a highly supported clade which is placed (albeit with a low support) as a sister species of A. robustus from Montenegro and Bosnia and Herzegovina. The COI sequences form a unique cluster (BOLD:AFC4126), with the nearest neighbouring BIN being BOLD:ADZ9348 which includes 54 specimens from Germany, Montenegro, Romania, Bosnia and Herzegovina, Austria, Italy, Albania and Greece assigned to A. robustus . The genetic distance (11.22% p - distance) between these two clades indicates a long independent history of these species.

Discussion — The new species from Sardinia morphologically resembles Atractides robustus ( Sokolow, 1940) , originally described as a subspecies of A. nodipalpis . From the latter species, A. robustus can be separated with certainty only in males (IV-L-4/5 with pointed lateral sheets covering the articulation of the next segments, P-4 sword seta proximal to proximo-ventral seta; Gerecke 2003). Atractides robustus was originally described by Sokolow (1940) from the affluents of Kuban River in the Caucasus. Recently the taxonomic status of A. robustus was questioned by Pešić et al. (2023c) who showed the presence of at least two lineages within A. robustus . The first lineage encompasses three BINs (BOLD:AEI1810, BOLD:AEK3669, BOLD:AED3548) of specimens from Eastern Turkey and Northern Iran, which probably belong to the same species as indicated by the results of the ASAP delineation procedure ( Fig. 8 ). Considering the proximity of the locality from which these BINs originate and the locus typicus of A. robustus , it seems appropriate to assume that this lineage is conspecific with the latter species. The second lineage, on the other hand, includes populations from Central Europe and the Balkans which fall within BIN cluster BOLD:ADZ9348. As emphasized by Pešić et al. (2023c), the latter populations from Central Europe and the Balkans might represent a new sister species but the final decision needs to be postponed until material of A. robustus from its locus typicus in the Caucasus is available.

The new species from Sardinia differs in both sexes from Atractides robustus in the acetabula being comparatively smaller, roundish and arranged in a curve (vs. larger, subtriangular in shape and showing a triangular arrangement in the latter species). Furthermore, in males of A. robustus , both anterior and posterior margins of the genital field are strongly indented, anteriorly with a small projection in the centre of the indentation and Ac-3 rather long and with the anterior margin approaching the posterior margin of Ac-1 (see Figs. 6B and -F for comparison).

Remarks — The previous records of A. robustus from Sardinia ( Gerecke 2014b) likely should be assigned to the new species.

Distribution — Italy (Sardinia).

Figures

Figure 6A-E Atractides disabatinoi sp. nov., holotype ♂ [CCDB_44301_HO9], ITALY, Sardinia, Comune di Fluminimaggiore, outflow of Sorgente Pubusinu, It 2022-2a. A – IV-L-4 and -5 (arrow indicate pointed lateral sheet covering the articulation of the next segment); B – genital field; C – I-L-5 and -6; D – palp, lateral view; E – palp, medial view. F A. robustus (Sokolow, 1940), ♂, MONTENEGRO, Morača river: genital field. Scale bars = 100 μm.

Figure 7A-C. Atractides disabatinoi sp. nov., paratype ♀ [CCDB_44310_HO6], ITALY, Sardinia, Comune di Fluminimaggiore, Sorgente Pubusinu, It 2022-1c. A – coxal and genital field; B – palp, medial view; C – I-L-5 and -6. Scale bar = 100 μm.

Figure 8. Neighbour-Joining tree of the genus Atractides obtained from 64 nucleotide COI sequences. The results of species delimitation by ASAP procedure are indicated by vertical bars.