Sperchon milisai, Pešić, 2022

Pešić, Vladimir, 2022, Sperchon milisai nov. sp., an overlooked new species of water mites (Acari, Hydrachnidia, Sperchontidae) from Montenegro and Croatia, based on morphological and DNA barcode evidence, Ecologica Montenegrina 51, pp. 81-92 : 86-91

Sperchon milisai sp. nov.

http://zoobank.org/ urn:lsid:zoobank.org:act:FFF79B2D-A5DD-418F-B7E4-C980376104C2

Fig. 3-5

Material examined — Holotype ♂ ( RMNH), dissected and slide mounted, Montenegro, Bar , Rumija Mt. , stream Rikavac above Stari Bar, 42.1001 N, 19.1432 E, 3 June 2020, leg. Pešić. Paratypes: 4 ♀, same data as holotype , two specimens sequenced (CCDB-3867-D01, CCDB38233 C01) , one specimen (CCDB-3867- D01) dissected and slide mounted; 1♀, sequenced ( CCDB 38362 G11), Croatia, Istria, Kanal Botonega , 45.3558 N, 13.8624 E, 18 April 2018 leg. Miliša.

Diagnosis — In both sexes the dorsum has several isolated plates; excretory pore smooth; palp stout, L/H ratio P-2 1.1-1.2, P-3 1.7-1.8; III/IV-L with less densely arranged plumose dorsal setae (IV-L-4 ˂ 10 setae).

Description: Integument dorsally and ventrally reticulate; dorsum with 10 paired muscle attachment plates; from anterior to posterior: medially, (1) round praefrontalia, (2) large plates consisting of fused postfrontalia and postocularia, (3) small plate with fused Dc-1 and Dc-2, (4) Dc-3 close to each other, (5) Dc-4 larger and more distanced from each other than Dc-3, (6) Dc-5 and, laterally, (7–10) Dl-1-4, Dl-1-2 very small, Dl-3-4 larger on a round platelet located at the levels of interspace Dc-3/4, and interspace Dgl-5/Lgl-4, respectively. Venter: Cx-I+II medially close to each other, but not fused ( Fig. 3 ); Cx-III with a glandularium (Cxgl-4). Genital field: Ac-1-2 longish, Ac-3 roundish. An unpaired pre- and postgenital sclerite in male well distanced from genital field; excretory pore smooth ( Figs. 3 , 4F ). Ejaculatory complex in male as given in Figures 5 D-E.

Gnathosoma with rostrum shorter than gnathosomal base ( Fig. 4D ). Palp: P-1 without a dorsal seta; P-2 with long distoventral projection, at its tip bearing three fine setae; ventral margin of P-3 convex or nearly straight; P-4 with small ventral peg-like setae, the distal one far distally ( Figs. 5 A-B).

Leg segments slender, III/IV-L with a row of a densely plumose dorsal setae ( Fig. 5C ); ambulacrum bearing a long dorsal and a shorter ventral clawlet.

Measurements. Male — Idiosoma L 641, W 491; distance between anterior end of Cx-I and posterior end of Cx-IV, 383; Cx-III W 458; L Cx-I+II 197, Cx-III+IV 211. Genital field L/W 158/128, genital valves L 158; L Ac-1-3: 56, 53, 34-38. Ejaculatory complex L 226.

Palp total L 510, dL/H, dL/H ratio: P-1, 30/58, 0.51; P-2, 115/100, 1.15; P-3, 147/84, 1.7; P-4, 177/39, 4.6; P-5, 41/19, 2.2; L ratio P-2/P-4 0.65. Gnathosoma L 188; chelicera L 208, basal segment L 150, claw L 63, L ratio chelicera basal segment/claw 2.4. Leg segments dL: I-L: 65, 83, 84, 142, 131, 163; IV-L: 100, 106, 119, 229, 228, 228.

Female — Idiosoma L 944; distance between anterior end of Cx-I and posterior end of Cx-IV, 447; Cx-III W 606; L Cx-I+II 247, Cx-III+IV 292. Genital field L/W 191/166, genital valves L 175-178, pregenital sclerite W 74; L Ac-1-3: 67-69, 63, 44.

Palp total L 773, dL/H, dL/H ratio: P-1, 35/84, 0.42; P-2, 174/156, 1.12; P-3, 238/130, 1.8; P-4, 270/59, 4.6; P-5, 56/25, 2.2; L ratio P-2/P-4 0.65. Gnathosoma L 272; chelicera L 309, basal segment L 225, claw L 88, L ratio chelicera basal segment/claw 2.6. Leg segments dL: I-L: 69, 97, 116, 191, 197, 209; IV-L: 161, 156, 161, 316, 322, 306.

Etymology — Named after Prof Marko Miliša (University of Zagreb, Croatia), a good friend and outstanding scientist, in appreciation for his inspiring work on the aquatic ecosystems of the Balkans.

Distribution: Montenegro ( Fig. 6 ) and Croatia. Remarks — In regard to the shape of dorsum with several isolated plates in both sexes, stout palps (P-4 L/H 4.5–5.4), IV-L-3-5 with densely arranged plumose dorsal setae, and the shape of ejaculatory complex, the new species from Montenegro and Croatia resembles S. ampliscutatus Pešić & Smit, 2020 and S. hispidus Koenike, 1895 . The latter species can easily be separate from S. milisai sp. nov. by having a sclerotized excretory pore. The presence of a smooth excretory pore makes the new species similar to S. ampliscutatus Pešić & Smit 2020 , a species only known from a stream in the Tian Shan mountains in Kyrgyzstan ( Pešić and Smit 2020). The latter species can be separated from the new species by more densely arranged plumose dorsal setae on IV-L-3-5 (in female IV-L-4 of S. ampliscutatus ˃ 12, in S. milisai sp. nov. ˂ 10 setae), comparatively slender palpal segments, especially P-2 and P-3, in both sexes (dL/H P-2 1.3, P-3 1.9-2.0, data taken from Pešić and Smit 2020) and in the male by fused Dc-3, and a more roundish genital field (compare Fig. 3 with Fig. 16b in Pešić and Smit 2020).

The phylogenetic analysis based on COI data prooved close relationship of the new species of the Western Balkans with S. ampliscutatus from Kyrgyzstan. However, the high genetic distance (COI 15.51±1.6% K2P) between the new species and S. ampliscutatus suggests a long independent history of these two species.

It is possible, that the female of the new species, due to the unsclerotized excretory pore, was confused in the past with Sperchon clupeifer , a species often reported from streams in Europe including the Balkans ( Pešić et al. 2010, 2018). The latter species can easily be separate from the new species as males are bearing a dorsal shield, more slender palps (P-4 L/H ratio ˃ 5.5) and a differently shaped ejaculatory complex.

Figures

Figure 3. Sperchon milisai sp. nov., holotype ♂, Rikavac, Montenegro: idiosoma, ventral view. Scale bar = 100 µm.

Figure 4. Sperchon milisai sp. nov. (A, C-D, holotype ♂; B, E-F, paratype ♀), Rikavac, Montenegro: A – idiosoma, dorsal view; B – idiosoma, dorsal view, partially; C – chelicera; D – gnathosoma in dorsal view; D – genital field and left coxae; F – excretory pore area. Scale bars = 100 µm.

Figure 5. Sperchon milisai sp. nov. (B-E, holotype ♂; A, paratype ♀), Rikavac, Montenegro: A-B – palp, medial view; C – IV-leg; D – ejaculatory complex; D – photograph of ejaculatory complex. Scale bars = 100 µm.

Figure 6. Rikavac stream in Montenegro - locus typicus of Sperchon milisai sp. nov. A – view from Old Bar. B – sample site.