Unionicola (Majumderatax) srilankana, Pešić & Zawal, 2018

Pešić, Vladimir & Zawal, Andrzej, 2018, A new species in the water mite subgenus Majumderatax Vidrine, 1993 from Sri Lanka (Acari: Hydrachnidia), Zootaxa 4457 (2), pp. 346-350 : 346-349

Unionicola (Majumderatax) srilankana sp. nov. ( Figs. 1–3 )

Type material. Holotype female ( RMNH), dissected and slide mounted, Sri Lanka, Mahaweli River E of Gallella; slow water flow, width 15 m, depth 0.5 m, sandy bottom with organic matter, Eichhornia crassipes on water surface, 7°54'35.6"N, 81°06'15.2"E , 39 m asl., 2.i.2017, leg. A. Zawal. Paratypes: one male, one deutonymph, same data as holotype, dissected and slide mounted ( RMNH) .

Diagnosis. Dorsum with a two pairs of muscle attachment platelets; P-4 with a serrated hyaline margin and two proximal projections on ventral margin; in the female anterior pair of genital plates medially with a cone-shaped extension bearing three peg-like setae. Cx-II and -III with hook-like extensions.

Description. General features (Adults). Dorsum with two pairs of muscle attachment platelets, anterior platelet elongated and close to each other, medial to Dgl-1, posterior platelet further apart, posteromedial to Dgl-2, knob-shaped ( Fig. 1A ). Coxae with a reticulate pattern, Cx-II laterally with two hook-like extensions, Cx-III laterally with two hooklike extensions. Cx-IV each with a short posterior apodeme ( Fig. 1B ) and a laterally directed extension. I-L-5 distally with three strong setae, two short stout setae located at distal margin and one larger and blade-like ( Fig. 1E ). Palp: P-2 medially with two short serrate setae; P-4 with a hyaline serrated ventral margin and with a small seta and two proximal projections on ventral margin, one distal bearing a peg-like seta; P-5 claw bifurcated into two very long, slender clawlets ( Fig. 1C ). Legs: number of swimming setae: III-L-4, 3; III-L-5, 3; IV-L-4, 3; IV-L-5, 3.

Female (holotype). Idiosoma L 590, W 465. Genital field with paired anterior wing-shaped plates, two acetabula and medially a cone-shaped extension bearing three peg like setae, posterior plates with three acetabula in triangular arrangement ( Fig. 1G ). Palp: total L 412, dL/H, dL/H ratio: P-1, 19/55, 0.34; P-2, 128/80, 1.6; P-3, 42/71, 0.59; P-4, 159/ 44, 3.6; P-5, 64/36, 1.79; L P-2/P-4 ratio 0.81. Gnathosoma L 188, W 103; L chelicera 152, cheliceral claw 89. Legs: dL of I-L-4-6: 100, 89, 109; L of I-L-5 blade-like distoventral seta 63; dL of IV-L: 73, 92, 108, 145, 172, 145.

Male (paratype). Idiosoma L 460. Genital field (L/W 80/131) with acetabula grouped, two anteriorly and three posteriorly and with a few small setae scattered over the genital plates ( Fig. 2A ): Palp ( Fig. 2B ): total L 374, dL/H, dL/H ratio: P-1, 16/47, 0.33; P-2, 103/69, 1.49; P-3, 39/58, 0.68; P-4, 144/43, 3.3; P-5, 72/30, 2.4; L P-2/P-4 ratio 0.72. Legs: dL of I-L-4-6: 88, 86, 88; L of I-L-5 blade-like distoventral seta ( Fig. 2C ) 55; dL of IV-L-4-6: 109, 152, 161.

Deutonymph. Idiosoma L 331. Dorsum with one pair of muscle attachment platelet. Provisional genital field with two pairs of acetabula ( Fig. 3A ). Palp: total L 268, dL/H, dL/H ratio: P-1, 12/36, 0.33; P-2, 73/39, 1.88; P-3, 28/38, 0.75; P-4, 102/36, 2.83; P-5, 53/22, 2.43; L P-2/P-4 ratio 0.72; P-2 with one medial serrate seta ( Fig. 3B ). Legs: dL of I-L: 34, 39, 56, 58, 57, 78; L of I-L-5 blade-like distoventral seta 50; dL of IV-L: 39, 47, 59, 84, 103, 116; number of swimming setae: III-L-4, 2; III-L-5, 2; IV-L-4, 2; IV-L-5, 2.

Etymology. The new species is named after its occurrence on Sri Lanka.

Remarks. The combination of P-4 with a hyaline serrated ventral margin bearing a small seta and the two medial serrate setae on P-2 makes the new species from Sri Lanka most similar to Unionicola grandiseta Savatenalinton & Smit, 2017 described on the basis of two females from Thailand ( Savatenalinton & Smit 2017). The female of latter species can easily be distinguished from Unionicola srilankana sp. nov. in having one pair of platelet on the dorsum, one small ventral seta located behind the hyaline serrated margin of P-4, and with one peg-like seta only on the anterior genital plate.

Distribution. Sri Lanka; known only from the type locality.

Figures

FIGURE 1. Unionicola srilankana sp. nov., female holotype, Mahaweli River E of Gallella, Sri Lanka: A = idiosoma, dorsal view; B = idiosoma, ventral view; C = palp; D = palp (P-1-3); E = I-L-4-6; F = IV-L-2-6 (inset claw); G = genital field. Scale bars = 100 µm.

FIGURE 2. Unionicola srilankana sp. nov., male paratype, Mahaweli River E of Gallella, Sri Lanka: A = idiosoma, ventral view; B = palp; C = blade-like distoventral seta at I-L-5. Scale bars = 100 µm.

FIGURE 3. Unionicola srilankana sp. nov., deutonymph, Mahaweli River E of Gallella, Sri Lanka: A = idiosoma, ventral view; B = palp; C = I-L-5 and -6. Scale bars = 100 µm.