Monatractides tristis ( Lundblad, 1941 )

Pesic, Vladimir & Smit, Harry, 2007, First records of water mites (Acari: Hydrachnidia) from Bhutan, with description of two new species, Zootaxa 1613, pp. 45-56 : 53

Monatractides tristis ( Lundblad, 1941)

( Figs. 32–38 )

Material examined. Bhutan: Pele La, 21.iii.2002, 3200 m asl. one female ( ZMAN), dissected and slide mounted in Hoyer's fluid; Dochu La, 28.v.2002, 2800 m asl., one female ( ZMAN).

Morphology. Female (from Pele La, in parentheses some measurements of the specimen from Dochu La): Idiosoma (ventral view: Fig. 33 ) L 1528 (1413), W 1238 (1106), dorsal shield ( Fig. 32 ) L 1275 (1175), W 1056, L/W ratio 1.21; dorsal plate 1156; shoulder plate L 356, W 168, L/W ratio 2.1; frontal plate L 213, W 156, L/W ratio 1.37; shoulder/frontal plate L ratio 1.67; capitular bay L 241, its lateral margin with knobshaped protrusions: one pair at apical tip of Cx-1, two further pairs distally and proximally from subapical seta; Cx-1 total L 469, Cx-1 medial L 228, Cx-2+3 medial 60; ratio Cx-1 L/Cx-2+3 medial L 2.1; Cx-1 medial L/Cx-2+3 medial L 7.8; genital field L/W 313/266, L/W ratio 1.2; egg maximum diameter L 268–281; distance genital field–excretory pore 363, genital field–caudal idiosoma margin 625; capitulum ( Fig. 36 ) ventral L 266; chelicera ( Fig. 37 ) L 313, H 47, L/H ratio 6.7, basal segment L 257, claw L 55, L claw/basal segment ratio 2.1; palp ( Figs. 34–35 ) total L 319, dL and %L (in parentheses, given as % of total L): P-1 35 (11.0), P-2 99 (31.0), P-3 69 (21.6), P-4 87 (27.3), P-529 (9.1); P-2/P-4 ratio 1.14; distal margins of P-2 and P- 3 with denticles, P-4 with a strong rather long mediodistal peg-like seta; L of distal segments of first leg ( Fig. 38 ): I-L-4 194, I-L-5 181, I-L-6 160.

Remarks. Due to the large dimensions of the idiosoma (dorsal shield L> 1000 m), and the presence of three pairs of knob-shaped protrusions at the margin of the capitular bay the specimens from Bhutan show a general conformity with descriptions given for Monatractides tristis by Lundblad (1967). Differences (in parentheses data taken from Lundblad 1967) are found in its large idiosoma and palp dimensions (e.g., idiosoma L 1293, dorsal shield L 1055, genital field L/W 257/225, palp total L 290). As some important characters, such as the presence of denticles at the distal margins of P-2 and P-3, have not been clearly reported in Lundblad’s description, our assignment to M. tristis is provisional.

Distribution. Burma. New for Bhutan.

Figures

FIGURE 32. Monatractides tristis (Lundblad), female: dorsal shield. Scale bar = 100 m.

FIGURE 33. Monatractides tristis (Lundblad), female: ventral shield. Scale bar = 100 m.

FIGURES 34 – 38. Monatractides tristis (Lundblad), female: 34 = palp, medial view; 35 = palp, lateral view; 36 = capitulum; 37 = chelicera; 38 = I – L- 5 / 6. Scale bars = 100 m.