Monatractides (Monatractides)

Pešic, V. & Smit, H., 2016, New records of water mites from Southeast Asia (Acari: Hydrachnidia) with the description of two new genera and 12 new species, Acarologia 56 (3), pp. 393-433 : 394-396

Monatractides (Monatractides) sp.

( Figure 1 )

Material examined — Vietnam, 15-44-1 Bach MAE National Park, brook with a pool behind a natural barrier, 16°11’15.5"N, 105°50’54.7"E, alt. 1130 m a.s.l., water depth 0.2 m, substrate: leaves in a lentic bay, 2.v.2015, 0/1/0 (mounted) .

Morphology — Female: Idiosoma elongatedoval; shoulder plates only slightly longer than frontal plates; frontal margin medially straight between large anterolaterally pointed apodemes (Figure 1A); Cxgl-4 located far anteriorly, near tips of Cx-I; gnathosomal bay deep, U-shaped; suture lines of Cx-IV distinct, originating from lateral edge of genital field and extending posteriorly beyond posterior margin of genital field; genital field large and pentagonal in shape, anteriorly enlarged, laterally straight or slightly convex, tapering posteriorly; excretory pore and Vgl-2 well separated from the line of primary sclerotization, Vgl-2 posterior to excretory pore; gnathosoma with long dorsal apodemes, rostrum truncated ( Figure 1E ); ventral and dorsal setae of P-2 and P-3 relatively strong and long, P- 2 and P-3 distal margins without pointed tips, P-4 stout, ventral setae short, not reaching the tip of P-5 ( Figure 1D ).

Measurements — Idiosoma L 792, W 567; dorsal shield L 663, W 459, L/W ratio 1.44; dorsal plate L 606; shoulder plate L 150 – 156, W 73 – 75, L/W ratio 2.0-2.1; frontal plate L 130 – 131, W 72 – 74, L/W ratio 1.76 – 1.8; L shoulder/frontal plate ratio 1.15 – 1.2. Gnathosomal bay L 141, Cx-I total L 256, Cx-I mL 116, Cx-II+III mL 54; ratio Cx-I L/Cx- II+III mL 2.21; Cx-I mL/Cx-II+III mL 4.8. Genital field L/W 156/146, ratio 1.07; egg maximum diameter 203; distance genital field-excretory pore 209, genital field-caudal idiosoma margin 325. Chelicera total L 208; palp total L 185, dL/H, dL/H ratio: P- 1, 26/25, 1.07; P-2, 54/39, 1.4; P-3, 39/32, 1.22; P- 4, 46/23, 2.0; P-5, 20/11, 1.9; L P-2/P-4 ratio 1.17. Legs: dL of I-L-4–6: 102, 103, 103; I-L-6 H 84, dL/H I-L-6 ratio 1.22.

Remarks — The single female from Vietnam resembles superficially specimens tentatively included in the so-called M. macroporus (K. Viets, 1935) -complex (see Wiles 1991, Peši´c and Smit 2009, 2014b). This group includes several similar species known from SE Asia, i.e., M. angulatus (Walter, 1928) ( India) , M. macroporus (K. Viets, 1935) (Sumatra, Java, Borneo), M. major (K. Viets, 1935) (Java) , M. longiventris (Viets, 1939) (Java, Borneo), M. tranversalis (Lundblad, 1941) ( Myanmar) , M. nondescripta (Cook, 1966) ( India) , M. minor Wiles, 1991 ( Malaysia) and M. epiales Peši´c & Smit, 2014b (Borneo). The specimen from our study differs in less narrower gnathosomal bay and somewhat shorter P-4 (L P-4/P-3 ratio ≈ 1.2). In this character state, it agrees with M. minor Wiles, 1991 from Malaysia, a species differing in minor idiosoma and palp dimensions and four dorsoglandularia on the dorsal plate (Wiles 1991). Understanding the taxonomic position of the species of this complex species is not possible without the application of molecular techniques ( Peši´c and Smit 2014b), so introducing a new species on basis of a female will create more confusion given the present state of knowledge of this species.

Figures

FIGURE 1: Monatractides (Monatractides) sp., female, Bach MAE National Park, Vietnam: A – frontal margin of idiosoma, dorsal view; B – dorsal shield; C – idiosoma, ventral view; D – palp, lateral view (P-1 lacking); E – gnathosoma; F – I-L-5 and -6. Scale bars – 100 µm.