Monatractides macroporus K. Viets, 1935

Pesic, Vladimir & Smit, Harry, 2009, Water mites of the family Torrenticolidae (Acari: Hydrachnidia) from Thailand, Part II. The genus Monatractides K. Viets, Zootaxa 2012, pp. 1-27 : 20-23

Monatractides macroporus K. Viets, 1935 - complex

( Figs. 85–102 )

Material. Thailand: Fast flowing stream crossing road to Den Ya Kat Station, 410 m asl, Chiang Dao NP, 23.xi.2007, 19° 19.735 N 98° 56.201 E, leg. Smit 1/0/0 (0/1/0 mounted); Pong Creek crossing road to Muang Kong, Doi Chiang Dao, 477 m asl, 22.xi.2007, 19° 24.774 N 98° 55.127 E, leg. Smit 1/1/0 (1/1/0 mounted).

Morphology. Male (from Den Ya Kat Station): Idiosoma (ventral view: Fig. 86 ) L 675, W 469; dorsal shield ( Fig. 85 ) L 531, W 394, L/W ratio 1.35; dorsal plate L 483; shoulder plate L 122, W 56, L/W ratio 2.2; frontal plate L 117, W 53, L/W ratio 2.2; shoulder/frontal plate L ratio 1.04; capitular bay L 148, W 28, L/W ratio 5.3; Cx-1 total L 253, Cx-1 medial L 103, Cx-2+3 medial 66; ratio Cx-1 L/Cx-2+3 medial L 3.8; Cx-1 medial L/Cx-2+3 medial L 1.56; genital field L/W 134/100, L/W ratio 1.34, ejaculatory complex L 184; distance genital field–excretory pore 141, genital field–caudal idiosoma margin 213; capitulum ( Fig. 87 ) ventral L 135; chelicera ( Fig. 88 ) L 156; palp ( Fig. 89 ) total L 148, L and %L (given as % of total L): P-1 20 (13.5), P-2 41 (27.7), P-3 32 (21.6), P-4 38 (25.7), P-5 17 (11.5); P-2/P-4 ratio 1.08; L I-Leg-4-6 ( Fig. 90 ): 74, 79, 76.

In addition we give measurements of the male and female from Pong Creek which are suspected to belong to the same species (general differences see below (in the “remarks”-section)).

Male (from Pong Creek): Idiosoma (ventral view: Fig. 92 ) L 581, W 372; dorsal shield ( Fig. 91 ) L 460, W 322, L/W ratio 1.4; dorsal plate L 425; shoulder plate L 103–109, W 48, L/W ratio 2.1; frontal plate L 100–103, W 45, L/W ratio 2.2; shoulder/frontal plate L ratio 1.0–1.09; capitular bay L 130, W 31, L/W ratio 4.2; Cx-1 total L 219, Cx-1 medial L 88, Cx-2+3 medial 68; ratio Cx-1 L/Cx-2+3 medial L 3.2; Cx-1 medial L/Cx-2+3 medial L 1.3; genital field L/W 109/88, L/W ratio 1.24, ejaculatory complex L 138; distance genital field–excretory pore 127, genital field–caudal idiosoma margin 187; capitulum ( Fig. 95 ) ventral L 129; chelicera L 144; palp ( Figs. 93–94 ) total L 143, L and %L (given as % of total L): P-1 21 (14.6), P-2 39 (27.1), P-3 28 (19.4), P-4 39 (27.1), P-5 17 (11.8); P-2/P-4 ratio 1.0; L I-Leg-5-6 ( Fig. 96 ): 79, 73.

Female (from from Pong Creek): Idiosoma (ventral view: Fig. 98 ) L 713, W 484; dorsal shield ( Fig. 97 ) L 600, W 400, L/W ratio 1.5; dorsal plate 563; shoulder plate L 144, W 56, L/W ratio 2.6; frontal plate L 114, W 53, L/W ratio 2.2; shoulder/frontal plate L ratio 1.26; capitular bay L 147, W 38, L/W ratio 3.9; Cx-1 total L 256, Cx-1 medial L 109, Cx-2+3 medial 44; ratio Cx-1 L/Cx-2+3 medial L 5.8; Cx-1 medial L/Cx-2+3 medial L 2.5; genital field L/W 153/122, L/W ratio 1.25; distance genital field–excretory pore 178, genital field–caudal idiosoma margin 256; capitulum ( Fig. 101 ) ventral L 164; chelicera L 185; palp ( Fig. 100 ) total L 168, L and %L (given as % of total L): P-1 24 (14.3), P-2 49 (29.2), P-3 33 (19.6), P-4 46 (27.4), P-5 19 (11.3); P-2/P-4 ratio 1.07; L I-Leg-4-6 ( Fig. 102 ): 87, 88, 89; L/W ratio I-Leg-6: 2.3.

Remarks. This species belong to the M. macroporus ( K. Viets, 1935) species-complex characterized by the presence of anteriorly slender and elongated Cx-1, a relatively short medial suture line of Cx-2+ 3 in both sexes, and a narrower capitular bay. There are seven similar species in this complex: Monatractides macroporus ( K. Viets, 1935) , M. macrognathus ( K. Viets, 1935) , M. major ( K. Viets, 1935) , M. minor ( Wiles, 1991) , M. longiventris ( Viets, 1939) , M. angulatus ( Walter, 1928) and M. nondescripta ( Cook, 1967) . Lundblad (1971) considered M. macrognathus and M. macrognathus major synonymous with M. macroporus ; and M. transversalis (Lundblad) synonymous with M. longiventris . Wiles (1991) raised M. macrognathus major to a full species, M. major (Viets) . Monatractides angulatus is known from a single female specimen, and differs in the shape of capitular bay which proximal end is rectangular. According to Wiles (1991), M. major and M. minor have four dorsoglandularia in the area of primary sclerotization of the dorsal plate, whereas M. macrognathus and M. macroporus have only two. M. minor closely resembles M. major but differs in minor idiosoma dimensions, the anterior dorsoglandularia on the dorsal plate lying near the anterior end of the medial muscle scar while the anterior margins of the posterior platelets are more swollen ( Wiles 1991), while P-4 is somewhat shorter in M. minor . According to Wiles (1991) it may well be that M. minor is a variety of M. major and that intermediate specimens may be found. Monatractides macroporus has a narrower capitular bay than M. macrognathus but this character is known to be variable in this species (see Lundblad 1971: 320). Due to the frontal plates, which are of equal dimension, or slightly shorter than the shoulder plates (shoulder/frontal plate L ratio 1.0–1.09), the male specimen from Thailand is similar to M. nondescripta (Cook) . However, M. nondescripta has four dorsoglandularia on the area of primary sclerotization of the dorsal plate (see Cook 1967: Fig. 258), while the male specimen from Den Ya Kat Station has only two. The male specimen from Pong Creek has four dorsoglandularia on the area of primary sclerotization of the dorsal plate suggesting that this may not be a reliable taxonomic character. Furthermore, specimens from Pong Creek differ from the male from Den Ya Kat Station in the absence of ventral seta on P-3 on both palps, a character found only as an aberration in Monatractides species. Due to the presence of a very narrower capitular bay (L/W ratio>4.0), well developed Cxgl-4, and Cx-1 anteriorly very slender and elongated, the male specimens from Thailand show a general conformity with descriptions of M. macroporus . Furthermore, the female from Pong Creek differs from the male in the longer shoulder plates (shoulder/frontal plate L ratio 1.26) and matches the species description for M. macroporus .

Understanding the taxonomic position of the species from this group is not possible without additional material from a wide area and/or without the application of molecular genetics techniques.

Figures

FIGURES 85 – 90. Monatractides macroporus (K. Viets) - complex, male, Den Ya Kat Station: 85 = dorsal shield; 86 = idiosoma, ventral view; 87 = capitulum; 88 = chelicera; 89 = palp, medial view; 90 = I-Leg- 5 - 6; Scale Bars = 100 µm.

FIGURES 91 – 96. Monatractides macroporus (K. Viets) - complex, male, Pong Creek: 91 = dorsal shield; 92 = idiosoma, ventral view; 93 = palp, medial view; 94 = palp (P- 1 missing), lateral view; 95 = capitulum and chelicera; 96 = I-Leg- 5 - 6. Scale Bars = 100 µm.

FIGURES 97 – 102. Monatractides macroporus (K. Viets) - complex, female, Pong Creek: 97 = dorsal shield; 98 = idiosoma, ventral view; 99 = anterior portion of Cx- 1; 100 = palp, lateral view; 101 = capitulum and chelicera; 102 = I- Leg. Scale Bars = 100 µm.