Torrenticola semisuta ( Halík, 1930 )

Pesic, Vladimir & Smit, Harry, 2009, Water mites of the family Torrenticolidae Piersig, 1902 (Acari: Hydrachnidia) from Thailand, Part I. The genera Torrenticola Piersig, 1896, Neoatractides Lundblad, 1941 and Pseudotorrenticola Walter, 1906, Zootaxa 1982, pp. 38-62 : 42-44

Torrenticola semisuta ( Halík, 1930)

( Figs. 15–26)

Material. Thailand: stream near Ban Khoom , alt. 756 m, Doi Ang Kang, 20.xi.2007, 19° 56.905 N 99° 03.938 E, leg. Smit (2/1/0) , one male and one female dissected and slide mounted in Hoyer's fluid; stream W of Bankrang Camp, Kaeng Krachan NP, 30.xi.2007, 12° 48.106 N 99° 26.786 E, leg. Smit (4/1/0) , one male dissected and slide mounted in Hoyer's fluid; stream downstream of Huoay Meng , Waterfall, between Chiang Saen And Chiang Khong, 20.xi.2007, 20° 18.095 N 100° 22.454 E, leg. Smit (3/3/0) , one female dissected and slide mounted in Hoyer's fluid; fast flowing stream crossing road to Den Ya Kat Station, alt. 410 m, Chiang Dao NP, 23.xi.2007, 19° 19.735 N 98° 56.201 E, leg. Smit (2/2/0) ; River at km. 13, alt. 465 m, Doi Inthanon NP, 25.xi.2007, 18° 31.532 N 98° 39.091 E, leg. Smit (1/3/0) , one male and two females dissected and slide mounted in Hoyer's fluid; stream near Haewsai Waterfall, Nam Nao NP, alt. 425 m, 16.xi.2007, 16° 40.668 N 101° 41.856 E, leg. Smit (1/1/0) , one female dissected and slide mounted in Hoyer's fluid; Pong Creek crossing road to Muang Kong, Doi Chiang Dao, alt. 477 m, 22.xi.2007, 19° 24.774 N 98° 55.127 E, leg. Smit (11/11/0) , two males and two females dissected and slide mounted in Hoyer's fluid; unnamed creek crossing track from watchtower, Khao Yai NP 11.xi.2007, 14° 27.533 N 101° 20.386 E, leg. Smit (5/2/1).

Morphology. Male (from Ban Khoom): Idiosoma (ventral view: Fig. 16) L 600, W 475; dorsal shield ( Fig. 15) L 497, W 394, L/W ratio 1.26; dorsal plate 469; shoulder plate L 153, W 48, L/W ratio 3.19; frontal plate L 109, W 44, L/W ratio 2.5; shoulder/frontal plate L ratio 1.4; gnathosomal bay L 153, Cx-1 total L 288, Cx-1 medial L 134, Cx-2+3 medial 55; ratio Cx-1 L/Cx-2+3 medial L 5.2; Cx-1 medial L/Cx-2+3 medial L 2.4; genital field L/W 141/113, L/W ratio 1.25, ejaculatory complex ( Fig. 17) L 203; distance genital field–excretory pore 78, genital field–caudal idiosoma margin 113; capitulum ventral L 288; chelicera L 341; palp ( Figs. 18-19) total L 298, L and %L (in parentheses): P-1 35 (11.8), P-2 100 (33.6), P-3 47 (15.8), P-4 99 (33.2), P-5 17 (5.7); P-2/P-4 ratio 1.0; P-2 ventral projection strongly curved distally.

Female (from Ban Khoom): Idiosoma (ventral view: Fig. 21) L 713, W 569, dorsal shield L 588, W 469, L/W ratio 1.25; dorsal plate 550; shoulder plate L 172, W 56, L/W ratio 3,1; frontal plate L 131, W 50, L/W ratio 2.6; shoulder/frontal plate L ratio 1.3; gnathosomal bay L 172, Cx-1 total L 314, Cx-1 medial L 142, Cx- 2+3 medial 25; ratio Cx-1 L/Cx-2+3 medial L 12.6; Cx-1 medial L/Cx-2+3 medial L 5.7; genital field L/W 153/138, L/W ratio 1.1; distance genital field–excretory pore 141, genital field–caudal idiosoma margin 215; capitulum ventral L 331; chelicera L 381; palp total L 348, L and % L (in parentheses): P-1 42 (12.1), P-2 121 (34.8), P-3 56 (16.1), P-4 111 (31.9), P-5 18 (5.2); P-2/P-4 ratio 1.09; shape and setation as in male.

Remarks. Torrenticola semisuta is characterized by sub-apical Cxgl-4, a ventral projection on P-2 which curves distally, one (of 4) P-4 ventral setae long, a long rostrum and Cx-4 posteriorly extended well beyond genital field in both sexes ( Wiles 1997, Pesic et al. 2007). There is considerable variability in idiosoma measurements and in palp structure (see Figs. 18-20).

Two forms can be found in the same locality, the typical form, with long rostrum, a ventral projection on P-2 which curves distally and proportionally longer P-4 ( Figs. 23, 25). At the other extreme, the larger female specimens have a shorter, deeper rostrum, the ventral projection on P-2 which does not curve distally and proportionally shorter P-4 (see: Figs. 24, 26). However, there is an overlap (specimen from River at km. 13, has a longer rostrum and a shorter P-4). They have not been separated into two different species, even though it is possible to identify two groups within female specimens. Rostrum and palp shape in larger females might be a consequence of growth. Further studies on the variability of populations of T. semisuta from a wide area are necessary before we can assess the taxonomic status of these specimens.

Distribution. Thailand ( Wiles 1997), Peninsular Malaysia, Burma.