Todothyas

Sabatino, Antonio Di, Gerecke, Reinhard, Gledhill, Terence & Smit, Harry, 2009, On the taxonomy of water mites (Acari: Hydrachnidia) described from the Palaearctic, part 2: Hydryphantoidea and Lebertioidea, Zootaxa 2266, pp. 1-34 : 3-4

Todothyas (s. str.) colligera ( K. Viets, 1923)

Thyas rivalis colligera K. Viets, 1923

Thyas distinctus Tuzovskij, 2007 , nov. syn.

Material examined: Holotype Ƥ SMF 47561, Germany, Ratzeburg, Tümpelquelle im Walde 18.4.1919 Viets leg. 2421b; Germany, Bremen, Mahndorf, SMF 47527, (0/1/0) labeled " Thyas palustris ". The Netherlands, coll. B. Van Maanen: Kesteren, semipermanent clay ditch, 0 3.05.2002 (B782), (0/1/0); Broekhuizen, Broekhuizer Schuitwater, carr, 0 4.05.2002 (B785), (0/1/0), (B787), (0/1/0); Maartensdijk, 28.06.2003 (B847), (1/0/0); Vuilbemden, Roermond, 14.05.2005 (3687), (1/0/1).

Description: Frontal eye on a round or oval sclerotized ring. Frontalia fused to a elongated platelet. Dorsocentralia 1 and 2 separate in females, often fused in males. Coxae with a few setae only, Cx-I with 3-4 at anterior tip and 1-2 at medial margin. Medial margin of genital flap anteriorly straight, here bearing more slender setae, posteriorly strongly concave, embracing the acetabula 2-3, with 7-10 longer and stronger setae. Acetabula small. Excretory pore slit shaped, with a large, crescent-shaped anterior sclerite, posterior sclerite small and roundish or absent. Gnathosoma with normally developed rostrum - as in T. palustris , neither bent ventrally, nor elongated. Palp setation: P-1 2-3, P-2 6, P-3 4 (two shorter and two longer), P-4 with two hairlike distal setae dorsally, medially and ventrally. Male: Idiosoma length 1100-1150. Frontal eye plate diameter 70-85, fused frontalia L/W 58-67/27-36, fused dorsocentralia 1+2 L/W 54-67/32-35. Genital flap L 205-210; with 12 slender anterior, and 10 strong posterior setae; acetabula diameter Ac-1-3: 27-29, 27-31, 28-29. Gnathosoma length 205-225. Chelicera basal segment L/H 200-220/72-80, claw L 76-81. L/H P-1 56-58/58- 63, P-2 103-105/65-67, P-3 63-67/63-65, P-4 160-165/40-42, P-5 38-40/15-16. Female: Idiosoma L 1300. Frontal eye plate diameter 66, frontalia 54, dorsocentrale 1 63. Genital flap L 227; with 5-6 slender anterior, and 7-10 strong posterior setae; acetabula diameter Ac-1-3: 25-28, 28-34, 28-36. Gnathosoma L/W 255/175.

Discussion: Until recently, this species has been considered first a subspecies, later a synonym, of T. palustris ( Lundblad 1962, sub nom. T. rivalis ). In fact, the name-giving elongation of the posterior acetabular stalks is subject to variability both in T. rivalis and T. colligera and the diagnostic differences in palp setation has been overlooked by K. Viets (1923a) and most of the following authors. However, in the huge material determined as T. rivalis by K. Viets (material from Sweden, Russia, Germany, Austria, 43 specimens, SMF 47523-47560, 47562-47567), only one further specimen could be found that in reality represents T. colligera (SMF 47527). All other specimens have the palp setation typical for T. palustris (syn. T. rivalis ), with only one dorsal seta on P-1 and two setae on P-3. Obviously, this character is stable and allows to distinguish the two taxa as separate species.

From a comparison of our material with the careful description of Todothyas distinctus (Tuzovskij, 2007) results that this species is a junior synonym of T. colligera . Apart from slightly major dimensions in males, in measurement proportions and all details important for the diagnosis of Todothyas species our material from Germany and The Netherlands fits Tuzovskij's description.