Atractides pilosus, Schwoerbel, 1961

Gerecke, Reinhard, 2003, Water mites of the genus Atractides Koch, 1837 (Acari: Parasitengona: Hygrobatidae) in the western Palaearctic region: a revision, Zoological Journal of the Linnean Society 138, pp. 141-378 : 302

ATRACTIDES PILOSUS SCHWOERBEL, 1961

Syn. to A. tener Thor, 1899 : syn. nov.

Type series: Holotype ♀ CSM, Germany, Black Forest ATRACTIDES pilosus ♀ TYPUS; Gauchach So, 1960. Locus typicus: im hyporheischen Grundwasser der Gauchach, etwa 100 m vor Einmündung in die Wutach [without date]. State of conservation: many appendages damaged by crushing, chelicerae missing; both I-L, right III-/IV-L, gnathosoma and both palps separate laterally under separate cover, desiccated and crushed.

Discussion: Schwoerbel (1961b) considered A. pilosus a species bound to subsurface waters and compared it with A. subterraneus , a species with I-L-5 and -6 similar in shape, but differing in having much smaller dimensions and slender genital plates with acetabula arranged in a weakly curved line. The specimen is obviously a juvenile (very weak sclerotization, absence of secondary sclerite, nearly invisible integument striation). Also the weak pigmentation of the lateral eyes and the particular shape of the P-2 could be explained by the juvenile age of the specimen. In fact, notwithstanding the damage due to crushing, the fact that the ventral margins of left and right P-2 were differently shaped can still be seen, and thus the unusual, axeshaped extension of P- 2 in Schwoerbel’s figure 6b is best explained as an individual aberration. Apart from some differences explainable by juvenility (smaller dimensions, segments of some appendages thickened due to weak sclerotization) the holotype of A. pilosus agrees with females of A. tener : I-L-5 and -6 slightly modified, with S-1 and -2 homoiomorphic and slender, S-2 pointed; I-L-6 weakly curved, basally rather thick, narrowed in the centre, inflated on the level of the claw furrow; P-4 1: 1: 1, sword seta between ventral hairs, nearer the distoventral one. The sclerotization of the excretory pore is weakly developed, but a distinct oval area surrounding the pore slit marks the future sclerite ring. The hairs and fine ventral setae of IV-L-5/6 (after which it is named) are found in all controlled specimens of A. tener from southern Germany. In this scenario, the particular slow movements and bright white idiosomal colouration of the holotype of A. pilosus described by Schwoerbel should be considered as resulting from immaturity rather than adaptation to subterranean life; A. pilosus is thus a synonym of A. tener .