Atractides

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 : 196

ATRACTIDES TENUITARSUS ( KOMÁREK, 1921)

Megapus tenuitarsus Komárek, 1921

Syn. to Atractides nodipalpis ( Thor, 1899) : K. Viets, 1956

Type series: Missing, probably lost; type localities: larger forest streams in the Brdy mountains , in the lower reaches of the Cepkovsle y ¢, Albrechtsk y ¢, Cern y ¢ and other streams, July, August

Description. Male (original description): idiosoma L 830 Mm, W 630 Mm, integument rather thick and strong, without striation, but covered with fine spines; also, all sclerites covered with spines of this kind; coxal field L 430, W 600 Mm, coxae arranged close together (but in the figure membranous suture Cx-2/3 visible); I-L-6 slender; genital field as in A. nodipalpis , with anterior and posterior incision, approaching the caudal idiosoma margin; excretory pore smooth, Vgl-1 not fused to Vgl-2; gnathosoma L, 180 Mm; palp with P-4 sword seta inserted proximally, far from the centre of the segment. Female (original description): idiosoma L 1200, W 930 Mm; coxal field L 500, W 850 Mm, mediocaudal margin of Cx-1 + 2 and caudal margins of Cx-4 convex; I-L-5 dL 270–300 Mm, distally strongly thickened, I-L-6 dL 210 Mm, slender, narrowed centrally and not much thickened on the level of the claw pit, some measurements calculated from Komárek’s figure 2b: S-1 L 151, S-2 L 101 Mm, interspace 30 Mm, I-L-6 HA 33, HB, 19, HC 25 Mm; genital field as in A. nodipalpis, Ac in triangular arrangement; gnathosoma L 200, W 100 Mm; P-2 without evident ventrodistal protuberance; P-4 with ventral margin divided into three equal parts by insertions of the hairs, sword seta in the centre of the segment.

Discussion: Komárek described this species as very close to A. nodipalpis , but different in integument structure and shape of I-L-6. The presence of fine spines uniformely covering membranous and sclerotized areas of the idiosoma surface is a feature never found in other hygrobatid mites, probably an artefact due to microbial infection or chemical processes during state of conservation of the specimens. The measurements for I-L-6 provided in the original description or calculated from its drawings fall within the variation in A. nodipalpis . Unfortunately, it is not clear the I-L of which sex is represented in Komárek (1921: fig. 2b). From the rather slender terminal segment (and also from the text which treats mainly the female) one can deduce that he probably examined a female. He was not aware that there is also a certain degree of sexual dimorphism in A. nodipalpis , with I-L-6 more slender in females than in males. Based on present knowledge therefore the lack of type material notwithstanding, I confirm the synonymization of A. tenuitarsus with A. nodipalpis .