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 : 229-230

ATRACTIDES NONDILATATUS ( SOKOLOW, 1936)

Megapus nodipalpis nondilatatus Sokolow, 1936 Species dubia

Type series: May be missing. Not found in ZISP. Loci typici: (1) Park des Peterhofer Biologischen Instituts , Fluss Tschornaja (Sapao-joki) 31.VII.1924; (2) Gobzhinka-Bach beim Dorfe Gobzhitza, 08.VIII.1931, 25.VIII.1931; (3) Gobzhinka-Bach Oberlauf, unweit von den Scheunen, 19.VI.1933.

Material examined: SMNH 5317 Atractides nodipalpis nondilatatus Sokolow (1936) . Södermanland. Lännaån öster om Ekedalek 24.6.1933 Leg. O. Lundblad; probably a specimen fixed in ethanol with dark idiosomal contents and deformed membranous integument .

Description. Male (original description): P-2 ventrally with broadly rounded hump, without protruding tip, similar to A. fonticolus ; P-3 elongated (ventral L 1.5 times maximum H); P-4 rather slender, not protruding ventrally, insertions of ventral setae dividing ventral margin 1: 1: 1, sword seta inserted between the levels of ventral setae; anterior margin Cx-3 medially strongly protruding; Cx-4 large; I-L-5 and -6 as in A. nodipalpis , but I-L-6 more slender; anterior margin of genital field with tongue-shapened medial border.

Male from SMNH: juvenile (weak sclerotization of coxae and genital field, with some genital setae appearing separate from sclerite plate, deformation of P-3) with very large sword seta on P-4, arranged in the middle between insertions of ventral hairs.

Description following Lundblad (1956), based on another specimen ( SMNH 4109): integument lineated as in A. panniculatus ; genital field with plates only weakly fused anteriorly, with anterior and posterior indentation (see discussion of A. clavipalpis in Lundblad, 1956); P-2 ventral hump without protruding tip, P-3 ventrally concave, P-4 much less thick than in A. nodipalpis , sword seta L 35 Mm, in the middle between the insertions of ventral hairs, ventral margin 1: 1: 1; palp and I-L-5 and -6 measurements similar to 5317.

Female (original description): P-2 with ventrodistal edge only slightly reinforced, P-3 long, P-4 slender, both ventral setae short and not curved, sword seta between ventral hairs; medial portion of Cx-4 more slender than in male, legs as in male; gonopore long (210 Mm) genital plates more slender than in A. nodipalpis , L = 145 Mm, flanking the posterior half of gonopore.

Discussion: Due to the relatively slender P- 4 in both species, Sokolow considered A. nondilatatus to be closely related to A. tivdiae , a species here synonymized with A. nodipalpis . As already mentioned, thickness of P-4 varies considerably in A. nodipalpis , and is not suitable for defining separate taxa. The lack of information on important features such as integument surface structure, and shape, dimensions and arrangement of glandularia, does not allow for definitive considerations on the taxonomic state of A. nondilatatus . Due to the lack of type material, it must be considered a species dubia. Lundblad’s assignment of Swedish specimens was tentative, probably based on misshapen specimens of unclear taxonomic status. His further records refer to scattered sites in Germany, France and Spain, where single specimens attributed to A. nodipalpis nondilatatus were found mostly in the company of larger numbers of A. nodipalpis s.s., or A. nodipalpis robustus . This suggests that the specimens in question are best considered representatives of the stem species, somewhat irregular in shape and setation of palps.

However, we should continue paying attention to Atractides specimens with tongue-like anteromedial protrusion of male genital field, female genital field with Ac in a curved line, lineated integument (?) rather slender palp with P-2 missing a protruding ventrodistal edge, and P-4 not protruding at the level of the proximoventral hair. The finding of North European populations with a character combination like this could allow for a redescription of this doubtful taxon.