Atractides cerberus, 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 : 299-300

ATRACTIDES CERBERUS SCHWOERBEL, 1961

Syn. to A. oblongus ( Walter, 1944) : syn. nov.

Type series: Lectotype ♂, here designated, Germany, Black Forest , CSM ATRACTIDES cerberus ♂; Breg Oberlauf Insel 1.X.1959. State of conservation: idiosoma intact, but with left II-IV-L missing; both I-L, palps and gnathosoma laterally under separate cover, badly crushed . Paralectotype: ♂ ATRACTIDES cerberus ♂; Tiefenbach b. kl. Bohrerbach G.24. State of conservation: similar to lectotype but appendages more damaged and completely desiccated.

Material examined: Black Forest , CSM Steina G. 23 1 ♂ ; Steina G.21 1 ♀ Seebach , hyp. 1400 m 26.5.1961 1 ♂, 1 ♀ [labelled as ♂]; Wagensteig, hyp. GW 13.5.61 1 ♂; hyp. Grundw. Nebenbach Fischbach 1 ♂.

Discussion: Schwoerbel (1961a) compared this species in the original description with A. szalayi , a species described from Romania which is poorly known and in this revision is synonymized with A. oblongus . He considered as diagnostic differences the presence of sclerotized muscle attachments in the dorsal idiosoma of the male, a more slender P- 4 in females, and a basally narrowed I-L-6. In fact, A. cerberus is a representative of the A. spinipes – A. oblongus species group, characterized by smaller size, a weakly striated, nearly smooth integument, small glandularia, a rather slen- der coxal field, smooth excretory pore, fused Vgl-1 + 2, and I-L-5 with S-1 and -2 homoiomorphic and placed close together. A basally narrowed I-L-6 is found in both sister species, as well as in many other species of the genus, and cannot serve as a diagnostic feature. The difference in shape of the P-4 was based on published measurement data only. As mouthparts of all available specimens of A. cerberus are badly damaged, no control measurement is possible, but in general the L/H ratio is variable, mainly in mounted specimens, and species definitions cannot be based on such measurement ratios. Schwoerbel’s statement on the sclerotization of the muscle attachments is not confirmed by the revision of his preparations. As usual in softbodied Atractides , muscle attachments are characterized by granulated areas of the membrane just at those sites where paired sclerites are depicted in Schwoerbel’s fig. 10(b). However, neither in the lectotype, nor in the other mounted specimens, are attachment sclerites present.

Both the lectotype and (in parentheses) additional specimens examined agree with A. oblongus and differ from A. spinipes as follows (all dimensions in Mm). Males: coxal field L 265, median suture Cx-1 115 (100– 115) genital field L/W 90/87 (75–90/80–95). Females: median suture Cx-1 100–130. Several female specimens from springs at higher elevations, with considerably larger Ac, possibly represent a different species. However, the general morphology of the male holotype provides sufficient evidence for a synonymization of A. cerberus with the so far little known A. oblongus .