Aturus protzi Piersig, 1901

Gerecke, Reinhard, 2014, Studies on European species of the water mite family Aturidae Thor (Acari: Hydrachnidia), Zootaxa 3841 (1), pp. 1-46 : 17-19

Aturus protzi Piersig, 1901

Fig. 12

Material examined. Czech Republic: Aturus protzi , NHMB 4579 , 2 ♀♀, one dissected, palps on NHMB 4580 " Aturus protzi Piersig ♀ "Psg. S. Böhmerwald Mauth Bach unt. Bad 1899/1901" "Böhmerwald Coll. Piersig" "VIII/51,52". "Typus" (no type, see below; state: both specimens dried and squeezed); NHMB "XXIX/9, 3 ♂♂, without locality and date label "coll. Piers."; France: SMF 42928, 1 ♂, 1 ♀, " Frankreich, La puoade, 16.8.1948 Angelier coll. 7040"; Spain: SMNH NHRS-GULI 0 0 0 0 0 2775, 2 ♂♂ "4515 Aturus protzi Piers. ♂ Spanien, Bäck på Sierra Guadarrama 10.9.1935 Leg. O. Lundblad.".

Remarks. This species was first described from an unclear number of males and we cannot exclude that the specimens on slide NHMB XXIX/19 represent syntypes of A. protzi . Instead, the two females on slide NHMB 4579 derive from the area of the type locality, but the " Typus " label is obviously incorrect. Interestingly, in over hundred years since the first description, no attempt has been made to describe the female sex. The species was in most cases found together with other species of the genus, and no character states are known in both sexes that could be indicators of conspecifity.

Following the original description (and omitting some details without significance for species definition in Aturus ), male A. protzi are characterized by the following important features: Idiosoma with subparallel lateral margins, posteriorly equally rounded, without projections flanking the gonopore. Posterior part of dorsal shield flattened, in the transition area to ventral field on each side an anteriorly-directed bowed line of fine, denselyarranged setae embracing a subtriangular field covered by fine hair-like setae. Dgl-1 with strong bifurcated setae, all other Dgl with simple, long setae. Lgl-1–3 close to each other, but not in touch, in the dorsal furrow, Lgl-1 and –2 with strong, bifurcated setae, Lgl–3 with a long, but simple seta. Posterolateral and posterior idiosoma margin with numerous long and fine setae, none of these with "onion-like" basal inflation; the gonopore flanked by two pairs of enlarged, club-shaped setae. Genital field with ca. 9 pairs of Ac, three of them flanking the gonopore and directed ventrocaudally. Leg claws with dorsal and ventral clawlet. III-L-5 with numerous long ventral setae and one particularly elongated, distally spiralled "whip seta" in terminal position. IV-L-4 distally strongly thickened, bearing here three long and strongly enlarged sword setae, four long, slender, pointed setae and, slightly set off from distal margin, two curved setae with a distally denticulate margin. IV-L-5 curved, proximally with an obtuseangled projection surrounded by 3–4 strong, but short "elk horn" setae, which are distally truncated and strongly denticulate, and a line of equally-distanced slender and simple setae; distal margin bearing, in addition to several simple setae, one irregularly curved long and flattened seta branched into several fine tips.

The specimens from SMNH agree well with this description and allow some additional observations. Idiosoma L/W 350–360/290–300, dorsal shield L/W about 270/270. The fact that Piersig (1901) did not mention Lgl-4 is probably explained by the fusion Lgl-3+4, escaped to his attention. The fusion is documented by the presence of two gland pores and, in addition to the well-developed seta Lgl-3 a very fine hair like seta on the posteriormost platelet in the dorsal furrow. The setae arranged along the posterolateral and posterior margins are particularly fine and dense, anteriorly they extend to the upwardly-bent flanks of ventral shield which narrows the dorsal furrow posterior to Lgl-3+4, at the posterior margin they are gradually shortened from the lateral edge to the gonopore area. III-L-4 bears no particularly elongated distal setae. The setae number on III-L-5 is about 25. Most of them are strong, but simple and arranged in a dense longish group over the distal 2/3 of the ventral margin, but in addition to the particularly elongated distal whip seta, three further particular setae are found in the proximal part of the segment (arranged together on a flat posteroventral projection, slightly thickened and distally curved).

As documented by the widely agreeing descriptions, A. protzi is very similar to A. intermedius . Our observations on the latter (see above) show that several previously used character states are variable and thus of restricted taxonomic significance for defining A. protzi . This regards mostly the relative distance of Lgl-1/-2, shape of proximoventral margin of IV-L-5 (appearing bluntly pointed or equally convex, depending on little changes of its position) and number of whip-setae on III-L-5 (occasionally the second one is shortened could be interpreted as a normal seta); but possibly also the bi-/trifurcation of setae Dgl-1 and even the character most stressed for distinguishing the two sister species, the shape of the basal setae on IV-L-5 (shortened "leaf-like" setae in A. intermedius may take the "elk horn" aspect typical for A. protzi ).

The following, often not easily observed, details allow to distinguish A. protzi from A. intermedius (in parentheses): (1) seta Lgl-3 as long as setae of Dgl-2/3 (short, hair-like); (2) III-L-4 without (with) strong distal seta; (3) IV-L-4, apart from the sword setae, with two or three curved, branched setae (with simple setae only); (4) IV-L-5 basal setae stout, "elk-horn-shaped" (longish, "leaf-like", intermediate character states possible).

Figures

FIGURE 12. Aturus protzi, male. A. IV-L- 4 / 5 posterior (right: IV-L- 4, left: IV-L- 5); B. III-L- 4 / 5 posterior. Scale bar = 100 µm.