Ljania longissima Schwoerbel, 1962

Gerecke, Reinhard, 2014, Studies on European species of the water mite family Aturidae Thor (Acari: Hydrachnidia), Zootaxa 3841 (1), pp. 1-46 : 36

Ljania longissima Schwoerbel, 1962 —nov. stat.

Figs 25 F–H

1962b Ljania macilaenta longissima Schwoerbel, Zoologischer Anzeiger , 168, 294.

Material examined. Holotype, SMF, coll. Schwoerbel “ Ljania elongissima [!], Bizau”. Slide not marked as Type and without further information. The morphological study does not leave any doubt about the identity with the female described by Schwoerbel (“Bizauer Bach oberhalb Bizau, Vorarlberg ( Österreich), Okt. 1961 ”).

Remarks. The description of the only available specimen of this taxon merits some additional remarks. In general, new length measurements agree with Schwoerbel’s data, while width and height are strongly influenced by squeezing. In the case of the palp (the original description gives only the generally unusual basal segment height), new segment length measurements were taken and the height calculated from Schwoerbel’s (1962 b) Fig. 2 C.

Redescription. Idiosoma colouration indistinct, pale, lateral eyes not to be detected. Sclerotization of body and appendages very weak; idiosoma with a fine porosity that extends also to the strip medially separating Cx-IV. Idiosoma very slender (length/width 452/259 µm, ratio 1.7, dorsal shield L/W 439/239, ratio 1.8) and with nearly parallel lateral margins; dorsal furrow very narrow, bearing one glandular platelet in anterior part, but dorsal shield here not considerably indented. Anterolateral margins of Cx-I-III more projecting than given in Schwoerbel’s Fig. 2 a; distribution of ventral setae and glandularia as given in Fig. 25 F. Distance between IV-L-insertions 125 µm. Cx-IV lateral margins obliterated, posterior suture line forming little projecting lateral extensions and a very shallow medial bay embracing the ventroglandularia (Pe sensu Tuzovskij 2012), length ratio medial margin/ extensions 70/30 µm, ratio 2.3. Leg claws with dorsal clawlets distinctly shorter than ventral ones. Gnathosoma and chelicera stout, chelicera length 84 µm, ratio length/height 2.9, basal segment/claw 2.1. Palp rather small and slender, length/height (ratio, relative L) P-1, 26/19 (1.4, 14 %); P-2, 38/26 (1.5, 21 %); P-3, 38/25 (1.5, 21 %); P-4, 50/20 (2.5, 27 %); P-5, 32/12 (2.7, 17 %); total length 184. Setation incompletely visible, probably reduced by damage: P-2 and P-3 dorsally each at least one central and one distal, P- 4 in distal half one ventral, following Schwoerbel’s Fig. 2 c, 4 dorsal.

Discussion. Ljania longissima is similar to L. macilenta (data from Tuzovskij 2012) in the relatively slender idiosoma and the proportions of leg claws (with shortened dorsal clawlets). In addition to distinctly larger dimensions of L. macilenta (e.g. in females, idiosoma length/width 510–540/390–420, dorsal shield 470–500/ 335–360, palp total length 190–220) and a more robust shape (L/W idiosoma <1.5), the following differences underline that L. longissima should be regarded as a distinct separate species: (1) dorsal shield not indented on level of the glandularia (He sensu Tuzovskij 2012) in dorsal furrow; (2) length relation medial margin/posterior extension Cx-IV low, <2.0; (3) posterior margin Cx-IV forming a deep bay with rectangular edges at level of ventroglandularia; (4) palp distinctly more stout, in particular P-4, which is also relatively longer (> 30 % total length).

The listed differences show that the specimen in question cannot be considered a kind of variety of L. macilenta as later suggested by Schwoerbel (1964). In the shape of Cx-IV Ljania longissima differs distinctly from all other Ljania species described so far.

Figures

FIGURE 2. Aturus crinitus (I 181), SEM photographs. A. – D. male; A. IV-L- 4 – 5 anteroventral; B. IV-L- 4 – 5 posteroventral; C. dorsum; D. posterolateral idiosoma; E. female genital field posterolaterally. Scale bars: A – B, E: 20 µm, C – D 50 µm.

FIGURE 25. A. – E, Ljania bipapillata. A. – B., female; A. venter; B. palp; C. – E. male; C. dorsum; D. palp; E. venter, F. – G. Ljania longissima female; F. venter; G. palp; H. chelicera; I. – K. Ljania macilenta, male; I. palp; K. venter. Scale bars = 100 µm.