Liebstadia OUDEMANS

Miko, L. & Weigmann, G., 1996, Notes on the genus Liebstadia Oudemans, 1906 (Acarina, Oribatida) in Central Europe, Acta Musei Nationalis Pragae, Series B, Historia Naturalis 52, pp. 73-100 : 94-98

[Genus Liebstadia OUDEMANS ]

Discussion

The special lamellar-sublamellar complex with the lamella touching the Insertion point of interlamellar seta is regarded as a specific and apomorphic character of the genus Liebstadia . Other characters with diagnostic value are less specific and obviously often developed convergently in different genera within the Oripodoidea : i.e. having prolamella and sublamella, 10 notogastral setae, 3-4 areae porosae. 4 genital setae, legs monodactyl - some of which are considered typical for scheloribatid mites.

The monodactyly of the Liebstadia species is (along with the habitual similarity in dorsal view) the reason that some of them have been placed within the genus Protoribates BERLESE, 1908. This is the only generic character given by Berlese (1908) to separate Protoribates from Scheloribates . Recent research has shown that some Protoribates auct. species in the literature belong to the revised genus Protoribates (Weigmann et al. 1993), and some other species with the specific lamellar complex (" Liebstadia type") belong to Liebstadia as defined in this paper, in accordance with Weigmann (1969) and Wunderle et al. (1990). Additional species of " Protoribates ", Liebstadia and other related genera, described worldwide, will likely belong to the genus Liebstadia as described here. However, usually no lateral drawings present in the literature, and for this reason it is very difficult to determinate the generic Status. Further more, at least in some recently described species of the genus Liebstadia the position in the genus cannot be proven from the original description (see discussion of the species L. humerata below).

As we do not intend to produce a worldwide revision of the Liebstadia species we have focused only on the Central European species on which we have enough information. Some other species are discussed, using the original descriptions and redescriptions from the literature, or (as in the case of Willmann's species Protoribates novus and P. austriacus ) on the basis of the original material, which is unfortunately not sufficient for redescription. Generally, the most important fact is that the always immovable pteromorphs of Liebstadia species show a high diversity in shape, forming a coutinuous row from small toothlike blades ( L. humerata . L. similis ), over small rounded blades, not bent downwards ( L. longior ) to large pteromorphs bent downwards ( L. pannonica , L. willmanni sp. nov.), without recognizable gaps (see also Perez-Inigo 1993). Therefore, the shape of pteromorphs cannot be used as a generic character. This result raises the immediate question of which diagnostic character of the pteromorph development should be used in the other scheloribatid genera, e.g. Scheloribates vs. Hemileius , as the use of this character for family separation seems to be unacceptable (e.g. Perez-Inigo 1993). This question needs further detailed investigation and will be discussed in a later paper.

Liebstadia belongs to the family Scheloribatidae GRANDJEAN, 1933 in the conservative view of Grandjean (1958). Balogh and Balogh (1992) put Liebstadia into the family Protoribatidae BALOGH and BALOGH. 1984, which we believe to be a mixed composition of members from different families. The nominal genus Protoribates belongs to Haplozetidae , while Liebstadia definitely does not (see Weigmann et al. 1993 for further discussion).

Except for the continual change of pteromorph shapes, two trends are easily recognizable: the changes in dorsoventral thickness and the form and shape of the sensillus (see figs 1c, 5b, 12a, 17b). Considering the known facts on the ecology of the different species, we recognized two typical "life forms" of Liebstadia :

(a) the species with large body size, dorsoventrally thick, with a longer sensillus stalk and moreless lanceolate sensillus head (e.g. L. similis ).

(b) the species with very flat, oblonged body of medium size, with the sensillus stalk short and sphaerical or sub-sphaerical sensillus head ( L. humerata . L. longior ).

In addition to the two mentioned forms intermediates could also be found (e.g. L. pannonica ). Probably, the life-form (a) belongs to the species living in the litter, soil surface or surface layer of the soil, and the life-form (b) seems to be an adaption for life in flat moss/lichen growths or the crevices and slots of tree bark. The intermediate forms were found mostly in grasslands or in shrub formations.

Some other " Protoribates " auct. species known from central Europe, are considered to be in fact Liebstadia . Both individuals of Liebstadia nova (WILLMANN 1953) comb. nov. (= Protoribates novus WILLMANN, 1953) studied from Willmanns original slide (Staatssammlungen Munich, labeled: "K6-91, Protoribates novus sp. nov., det. C. Willmann, G 294'') axe strongly damaged, and no longer usable for redescription. Nevertheless. from the slide it is clear that the species has no 11 notogastral setae. The eleventh seta in Willmann's description is most probably the lyrifissure, which is also visible on the damaged specimens in the slide. From the characters visible, the species belongs to Liebstadia as defined here, and probably is a synonym of L. pannonica . A definitive classification requires the study of topotypical material. Mahunka (1987) reported on the species from Kiskunság National Park in Hungary, but without notes on specific characters. The species was reported as being sylvan (found in plant association Junipero-Populetum albae).

The classification of Liebstadia austriaca (WILLMANN, 1953) comb. n. (= Protoribates novus WILLMANN, 1953) is very similar. The original material of Willmann (3 slides from Staatssammlungen Munich labeled: "K6-68 (E4/0-3) Protoribates austriacus sp. nov. ", "K6-69 Liebstadia , A 77/0-3, Admont, det. E. Leitner" with " Protoribates austriacus " added by pencil, and "K6-70 Protoribates austriacus sp. nov. ") cannot be used for redescription, but from the crushed individuals in the slides it is clear, that it is a species of Liebstadia , according to the present description. Moreover, considering the body shape and form of the sensillus, the species is probably also a synonym of the presently redescribed L. pannonica . As in previous species, definitive classification is possible only after the study of topotypical material.

The species Protoribates serratomarginatus , described by Mahunka (1983) from the Hortobágy National Park in Hungary is definitely Liebstadia (see figs 30 and 32 of original description). The species is nearly identical (from comparison of available description and drawings) with the nominal species Liebstadia similis . Typical characters of the species, as given by author, are: serrated to denticulated edge of pteromorphs. comparatively long notogastral and prodorsal setae and body size. We did not study the Hungarian material, but the description and pictures closely resemble our material from Germany (2 specimens - 1 female and 1 male from Leipzig, 14. 7. 1991, leg. W. Dunger), which belongs to Liebstadia similis sensu lato. We also note the remark of Wunderle et al. (1990), that the border of the pteromorphs of L. similis is slightly undulated or denticulated. The only other notable difference is in body size: Mahunka gives a length of 431 - 498 µm and a width of 245-302 µm for Protoribates serratomarginatus , while the measurements for L. similis are 500- 565 x 330-360 µm (Wunderle et al., 1990). Measurements of specimens studied from Leipzig were more or less intermediate: length 500 µm (male) and 525 µm (female). respectively, and width 320 µm, so the body size is not usable as a differential character. Remaining characters, i.e. slender body and comparatively longer notogastral and prodorsal setae, are insufficient to establish a species. Differences between this form and L. similis are in the same range as differences between the nominate form and form with long notogastral and prodorsal setae, described here (" longisetosa "). Also, the identity of a Hungarian form and " longisetosa " is not fully excluded. All the questions mentioned could be solved by the further study of the Hungarian material. At present stage of our knowledge the name Liebstadia similis serratomarginata comb. nov., stat. nov. is proposed for the Hungarian form.

Mahunka (1987) described the species Liebstadia ahumerata from the juniper litter from Kiskunság Nat. Park. Hungary. The differential diagnosis in the description is lacking. The placement of the species in Liebstadia is probable, but in the original drawing of the lateral prodorsum (fig. 53) the interlamellar seta does not touch the lamella. As seen from the dorsal view (fig. 51), the setae in cannot be placed in so large distance from the lamella, as shown in the fig. 53, so very probably the proximal (right) seta in is omitted and instead the distal (left) seta is depicted. If the Position of seta in is on the lamella, the species could be placed in Liebstadia . In this case the difference from other similar Liebstadia species must be defined. The author states in the description that the species has only three pairs of small areae porosae (similarly as L. longior . L. humerata or L. willmanni sp. nov.), on the other hand, the depicted specimen (fig. 51) has four pairs of areae (along with the small size, and somewhat different shape of the sensillus head it could be a specific character). To determine, if the species is or is not a synonym of some of the known species, further evaluation must be done.

Several addidonal species of Liebstadia were reported from the Mediterranean area and the Balkan Penninsula. According to Perez-Inigo (1993), 5 species of Liebstadia are present in the Spanish fauna. The species L. humerata , sensu the mentioned papers differs from the species, as redescribed by Wunderle et al. (1990) by its 4 pairs of areae porosae and possibly (according to fig. 77B) by longer interamellar and lamellar setae. On the other hand, it is nearly identical with Liebstadia humerata sensu Seniczak (1990, fig. 9). Because no more details of adult morphology are given in hoth papers (especially the lateral view: bothridial area and pteromorphs, ventral side, leg chaetotaxy etc.), the real position of these species is uncertain. The body shape, position of seta lp, sensillus shape and the classification of bothridia is very similar to the new species L. willmanni (especially the form "A" from Slovakia), described here. On the other hand, the presence of 4 pairs of areae porosae resembles that of the species L. pannonica . It is not excluded, that presence of 3 pairs of areae in L. humerata or L. willmanni could be variable, and that populations with 4 pairs could exist (see also the opinion of Wunderle et al. 1990). More detailed study may also show, that L. humerata sensu Seniczak and L. humerata sensu Perez-Inigo represent a new, undescribed species of Liebstadia . The next two species from Spain ( L. gallardoi and L. microptera ) are most probably Mediterranean forms, not present in Central Europe. The pteromorphs of last two species are developed similarly to L. longior , however, the differences in number of areae porosae, shape of sensillus and prodorsal setae are present.

The species Protoribates gratiosus VASILIU et CALUGAR (1973) is most likely also a species of the genus Liebstadia (but the lateral view is absent in the description, only the formulation "... et les poils interlamellaires fixes au milieu de la lamelle ..." is present in the description). If the species is in fact Liebstadia , the correct name should be Liebstadia gratiosa (VASILIU et CALUGAR 1973) comb. nov. In this case the species stands near the new species L. willmanni . The differences are in the length of prodorsal setae, the shape of bothridium, the shape of sensillus, and general body length and form: the presence of only 9 notogastral setae (seta lp missing) seems to be improbable.

In conclusion, the following key could be used for the determination of Central-European species of Liebstadia (see also the table 1 with characters of studied species):

1 Body more or less elongated and flat, ratio length:dorsoventral thickness over 3.3:1. Three pairs of areae porosae developed usually, sensillus with short stalk and globular, globular-fusiform or fusiform head. Bothridial lamellae (bl, bl') missing or indistinct in lateral view. Length 310-440 µm..............................................................3

- Body more robust, not flat, ratio length:dorsoventral thickness under 3.1:1. Four pairs of areae porosae present, sensillus with longer stalk and fusiform or lanceolate head. Two bothridial lamellae (bl, bl') well developed, bothridium usually with posterolateral lobe or scale. Length 356 - 600 µm...........................................................2

2(1) Pteromorphs well developed, bent downwards, in lateral view reaching the acetabular area. Body size 350 - 430 µm, sensillus usually fusiform, rarely lanceolate .................................................... Liebstadia pannonica (WILLMANN, 1951)

- Pteromorphs developed as horizontal humeral blades, not bent downwards. Body size over 430 µm, sensillus lanceolate........................................ Liebstadia similis (MICHAEL, 1888)

3 (1) Pteromorphs well developed, bent downwards, in lateral view reaching or almost reaching the acetabular region. Sensillus fusiform or globular-fusiform in lateral view. Ventral surface microstriated, adanal area with distinct adanal ridge. Body size 352 - 439 µm.................................................. Liebstadia willmanni sp. nov.

- Pteromorphs not bent downwards, slightly developed or absent. Sensillus with more-less globular head. Ventral surface without a clear microstriation. Body size 310 - 395 µm...................................................4

4(3) Pteromorphs developed as a small triangular tubercle in humeral area or nearly absent. Tarsus III with 12 setae, genu I with 2+1 setae. Length-width ratio 1.85 - 2.40 ....................................................................... Liebstadia humerata SELLNICK, 1928

- Pteromorphs developed as distinct, rounded horizontal blades. Tarsus III with 15 setae, genu 1 with 3 + 1 setae. Length-width ratio 2.25 - 2.45, body extremely flat (length:dorsoventral thickness ratio over 4.5) .............................................. Liebstadia longior (BERLESE, 1908)