Lepidozetes singularis Berlese, 1910

Weigmann, Gerd, 2013, The genus Lepidozetes Berlese, 1910 (Acari: Oribatida: Tegoribatidae) in Europe with description of a new species, Zootaxa 3722 (4), pp. 493-500 : 494-497

Lepidozetes singularis Berlese, 1910

Lepidozetes singularis Berlese, 1910: 386 .

Lepidozetes singularis: Willmann 1931: 180 ; Hammer 1952: 61, fig. 97; Mahunka 1993: 233, fig. 16; Pérez-Iñigo 1993: 122, fig. 44b; Mahunka & Mahunka-Papp 1995: 205; Weigmann 2006: 359, figs. 191a,b.

Lepidozetes conjunctus Schweizer, 1922: 57 .

Lepidozetes conjunctus: Schweizer 1956: 354 ; Bayartogtokh & Aoki 1999: 108, figs 1–17.

Material examined. Slides of the Berlese collection in Istituto Sperimentale per la Zoologia Agraria, Florence, Italy, including the type specimen (from Italy).—Slides of the Willmann collection in Zoologische Staatssammlung in Munich (origin from northern Czech Republik, bog on mountain Novou Seninkou).—Slide with type specimen of Lepidozetes conjunctus of the Schweizer collection in Naturhistorisches Museum Basel, Switzerland.—12 unmounted specimens surrounding Basel ( Switzerland), collected by S. Sobeck 2001 from tree canopies (cf. Weigmann et al. 2004).—Two unmounted specimens from Schwarzwald Moutains (South-West-Germany), collected by B. Schnebele 1986 from lichens on tree bark.—Three unmounted specimens from the Sciliar region near Tires (Prov. Bolzano, Northern-Italy), collected by Irene Schatz 2006 from willow litter.—12 unmounted specimens from Sciliar (Prov. Bolzano, Northern-Italy), collected by H. Schatz 2006 from moss and grass under mountain pine, subalpine region.

Redescription of the adult. Diagnosis. Body length 380–510 µm; anterior border of lamellar shield rounded; sensillus with claviform head and moderately long stalk; tutorium angulated, distally with acute-angled dens; rostral seta stout, long (50–60 µm), heavily barbed, straight or bowed; setiform notogastral setae barbed, length about 25–38 µm; interlamellar setae small.

General characters. Body length 380–510 µm (400–510 µm in the studied specimens: females 445–510, n=21; males 400–450, n=10); length-width ratio about 1.5:1. Colour pale brown.

Prodorsum. Surface smooth; rostrum rounded, edge more or less protruding; lamellar shield rounded distally and laterally and constricted at the base. Setiform lamellar seta sparsely barbed, 45–60 µm long; interlamellar seta fine, small, 15–20 µm long; sensillus about 60 µm long, with claviform granulated head and moderately long stalk (figs 1a, 2). Tutorium angulate with long upper part and shorter part ventrad reaching insertion of leg I, distally with acute-angled dens about 25–45 µm in length. Rostral seta strong, long (50–60 µm), bushily barbed, straight or bowed.

Notogaster. Surface smooth. Anterior border overlapping posterior part of prodorsum with bothridia and insertion of interlamellar setae (fig. 1a); dorsophragmata large, broadly rounded, subparallel, well separated; movable pteromorphs protruding anteriorly, latero-anterior edge slightly concave (fig 2a). Ten pairs of fine setiform setae barbed, length about 25–38 µm. Porose areas roundish, Aa and A1 largest (diameter about 16 µm); five pairs of fissures.

Podosoma and ventral region. Pedotecta (Ptc) I well developed, upper posterior border concave (fig. 2a), Ptc II small. Custodium tooth moderately long, straight or bent (fig. 1b). Formula of epimeral setae 3-1-3-3, fine setae short (about 10 µm); six pairs of genital setae, 2-3 on anterior margin; one pair of aggenital setae, two pairs of anal setae (10-15 µm), three pairs of adanal setae (about 10 µm), ad 1 and ad 2 inserted parallel to posterior border of ventral plate, ad 3 and fissure iad lateral and parallel to anal shield.

Legs. All tarsi hetero-tridactylous. Formula of leg setation as follows (famulus included, solenidia given in parenthesis):

Distribution and ecology. The species occurs in the Holarctic region (Europe, North-America), mostly in subarctic, subalpine or montane areas. It is found in European bogs, in litter, in lichens on tree bark and in tree canopies. Obviously the species prefers cold climates.

Discussion. From today’s view, both species, Lepidozetes singularis and L. conjunctus , are described insufficiently in the original papers (Berlese 1910; Schweizer 1922), and also subsequent authors (Schweizer 1956; Shaldybina 1975; Mahunka 1993; Bayartogtokh & Aoki 1999) did not describe and image all important characters sufficiently, e.g. the tutorium and rostral setae. This contribution tries to present a revised redescription which is in accordance with type material.

Rostral setae. The type specimen slide of Berlese was studied in Florence in 1995 by the author. The stout and bushy rostral seta has been detected (fig. 3a), a character which is used by some authors to discriminate Lepidozetes species, but mostly the rostral setae are not described for L. singularis (Willmann 1931: fig 308; Mahunka 1993: fig. 16; Pérez-Iñigo 1993: p. 122, fig. 44b). When studying the slides of Willmann, typical stout and bushy rostral setae are visible (cf. fig. 3b). In the key of Shaldybina (1975: p. 338, fig. 850v), L. singularis is characterized by “lamellar setae very small, rostral setae not visible from the dorsal aspect” (translated from Russian text). Following this characterization, Bayartogtokh and Aoki (1999: 116, figs 27–40) indicate in a key for L. singularis : “rostral setae invisible”, for L. conjunctus : “rostral setae well developed” (“long barbed” in the description). Obviously “ Lepidozetes singularis ” sensu Shaldybina and sensu Bayartogtokh & Aoki is not Berlese’s species, but possibly “ L. conjunctus ” sensu Bayartogtokh & Aoki (1999) can be considered as Berlese’s singularis .

In the descriptions and figures of L. conjunctus by Schweizer (1922, 1956), no rostral setae are mentioned nor figured. But in one original draft, Schweizer draw a stout and barbed rostral seta. The type specimen is mounted on a microscope slide; it is heavily crushed and partly dried. Nevertheless the barbed rostal setae are visible (fig. 4). Regarding the rostral setae, there is no difference between L. singularis and conjunctus .

Tutorium. To the knowledge of the author, in the descriptions of all Lepidozetes species the structure of the tutorium is not mentioned nor illustrated except in L. latipilosus Hammer, 1952 from the Arctic North-America, which has an acute large dens distally. In all studied specimens of L. singularis from different European origins, the tutorium shows the angulated structure with a strong distal dens; this dens is variable in length, from 25–45 µm (cf. figs 2a,b). Unfortunately the author did not pay attention to the tutorium explicitly, when studying the slides in the collections of Berlese and Willmann. But the tutorium could be detected in the type slide of L. conjunctus (fig. 4), having an acute large dens distally. Regarding the tutorium structure, there is no difference between L. singularis and conjunctus .

Synonymy of Lepidozetes conjunctus . The length range of L. conjunctus varies from 378 until 432 µm after published and unpublished measurements of Schweizer (1922, 1956, values in the drafts). This range overlaps partly that by other authors and the actually measured range. The specimens of the type series of Berlese does not exceed 420 µm (Bernini 1971). Further characters (occasionally used in descriptions of other species) are not suitable to differentiate between L. singularis and L. conjunctus : rounded anterior border of lamellar shield, short interlamellar setae, length and shape of sensillus, length of notogastral setae, size and positions of porose areas of notogaster. Other specific characters, especially ventral ones, in the description of L. singularis above are not considered for L. conjunctus .

Mahunka (1993) published a sketchy drawing of the anterior dorsal part of a single “ L. conjunctus ” specimen, found in a cave near Genova ( Switzerland). Subsequently he advanced the view that L. conjunctus should represent a valid species (Mahunka & Mahunka-Papp 1995, 2004). I borrowed the specimen from the Museum of Natural History Genova and studied the characters in detail. Most characters fit into the frame of L. singularis as redescribed above (e.g. total length 450 µm; rostral setae stout and bushy). Minor differences are: anterior border of the lamellar shield slightly concave; anterior dens of tutorium shorter (20 µm, sharply pointed); custodium bent sidewards (more distinct than in some singularis specimens). These different characters do not coincide better with Schweizer’s L. conjunctus than with L. singularis but give no convincing basis to establish a new species. We must take into account that the single specimen may represent aberrant characters due to isolation in the cave.

This study confirms the general opinion in the literature (Willmann 1931; Bernini 1971; Marshall et al. 1987; Pérez-Iñigo 1993) that L. conjunctus is a junior synonym of L. singularis .