Contributions to Zoology, 79 (1) – 2010
The discovery of Scutovertex ianus sp. nov. (Acari, Oribatida) – a combined approach of comparative morphology, morphometry and molecular data
Tobias Pfingstl1,2, Sylvia Schäffer1, Ernst Ebermann1, Günther Krisper1
Keywords: cytochrome oxidase I, exochorion, monophyly, Scutoverticidae, taxonomy
Based on morphological, morphometric and genetic data Scutovertex ianus sp. nov. is described as a new oribatid mite species. The traditional comparison with the morphologically most similar congeneric S. minutus and S. sculptus demonstrated that the new species shares certain characters with both species, but can be clearly identified by indistinct cuticular notogastral foveae in combination with short spiniform notogastral setae. Furthermore the eggs of S. ianus exhibit a different fine structure of the exochorion. The morphometric analysis of 16 continuous morphological variables separated the three species, S. minutus, S. sculptus and S. ianus with a certain overlap indicating minor size and shape differences in overall morphology. The molecular phylogenetic analysis of mitochondrial COI gene sequences supported the monophyly of all three investigated species and confirmed S. ianus as separate species with high bootstrap values. Each performed analysis approves the discreteness of S. ianus and the results contradict the formerly supposed large intraspecific variability of the representatives of the genus Scutovertex. The records of S. ianus are as yet restricted to the Eastern part of Austria and to one location in Germany, but findings of intermediary Scutovertex specimens from other European countries may refer to this new species.
At present the oribatid mite genus Scutovertex Michael, 1879 consists of 23 species known worldwide (Subías, 2004), whereas more than the half is occurring on the European continent. Many of these live in extreme environments and can be found from the alpine zone to the marine littoral, on sun-exposed rocks and roofs, sparsely covered by lichens and mosses, as well as in saline soils and salt marshes and in inundation meadows (Krisper and Schuster, 2001; Krisper et al., 2002; Smrž, 1992, 1994; Weigmann, 1973). The species of this genus are supposed to exhibit variability in certain morphological features resulting in a difficult classification of some specimens (Weigmann, 2006). But recent publications have shown that intraspecific variation occurs only to a minor extent (Pfingstl et al., 2008) and revealed a few new species in Europe (Schäffer et al., 2008; Pfingstl et al., 2009; Weigmann, 2009) which may have formerly caused a disorder and the idea of certain unstable morphological characters in some members of this genus. In the course of the investigation of Austrian representatives of Scutoverticidae we encountered several Scutovertex specimens showing a mixture of S. minutus (Koch, 1836) and S. sculptus Michael, 1879 specific characters making a clear determination unfeasible. To clarify the status of these ‘intermediate forms’ and to test again the possibility of large variation within one species a detailed morphological examination and a morphometric as well as a genetic analysis were performed.
Material and methods
Rearing experiments were performed to obtain eggs and juvenile stages, and for this purpose individuals of Scutovertex ianus sp. nov. (species description in Appendix) were put into boxes of polystyrol supplied with plaster of Paris and the animals were fed with collected substrate and coccal green algae. For permanent slides the specimens were embedded in BERLESE mountant and for temporary slides lactic acid was used. Measurements and drawings were performed with a differential interference contrast microscope (Olympus BH-2). The SEM-micrographs were taken at the Research Institute for Electron Microscopy and Fine Structure Research, Graz, University of Technology, with a Zeiss Leo Gemini DSM 982.
The morphometric investigation was performed to confirm the discreteness of S. ianus and does not represent an identification tool. Multivariate analyses of data were carried out with the software PAST version 1.82b (Hammer et al., 2001). To test the intraspecific variability of S. minutus and S. sculptus, two populations of each species (S. minutus: Pogier n=21, Bachsdorf n=40; S. sculptus: Fließ n=21, Illmitz n=40) were analysed with a set of 16 continuous morphological characters, the variable body length was excluded (Pfingstl et al., 2009). The same set of variables of 40 individuals of each species (S. ianus: 18 females, 22 males; S. minutus: 20 females, 20 males; S. sculptus: 25 females, 15 males) was measured, logarithmized and then used for Principle Component Analysis (PCA) as well as Canonical Variates Analysis (CVA).
For the molecular phylogenetic analysis, the total genomic DNA was extracted from single ethanol-preserved specimens using the modified CTAB (hexadecyltriethylammonium bromide) method after Boyce et al. (1989). A 1259 bp fragment of the mitochondrial COI gene was amplified using the primers COI_Fsy (5´-GNTCAACAAWTCATWAAG-3´) and COI_Rsy (5´-TAAACTTCNGGYTGNCCAAAAAATCA-3´) for COI-region 1 (modified after Heethoff et al., 2007), Mite COI-2F and Mite COI-2R (Otto and Wilson, 2001) for COI-region 2. PCR amplification and sequencing followed the protocol described in Schäffer et al. (2008). Sequences are available from GenBank under the accession numbers specified in Table 1.
Sequences were aligned by eye in MEGA 3.1 (Kumar et al., 2004). Phylogenetic reconstruction by neighbour joining (NJ) were conducted in PAUP* 4.02a (Swofford, 2002) and Bayesian inference (BI) in MrBayes 3.1.2 (Ronquist and Huelsenbeck, 2003). We used Lamellovertex caelatus (Scutoverticidae) as outgroup. For Bayesian analysis COI gene was partitioned by codon position. Rate heterogeneity was set according to a gamma distribution with six rate categories (GTR model) for each data partition. Bayesian posterior probabilities (BPP) were obtained from a Metropolis-coupled Markov chain Monte Carlo simulation (2 independent runs; 4 chains with 2 million generations each; chain temperature: 0.2; trees sampled every 100 generations), with parameters estimated from the data set. The burn-in fraction was set to 20%. For NJ, the best-fit substitution model selected by the hierarchical likelihood ratio test (hLRT) implemented in Modeltest 3.06 (Posada and Crandall, 1998) was TVM+I+G (base frequencies: A = 0.2551, C = 0.1631, G = 0.1740, T = 0.4077; R-matrix: A↔C = 0.1754; A↔G = 9.9528; A↔T = 1.3001; C↔G = 0.2368; C↔T = 9.9528; G↔T = 1.0000; proportion of invariable sites: I = 0.5888; gamma shape parameter: α = 2.0069) according to sequencing analyses. Statistical support for the topology was assessed by bootstrapping (1,000 pseudo-replications). Intra- and interspecific pairwise distances (uncorrected p-distances) were calculated in MEGA 3.1.
Table 2a. Loadings of the 16 variables set on the first three principle components. Scutovertex minutes, population ‘Bachsdorf’ versus population ‘Pogier’.
Table 2b. Loadings of the 16 variables set on the first three principle components. Scutovertex sculptus, population ‘Illmitz’ versus population ‘Fließ’.
Morphometric analysis of Scutovertex ianus sp. nov., S. minutus and S. sculptus
To test the intraspecific variability of Scutovertex minutus and S. sculptus, two populations of each species were analysed with the 16 variables set. The PCA performed with the two populations of S. minutus resulted in three components accounting for 78.7% of total variation. Loadings are given in Table 2a. The projections of the principle component scores show complete overlap of the two clusters (Fig. 1a). The analysis of the two populations of S. sculptus produced three components accounting for 81.8% of total variance; loadings are listed in Table 2b. The projections of the principle component scores exhibit also complete overlap of the two populations (Fig. 1b).
Fig. 1a-b. Projections of the principle component scores: A) Scutovertex minutus; ■ = population ‘Bachsdorf’, ● = population ‘Pogier’; B) S. sculptus; + = population ‘Illmitz’, ❙ = population ‘Fließ’.
Fig. 1c-e. Scatterplots of the principle component scores: ∞ = Scutovertex ianus, + = S. sculptus, ◽ = S. minutus.
The Principle Component Analysis of the same variables set of S. ianus, S. minutus and S. sculptus produced three components accounting for 84.6% of total variance in the data (Table 3). PC1 (50.4% of cumulative variance) shows moderate loadings for all variables indicating small differences in overall size, the variable cusp length cl exhibits the highest value with 0.4257 (Table 4). PC2 accounts for 30% of the total variance and again the cuspis length shows the highest value (0.8529), all the other values are very low. PC3 (4.2%) resulted in high loadings for distance between genital- and anal opening dga (-0.6177) and prodorsum length pl (0.4098). The projection of PC1 versus PC2 shows three clusters with a small overlap of all three entities (Fig. 1c). Graph PC1 versus PC3 (Fig. 1d) presents large overlaps of all three clusters and the scatterplot of the scores of PC2 versus PC3 (Fig. 1e) illustrates a nearly complete overlap of S. ianus and S. minutus.
Table 4. Loadings of the 16 variables set on the first three principle components. Scutovertex minutus versus S. ianus versus S. sculptus.
The Canonical Variates Analysis produced a Wilk's lambda of 0.05234. The first canonical function describes 61.99% of the total variability and the second 38.01%. The F-value is 21.07 and p (same) is 4.46410-48. The projection of the two Canonical Variates displays a clear separation of S. ianus with only small areas of overlap with the clusters of S. minutus and S. sculptus (Fig. 2). An external validation of the data with a discriminant analysis resulted in 97.44% correctly classified specimens (p-same 1.85×10-18) comparing S. minutus with S. ianus and in 98.72% correctly classified individuals (p-same 1.85×10-21) comparing S. sculptus with S. ianus.
Fig. 2. Plot of canonical variate 1 versus 2: ∞ = Scutovertex ianus, + = S. sculptus, ◾ = S. minutus.
Table 5. Pairwise distances. ni = number of analysed individuals, dia = intraspecific distances (uncorrected), dis = interspecific distances (uncorrected).
Molecular phylogenetic analysis
The NJ tree supports the monophyly of all investigated species, with bootstrap values of 80-100 for all clades, representing the species S. ianus sp. nov., S. sculptus, S. minutus, S. pileatus Schäffer and Krisper, 2007 and Lamellovertex caelatus (Berlese, 1895) as the outgroup. The Bayesian tree also shows a clear separation of the species with posterior probabilities of 100 (Fig. 3a-b). Mean pairwise distances within and between the Scutovertex species are shown in Table 5. Interspecific distance between S. ianus and L. caelatus amounted to 23.2%. Intra- and interspecific pairwise distances are plotted as histograms in Fig. 4.
Geographic distribution of Scutovertex ianus sp. nov.
The occurrence of S. ianus is currently limited to areas in Central Europe (numbers in brackets refer to Fig. 5). In Austria there are four records including the ‘locus typicus’ Admont  in Styria and the other three sample locations are Stiwoll  and Schladming  in Styria and Traun  in Upper Austria. The fifth record of this species is Mosbach near Heidelberg  in Germany, where only one single specimen was found. Scutovertex ianus seems to live in habitats (mosses) with a high permanent humidity as the sample locality in Admont is located at the border of a bog and the area in Traun is a floodplain.
The morphological similarity of S. ianus sp. nov. with S. sculptus and especially with S. minutus may lead to the assumption that this new species represents only a deviating population of one of the two above mentioned species. However a recent publication (Pfingstl et al., 2008) showed that S. sculptus individuals from different European countries are consistent with each other, the found morphological variation is negligible and the differences of S. ianus to S. sculptus are far beyond this intraspecific range of variability. Schäffer et al. (2007) stated that the members of S. minutus vary only in the number of notogastral setae, shape of lamellar cusps and of prodorsal ridges and again the members of S. ianus exceed these variances. The present results confirm that S. ianus is not just a product of the variation within one species. The differences are also not caused by sexual dimorphism, as the males and females of any Scutovertex species only vary in body size and the possession of a spermatopositor or ovipositor. The detailed morphological examination showed stable characters of all investigated S. ianus individuals and revealed that the combination of indistinct cuticular foveae on the notogaster and spiniform notogastral setae represents the set of characters being specific for this species (Table 6).
Table 6. Comparison of selected morphological characters of 11 Scutovertex species. ? = no information available.
Another morphological aspect approving S. ianus as valid species is the structure of the exochorion. Krisper et al. (2008) already found out that the fine structure of the egg shell of the genus Scutovertex is species specific. The comparison of the exochorion of S. ianus, S. minutus and S. sculptus (Fig. 6a-c) reveals differing shapes of fundamental structures. The fungiform structures and granules of S. minutus are shaped amorphous whereas S. ianus and S. sculptus show precise formations but the tops of the fungiform formations of S. ianus are conspicuously more flattened than in S. sculptus.
Fig. 6a-c. SEM-micrographs of exochorion structures: A) Scutovertex ianus; B) S. minutus; C) S. sculptus.
The morphometric analysis of different populations of S. minutus and S. sculptus showed a complete overlap within each species in all graphs. These results demonstrate stable intraspecific morphological variables and contradict the formerly supposed high intraspecific variability of these two species (Weigmann, 2006). On the basis of the stable morphology of the latter species, the multivariate analysis of S. minutus, S. ianus and S. sculptus confirmed the existence of a new entity with a good separation. Although there is overlap in all graphs, the projections PC1 versus PC2 and especially the CVA scatter plot exhibit a clear grouping. The projection PC2 versus PC3 fails to discriminate S. ianus and S. sculptus because the differences in body shape between these two taxa are of minor extent. Scutovertex minutus is well separated along the PC2-axis representing significant shape differences. In summary S. ianus and S. sculptus differ from each other mainly in body size, whereas S. minutus diverges from the latter two primarily in body shape. Earlier morphometric investigations of S. minutus and two epilittoral Scutovertex species (Pfingstl et al., 2009) using the same set and even a smaller set of variables resulted in an unambiguous separation and demonstrated clearer size and shape differences in overall morphology of these species. Scutovertex ianus represents nevertheless a distinct cluster bearing in mind that the well distinguishable and morphologically stable S. minutus and S. sculptus show comparable overlapping areas in this analysis.
The molecular phylogenetic analysis of the COI gene highlights the monophyly and the discreteness of all three investigated Scutovertex species with high bootstrap values. Scutovertex ianus is represented in the NJ tree as the sister group of S. sculptus and is therefore more closely related to the latter species than to S. minutus. This relationship is not clearly reflected in the morphological similarities of the species; only the exochorion structure of the eggs seems to refer to this correlation.
The combined approach of comparative morphology, morphometry and genetic data justifies S. ianus as an indisputable species. Different works (Strenzke, 1943; Schäffer and Krisper, 2007; Pfingstl et al., 2008) affirmed the clear distinction between S. minutus and S. sculptus but could not explain the existence of intermediate forms. The detection of S. ianus leads us to a possible explanation as former findings of deviant individuals of S. minutus or S. sculptus may refer to this new species. The existence of as yet undetected species may generally induce confusion about the intraspecific variability of a species. Polderman (1977) discovered the new species S. pilosetosus Poldermann, 1977 and revealed that the whole Dutch collection of S. minutus consisted of this new species. Pfingstl et al. (2009) believe their recently described S. arenocolus Pfingstl and Schäffer, 2009 could be responsible for mistaken records of S. minutus in certain coastal areas and Weigmann (2009) supposes that findings of a small sized S. minutus in Spain may refer to his newly described S. mikoi Weigmann, 2009. All these facts point to a more limited intraspecific variability and to a higher species diversity of the genus Scutovertex than formerly supposed (Haarlov, 1957; Pérez-Iñigo, 1993; Weigmann, 2006).
We want to thank Elke McCullough, Julia Jagersbacher-Baumann and Nina Grafeneder for providing us with substrate samples and specimens respectively. The authors also want to thank Prof. Dr. Ferdinand Hofer, head of the Research Institute for Electron Microscopy (FELMI) and his team realizing the SEM-micrographs. This work was supported by the Austrian Science Foundation (FWF, project number P19544-B16).
Received: 9 July 2009
Accepted: 9 February 2010
Published online: 29 March 2010
Editor: J.A. Miller
Berlese A. 1895. Scutovertex caelatus Berl. n. sp. Acari, Myriapoda et Scorpiones hucusque in Italia reperta 74.
Boyce TM, Zwick ME, Aquadro CF. 1989. Mitochondrial DNA in the bark weevils: size, structure and heteroplasmy. Genetics 123: 825-836.
Hammer O, Harper DAT, Ryan PD. 2001. PAST: Palaeontological Statistics software package for education and data analysis. Palaeontologia Electronica 4: 1-9.
Haarlov N. 1957. Microarthropods from Danish Soils. Systematics. Spolia Zoologica Musei Hauniensis 17: 1-60.
Heethoff M, Domes K, Laumann M, Maraun M, Norton RA, Scheu S. 2007. High genetic divergences indicate ancient separation of parthenogenetic lineages of the oribatid mite Platynothrus peltifer (Acari, Oribatida). Journal of Evolutionary Biology 20: 349-401.
Krisper G, Schuster R. 2001. Umweltansprüche und Verbreitung der Hornmilbe Provertex kühnelti Mihelcic, 1959 (Acari, Oribatida) in Österreich. Mitteilungen des naturwissenschaftlichen Vereines Steiermark 131: 141-146.
Krisper G, Schmikl M, Ebermann E. 2002. Erstnachweis der felsbewohnenden Hornmilben Scutovertex pictus Kunst, 1959 und Lamellovertex caelatus (Berlese, 1895) (Acari, Oribatida) für Österreich. Mitteilungen des naturwissenschaftlichen Vereines Steiermark 132: 193-196.
Krisper G, Pfingstl T, Ebermann E. 2008. SEM-Investigations on the exochorion of scutoverticid eggs. Soil Organisms 80: 217-221.
Koch LC. 1835. Cepheus minutus. Deutschlands Crustaceen, Myriapoden und Arachniden (Regensburg), Heft 3, Tab. 12.
Kumar S, Tamura K, Nei M. 2004. MEGA3: integrated software for molecular evolutionary genetics analysis and sequence alignment. Briefings Bioinformatics 5: 150-163.
Michael AD. 1879. A contribution to the knowledge of the British Oribatidae. Journal of the Royal Microscopical Society London 2: 225-251.
Mihelčič F. 1957. Oribatiden Südeuropas VII. Zoologischer Anzeiger 159: 44-68.
Otto JC, Wilson KJ. 2001. Assessment of the usefulness of ribosomal 18S and mitochondrial COI sequences in Prostigmata phylogeny. Pp. 100-109 in: Halliday RB, Walter DE, Proctor HC, Norton RA, Colloff J, eds., Acarology. Proceedings of the 10th International Congress. Melbourne: CSIRO Publishing.
Pérez-Iñigo C. 1993. Acari, Oribatei, Poronota I. Fauna Iberica. vol. 3. Madrid: Museo Nacional de Ciencias Naturales.
Pfingstl T, Schäffer S, Ebermann E, Krisper G. 2008. Intraspecific morphological variation of Scutovertex sculptus Michael (Acari: Oribatida: Scutoverticidae) and description of its juvenile stages. Zootaxa 1829: 31-51.
Pfingstl T, Schäffer S, Ebermann E, Krisper G. 2009. Differentiation between two epilittoral species, Scutovertex arenocolus spec. nov. and Scutovertex pilosetosus Polderman (Acari: Oribatida) from different European coasts. Zootaxa 2153: 35–54.
Polderman PJG. 1977. Scutovertex pilosetosus nov. spec. from the Netherlands (Acari, Oribatida). Entomologische Berichten, Amsterdam 37: 129-132.
Posada D, Crandall K. 1998. MODELTEST: testing the model of DNA substitution. Bioinformatics 14: 817-818.
Ronquist F, Huelsenbeck JP. 2003. MrBayes 3: Bayesian phylogenetic inference under mixed models. Bioinformatics 19: 1572-1574.
Schäffer S, Krisper G. 2007. Morphological analysis of the adult and juvenile instars of Scutovertex minutus (Acari, Oribatida, Scutoverticidae). Revue Suisse de Zoologie 114: 663-683.
Schäffer S, Krisper G, Pfingstl T, Sturmbauer C. 2008. Description of Scutovertex pileatus sp. nov. (Acari, Oribatida, Scutoverticidae) and molecular phylogenetic investigation of congeneric species in Austria. Zoologischer Anzeiger 247: 249-258.
Schäffer S, Koblmüller S, Pfingstl T, Sturmbauer C, Krisper G. (in press a). Contrasting mitochondrial DNA diversity estimates in Austrian Scutovertex minutus and S. sculptus (Acari, Oribatida, Brachypylina, Scutoverticidae). Pedobiologia, doi:dx.doi.org/10.1016/j.pedobi.2009.09.004.
Schäffer S., Pfingstl T, Koblmüller S, Winkler KA, Sturmbauer C, Krisper G. (in press b). Phylogenetic analysis of European Scutovertex mites (Acari, Oribatida, Scutoverticidae) reveals paraphyly and cryptic diversity: A molecular genetic and morphological approach. Molecular Phylogenetics and Evolution, doi:dx.doi.org/10.1016/j.ympev.2009.11.025.
Schuster R. 1958. Beitrag zur Kenntnis der Milbenfauna (Oribatei) in pannonischen Trockenböden. Sitzungsberichte der Österreichischen Akademie der Wissenschaften / Mathematisch-Naturwissenschaftliche Klasse, Abt. 1, 167: 231-235.
Sitnikova LG. 1975. Family Scutoverticidae Grandjean, 1954. Pp. 246-254 in: Ghilarov MS, Krivoluckij DA, eds., Opredelitel obitajuščih v počve kleščej. Moskva: Nauka.
Smrž J. 1992. The ecology of the microarthropod community inhabiting the moss cover of roofs. Pedobiologia 36: 331-340.
Smrž J. 1994. Survival of Scutovertex minutus (Koch) (Acari: Oribatida) under differing humidity conditions. Pedobiologia 38: 448-454.
Strenzke K. 1943. Beiträge zur Systematik landlebender Milben, I/II. Archiv für Hydrobiologie 40: 57-70.
Subías LS. 2004. Listado sistemático, sinonímico y biogeográphico de los ácaros oribátidos (Acariformes: Oribatida) del mundo. Graellsia 60: 3-305 (Update 2009: http://www.ucm.es/info/zoo/Artropodos/Catalogo.pdf).
Swofford DL. 2002. PAUP* Phylogenetic analysis using parsimony (* and other methods), version 4.Sunderland (MA): Sinauer Associates.
Weigmann G. 1973. Zur Ökologie der Collembolen und Oribatiden im Grenzbereich Land-Meer (Collembola, Insecta - Oribatei, Acari). Zeitschrift für wissenschaftliche Zoologie 186: 295-391.
Weigmann G. 2006. Hornmilben (Oribatida). Die Tierwelt Deutschlands, begründet 1925 von Friedrich Dahl. 76. Teil. Keltern: Goecke and Evers.
Weigmann G. 2009. Oribatid mites (Acari: Oribatida) from the coastal region of Portugal. III. New species of Scutoverticidae and Scheloribatidae. Soil Organisms 81: 107-127.
Willmann C. 1953. Neue Milben aus den östlichen Alpen. Sitzungsberichte der Österreichischen Akademie der Wissenschaften/Mathematisch-Naturwissenschaftliche Klasse, Abt. 1, 162: 449-519.
Description of Scutovertex ianus sp. nov.
Genus Scutovertex Michael, 1879
Holotype. ZMB 48049 (Museum of Natural History, department of Arachnids, Myriapods and Stemgroup Arthropoda, Humboldt-University Berlin), 1 female, Admont (Austria, Styria), moss on a rock at the edge of a bog, August 8th 2007, leg E. McCullough.
Paratypes. ZMB 48050, 1 male, 2 females; 2007/ 37861 (Senckenberg Museum für Naturkunde Görlitz, Sektion Arachnida) 1 male, 3 females; RMNH.ACARI.163 (Netherlands Centre for Biodiversity Naturalis, Leiden) 1 male, 3 females. All paratypes from the same locality as holotype.
Other material. Schladming (Styria), moss from a stone wall in front of town hall, 16th March 2005, leg S. Schäffer (Coll. Pfingstl, slides no. 608, 611); Traun (Upper Austria), moss from rocks in floodplain, June 6th 2006, leg. N. Grafeneder (Coll. Pfingstl, slide no. 1224); Stiwoll (Styria), mosses from a graveyard wall, September 6th 2006, leg. S. Schäffer (Coll. Pfingstl, slides no. 609, 610, 612); Admont (Styria), mosses on rocks, August 8th 2007, leg. E. McCullough (Coll. Pfingstl, slides no. 599-602, 762-772; material in ethanol no. 147-151).
Diagnosis. Habitus corresponding to typical Scutovertex. Average length 591 µm, average body width 351 µm. Colour dark brown. Cuticle pusticulate, cerotegument granulate. On anterior part of notogaster irregularly distributed foveae and irregularly shaped ribs. Cusps long, lamellae distinct. Two strongly converging and anteriorly fused ridges on interlamellar field reaching translamella. Sensillus clavate and spinose. 10 pairs of short and spiniform notogastral setae.
Differential diagnosis. Scutovertex ianus can be distinguished from S. alpinus by the large indistinct notogastral foveae and the different body size. Scutovertex arenocolus differs from S. ianus in possessing not fused prodorsal ridges and slightly broadened and spinose notogastral setae. Scutovertex mikoi can be distinguished from S. ianus by its conspicuous smaller body size, not fused prodorsal ridges, 9 pairs of notogastral setae and the lack of gastronotic foveae. The differences between S. ianus and S. minutus are the not fused prodorsal ridges and the non-existence of notogastral cuticular foveae in the latter species. Scutovertex pannonicus can be distinguished from S. ianus by its obvious larger body size and distinct large cuticular foveae on the notogaster. Scutovertex perforatus also possesses distinct cuticular foveae and differs in this aspect from S. ianus. Scutovertex pileatus can be distinguished from S. ianus by the not fused two pairs of prodorsal ridges, the absence of cuticular foveae and the continuous transverse ridge on mentum. Scutovertex pilosetosus is distinctly larger than S. ianus and lacks the median part of the transverse ridge on the mentum. Scutovertex rugosus shows different notogastral setae and S. sculptus can be distinguished from S. ianus by the not fused prodorsal ridges and broadened and spinose posterior notogastral setae (Fig. 7a-c, Table 6).
Fig. 7a-c. Examples of different character states in Scutovertex species (see Table 6): A) prodorsal ridges; B) shape of notogastral setae; C) transverse ridge on mentum.
Description of holotype. Body length (N=49) 533-640 µm. Body width (N=46) 304-391 µm. Prodorsum: cuticle strongly pusticulate. Sensillus (Se) long, clavate, serrate and flattened. Cup-like bothridia with a posterior ridge running caudally (Fig. 8a). Interlamellar and exobothridial setae absent. Lamellae slightly converging, connected by translamella. Long cusps, lamellar setae (le) spiniform and serrate. Rostral setae (ro) robust and smooth strongly bent inwards. Two strongly converging ridges between lamellae fused in anterior part of interlamellar field reaching translamella. V-shaped tutorium strongly projecting (Fig. 8b). Gastronotic region (Figs 9a, 10a): cuticle pusticulate with indistinct foveae on anterior half of notogastral region, cerotegument granulate. Lenticulus with lateral concave margins, posterior part broadened. Posterior to lenticulus irregularly shaped ridges. Ten pairs of short spiniform notogastral setae: c2, la, dm, lp, h1-h3, ps1-ps3 (Fig. 9c). Setae h1-3 and ps1-3 with minimal serration (Fig. 10b), all setae except c2 and la inserted on small humps. Humeral angle well developed. Five pairs of lyrifissures on gastronotic region: ia, im, ih, ips, ip; ia located laterally on a small cuticular nodule ventrally to humeral angle (Figs 8a, 11a). Lyrifissure im slit-shaped, laterally and posterior to seta la; ih and ips next to each other on posterior lateral border of the notogaster and ip between setae h1 and ps2. Orifice of opisthonotal gland next to seta lp, well discernable. Three pairs of small sacculi S1-3 representing octotaxic system, SA not developed. Subcapitulum and camerostome: cuticle strongly pusticulate. Inner margin of camerostome consisting of rostrophragma. Median rostral lobe forming anterior border of camerostome and longish triangular lamellae flanking rostrophragma laterally (Fig. 9b). Mentum with long spiniform setae h and discontinued variable transverse ridge (Fig. 11b). Setae a and m long acuminate and slightly serrate. Rutellum broad with three teeth, first one largest. Pedipalp pentamerous, chaetome: 0-2-1-3-9 (solenidion excluded), solenidion inclined reaching eupathidium acm (Fig. 11c). Longish porous axillary sacculus as located at basis of pedipalp. Ventral region of idiosoma (Fig. 9b): cuticle pusticulate forming distinct ribs on posterior part of ventral idiosoma. Epimeral setation (I-IV): 3-1-2-2. Pedotectum I (PtI) large, covering acetabulum I completely. Pedotectum II (PtII) also large, Y-shaped in dorsal view and drop shaped in lateral view (Figs 8b, 11a). Genital setation 6+6 (no variations observed). The first two genital setae the longest, inserting side by side, the others arranged in a longitudinal row. Genital valves anteriorly broadened and surrounded by a circular cuticular elevation. A rostrad arcuated cuticular rib anterior to genital opening. One pair of spiniform aggenital setae ag. Posterior to genital opening whole ventral region crossed transversely by a narrow and slightly caudad curved rib. Two pairs of anal setae, an1-2. Anal valves posteriorly broadened. Three pairs of acuminate adanal setae ad1-3. Lyrifissure iad in paraanal position. Preanal organ cup-shaped. Legs (Fig. 12a-d): tridactyl, heterodactyl, claws dorsally slightly dentate; median claw largest. Cuticle from trochanter to femur pusticulate and from genu to tarsus rugose, forming a few strong ribs. Tibial setae robust and serrate. Ventral and lateral tarsal setae also serrate. Solenidia ϕ1-2 inserting distally on large apophysis of tibia I. Legs showing Scutovertex-typical tracheae. Leg chaetome without solenidia: I (1-4-3-4-18), II (1-4-3-4-15), III (2-2-1-3-15), IV (1-2-2-3-12). Solenidia: I (1-2-2), II (1-1-2), III (1-1-0), IV (0-1-0). Eggs (Fig. 13a-b): the exochorion consists of two different structures which are dispersed over the whole endochorion. There are large fungiform formations and smaller cones each of them with a granular surface.
Fig. 8a-b. Scutovertex ianus SEM-micrographs: A) bothridium and sensillus; B) prodorsum in lateral view.
Fig. 9a-c. Scutovertex ianus (female): A) dorsal view; B) ventral view; C) notogastral setae in detail.
Fig. 11a-c. Scutovertex ianus (male): A) lateral view; B) subcapitulum; C) left pedipalp antiaxial view.
Fig. 12a-d. Scutovertex ianus (female): A) right leg I antiaxial view; B) right leg II antiaxial view; C) right leg III antiaxial view; D) left leg IV paraxial view.
Remarks. Unfortunately, the holotype and paratypes of S. minutus of the collection of C.L. Koch are missing (see Schäffer and Krisper, 2007: 676). Furthermore, no information on the whereabouts of the type specimens of S. sculptus is available. Therefore the identification of these two species is based on the detailed descriptions given by Schäffer and Krisper (2007) and Pfingstl et al. (2008). Sample locations for S. minutus: Asparn, Unterstinkenbrunn (Lower Austria), mosses and lichens on a tiled roof, 16th November 1996, leg. E. Ebermann; Graz, Bachsdorf (Styria), mosses on a roof, 8th May 2005, leg. J. Jagersbacher-Baumann; Pogier (Styria), mosses on rocks, 12th October 2006, leg. S. Schäffer; S. sculptus: Illmitz (Burgenland), shore of lake Zicklacke, 16th September 2005, leg. G. Krisper; Ernstbrunn (Lower Austria), mosses on a rock, 29th March 2005, leg. E. Ebermann; Fließ (Tyrol), sun exposed mosses, 11th June 2007, leg. H. Schatz; S. pileatus: all from mosses on rocks, Laas, 28th March 2005, leg. S. Schäffer, Schütt, 8th August 2005, leg. S. Schäffer, Ruin Hochosterwitz, 26th June 2005 (Carinthia), leg. S. Schäffer.
Etymology. The new species shares certain morphological characteristics with Scutovertex minutus and S. sculptus resulting in an intermediate appearance. Therefore the species is named according to ‘Ianus’ the two headed Roman god who is also a symbol for ambivalence.
Identification key for European Scutovertex species
Diagnosis for the genus Scutovertex (according to Weigmann 2009, with minor modification).
Notogaster ovoid and medially fused with prodorsum; lamellae distinct but slender, with cuspis; translamella narrow; interlamellar setae absent; camerostome with separated rostrophragma inside border of rostrum forming a second anterior border, without genal incision; notogaster with longish lenticulus. 9-12 pairs of notogastral setae. Octotaxic system usually present as 3 pairs of saccules; ano-genital setation: 6 g, 1 ag, 2 an, 3 ad; epimeral setation 3-1-2-2; tutorium weakly developed; pedotecta I and II well developed; legs tri- and heterodactylous; trochanter III and IV with tracheae curving along inner wall; all femora with tracheae reaching into tibia.
1 cuticular foveae on gastronotic region → 2
- cuticular foveae on gastronotic region absent → 8
2 (1) foveae indistinct → 3
- foveae distinct → 10
3 (2) prodorsal ridges convergent → 4
- prodorsal ridges anteriorly fused, body length 655-718 µm → S. pilosetosus Poldermann, 1977
4 (3) notogastral setae broadened → 5
- notogastral setae spiniform, body length 533-640 µm → S. ianus sp. nov.
5 (4) cuspis length > 15µm → 6
- cuspis length < 15µm, body length 527-614µm → S. arenocolus Pfingstl and Schäffer, 2009
6 (5) setae la barbed → 7
- seta la smooth, body length 521-671µm → S. sculptus Michael, 1879
7 (6) cuticle on gastronotic region granular, body length 630-680µm → S. perforatus Sitnikova, 1975
- cuticle on gastronotic region with oblong lines, body length 581-630µm → S. rugosus Mihelčič, 1957
8 (1) cerotegument granular → 9
- cerotegument forming thick nodes, body length 481-575µm → S. pileatus Schäffer and Krisper 2007
9 (8) 9 pairs of notogastral setae, body length 378-445µm → S. mikoi Weigmann, 2009
- 10-12 pairs of notogastral setae, body length 550-659µm → S. minutus (C.L. Koch, 1835)
10 (2) large cuticular foveae on gastronotic region, body length 773-800µm → S. pannonicus Schuster, 1958
- small cuticular foveae on gastronotic region, body length 477–527µm → S. alpinus Willmann, 1953