New and known records of Oppiidae (Acari, Oribatida) from Romania

In this paper two newly recorded species of the family Oppiidae are presented, namely Ramusella alejnicovae (Krivolutsky and Gatilova, 1974) and Lauroppia iranica Akrami and Subías, 2008. Additionally, recent records of two other rare species, i.e., Multioppia (M.) perfecta Mahunka and Topercer, 1983 and Ramusella sengbuschi tokyoensis (Aoki, 1974) are given. For each species, a redescription and illustration based on Romanian material is provided and compared with existing descriptions, and data regarding world distribution and ecological requirements are analyzed. In addition, the status ofMultioppia (Hammeroppia) insolita Ivan and Vasiliu, 1999, a species considered as a possible synonym of M. (H.) wilsoni laniseta Moritz, 1966 (Subías 2004 updated 2018) is discussed, and reasons to deem insolita as a valid species are pointed out.


Introduction
The family Oppiidae is one of the largest and diverse families of oribatid mites with more than 1000 known species that populate various edaphic habitats across the world. To date, the Romanian oribatid mite fauna comprises about 90 oppiid species, whereas 22 of them were described as new species in the last two decades (e. g., Ivan and Vasiliu 1999, Vasiliu and Ivan 2009, Mahunka 2004, 2005. Some other species were recorded as faunistic novelties (e.g., Ivan 2007, Ivan andCălugăr 2013).
The list of oppiid mites comprises both frequent, eurytopic species and some uncommon, rarely collected, possibly stenotopic ones. Of the second category, four recently recorded species are included in this study, as follows: Multioppia (M.) perfecta Mahunka and Topercer, 1983, Ramusella sengbuschi tokyoensis (Aoki, 1974), Ramusella alejnicovae (Krivolutsky and Gatilova, 1974) and Lauroppia iranica Akrami and Subías, 2008. In this study a brief description and illustration for each species and analysis of data regarding world distribution and ecological requirements are provided. These redescriptions based on material collected in Romania aim to illustrate species variability, both from morphological and biometrical point of view and, in some cases, to contribute to determination of their taxonomical status. In addition, the status of Multioppia (Hammeroppia) insolita Ivan and Vasiliu, 1999 is discussed, based on comparative analysis of diagnostic characters of this species and the close related taxa.

Materials and methods
The material used in this study was collected in the context of several projects, both by the author and other team members, as follows: O. Ivan (Multioppia (M.) perfecta, Multioppia (H.) insolita, Ramusella sengbuschi tokyoensis), N. Vasiliu (Lauroppia iranica) and A. Călugăr (Ramusella alejnicovae). More data regarding the examined material are given in the description of each species in Results section further below.

Results
Multioppia (Multioppia) perfecta Mahunka and Topercer, 1983 (Figure 1) Literature used for identification -Mahunka and Topercer 1983. Measurements -Body length 235-247, body width 120-140 (7 specimens). Description of Romanian specimens -Body color light yellowish, cuticle smooth excepting lateral part of podosoma. Rostrum entire, widely rounded. Rostral setae relatively long (20-23), uniformly arched and ciliated. Lamellar and interlamellar setae thin and simple, similar in length (8-10). Exobothridial seta fine and simple, hardly observable in dorsal view, slightly shorter than le and in (7-8). Lamellar and translamellar lines present. Three pairs of spots visible between insertion points of in setae, large foveolae border lamellar lines laterally. Sensillus relatively long (40-43) fusiform, pectinate. Distal part expanded, asymmetrical, with 15-16 fine branches on lateral side, arranged in two rows convergent at the tip; each row comprises one short branch distally, 6 longer branches (longest ones in the middle) and one short branch proximally (Figure 1 B). Notogaster with 13 pairs of setae fine, simple and short (15-18) excepting c that is minute, but discernible. Distribution of notogastral setae is characteristic for Multioppia subgenus, thus dm occurs behind im lyrifissure (Vasiliu and Ivan 2009). Ventral side shows no differences from the original description (Mahunka and Topercer 1983). Epimeres well defined, with polygonal ornamentation in medial part; epimeral setae simple and short, placed according to the formula 3:1:3:3, setae 3c and 4c longer than the medial ones. Genito-anal region with usual configuration and the setal formula 5:1:2:3, all these setae fine and simple.
Remark -The main characters of this species were found in Romanian specimens. However, some differences from the original description should be noticed, i.e., the shape of translamellar line (straight, with obvious lateral angles in type material) and sensillus with ciliation apparently on both sides (Mahunka and Topercer 1983, Figures 7, 9), distinct from the sensillus structure above described based on Romanian material.
Distribution and ecology -Multioppia perfecta was described from Slovakia (cultivated soil). Currently, it is considered a Central and South European element (Subías 2004(Subías , updated 2018, but apart from Romania this species was not yet mentioned in the fauna of other countries in this region (e.g., Hungary, Germany, Czech Republic, Poland, Austria) (Mahunka and Mahunka-Papp 2004;Miko 2006Miko , 2016Niedbała and Olszanowski 2008;Krisper et al. 2017). In Romania it was firstly recorded in some grassland ecosystems (both hayfields and pastures) from the North-Eastern region (Ivan 2007), and recently it was collected from the soil of Robinia pseudoacacia plantation, on degraded land, in the same region of the country (Fereşti-Velniţa, Vaslui county, 46°47'36"N, 27°43'49"E, 13.05.2015). However, occurrence analysis of M. perfecta shows that it is not a common species, its requirements being not clear; probably it has a discontinuous distribution in the Central and Southeastern Europe, depending on some peculiar bio-edaphic conditions. Ivan and Vasiliu, 1999 (Figure 2) The main diagnostic characters of this species compared with the close related taxa are summarized in Table 1. The shape of sensillus ( Figure 2), granulated surface of mentum and epimeres 1 and 2, and the length of epimeral setae of b and c series differentiate this species from M. wilsoni Aoki, 1964 species group, especially from M. wilsoni laniseta Moritz, 1966. Subsequent redescriptions of M. laniseta (Miko 2006, Seniczak et al. 2014) support the above mentioned differences, particularly in terms of sensillus shape.   Multioppia (Hammeroppia) insolita was firstly identified in litter of Quercus frainetto forest from Olt county (Southern Romania). It is a really rare species, being found subsequently as few specimens in some forest plantations from the Danube Delta (Ivan et al. 2006), and recently in the soil of Robinia pseudoacacia plantation, on degraded land in Vaslui county (Eastern Romania) (Fereşti-Săratu, 46°45'59"N, 27°42'48"E, 13.05.2015).
In the context of some ecological investigations carried out in different ecosystem types from North Eastern Romania, some species were recorded for the first time in the country, and  Hammer, 1968 (Ivan andCălugăr 2013). Detailed review of this faunistic material evidenced some differences from both the original description (Hammer 1968) and the later one provided by Subías and Arillo (2001), especially in the structure of sensillus, i.e., the presence of spines on its inner part (Figure 3 B). The main characters observed in our specimens are included in Table 2, in comparison with closely related taxa (Subías 2004(Subías , updated 2018.
Remarks -The material examined (5 specimens) proved to be more similar with Ramusella tuberculata Mahunka and Topercer, 1983, despite some differences, namely sensillus with spines on its inner part, epimeral setae relatively short, among them only 3c and 4c ciliated (in original description "sensillus with lanceolate head bearing 11 long and strong cilia" and "epimeral setae long and ciliated"). Also, comparative analysis of data in Table 2 evidences that the presumable synonymy of tuberculata and tokyoensis need thorough investigation based on the type material. However, taking into account the similarity of most characters, our material was identified as R. (R.) sengbuschi tokyoensis, according to the current classification of Oppiidae suggested and developed by Subías (2004Subías ( , updated 2018. Distribution and ecology -Ramusella (R.) sengbuschi Hammer was described from New Zealand, currently being considered as pantropical and subtropical element (except Ethiopian), while ssp. tokyoensis is supposed to be distributed in the Southern Palaearctic (Subías 2004(Subías , updated 2018. In Europe R. (R.) sengbuschi was recorded in Spain and Portugal, also in Italy and Greece (Subías and Arillo 2001); it was also listed in Caucasus (Shtanchaeva and Subías 2010) and in Austria, with note "sub Ramusella tuberculata Topercer, 1983" (Krisper et al. 2017). Literature data (Aoki 1974, Mahunka and Topercer 1983, Subías and Arillo 2001 indicate that both subspecies were reported mostly in anthropogenic habitats (urban, cultivated or contaminated soils). In Romania R. (R.) sengbuschi tokyoensis was found also in a cultivated soil (wheat crop, Cănţălăreşti, Vaslui county, 46°45'58"N, 27°35'29"E, 25.05.2013), but never in natural habitats.
Distribution and ecology -Southern Palaearctic (Subías 2004(Subías , updated 2018. Ramusella alejnicovae was described from Volga territory in Russian Federation, and later reported in Southern Siberia, Mongolia and Caucasus (Bayartogtokh 2010, Shtanchaeva andSubías 2010). In terms of ecology it is considered a typical inhabitant of grassland soil in steppes (Bayartogtokh 2010). This is the first record of R. alejnicovae in Romania; it was found in  Description of Romanian specimen -Light brown in color, body surface smooth. Rostrum entire, prominent. Prodorsal setae thin, with the following relation between their lengths: le (10) < ex (20) < in (23) < ro (28). Costulae present with characteristic shape: posterior part semicircular, surrounding the insertion of in seta, and distal part, weakly shaped, divergent, extended beyond the insertion of le seta; a narrow chitinous stripe between bothridium and costula can be also observed (Figure 5 B, C). Sensillus long (55), its distal part fusiform -elongated and bipectinate, with 7 thin and short branches. Notogaster oval elongated with anterior margin straight and crista present. Ten pairs of thin and simple notogastral setae; la, lm, lp longer than remaining ones (c, h and p series) (20, 13, respectively). Ventral side with characteristic configuration (Figure 5 D). Epimeral setae thin, placed according to the formula 3:1:3:3. Lateral setae, except 1c longer (13) than median ones (8); 1b, 3c, 4a and 4c bifurcated. Genito-anal region with the setal formula 6:1:2:3. All setae simple, thin and short, ad and ag slightly longer (10) than an (8); g 1 twice as long as g 2 -g 6 . Lyrifissure iad in paraanal position.
Remark -Analyzing the original description of L. iranica (Akrami and Subías 2008), some differences appeared remarkable in the examined material, especially the larger body size (370 x 206 beside 330 x 170 in Iranian specimens), but also the aspect of some prodorsal setae (ro, in and ex) described as "finely barbed" or "with some barbs" that were not observed as such. However, all the other characters mentioned by authors in their description are found in Romanian material, thus it was assigned to this species.
Distribution -Lauroppia iranica was described from Iran and no other citations of this species are available so far, when we mention it as a first record for Romanian fauna. It was identified in an earlier collection from Cheia, Constanţa county (44°29'7"N, 28°26'30"E, 28.04.1993; registered as Lauroppia sp.), in the soil of a xerophilous grassland, currently included in Natura 2000 site ROSCI 0215. It can be assumed that this species remained here in a refuge, after the Black Sea transgression in Quaternary, thus this new record is also significant from zoogeographical point of view.