TWO INTERESTING DAMAEID MITES (ACARI, ORIBATIDA, DAMAEIDAE BERLESE, 1896) FROM THE BRITISH ISLES AND SVALBARD (SPITSBERGEN, NORWAY), WITH A DESCRIPTION OF KUNSTIDAMAEUS ARCTICUS N.SP.

Two species of the family Damaeidae (Acarina, Oribatida) are described and documented. Kunstidamaeus arcticus n.sp. was found in Svalbard (Spitsbergen) and differs from all other known species of the genus by having only five pairs of genital setae; by the specific development at the base of the prodorsum, where tubercles Ba are replaced by a multiple of small tubercles, by minute and hardly visible spinae adnatae, by the characteristic shape of the sensillus and other characters. The other species, belonging to the genus Epidamaeus, was found in North-West England and stands near to E. floccosus Behan-Pelletier and Norton, 1985, but differs by the development of sensillus, spinae adnatae unilaterally with one tooth and by the notogastral setae inserted on cuticular thickenings. The single available specimen did not allow us to decide with certainty about it´s specific status, which in the future may prove to be a separate species. The relationships of the two species found are discussed.


INTRODUCTION
Oribatid mites of the genus Kunstidamaeus and Epidamaeus were differentiated at generic level only recently (see Miko, , 2010Miko and Mourek, 2008). Kunstidamaeus Miko, 2006 can be distinguished from Epidamaeus (and other Damaeus sensu lato) species by presence of typical set of tubercles Ba and La in dorsosejugal area, absence of centrodorsal tubercles Da, and by presence of more or less developed, usually pointed or finger-form perpendicular apophysis P laterally on prodorsum. Species of this genus are represented in northern and western Europe by 9 species (see Subías, 2004;updated Internet version 2011), and morphologically can be grouped into three groups ("lengersdorfi", "tecticola", and "tenuipes" groups, see Miko and Mourek, 2008 for details). The species of genus Epidamaeus are known from a broad range of habitats, mostly in mountain, boreal, subarctic and arctic zones of the Holarctic ecozone, what was well documented by e.g. Behan-Pelletier and Norton (1983Norton ( , 1985. Epidamaeus is a species-rich genus (over 75 species), with many undescribed species still to be expected. At least some of the known species may be, however, after further study transferred to Kunstidamaeus. This article brings together the descriptions of two interesting species collected in the British Isles and Spitsbergen, with a designation of Kunstidamaeus arcticus as a new species.

MATERIALS AND METHODS
Material has been provided from the collection of the second author (F.D.M.) with details of location and date found given in the descriptions below. The British material (Epidamaeus sp.) was collected from sieved coarse detritus and extracted using the standard method of Berlese-Tullgren funnels. Details of the collection and extraction of the Svalbard material are unknown.
All individuals, previously preserved in alcohol, were examined unmounted and studied after maceration in lactic acid in open cavity slides. Holotypes of K. arcticus will be deposited in the Acarological collection of Prague National Museum (Czech Republic), whilst paratypes will be kept (in alcohol) in the collections of L. Miko (1 paratype) and F.D. Monson (3 paratypes). Single individual of Epidamaeus sp. will be kept in the collection of L. Miko.
In the present paper, we follow the morphological terminology and abbreviations developed by Grandjean (1960) and modified by subsequent authors (see Miko and Mourek, 2008 for complete references and a list of abbreviations). For leg setae, Grandjean´s notations, as reviewed by Norton (1977) were used. The drawings and measurements were made following the same methodology as in our previous works (see Mourek, Miko and Skubała, 2011 for details).

Kunstidamaeus arcticus n.sp. (Figs. 1-3)
Diagnosis -Kunstidamaeus with a short, slightly dilated sensillus covered distally by cerotegument; tubercle Ba absent; with a set of variably developed small tubercles present at the basis of prodorsum; and with weakly developed spinae adnatae. Ventral side with a paired anterior ventromedial apophyse, with most epimeral setae inserted on distinct tubercles; only 5 pairs of genital setae present.
Description of the adult.
Material examined -Holotype and four paratypes, collected by S. Coulson from soil of tundra heath in Svalbard (Spitsbergen, Norway), sample number OR 804, 1991OR 804, -1993. More detailed information about the collected material is not available to us.
Integument -Surface of body and legs, except distal parts of tarsi, covered mostly by filamentous and columnar cerotegument, which has, on prodorsum, anterior and central part of notogaster and on ventral plate, a very characteristic appearance: individual, rather short and distinctly attenuated filaments each with a slightly expanded, buttonlike base. Lateral part of sejugal area, propodolateral apophyse and parastigmatic apophyses with granular cerotegument. Distal part of sensillus with a very specific, short, but distinct, fine "leaflike" cerotegument ( Fig. 2J). Body surface under cerotegument finely granulated, with the granulation well visible on the prodorsum and the ventral plate.
Remarks -The species has several unusual characters distinguishing it from all other Kunstidamaeus (and Epidamaeus) species. The most unusual being the presence of only 5 genital setae per plate, whilst, the normal number for both genera and all Damaeidae is 6 setae per plate. The combination of the presence of a typical apophyse P perpendicular to the body axis together with prodorsal tubercles La and Ba is typical for Kunstidamaeus, and the similar combination of apophysis P and tubercle La let us to assign the species to this genus. However, in K. arcticus n.sp., postbothridial tubercles are absent, whilst a row of 3-4 small tubercles at each side of prodorsum base has developed instead, in some individuals. One could speculate about the homology of this structure with tubercles Ba or Da. However, this structure is variable in our material, and in some individuals is only weakly developed. This suggests that the homology is questionable and the structure may have evolved independently. The idea is, in our view, supported also by the very unusual presence of paired tubercles VM in the medial part of the ventrosejugal groove. The single, unpaired ventromedial tubercle VM is known from this area in only a few species of Epidamaeus eg. E. fortispinosus Hammer, 1967 andE. hastatus Hammer, 1967. The latter of the two species shares some more similarities (see Behan-Pelletier and Norton, 1985 for details), e.g. shape of spinae adnatae, exobothridial setae and partly also the relatively short, lanceolate sensillus, and, more importantly, a thickened cuticle at the basis of prodorsum. To our knowledge, unique to K. arcticus n.sp. is also the presence of a distinctly thickened cuticle at the ventral part of the proximal end of tarsi III and IV. Another unusual character belonging to the new species is the presence of a second antiaxial accessory seta, ventral to seta v2' on tarsus I, whilst the same seta on tarsus IV is absent. Absence of this seta on tarsi I and IV is a typical character shared by most of the species of Epidamaeus and Kunstidamaeus within the Damaeus (sensu lato) complex, and, if occasionally present, they are developed always on both legs. On the other hand, the weak development of the spinae adnatae is not sur-prising -the tendency of minimization and weakening of spinae adnatae seems to be quite common within the Damaeidae from northern Arctic areas, as demonstrated by Behan-Pelletier and Norton (1983). This unique combination of characters, combined with the very characteristic shape of the cerotegument, sensillus and presence of only 5 genital setae clearly differentiates this species from all other known species. Based on the presence of short sensillus (appearing distally slightly dilated), shape and size of the notogastral setae and presence of granular cerotegument, the new species shows similarities to the species-group "tenuipes", but given the specific characters described above, it should be considered as self-standing within the Kunstidamaeus.

Epidamaeus sp.
(aff. floccosus Behan-Pelletier and Norton, 1985) ( Fig.4-7) This species of Epidamaeus resembles the species Epidamaeus floccosus Behan-Pelletier and Norton, 1985 (see discussion below), but bears also some differing characters, namely a conspicuous transverse ridge behind the prodorsal tubercles Ba; elongated anterior parastigmatic apophyse Sa; spinae adnatae with lateral dents; and smooth, long notogastral setae inserted on cuticular thickenings. These characters would allow to establish a new species within Epidamaeus. However, taking into account that we had only a single, even slightly damaged, individual available, it was impossible to decide on stability and variability of the characters. Therefore, the potential decision on the specific status is left for later until broader material is available.
Description of the adult. Integument -Body covered by cotton-like filamentous cerotegument in the sejugal area and laterally around leg insertions. Cuticle of prodorsum smooth, with notogaster finely granulated. Ventrally, with net-like pattern on the mentum, epimeres I-II and genital plates. Cuticle of all femora and trochanters II-IV with a distinct 'netlike' pattern.
Prodorsum (Figs. 4A, 5A-B, D-E, 6A-E) -Regularly triangular in shape, with lateral part above insertions of legs II rounded and without an apophysis P. Proximal part of trochanters I and II covered by the tectum, projecting laterad and lateroposteriad from the lateral part of prodorsum (Fig. 5D). Parastigmatic apophyses very different in shape; anterior apophyse Sa prolonged, narrow, pointed, perpendicular to the body axis, about four times longer than Sp, which is short, triangular, blunt and pointing anteriad (Fig. 5E). Anterior postbothridial tubercles (Ba) present, distinct but relatively small and opposed posteriorly by a broad, transverse, transparent ridge. Rostrum broadly rounded, with an indistinct, broad central lobe. Short, indistinct oblique ridges present latero-anteriorly to insertion points of lamellar setae. Similarly, short ridges present laterally, behind insertions of leg I, projecting anteriad from bothridial area. Both structures combined together slightly resemble lamellar ridges present in other oribatids. Prodorsal setae fine and relatively long; rostral and lamellar setae unilaterally with small, hardly visible spines; other prodorsal setae smooth. Lamellar setae (75 µm) slightly longer than rostral (58 µm). Exobothridial setae strongly curved, fine, and slightly shorter than ro (50 µm) (Figs. 6C-E). Interlamellar setae clearly the most robust on the prodorsum, nevertheless, both broken and missing distal part. Remaining basal part around 37 -40 long, overall length is difficult to judge, but it is assumed they may reach about 60-80 µm (Fig. 6B). Bothridium typical of the Damaeidae, funnel-like, with a transparent, round and expanded rim. Sensillus smooth, elongate, setiform, attenuated distally, without a flagellate tip; about 140 µm long (Fig. 6A).
Notogaster (Figs. 4A, 5G, 6F-H) -Circular, with strong, medium long spinae adnatae, both distally with strong, lateral teeth (Fig. 5G). Notogastral setae fine, smooth and relatively long (c1 and c2 about 75 µm), some, however, with broken distal parts, with lm, lp (one side only) broken in part, or completely (Figs. 4A, 6F-G). All notogastral setae inserted on cuticular thickenings, forming small tu-bercles or short ridges, and more pronounced on posterior part of notogaster. Proximal part of setae, near insertion points, slightly narrower and more transparent than remainder of setae. Setae of ps series finer and shorter than remainder, ps2 about 50 µm with ps3 about 25 µm long (Fig. 6H). Lyrifissures normally developed; openings of notogastral glands well visible, with a small "cap" of a transparent secretion. A pair of pores present in posterior central part of notogaster, axial to insertions of setae lp.

Remarks -The individual stands very near
to Epidamaeus floccosus Behan-Pelletier and Norton, 1985, having very similar or identical development of tubercles and ridges in the sejugal area; parastigmatic apophyses or ventral tubercles are generally of very similar appearance as well. Still, there are also several characters which clearly differ. The british individual is larger; sensillus is shorter, without flagellate end and not covered distally by cerotegument as in E. floccosus. Notogastral setae (particularly l and h series) are inserted on tubercles or short ridges; anterior notogastral setae are finer and longer and, conversely, setae ps1-ps3 are much shorter than in E. floccosus. Ventral setae of our individual are shorter and most of the epimeral setae are inserted on tubercles. Legs differ slightly, also, in having finer and generally shorter setae, and all genual solenidia are longer than the coupled setae d (whilst in E. floccosus, coupled setae are longer than solenidia). Presence of teeth on spinae adnatae on our individual may be an easily observable difference, but it is difficult to judge if this character is stable. Similarly developed spinae adnatae have been observed on some individuals of E. aborigensis Behan-Pelletier and Norton, 1985, together with individuals where they had developed normally, without teeth or protuberances. As stated above, if the differences found will be proved stable by study of broader material, they justify in our view a status of new species to be proposed. As our attempts to find more individuals were not successful, we brought detailed description here to allow for comparison, and hopefully also for finding of more individuals by other authors, who may have collected the species without attempting detailed determination. Authors will be greatly appreciating if such a material, if exists, was provided them for further study.