Two new species of Pachylaelaps Berlese, 1888 from the Iberian Peninsula, with a key to European species (Acari, Gamasida, Pachylaelapidae)

Abstract Pachylaelaps (Pachylaelaps) pyrenaicus sp. n. and Pachylaelaps (Longipachylaelaps) brevipilis sp. n. (Acari, Pachylaelapidae) are described and illustrated based on specimens from litter and soil detritus of forest habitats in Spain (Pyrenees Mts) and Portugal (Serra da Labruja Mts), respectively. An identification key to European species of the genus Pachylaelaps Berlese, 1888 is provided.


Introduction
Pachylaelapid mites (Acari, Mesostigmata, Gamasida, Eviphidoidea) represent a cosmopolitan group of free-living mites with extraordinarily wide ecological and behavioural diversity (including more than 230 known species and 16 genera worldwide). They constitute an important component of the fauna in all soil microhabitats of the temperate zone of the northern hemisphere. They colonise various soil substrates, especially leaf litter and decomposing organic detritus (Mašán and Halliday 2014).
When compared with other taxa of edaphic mesostigmatic mites, Pachylaelaps are relatively little-known in Europe. The almost identical appearance of individual species, which causes difficulties in species identification, may also explain the small number of papers exclusively devoted to the European species of the genus Pachylaelaps (Evans and Hyatt 1956, Hirschmann and Krauss 1965, Koroleva 1977b, 1978, Moraza and Peña 2005. The most recent review and general summary of Pachylaelaps species was by Mašán and Halliday (2014), with a checklist of world species.
The main aim of this paper is to describe two new soil-inhabiting species of the little known genus Pachylaelaps, compare them with other morphologically similar congeneric species, and provide an updated identification key to the European species of this genus.

Materials and methods
Collected mites were extracted from the litter and soil detritus by means of a modified Berlese-Tullgren funnel equipped with a 40 Watt bulb, and preserved in ethyl alcohol. Before identification, the mites were mounted onto perma nent microscope slides, using Swan's chloral hydrate mounting medium. Illustrations were made by H. H. Özbek using a normal optical microscope equipped with a drawing tube. A Leica DM 1000 light microscope equipped with a stage-calibrated ocular micrometer and a Leica EC3 digital camera was used by P. Mašán to obtain measurements and photos. Measurements were made from slide-mounted specimens. Some multiple images were combined using the CombineZP software program (Hadley 2010). Lengths of shields and legs were measured along their midlines, and widths at their widest point (if not otherwise specified in the description). Dorsal setae were measured from the bases of their insertions to their tips. Measurements are mostly presented as ranges (minimum to maximum). The terminology of dorsal and ventral chaetotaxy follows Lindquist Figures 1-2. Pachylaelaps (Pachylaelaps) pyrenaicus, female, with setal notation of some idiosomal setae and glandular poroids. 1 Dorsal idiosoma 2 Ventral idiosoma. reaching dorsal surface close to setae z1. Dorsal setae long (the longest setae more than 100 μm in length), and seta j5 with tip reaching base of following seta z5. Cheliceral digits unidentate. Male palptibia with two well developed petal-like projections. In female, ventrodistal femur with small spine-like process associated with a seta. Terminal part of male tarsus II with only one spur-like distal seta (pl1). Sperm induction system with tubular components: tubes irregularly formed, folded, curved or with small bumps on distal sections, progressively widened basally; basal part widely abutting to anterior margin of coxa IV.
Sperm induction structures (Figures 3,(13)(14)(15)(16). Tubes of sperm induction system relatively well developed, well sclerotized, broadened basally, and narrowed distally; worm-like distal section irregularly formed, folded, curved or with small bumps; basal section widely abutting to anterior margin of coxa IV. Gnathosomal structures 19). Corniculi elongated and horn-like; laciniae densely pilose, slightly longer than corniculi; deutosternum slightly widened medially, with six rows of denticles; subcapitular setae smooth and needle-shaped ( Figure  4). Epistome with wide subtriangular base, elongate and narrow central neck and thin apical part crenelated on anterior margin; lateral margins of basal part with delicate denticulation; apical section not expanded or only very slightly expanded anteriorly, terminally truncate and with a row of four to seven prongs ( Figure 5). Cheliceral digits relatively elongate and slender (Figures 6, 19), 100-110 μm long; fixed digit of chelicera with terminal hook, small and obtuse subapical denticle, and one larger and flattened distal tooth associated with pilus dentilis; movable digit armed with relatively thin terminal hook and one subdistal tooth.
Legs. Leg setation normal for genus (Mašán 2007). Femur II with a small spinelike process on ventral distal surface, process associated with a seta. Tarsus II with two spur-like distal setae pl1 and pl2 (Figure 7). male. Idiosoma (Figure 8). Dorsal shield 810 μm long and 492 μm wide, suboval (length/width 1.65). Sternal, genitiventral, peritrematal, metapodal, and anal plates are fused together to form an entire holoventral shield bearing nine pairs of setae (excluding three circum-anal setae); the shield irregularly reticulate on surface. Dorsolateral and ventral soft integument with eight pairs of setae (see diagnosis). Dorsal and ventral chaetotaxy and other characters as in female.
Gnathosomal structures (Figures 9,10,17,18). Cheliceral spermatodactyl elongated, ensiform, 162 μm long (about 1.5 times as long as movable digit of chelicera), slightly widened in basal section, pro gressively tapering toward tip and slightly undulate medially; sperm ductus well defined ( Figure 9). Palptibiae normal, not thickened (when compared with other palp segments), each bearing a pair of well-developed petal-like projections on proximal ventral surface (see Figures 17 and 18); outer petal markedly larger than inner one, and longer than cross-sectional radius of palptibia.
Legs. Medial segments of legs II spurred on their distal ventral surface: femur with one robust spur, genu and tibia each with a small knob-like spur, as in Figure 11. Femoral spur broadened basally, produced into obtuse and rounded apex; associated axillar seta pv1 inserted in a small tubercle ( Figure 11). Terminal part of tarsus II with only one spur-like distal seta pl1; seta pl2 needle-shaped ( Figure 12).
Etymology. The epithet of this species is derived from the Latin name "Pyrenaei Montes" and alludes to the type locality situated in the Pyrenees Mountains.
Taxonomic notes. The new species may be distinguished from all other congeners especially by the following combination of characters: (1) in female, tubiform spermathecal structures irregular, with worm-like distal sections having some bends, folds and small bumps, and expanded base widely abutting the anterior margin of coxa IV; (2) female chelicera with flat to truncate subdistal tooth on fixed digit; (3) epistome with narrow central projection bearing a row of four to six denticles; (4) male palptibia with two well developed petal-like projections; (5) terminal part of male tarsus II with only one spur-like distal seta, pl1 (6) cheliceral spermatodactyl simple, ensiform, slightly undulate medially, without irregular convexities or projections on its margin. Mašán (2007) divided the European members of the subgenus Pachylaelaps into five clusters of species: (1) the bellicosus group (P. bellicosus and P. multidentatus), with separate position of slit-like poroid structures gdZ1 and gdS4 on dorsal shield, multidentate cheliceral digits, spermathecal tubiform structures simple, transparent (weakly sclerotized) and relatively longer, and males apparently absent; (2) the denticulatus group (P. denticulatus only), possessing separate position of slit-like poroid structures gdZ1 and gdS4, three projections on male palptibia, one spur-like distal seta on tarsus II in male, and bidentate cheliceral digits; (3) the ensifer group (P. armimagnus, P. carpathimagnus, P. ensifer, P. troglophilus and P. sacculimagnus), characterized by the adjacent position of slit-like poroid structures gdZ1 and gdS4, robust size of idiosoma, spermathecal tubiform structures (if detectable) elongated and weakly sclerotized, and presence of 2-4 palptibial projections in male and two spur-like distal setae on tarsus II in both adults; (4) the imitans group (P. imitans, P. insularis, P. resinae and P. terreus), with adjacent slit-like poroid structures gdZ1 and gdS4 having their openings in a common infundibulum, spermathecal tubiform structures short, conical to cylindrical and strongly sclerotized, two palptibial projections in male, and small lobe-like convexity on ventral margin of cheliceral spermatodactyl; (5) the pectinifer group (P. littoralis and P. pectinifer), characterized by the adjacent position of slit-like poroid structures gdZ1 and gdS4, Y-shaped spermathecal tubiform structures, absence of palptibial projections in male, and presence of two spur-like distal setae on tarsus II in both adults.
In this classification scheme, Pachylaelaps (Pachylaelaps) pyrenaicus should be considered as a species with a separate position among the all above mentioned species groups because it possesses a unique combination of main diagnostic characters. Some morphological characters of P. (P.) pyrenaicus are not consistent with those found typically in the individual species groups. The adjacent position of slit-like poroid structures gdZ1 and gdS4 on dorsal shield and unidentate cheliceral digits in the new species are in contradiction with the definition of the bellicosus and denticulatus groups. The male palptibia has two petal-like projections in P. (P.) pyrenaicus, where the pectinifer group species does not have these structures developed. In the robust species of the ensifer group, tarsus II has two spur-like distal setae in adults, but this character is found in the smaller new species only in females. In addition, in P. (P.) pyrenaicus, the tubular structures of sperm induction system have a distinctive form which is not known in the other species of the genus, but is especially different from the members of the imitans group that are characterized by short, conical to cylindrical, and strongly sclerotized spermathecal tubes.
Diagnosis. Soft integument with decreased number of 13 pairs of setae in female and ten setal pairs in male. Dorsal setae J5 well developed, slightly longer than setae J4. Prestigmatic section of peritreme long, with anterior tip reaching dorsal surface close to setae z1. Dorsal setae relatively short (longest setae not exceeding 35 μm in length), with their tips not reaching bases of following setae. Cheliceral digits unidentate; pilus dentilis conspicuously enlarged (in female) or vestigial (in male). Male palptibia with two petal-like projections, shorter than cross-sectional radius of palptibia. Terminal part of male tarsus II with only one spur-like distal seta (pl1). Sperm induction system with tubular components: tubes relatively shorter, with club-shaped apical section, straight or variously curved; basal part not markedly expanded, thin, associated with inner middle surface of coxa IV.
Legs. Medial segments of legs II spurred on their distal ventral surface: femur with one robust spur, genu and tibia each with a peg-like spur, as in Figure 41. Femoral spur broadened medially, produced into widely rounded apex, with a small subdistal tubercle ( Figure 41). Terminal part of tarsus II with only one spur-like distal seta, pl1 ( Figure 42).
Etymology. The specific name of the new species is derived from the Latin words "brevis" (short) and "pilum" (hair), and it alludes to the fact that the species has the shortest idiosomal setae among its congeners. Taxonomic notes. The main diagnostic character states for Pachylaelaps (Longipachylaelaps) brevipilis are the presence of shorter idiosomal setae (e.g., j5 < j5-z5, J1 ≈ ½ x J1-J2), the relative length of dorsal setae J4 and J5 (setae J5 negligibly longer than J4, about 1.04-1.14 times as long as J4), the existence of sexual dimorphism in the pilus dentilis (markedly enlarged and spiniform in female, minute and slender in male), the form of the tubular structures of the sperm induction system (tubes shorter, with clublike terminal part), the form and length of the cheliceral spermatodactyl (sword-like, less than twice as long as movable digit), and the length of the dorsal shield (small species, with dorsal shield 470-510 μm long in males, and 510-565 μm long in females).
The presence of relatively short dorsal setae (at least in a central row), along with subequal setae J4 and J5, is also the feature of three other Pachylaelaps (Longipachylaelaps) species, namely P. (L.) bifurciger, P. (L.) dubius and P. (L.) silviae.
The new species may be reliably distinguished from the above mentioned congeners by the characters presented in Table 1, and with the help of the identification key provided below.

Key to European species of the genus Pachylaelaps (females)
Partial keys to the European species of Pachylaelaps may be found in Hirschmann and Krauss (1965), Karg (1971Karg ( , 1993, Koroleva (1977a), and Mašán (2007). The identification of Pachylaelaps species is complicated by the inaccurate and inadequate descriptions of some species. Mašán (2007) and Mašán and Halliday (2014) attempted to clarify the concept of the genus by removing many species that obviously belong in other genera such as Onchodellus Berlese, 1904 andPachydellus Mašán, 2007. Due to vague and inadequate original descriptions, the particular structures of the sperm induction system, palptibial outgrowths and some other important characters remain unknown in a large number of species. Therefore several species are not included in the keys presented in this paper, namely Pachylaelaps    Openings of slit-like poroids gdZ1 and gdS4 closely adjacent; projection on genu II small, subconical, with thin and rounded apex; cheliceral sperma-