A new species of the genus Opilioacarus With, 1902 (Acari: Opilioacarida) for the Iberian Peninsula

This paper certifies the presence of the family Opilioacaridae in the Iberian Peninsula. It is represented by a new species of the Order Opilioacarida, Opilioacarus baeticus, from three localities, plus a photographic record, from southern and southeastern Spain. O. baeticus is described based on adult of both sexes and female tritonymphal instar. A key to genera of the family Opilioacaridae and species of the genus Opilioacarus is given.


Introduction
The Order Opilioacarida comprises one family of longlegged mites, brownish gray and with distinctive blue or purple pigment patterns on the boy and legs. These mites possess ancestral attributes such a segmented opisthosoma, some species have three pairs of lateral eyes and tarsi IIV divided. They are large mites (1.5 to 2.5 mm in length) living in caves, under rocks and in litter, in semiarid environments, tropical forest and warm temperate regions of the world. Opilioacarid mites have been observed feeding on pollen, fungal spores and arthropods remains. In their ontogenetic development, include a prelarval instar able to move although it cannot feed (Walter and Harvey 2009).
The family Opilioacaridae currently includes 53 valid taxa (with two subspecies and three fossil species) distributed in 13 genera (Araújo et al. 2020). Although the family has been recorded around the World (Harvey 1996), the genus Opilioacarus With, 1902 is the only member in the Mediterranean region.
Opilioacarus segmentatus With, 1902 was the first Opilioacarid mite described. This species, together with two new species of the new genus Eucarus, currently O. italicus (With, 1904) and Adenacarus arabicus (With, 1904), was the base to create the suborder Notostigmata by With (1904). Opiloacarids were the great unknown group of mites until the works of Grandjean (1936), Redikorzev (1937), and Chamberlin and Mulaik (1942). In the 1960s these mites began to be taken into consideration (Naudo 1963; Brignoli 1967; Hammen 1968, 1969, 1977; Coineau and Hammen 1979; Leclerc 1989, and since the beginning of the current century, the works are numerous both describing new taxa (JuvaraBals and Baltac 1977; Vázquez and Klompen 2002, 2010, 2015; Bernardi et al. 2012, 2014; Vázquez et al. 2014, 2016; Klompen and Vázquez 2015; Araújo et al. 2018a and providing information on postembryonic development . However, information on the geographic distribution, biology and ecology of the group is scarce (Leclerc 1989; Harvey 1996; Walter and Proctor 1998. At present, the genus Opilioacarus includes two fossil species -O. aenigmus Dunlop et al. 2004 from the Baltic amber (Eocene) and O. groehni Dunlop & Bernardi, 2014 from the Cretaceous Burmese amber -, and three living species: O. segmentatus from Algeria, O. italicus from Sicily and O. brignolii Araújo & di Palma, 2018 from southern Italian peninsula and Sardinia (previously cited as O. italicus by Brignoli in 1967), although its authors do not ruled out that O. brignolii could be a junior synonym of O. italicus.
Opilioacarus italicus was firstly described based on a nymphal instar and Brignoli (1967) redescribed what he considered that species from Sardinia and Apulia, confirming its proximity to O. segmentatus. The later species, redescribed by Grandjean (1936) including information on different types of setae on the palp tarsus, was reported from Uzbekistan (Krivolutsky 1965) and Greece (Thaler and Knoflach 2002), although taking into account biogeographical considerations the ascription to O. segmentatus seems doubtful. On the other hand, Araújo et al. (2018b) ensure the type species of O. italicus is lost, consider it a nomen dubium because its description can be applied to almost all Opilioacaridae, making a proper identification impossible, and describe O. brignolii based on the material recorded by Brignoli (1967), assuming that it could be conspecific, thus a junior synonym of O. italicus.
Opilioacarus italicus and O. segmentatus have been separated by their different idiosomal ornamentation, abdominal shape, and leg proportions, and without a doubt their geographical distribution should be also considered important for the separation of both species.

Materials and methods
Specimens of this new species were directly collected by hand using a brush or collected using pitfall traps. Mites were preserved in 70% ethanol and later mounted using Hoyer's medium on microscope slides after digestion with Nesbitt's fluid and sealed with GLPT insulating varnish. Morphological observations, measurements, and illustrations were made using compound microscopes equipped with differential interference contrast and phase contrast optical systems, drawing tubes, and stagecalibrated eyepiece micrometers.
Measurements of structures are given in micrometers (µm), indicating the ranges among specimens measured. Idiosoma and prodorsal shield lengths are along midline, from anterior margin of vertex to caudal margin. Leg lengths are from base of the trochanter to apex of the tarsus, excluding the pretarsus. Distinction of porelike structures on the idiosomal integu ment are either poroids (lyrifissures) or glandular openings (solenostomes), as distinguished morphologically are depicted in circular form, poroids in elliptical or slit form.
Specimens of the new species are deposited in the Museum of Zoology, University of Navarra (MZUNAV), Pamplona (Spain), in the Arachnological Collection of the Department of Zoology and Animal Cell Biology (ZUPV), University of the Basque Country, Leioa (Spain), and in the Acari Collection of Experimental Station of Arid Zones (EEZACSIC), Almería (Spain).

Diagnosis of the genus Opilioacarus
The following combination of characters implements the diagnosis given by Araújo et al. (2018b): Prodorsum with two pairs of lateral eyes; opisthosomal setae restricted to the preanal segment with three to six dorsal setae and one or two pairs of lateroventral setae; abdominal segment with numerous lyrifissures and glands openings arranged in transverse rows; four pairs of stigmata. Leg I is less than three times the length of the idiosoma; telotarsus I with crownlike eupathidion (ζ1) close to a posterodosal group of six sensilla; shortest leg II lacks prefemur and bears a bifid dorsal acrotarsal solenidia. With's organ is membranous and discoid; gnathosomal dorsal solenidia pl4 short and blunt at the base of rutellum. Tritosternum with two setae on each sternapophysis. Adults palptarsus with four or five foliate setae d1 and one pectinate seta d2. Cheliceral movable digit with one tooth.

Diagnosis of Opilioacarus baeticus new species
Zoobank: 143C7A68-2830-4D27-BF59-A4882A12AA2C Palp tarsus with five foliate setae d1, each with three lobes, and pectinate seta d2; sternal verrucae with st1 and four or five (females) or three or four (males) tapering ribbed setae; area between sternal and genital verrucae with two pairs of long, stout and ribbed, tapering setae (st2-st3) similar to st1 and st5 and three to six pairs of stout and ribbed setae in both sexes; pregenital verrucae with st5 and five to seven stout and ribbed setae in both sexes; female lacks pregenital setae, and with five eugenital short, tapering and ribbed setae; males with five tapering, short and smooth pregenital setae in a trapezoidal area and five genital setae in a lobulated area. Anal valves with 12-13 stout and ribbed setae each. Cheliceral movable digit of adults with one ventral fimbriate process; female palptarsus with 23 ch setae, male with 16-18 ch setae, both sexes with 14 sm setae. Preanal segment with five dorsal and one pair of lateroventral stout and ribbed setae. Legs IV longer than body length; basitarsus I with a basal dorsal seta short, thick and barbed; tibia II-IV coronida present; genu II-IV with a dorsodistal sensorial seta enlarged and barbed, femur II-IV with a dorsal longitudinal row of blunt setae s, and femur II-IV with dorsal longitudinal rows of short blunt setae.
Idiosoma dorsum -Prodorsum. Prodorsal shield covered with round tubercles, pigmented around eyes and in the medial central region, with a dark blue frame, and posterior convex pigmented band ( Figure 1B); shield with two pairs of eyes; stout, ribbed setae 16-23 µm long, and one pair of lyrifissures antiaxial to anterior eyes; shield with rounded or slightly acuminate anteriorly margin and a convex row of nine setae at the posterior region ( Figure 1C); male 500-597 µm long, 508-778 µm wide at eyes level; female 583-694 µm long, 805-1000 µm wide.
Opisthonotum dark blueviolet with a sharp distinction between colored tergites and pale interarticulated membranes ( Figures 1A, 11D); integument coniculate; nymphs may have a bright blue color ( Figure 11C). The first twothree abdominal segments marked by distinct grooves and indistinct muscular spots, other segments only marked by distinct spots and an arrangement of lyrifissures and glands ( Figure 1A). Except for preanal segment with a row of five dorsal setae and one pair of ventrolateral setae in both sexes ( Figure 4F, G), other idiosomal segments lack setae, but with numerous lyrifissures and glands openings arranged in transverse rows. Four pairs of stigmata.
Preanal region. Preanal XVI segment without dorsal and ventral setae; preanal segment XVII with five dorsal setae ( Figure 4F) and one pair of ventral setae.
Anal valves each with stout ribbed setae ( Figure 4G), 12-13 in female and male, six or seven lyrifissures and one to six gland openings.
Legs -Legs with blueviolet stripes and different types of setae, apart from special sensilla on tarsus I ( Figure 5B, C: palmate, stout ribbed setae with barbed margin, fanshaped setae, occasionally with a tiny terminal tip ("papillate" type "p" setae of different length) ( Figure 6G); tapering, smooth setae "s"; tapering and barbed setae, and smooth acute setae.
Legs I. Leg I longer than the body and longer than legs II, III and IV; leg I twice as long than the shortest leg III. Telotarsus I ( Figure 5AC) 336 µm long, with proximal cuticle ornate (approximately first two whorls of setae), other setae on smooth cuticle. Pretarsus with two welldeveloped sessile claws; Haller's organ with two sensilla in a cavity ( Figure 5C) and distal posterodorsal cluster of seven sensilla ( Figure 5B): sensillum ζ1 with crownlike tip inserted close to group of sensilla; ω1 and ω2 rodlike with blunt tip, ω3 and ω4 rodlike with filiform tip, ω5 conical, and ω6 spiked mazelike; three anterodorsal sensilla ω with filiform tips at the same level than ζ1; other long telotarsal setae with blunt tips.
Basitarsus I ( Figure 5D) slightly longer than telotarsus, 358 µm long; three basal whorls with dorsal and lateral setae serrate, smooth ventral setae, and at least three short blunt solenidia; one barbed dorsal setae shorter and thin than other dorsal setae. Three distal whorls with smooth, blunt tips setae; soft articular tegument between telo and basitarsus with two ventral lyrifissures.
Trochanter ( Figure 6F) 454 µm long; distal region with a whorl of 10 stout, ribbed setae and proximal region with 2 setae r; except for 7 setae r type, other setae on the segment are palmate, p setae ( Figure 6G).

Material examined
This species has been found in three localities, plus a photographic record, from southern and southeaster Spain

Etymology
The specific epithet refers to the geographical name of the Betic mountain ranges of the Andalusian System where the specimens were found.

Geographical distribution
Opilioacarus segmentatus was previously reported from several localities in Algeria (With 1902; Grandjean 1936 and from several Greek Islands: Korfu (Silvestri 1905) in the Adriatic sea and Crete (Thaler and Knoflach 2002) and Kassos, Karpathos and Rhodes (Beron 1990) along the southern limits of the Aegean sea. There are also two records from Peloponese, Leonidion by Ludicke and Madel (1937) and Areopoli by Thaler and Knoflach (2002). The new Iberian species expand 800 km the distribution area of Opilioacarus westward. This suggests that the distribution could include the northern part of Morocco (the Rif) also because of the emerged connection between the African Rifean region and the Iberian Betic region, the Gibraltar arc, that closed the Mediterranean sea and drove the Mesinian salinity crisis, about 6 Mya. This event favoured biotic exchange between Africa and Iberia to several mammals (Agustí et al. 2006) and invertebrates adapted to arid land, as scorpions of the genus Buthus (Gantenbein 2004), and could favoured the colonisation of the Betic region by the genus Opilioacarus. But, in respect with Greek records, intermediate land masses as Sicily and the Italian Peninsula were occupied by other species (O. italicus and O. brignolii) and a biogeographical connection between the Aegean region and Algeria is not known, thus suggesting that greek records of O. segmentatus belong to a distinct species.

Taxonomic considerations
According to the original description of O. segmentatus, to its short redescription given by Grandjean in 1936 (who did not examined the types), and to data given by Araújo et al. (2018), several inconsistencies or lack of information are detected regarding the number of setae ch on palptarsus and pregenital setae.
The number of palpal setae d1 is five, character not mentioned by With (1902With ( , 1904. The number of setae ch in palptarsus varies from the 16 setae illustrated by Grandjean in 1936 (see fig. 5A) to "17+" in males mentioned by Araújo et al. (2018).
The number of setae on pregenital capsules varies from three (Araújo et al., 2018) to five to eight indicated by With (see Plate V, figure 10) and Grandjean. With (1904) illustrated a male specimen (see Plate IV, figure 3) since pregenital setae can be observed between the capsules. Only Araújo et al. (2018) indicate the presence of nine or 10 setae in anal valves. However, the authors mentioned above did not indicate the instar and sex of the specimen when giving this quantitative information.
When studying a female tritonymphal instar of the Iberian O. baeticus specimens, its characters direct us to identify it as O. brignolii (palps with four setae d1, 15 setae ch, and three setae on pregenital capsule (st5+2). However, adult of both sexes clearly differ from O. brignolii and characters of mature instars (both sexes) lead us to think about their belonging to a species close to O. segmentatus. We did not ask for the types of O. segmentatus because, as mentioned by Araújo et al. (2018), the syntypes deposited at ZMUC and MNHN did not allow them to make a proper redescription of O. segmentatus. Despite the similarities found in the descriptions of O. segmentatus given by With (1902With ( , 1904 and Grandjean (1936) with O. baeticus n. sp. we assign these specimens to a new species and take the opportunity to make a description of the species that implement and provides new data from previous descriptions of the species of this genus. The great similarities may suggest that this new species could be a junior synonym of With's species.
Differences between O. baeticus n. sp., O. segmentatus and O. brignolii are indicated in the following tentative key to genera. This key does not include O. italicus because its description is incomplete disallowing a proper evaluation of characters.
Key to the world genera of the Opilioacaridae

Remarks
According to the dimensions given for adults specimens, O. segmentatus appears to be a species larger than O. brignolii (twice its length) and slightly smaller than O. baeticus n. sp.; O. italicus, known only by a tritonymph of 1.25 mm, thus larger than most adults specimens of O. brignolii.
Ours sincere thanks to Jose Carrillo and Eduardo Mateos for providing the photographic material of this species, and to Jordi Moya and Eva de Mas for providing specimens from Almería and their suggestions and revision of the manuscript.