Opilioacarus thaleri, Vázquez & Herrera & Just & Lerma & Chatzaki & Heller & Král, 2021

Vázquez, Maria Magdalena, Herrera, Ivalú Macarena Ávila, Just, Pavel, Lerma, Azucena Claudia Reyes, Chatzaki, Maria, Heller, Tim Lukas & Král, Jiří, 2021, A new opilioacarid species (Parasitiformes: Opilioacarida) from Crete (Greece) with notes on its karyotype, Acarologia 61 (3), pp. 548-563 : 552-560

Opilioacarus thaleri n. sp. Vázquez, Ávila and Just

Zoobank: 9E2813B3-3B51-424B-A57C-85DD2F0C95C4

Figures 3–10

Material examined — Specimens examined were collected manually by J. Král, 1.– 8. V. 2019 in Greece, western Crete, Georgioupolis, hill to the west of the town, 35.372193°

N, 24.256336° E. To evaluate characters, the slides were prepared from holotype female, 3 paratype females, and 4 paratype males. Specimens dissected for chromosomes were preserved in 96% ethanol. Some of them (6 females, 4 males) were also slide-mounted. These specimens are also designated as paratypes. The type material is deposited in the collection of JK (Department of Genetics and Microbiology, Charles University, Prague, Czech Republic).

Etymology — This species is dedicated to Konrad Thaler and his wife Barbara ThalerKnoflach, outstanding Austrian arachnologists, who collected and reported opilioacarids from several places in Greece ( Thaler and Knoflach 2002).

Diagnosis — Palp genu with ~6 p – type setae, palp femur with 13 p – type setae. Palp tarsus with foliate setae d1 with 3 rounded ending acute lobes each and 1 thin pectinate seta d2. Males and females differ by number of setae d1. While males exhibit 6 setae d1, females shows only

5 d1 setae. Pregenital region in males with 3 short and thick, ribbed and blunt pregenital setae. Pregenital region in females without pregenital setae. It has 6 eugenital setae. Genital region in males with 11 thin and lightly serrated and tapering setae. Ovipositor of the simple type, folded with 2 pairs of glands and two pairs of ducts on the basis. Internal basal structure of the ovispositor smooth, without any spikes, bifurcated on the top.

Description

Measurements

Measurements are summarized in Table 1.

Gnathosoma

Chelicera ( Figure 4A ). Basal segment with 1 seta, fixed digit with 3 setae. All setae are lightly barbed. Dorsal and antiaxial lyrifissures well developed. Fixed digit with one tooth, movable digit with 1–3 teeth and a well developed terminal hook. Movable digit with large denticle and two very small denticles. Without sexual dimorphism.

Subcapitulum ( Figure 4B ). All four pairs of paralabial setae are present: pl1 small, conical; With´s organ (pl2) membranous, hyaline, discoid and barbulated. Rutella pl3 () with 1 row of 5 teeth, inserted dorsolaterally; pl4 small but distintct, inserted dorsally on subcapitulum.

In addition, 4 circumbuccal cb () and 5–7 medium and subcapitular, latero-ventral (ventral medium in part), latero-ventral medium, latero-dorsal medium, ventral posterior, and lateroventral posterior setae. Females with 5 subcapitular setae, males with 7 subcapitular setae. Lateral lips with distinct channels.

Palp ( Figures 5–7 , Tables 2, 3). Trochanter with 4 ribbed, tapering setae (= r – type) in females ( Figure 5A ), males with 5 r – type setae ( Figure 6A ); femur with 7 papilliform setae (=

p – type) in females ( Figure 5B ), males with 13 p – type setae ( Figure 6B ); genu with 4 p – type setae and 19 r – type setae in females ( Figure 5C ), males with 6 p – type setae and 29 r – type setae ( Figure 6C ); tibia with 17 long lightly serrate and pointed setae s (= – type) and 20 r – type setae and two thin smoth sensilla ss () in females ( Figure 5D ), males with 26 s – type setae and

36 r – type setae and 2 ss ( Figure 6D ). Tibia and tarsus partially fussed. Tarsus with 6 foliate

(d1 – type) and 1 pectinate (d2 – type) setae in males ( Figure 7A–B ). Females with 5 foliate d1

setae and 1 pectinate d2 ( Figure 7C–D ). Females with 6 v1, 3 v2, 3 ss, 14 ch, 5 sm1, 3 sm2.

Males with 8 v1, 3 v2, 3 ss, 12–14 ch, 6 sm1, 3 sm2 ( Table 3). Lyrifisures iα and iπ present

( Figure 7A–B ). Pretarsus with a pair of well-developed, smoth, sessile claws ( Figure 7 ).

Idiosoma

Color. Light blue and violet body; combination of blue-purple and white stripes on the legs.

Sternogenital region ( Figures 8–9 , Table 4). Sternal verrucae in adults each with 3–4 large serrate and pointed and 1 composite st (1) setae. Remaining sternal region with 4–5 pairs of stout, ribbed, setae with blunt-tips, and 2 pairs of composite st (1) setae in both females and males. Pregenital capsules each with 1 long tapering seta st5 () and 4–5 stout, ribbed,

blunt-tipped setae ( Table 4).

Pregenital area in males with 3 short ribbed blunt-tips pregenital setae ( Figure 8A ).

setae follows Grandjean (1936) and Vázquez and Klompen (2002).

Pregenital area in females without pregenital setae ( Figure 8B , Table 4). It has 6 thin lightly serrated eugenital setae ( Figure 9A , Table 4). Genital region in males with 11 thin lightly serrated genital setae ( Figure 8A ). Ovipositor folded, with two pairs of gland-like structures and a pair of ducts. Internal basal structure smooth, without any spikes, bifurcated on the top

( Figure 9B ).

Dorsum. Prodorsal shield in adults with 60–70 stout ribbed setae and two pairs of lateral eyes. Dorsal idiosoma between the shield and the pre-anal segment without setae, but with numerous lyrifissures arranged in transverse rows. Pre-anal segment with 4–5 dorsal and two lateroventral short, stout and ribbed setae ( Figure 9C ). Anal plates with 12–13 papilliform setae. Dorsum without sexual dimorphism.

Taxonomic remarks

The material collected in Crete, Greece allowed us to describe a new species O. thaleri and to compare it with O. segmentatus , O. brignolii and O. baeticus . It should be underlined that the diversity of Opilioacarus could be higher than recognized. Specimens from other Greek localities [Peloponnese ( Thaler and Knoflach 2002), island of Korfu ( Silvestri 1905), islands of Kasos, Karpathos and Rhodes ( Beron 1990)] were not revised yet. Moreover, data on Opilioacarus indicate that this genus occurs throughout all the coast of Mediterranean Sea forming many species, which inhabit a narrow geographic region.

The number of the setae on the penultimate segment is one of the main characteristics of the genus Opilioacarus . There are 4–5 dorsal and two lateroventral stout ribbed setae in both female and male. This characteristic is constant in the genus. The genus Neocarus has only one dorsal and two lateroventral stout ribbed setae on the penultimate segment.

There is some variation in the number of setae on the palp among Opilioacarus species. Opilioacarus segmentatus and O. baeticus have 5 foliated d 1 type setae on the palp ( Grandjean 1936 ; Moraza et al. 2021) while O. brignolii has 4 foliated d 1 type setae ( Araújo et al. 2018b). Males of O. thaleri present 6 foliated d1 setae while females of this species have 5 foliated d1 (this study). The lowest number of ch – type setae was found in O. brignolii (11–14) ( Araújo et al. 2018b) and O. thaleri (12 in females and 14 in males) (this study). Opilioacarus segmentatus has 16 ch setae ( Grandjean 1936) while O. baeticus exhibits 23 ch setae in females and 16 ch setae in males ( Moraza et al. 2021).

In the genital area, the differences among Opilioacarus species are also significant. Pattern of eugenital setae in female pregenital area is often species-specific. Opilioacarus segmentatus and O. baeticus exhibits 5 eugenital setae ( Grandjean 1936 ; Moraza et al. 2021). Opilioacarus brignolii presents 4–9 smooth eugenital setae ( Araújo et al. 2018b) while O. thaleri shows

6 of these setae (this study). Pattern of setae in male pregenital and genital area is also species-specific. Males of O. brignolii have in trapezoidal area 2–7 acute ribbed genital setae ( Araújo et al. 2018b). Males of O. segmentatus have 5 short tapering and smooth pregenital setae ( Grandjean 1936). Males of O. baeticus have 5 pregenital and 5 genital setae ( Moraza et al. 2021) while males of O. thaleri have 3 short ribbed blunt pregenital setae and 11 slightly serrated acute genital setae (this study), which is a very significant difference. Finally, there are significant interspecific differences in morphology of the ovipositor. In O. thaleri the ovipositor has 2 pairs of glands and 1 pair of ducts on the basis of the ovipositor. These structures were found neither in O. brignolii ( Araújo et al. 2018b) or O. baeticus ( Moraza et al. 2021) .

Karyotype

In the present study, we reported for the first time chromosome data of opilioacarids. The female karyotype consists of 16 large monocentric chromosomes, predominantly with acrocentric morphology ( Figure 10 ). The karyotype of O. thaleri n. sp. corresponds to the karyotypes of parasitiform suborders Ixodida and Mesostigmatida in terms of diploid number and chromosome morphology. While chromosomes of these groups were studied intensely due to their medical and economical importance, there are no cytogenetic data on Holothyrida, the fourth parasitiform suborder. Like in O. thaleri , 1) ixodids and mesostigmatids exhibit a low number of monocentric chromosomes (the diploid set of ixodids ranges from 12 to 32 chromosomes and diploid set of mesostigmatids from 6 to 26 chromosomes), and 2) karyotypes of most ixodids and mesostigmatids are predominated by acrocentric chromosomes ( Oliver 1977, 1989 ; Norton et al. 1993). These features could be plesiomorphic for parasitiform mites.

Figures

Figure 3 Opilioacarus thalerin. sp., dorsal view on an adult specimen in ethanol.

Figure 4 Opilioacarus thalerin. sp., gnathosoma. A – chelicera, female. Fixed digit with 3 lightly barbed setae (a) and lyrifissure (b). Movable digit with one large tooth and 3 denticles (c). Basal segment with one seta (d); B – subcapitulum. Paralabial setae pl1, With´s organ pl2, rutellum pl3, circumbucal setae cb, and channels ch.

Figure 5 Opilioacarus thalerin. sp., female palp. A – trochanter; B – femur; C – genu; D – tibia. Axial (left) and antiaxial (right) view. E – particular types of setae.

Figure 6 Opilioacarus thalerin. sp., male palp. A – trochanter; B – femur; C – genu; D – tibia. Axial (left) and antiaxial (right) view. E – particular types of setae.

Figure 7 Opilioacarus thalerin. sp., palp tarsus, male (A–B) and female (C–D). Ventral (left) and dorsal view (right). E – particular types of setae.

Figure 8 Opilioacarus thalerin. sp., sternogenital area. A – male; B – female, C – particular types of setae. Pregenital region pg, genital region gen.

Figure 9 Opilioacarus thalerin. sp., female. A – eugenital setae; B – ovipositor; C – setae on penultimate segment.

Figure 10 Opilioacarus thalerin. sp. (2n = 16), female mitotic metaphase stained by Giemsa. Note predominance of acrocentric chromosomes. One large pair is probably metacentric (arowheads).