Onchodellus circularis Özbek 2023, sp. nov.
Creators: name: Özbek, Hasan Hüseyin
Publisher: name: Zenodo
Year: 2023
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Arachnida
Mesostigmata
Pachylaelapidae
Onchodellus
Onchodellus circularis

description: Onchodellus circularis sp. nov.
(Figures 5–6, 11, 14, 18, 22–23, 28, 33–35, 38–39, 43)
Diagnosis: Dorsal shield covered with distinct punctation; setae J5 distinctly shorter than J4; soft integument of idiosoma with nine pairs of setae; anterior tips of peritremes extending to dorsal side of shield; one pair of posterolateral teat-like gland pores gdS4 on shield. In male, cheliceral spermatodactyl leaf-like, its length half that of moveable digit; tarsus II with spur-like distal seta pl1 and larger, well-developed opposite mediolateral process.
Material examined: Holotype, female, Gümüşhane, Kürtün Town, Örümcek Forest, 40° 39′ N, 39° 01′ E, alt. 1455 m, 1 June 2009, litter under Picea sp. Paratypes: one male, same data as holotype; one female, Gümüşhane Province, Tahtamur Wold, 40° 44′ N, 39° 03′ E, alt. 1708 m, 24 November 2013, in moss.
Female
Dorsum (Figure 5). Dorsal shield well sclerotised, 530–560 long, 380–390 wide at widest point, length/width 1.35–1.47, oval, surface reticulate and punctate (Fig. 38), with 30 pairs of smooth and pointed setae, clunal setae J5 about 14 long, J4 60–65, the ratio J4 / J5 4.28–4.33; a pair of posterolateral teat-like gland pores gdS4 on shield, gdZ1 subcircular and paraxial to setae Z2. Dorsal setae j1 about 20–24; z1 about 14, j4, j5, j6, z5, s6, r5 30–40, S1 and S3 20–30 long, other dorsal setae lengths between 50 and 68 long.
Venter (Figure 6). Sternal shield 170–180 long, 110–115 wide at level of coxae II, its surface decorated with reticulate pattern, bearing four pairs of pointed setae and three pairs of pores; st1 55, slightly longer than st2 (50); st3 and st4 equal in length (35). Genitiventral shield wider than long, length/width about 0.91, decorated with polygonal pattern, with two pairs of setae (Fig. 39). Anal shield 70 long, 110–120 wide, length/width 0.58–0.59, triangular. Metapodal shields rounded. Lateral and opisthogastric soft integument with nine pairs of setae. Anterior tips of peritremes extend to dorsal side of idiosoma, between setae z1 and z2.
Spermathecal apparatus. Sperm access system associated with coxae III, tubes long, slender, and thin (Fig. 14).
Gnathosoma. Hypostome with seta h3 longest, h2 and palp coxal seta pc shortest and subequal in length; corniculi horn-like, deutosternal groove with six rows of denticles. Epistome with straight denticulate lateral margins and central projection with apical denticle (Fig. 11), and its surface decorated with lines and punctation (Fig. 43). Movable digit of chelicera 68 long, fixed digit about 70 long (to dorsal seta). Arthrodial brush short.
Legs. Chaetotaxy normal for the genus (Mašán, 2007). Tarsus II with a thicker spur-like seta pl1 (Fig. 18).
Male
Dorsum. Ornamentation and dorsal chaetotaxy as for female.
Venter. Holoventral shield ornamented with the reticulate pattern and bearing 5 pairs of needle-like setae and 3 pairs of pores, and a pair well sclerotised ear-like process near st1 (Fig. 22). Opisthogastric region of the shield with three pairs of setae, three circum-anal setae.
Gnathosoma. Epistome as for female. Moveable digit of chelicerae 60 long, with a large subdistal tooth and a large terminal hook, spermatodactyl very short, leaf-shaped, 30 long, and its length half that of moveable digit (Fig. 28). Fixed digit with a subdistal tooth, a subdistal denticle and a large terminal hook, pilus dentilis clearly visible. Palptibiae without any processes. Arthrodial brush short.
Legs. Tarsus II with a spur-like seta p11 and strong opposite mediolateral apophysal spur; apophysal spur large and longer than pl1 (Figs 23, 33). Trochanter II with prominent median process; femur II with large, finger-like, spur-like process; genu and tibia each with small ventral process (Figs 33, 35). Trochanter IV with distal process and adjacent, well-developed, strong, and thicker setae (Fig. 34).
Etymology. The name of this species refers to the circular metapodal shield on the ventral idiososma of females.
Taxonomic notes. Onchodellus circularis differs from most species of the genus by the presence of a specific leaf-like spermatodactyl and a well-developed mediolateral process on the tarsus II of the male, rounded metapodal shields, specifically shortened setae S1 and S3, and a smaller number of setae on the soft integument of the idiosoma of the female, but can be compared with species of the O. falcifer group and the O. islandicus group as defined by Mašán (2007). These species groups share the features of a spermatodactyl that is shorter than the length of moveable digit and has 2–3 distal branches or is broadened like a leaf. This new species can be compared with the O. islandicus group, but there are important main differences in male and female specimens, as the anterior ends of the peritreme in O. circularis reach the dorsal surface of the shield, whereas in the species of the O. islandicus group, the peritreme is distinctly shortened and the anterior ends do not reach the dorsal surface of the shield.
It is also compared with species of the O. falcifer group, especially with male specimens. The male of O. circularis is clearly distinguished from all others by the presence of a larger, well-developed mediolateral process on the tarsus II, which is not present in males of this group. In addition, it differs from O. falcifer (Hirschmann & Krauss, 1965) and O. canariensis (Moraza & Peña, 2005) in having a non-branching, leaf-shaped spermatodactyl (two branches in O. canariensis, three branches in O. falcifer) and differs from O. nidicolens (Koroleva, 1977) and O. brevicrinitus (Hirschmann & Krauss, 1965) by the specific shape of the spermatodactyl, only one process on the genu II and tibia II, and a distinct process on trochanter II. The female specimens are easily distinguished from the others in the genus because they have some specific character states, such as rounded metapodal shields, nine pairs of setae on the soft integument of the idiosoma, punctate surface of the dorsal shield. Ýt can be compared with O. calcaratus (Koroleva, 1977) in that setae J4 are longer than 50 and setae J5 are shorter than 16, but they differ in a different J4/J5 ratio (less than 5 in O. circularis, more than 5 in O. calcaratus), the shape of the metapodal shield (not rounded in O. calcaratus), the surface of the dorsal shield with distinct punctation, and diagnostic features in the males, such as the mediolateral process, which is shorter or the same length pl 1 in O. calcaratus, significantly larger and longer than pl 1 in O. circularis, and the anterior part of the holoventral shield (a pair of well-sclerotised ear-like processes in O. circularis (Fig. 22), which are absent in O. calcaratus) (Hirschmann & Krauss, 1965; Koroleva 1977)
description: Published as part of Özbek, Hasan Hüseyin, 2023, The genus Onchodellus Berlese in Türkiye (Mesostigmata: Pachylaelapidae), with a new record and three new species, pp. 285-296 in Zootaxa 5263 (2) on pages 289-291, DOI: 10.11646/zootaxa.5263.2.7, http://zenodo.org/record/7801139