Onchodellus marginatus Özbek & Halliday, 2024, sp. nov.
Creators: name: Özbek, Hasan Hüseyin
name: Halliday, Bruce
Publisher: name: Zenodo
Year: 2024
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Arachnida
Mesostigmata
Pachylaelapidae
Onchodellus
Onchodellus marginatus

description: Onchodellus marginatus sp. nov.
(Figs 9, 12–18)
Diagnosis (Female)
Idiosoma distinctly reversely ovate; two pairs of postero-lateral teat-like gland pores present (gdZ1, gdS4), seta Z2 positioned on extreme edge of dorsal shield; J4 and J5 of different length, J5 very short (8–15), ratio of J4 / J5 2.6–4.7, anterior tips of peritremes extending over dorsal side of shield and far from base of setae z1; metapodal shields oval shaped and abutting postero-lateral corners of peritrematal shields; soft integument of idiosoma with 13 pairs of setae.
Material examined. Holotype female, Türkiye, Gümüşhane Province, Kürtün town (40° 39’ N, 39° 00’ E), altitude 1845 m a.s.l., in moss, 28 October 2013; three females, same data as the holotype; two females, Giresun Province, Kovancık village (40° 52’ N, 38° 51’ E), alt. 90 m a.s.l., in litter under Camellia sinensis, 12 September 2008; one female, Gümüşhane Province, Kürtün town (40° 39’ N, 38° 59’ E), altitude 1994 m a.s.l., in litter under Abies sp., 12 October 2013.
Description. Female.
Dorsum (Fig. 12). Dorsal shield 560–650 long, 410–500 wide at widest point, length/width 1.30–1.43, distinctly reversely ovate, surface ornamented with transverse lines, with 30 pairs of smooth and pointed setae and two pairs of postero-lateral teat-like gland pores gdZ1 and gdS4, well separated; gland pores gdZ1 situated between setae Z1 and Z2, dorsal setae Z2 situated at extreme lateral margin of dorsal shield. Anterior setae distinctly longer than posterior setae. Setae j2, j3, j4, s2, s5, s6, r2, r3 and r5 more than 50 long (50–60), z2, z4 and s4 slightly longer (60–70), other dorsal setae 35–50 long, except some setae j1 20–25, z1 10–15, J5 8–15 long. Ratio of J4 / J5 2,6–4,7 (J4 35–40).
Venter (Fig. 13). Sternal shield 165–180 long, 100–110 wide at level of coxae II, its surface decorated with reticulate pattern, with four pairs of pointed setae and three pairs of pores; st1–st5 40–55 long. Genitiventral shield 200–210 long, 230–245 wide, wider than long, length/width 0.85–0.89 ornamented with lines and punctation, with two pairs of setae. Anal shield 75–95 long, 125–140 wide, length/width 0.60– 0.71, triangular. A pair of oval metapodal shields present, abutting postero-lateral corners of peritrematal shields. Lateral and opisthogastric soft integument with 13 pairs of setae (six pairs of marginal and seven pairs of opisthogastric). Anterior tips of peritreme extending to dorsal side of idiosoma, between setae z1 and z2.
Spermathecal apparatus. Tubes of spermathecal system connected to coxae III, long, apical portion slightly widened, conically shaped (Fig. 14).
Gnathosomal structures. Hypostome with seta h3 longest, h2 and palp coxal seta pc shortest and subequal in length; corniculi horn-like and lanceolate, deutosternal groove with six rows of denticles (Fig. 15). Epistome with straight denticulate lateral margins and central projection with strong apical denticle (Fig. 16). Movable digit of chelicera about 65 long, with a large subdistal tooth, a small subdistal tooth, and simple terminal hook; fixed digit about 65 long (to dorsal seta), with a short and thick pilus dentilis (Fig. 9). Arthrodial brush short.
Legs. Chaetotaxy normal for the genus (Mašán, 2007a). Coxae I with distally located triangular process (only in one specimen seen ventrally, it is not visible in other specimens seen dorsally; Fig. 17). Tarsus II with a thicker spur-like seta pl1 (Fig. 18).
Male and immature stages. Not found.
Etymology. The name of this species refers to seta Z2, which is located on the outermost edge of the dorsal shield.
Remarks
Onchodellus marginatus differs from similar species of the genus by the position of seta Z2, which is extremely close to the lateral margin of the dorsal shield, the slightly antiaxial position of the glandular pore gdZ1. This position of Z2 could be due to the fact that the margins of the dorsal shield are clearly curved towards the ventral side of the idiosoma. For a further comparison of other features we can refer to the detailed work of Mašán (2007a).
Mašán (2007a) evaluated the species grouping of some species of the genus Onchodellus and found five species groups and some non-grouped species. Onchodellus marginatus could be included in the O. strigifer group because it shares some important characters based on female specimens with this species group, such as two teat-like gland pores gdZ1 and gdS4 located close to each other, anterior tips of the peritreme extending to the dorsal side of the idiosoma, pores gdZ1 near setae S3 and setae J5 less than 20. Mašán (2007a) presented five species in this group, namely O. strigifer (Berlese, 1892), O. neglectus Mašán, 2007, O. slovacus Mašán, 2007, O. striatifer Mašán, 2007, O. tegulifer Mašán, 2007. Later Şahin & Özbek (2018) added O. montanus to this group and Özbek (2023) added O. kosensis, so we can compare Onchodellus marginatus with seven species in this species group.
Onchodellus marginatus is clearly distinguished from O. strigifer, O. neglectus, O. slovacus, O. striatifer, and O. montanus by the different number of setae on the opisthogastric soft integument (13 in O. marginatus; 11 in O. strigifer; 14 in O. neglectus; 10 in O. slovacus; 12 in O. striatifer; 11 in O. montanus). It has the same number of setae on the opisthogastric soft integument as O. tegulifer and O. kosensis, but differs from them by the different ornamentation on the dorsal and ventral shields, and the different shape and position of the metapodal shield, which is oval and attached to the posterior corner of the peritrematal shield in O. marginatus, while in O. tegulifer and O. kosensis is rod-shaped and free. These species also differ in the length of dorsal shield (560–650 in O. marginatus, 510–560 in O. tegulifer, 470–550 in O. kosensis); and the length of seta J4 (35–40 in O. marginatus, 20–30 in O. tegulifer, 40–42 in O. kosensis).
description: Published as part of Özbek, Hasan Hüseyin & Halliday, Bruce, 2024, Two new species of mites in the family Pachylaelapidae from Türkiye (Acari: Mesostigmata), pp. 319-337 in Zootaxa 5514 (4) on pages 323-324, DOI: 10.11646/zootaxa.5514.4.2, http://zenodo.org/record/13914602