Sayanozercon, Marchenko, 2025

Marchenko, Irina I., 2025, The new genus Sayanozercon (Acari: Mesostigmata: Zerconidae) with description of five new species from South Siberia mountains (Russia), Zootaxa 5647 (2), pp. 151-195 : 152-153

Genus Sayanozercon gen. nov.

Type species: Sayanozercon mariannae sp. nov. Other included species: Sayanozercon adelaidae sp. nov., S. ergaki sp. nov., S. mikhaili sp. nov., S. shoricus sp. nov.

Diagnosis. The new genus is based on adult female and male material representing five newly described species. Adults of Sayanozercon gen. nov. can be distinguished from other genera of Zerconidae by the presence of an additional longitudinal latero-ventral shield extending between the peritrematal and ventrianal shields from setae r3 to R6; epistome with serrated central process with row of small median spines; smooth and acicular shape of all dorsal setae; podonotal setae z1 and z2 lost; unique morphology and sexual dimorphism of inguinal region with fibre brush of cuticular structure and two inguinal conspicuous poroids gvi and ivi; presence of pilus dentilis in fixed digit of chelicerae and sexual dimorphism of cheliceral denticulation – five teeth in female versus six teeth in male; sexual dimorphism of ventral chaetotaxy/porotaxy – setae st5, Zv1 lost in male and different location of gland gv2.

Description of Sayanozercon gen. nov.

Idiosomal dorsum. Large or mid-sized mites with rounded-oval or pear-shaped idiosoma, divided on two strongly sclerotised dorsal shields, without obvious ornamentation. All idiosomal setae smooth and pointed. Podonotal shield with 20 or 21 pairs of setae, setae z1 and z2 lost in all five species. Marginal seta r1 shortest in r -series, inserted at dorsal side, r3 seta is 3–4 times longer than r1 seta. Three podonotal glands are present, with various location of gland gdz5 (po3) in other species and five pairs of lyrifissures: idj1, idj3, idz4, ids4, idj6. Opisthonotal shield with 20–21 pairs of setae. Four podonotal glands present, with various location of gland gdZ1 (Po2) in other species. Opisthonotal shield with 13 pairs of lyrifissures: ids6, idS1, idz6, idS4, idZ4, idJ4, idJ5, idJ2, idJ3, doubled idJ1 and doubled idS3. Posterodorsal cavities rounded curvings, all equal size, located at posterior margin of opisthonotal shield.

Female venter. Additional latero-ventral shield is present, extending vertically from seta r3 to R6; with slight longitudinal reticulation. Peritrematal shields adjacent to additional latero-ventral shields anteriorly at level of coxae II and free at level of coxae III–IV. Peritrematal shield truncate at posterior margin, not fused with ventri-anal shield; with two conspicuous rounded poroids in inguinal region – gvi and ivi and fibre brush of cuticular structure. Peritrematal shields with smooth and pointed long setae r3; with lyrifissures ip1, ip2 and gland gp from each side. Peritremes very short. Large pair of endopodal sclerites between coxae III–IV with pair of setae st4 or outside sclerites. Adgenital sclerites presented each with 4–5 glands openings gv2. Ventrianal shield free, wide, with 21 smooth and pointed setae. Anal opening with two pairs of lyrifissures on each valve.

Male venter. Pair of latero-ventral shields shaped as in female, with reticulate ornamentation. Sternigenital shield with area of weak sclerotisation and weak reticulation between setae st1 and st2; with four pairs of setae (st1–st4), pair of st5 setae not developed, three pairs of lyrifissures and pair of glands gv1. Male peritrematal shields connected posteriorly to each other by fibre brush of cuticular structure; inguinal region with two pairs of conspicuous formations hollow inside—inguinal poroids gvi and ivi. Genital opening with two sclerites, eugenital setae present in S. mariannae sp.n. or not visible in other species. Ventrianal shield free, with multiple glands gv2 located on anterior margin; with 19 smooth and pointed setae; pair of setae Zv1 not developed.

Gnathosoma . Epistome with irregularly serrated lateral edges, serrated middle process with median row of small spines and medial ridge located posteriorly to row of spines. Chelicera with long dorsal seta, lateral (antiaxial) and dorsal lyrifissures; with smooth arthrodial corona and leaf-shaped pilus dentilis; apical sensorial depression presents. Sexual dimorphism of chelicerae denticulation: five teeth in female and six teeth in male. Deutosternal groove with seven transverse denticulate rows. Corniculi horn-like, internal malae extending beyond corniculi. Palpal chaetotaxy 2–5–6–12–15 with five free segments; pilose setae on palp trochanter v1 and v2; on palp femur d3, on palp genu al2; palp tarsal claw two-tined.

Legs. Legs of moderate length. All legs with pretarsi and paired claws. Pretarsus of legs II–IV with ambulacral stalk, tarsi I with sessile claws. Coxae I with dorsal incision, coxae II with antero-dorsal spine. Chaetotaxy of legs I–IV: coxae 2, 2, 2, 1; trochanters 6 (1 1/3 1), 5 (1 1/3 0), 5 (1 1/3 0), 5 (1 1/3 0); femora 13 (2 5/4 2), 11 (2 5/3 1), 6 (1 4/1 0), 6 (1 4/1 0); genua 13 (2 6/3 2), 11 (2 5/2 2), 10 (2 4/2 2), 10 (2 5/2 1); tibiae 14 (2 6/4 2), 10 (2 4/2 2), 9 (2 3/2 2), 9 (2 3/2 2); tarsi I–49 (6 29/9 5), II–IV 18 (3 7/5 3). Chaetotaxy of legs I–IV is typical for Zerconidae ( Halašková, 1969; Sikora, 2014). Legs of male without dimorphically modified setae.

Etymology. The genus name Sayanozercon reflects name of the Sayan Mountain in South Siberia, Russia. Gender feminine.

Species differential diagnosis.

A large number of characters differ between species of new genus Sayanozercon as shown in Table 1 and are listed below.

Idiosomal dorsum. Podonotal shield with 21 pairs of setae, seta s1 presented in S. adelaidae sp. nov., S. mikhaili sp. nov., S. shoricus sp. nov. and with 20 pairs of setae in S. mariannae sp. nov., S. ergaki sp. nov., where seta s1 is lost. Location of podonotal glands for all five species: gdj2 (po1) close to line connecting insertions of setae j2 and z3; gdj4 (po2) close to line connecting insertions of setae j4 and z4. Gland gdz5 (po3) usually located (for S. mariannae sp. nov., S. adelaidae sp. nov., S. ergaki sp. nov. and S. shoricus sp. nov.) close to line connecting insertions of setae z5 and s5, except for species S. mikhaili sp. nov., where it located near posterior edge of podonotal shield, close to line connecting insertions of setae s5 and z6. Opisthonotal shield with 20 pairs of setae in S. mariannae sp. nov., S. ergaki sp. nov., where four pairs of setae in J -series and 21 pairs of setae in S. adelaidae sp. nov., S. mikhaili sp. nov., S. shoricus sp. nov., where five setae in J -series. Seta J3 is lost in S. mariannae sp. nov. and seta J5 is lost in S. ergaki sp. nov. One species S. ergaki sp. nov. demonstrated sexual dimorphism of chaetotaxy: setae J3, J4 longest in female and shortest in male among setae in J- series. Opisthonotal adenotaxy presents different location of glands in other species. Location of opisthonotal gland gdZ1 (Po2) usually anterolateral to seta Z1 (species S. mariannae sp. nov., S. adelaidae sp. nov., S. ergaki sp. nov. and S. mikhaili sp. nov.), except for species S. shoricus sp. nov., where it placed on line connecting insertions of setae Z1 and Z2.

Idiosomal ventrum. Location of ventral setae st 4 in female varies among different species of Sayanozercon gen. nov. Setae st4 inserted on medial edge of endopodal sclerite in species: S. mariannae sp. nov., S. ergaki sp. nov. and inserted outside endopodal sclerite in species: S. adelaidae sp. nov., S. mikhaili sp. nov., S. shoricus sp. nov.

Gnathosoma . Three species: Sayanozecon mariannae sp. nov., S. ergaki sp. nov., and S. mikhaili sp. nov. demonstrated sexual dimorphism in denticulation of fixed digit of chelicera—five teeth in female and six teeth in male; structure of chelicerae of two other species is difficult to examine without dissection. Internal malae demonstrated two variations of structure: bifurcate apices in S. mariannae sp. nov., S. adelaidae sp. nov., S.shoricus sp. nov. and smooth pointed apices in S. ergaki sp. nov., S. mikhaili sp. nov.