Baikalozercon irbis, Marchenko, 2022

Marchenko, Irina I., 2022, Description of new genus Baikalozercon (Acari: Mesostigmata: Zerconidae) with two new species from South Siberia Mountains (Russia), Zootaxa 5120 (3), pp. 301-333 : 318-328

publication ID	https://doi.org/ 10.11646/zootaxa.5120.3.1
publication LSID	lsid:zoobank.org:pub:CF24D701-3121-47F9-8091-EE46C011957C
DOI	https://doi.org/10.5281/zenodo.6389431
persistent identifier	https://treatment.plazi.org/id/03BB87B0-FFB2-E920-FF5A-FC3DB271F951
treatment provided by	Plazi
scientific name	Baikalozercon irbis
status	sp. nov.

Treatment

Baikalozercon irbis sp. nov.

( Figures 41–63 View FIGURE 41 View FIGURES 42–43 View FIGURES 44–50 View FIGURES 51–53 View FIGURES 54–55 View FIGURES 56–59 View FIGURES 60–61 View FIGURES 62–63 )

Female ( Figs 41–53 View FIGURE 41 View FIGURES 42–43 View FIGURES 44–50 View FIGURES 51–53 , n=10)

Dorsal idiosoma ( Fig. 41 View FIGURE 41 ). Idiosoma pear-shaped, 1025–1060 long, 675–725 wide, divided into two shields that cover the entire dorsal idiosoma. Podonotal shield with festoon ornamentation, except mid-posterior region with smooth reticulation, anterior margin curved ventrally to form a vertex. The most anterior setae j1 the longest (55–63) of all setae, pilose, inserted on large bases on anterior margin of idiosoma. Vertex with setae z1, the shortest (20–25), slightly barbed and a pair of pore-like structures (glands) po1 visible on ventral side. All medial and lateral setae on dorsal shields slightly pilose (visible only with the use of oli immersion), located on rounded bases; marginal r-R setae inserted on rounded tubercles, slightly curved and feathered. Podonotal shield neotrichous, with 25–27 lateral setae of z, s -series (25–27), 25–29 medial setae of j -series (four pairs of them longer 35–37 long, others as lateral), 15–16 marginal setae of r -series (35–37) from each side; and four pair of pore-like structures (glands) po1–po4. Regions of podonotum between medial and lateral setae with groups of sigillae of longitudinal location. Opisthonotal shield neotrichous, with smooth reticulation in median region and festoon ornamentation in lateral regions ( Figs 41 View FIGURE 41 , 50 View FIGURES 44–50 ). Setae of J, Z and S -series in asymmetrical locations. Setae of J, Z and S series in asymmetrical position. Medial setae of J- series 15–23, 22–25 long; lateral setae 31–36, 30 long; and marginal R -setae 15–18 on raised tubercles (40–43) on each side; regions free of setae located in the depressions of the shield with two pairs of sigillae from each side. Region surrounding 6–7 posterodorsal sigillae with smooth reticulation and punctate at the corners of the cells. Four pairs of pores Po1–Po4 inserted in opisthonotum. Cribrum visible on the terminal end of shield between the posteriormost marginal setae.

Ventral idiosoma. ( Figs 42–47 View FIGURES 42–43 View FIGURES 44–50 ). Base of tritosternum 63–65 long and 35–37 wide, paired pilose laciniae free from each other along entire length, 107–112 long. First sternal platelet 50–52 long (along a vertical line through setae St1) and 100–107 wide, single, hollow inside; with irregular wavy edges along inner contour; with pair of St1 setae (60–63) and slit-shaped lyrifissures iv1 ( Figs 42 View FIGURES 42–43 , 45 View FIGURES 44–50 ). Second sternal platelet formed by two small separate rounded platelets with diagonal groove (25–27 x 25–35), with pair of St2 setae (55–57) and oval lyrifissures iv 2 in lateral position. Third sternal platelet entire, the largest, 137–142 long and 177–112 wide, with folded reticulation structure of cuticle; with a medial incision dividing the shield into two lobes in posterior part, not reaching level of St4 setae; with two pairs of setae St3, St4 of the same length (47–50); and slit-form lyrifissures iv3 ( Figs 42–47 View FIGURES 42–43 View FIGURES 44–50 ). Pair of large rounded glands gv1 located at the antero-lateral edge of the hyaline membrane surrounding largest sternal shield. Genital shield sack-shaped with extension in anterior and posterior parts, with narrowing in anterior third, 125–140 long and 155–170 wide at widest part; with setae St5 (20–25), and pair of internal genital sclerites.Anterior part of the genital shield (above narrowing) has a different cuticle structure than the posterior, as shown in Fig. 43 View FIGURES 42–43 . Lyrifissures iv5 inserted on soft cuticle outside of genital shield. The genital shield is surrounded by trapeziform membrane with mid-anterior incision opposite the same on the largest sternal shield. In typical position, anterior part of genital shield located under the largest sternal shield not reaching level of St4 setae. When pressed down on a slide, the third sternal and genital shields are displaced vertically as shown in Fig. 43 View FIGURES 42–43 . One pair of post-genital sclerites inserted between genital and ventri-anal shields. Endopodal sclerites present around of coxae III–IV. The anterior part of endopodal sclerite can partially extends under third sternal platelet. Exopodal sclerites fused with peritrematal shields in region of coxae III–IV. Peritrematal shields strongly sclerotised, ornamented with festoon reticulation along entire length; fused anteriorly forming a vertex. Six pairs of poroids inserted in peritrematal shields: gp1–gp3 and ip1–ip3 and two pairs of short setae of the same length (12–14): barbed z 1 in vertex and simple rx seta located opposite coxae III. Peritremes slightly undulating, very long, extending from mid coxa IV to mid coxa I, 350–370 long, with inner partitions. Metapodal platelets large, elongated in horizontal direction (15–20 x 105–120). Gland pores gv2 multiple, dispersed over surface: one pair of glands openings inserted on soft cuticle postero-laterally of genital shield, other 7–9 located on ventri-anal shield from each side. Ventri-anal shield broad, 425–440 long and 675–725 wide, fused to opisthonotal shield posteriorly at level of post-anal setae, with festoon reticulation in region above glands gv3, and smooth reticulation surround anal opening; with 10–11 opisthogastric smooth setae (27–30) and 11 marginal opisthonotal setae, pilose, slightly curved, on rounded tubercles from each side. Setae of Jv and Zv- rows are clearly distinguished (Jv1–Jv3, Zv1–Zv3), other setae in asymmetrical location. Anal area with smooth para-anal (20–25) and post-anal (30–35) setae; anal opening (52–62 x 50–52) with two pairs of lyrifissures on each valve ( Fig. 49 View FIGURES 44–50 ); cribrum extends from ventral to dorsal sides of idiosoma between the longest (58–70), barbed posteriormost marginal setae ( Fig.42 View FIGURES 42–43 ). Pair of glands gv3 located antero-laterally of paraanal setae.

Gnathosoma . ( Figs 48 View FIGURES 44–50 , 51–53 View FIGURES 51–53 ) Movable digit of chelicera 112–114 long, with four teeth in addition to apical hook; fixed digit 114–116 length, with seven (six in some specimens) teeth in addition to apical hook and tubular pilus dentilis with rounded tip ( Fig. 51 View FIGURES 51–53 ). Chelicera with dorsal seta (45–46), lateral (antiaxial) and dorsal lyrifissures; with serrated arthrodial corona and suboval area (“window”) on paraxial side with thin cuticle. Epistome ( Fig. 52 View FIGURES 51–53 ) with irregularly serrated lateral edges and smooth, long, bifurcated median projection. Corniculi 55–57 long and 27–29 wide. Internal malae protrude distinctly beyond corniculi ( Fig. 53 View FIGURES 51–53 ) with smooth elongated branches, barbed at base. Deutosternal groove with seven transverse denticulate rows, with four paired curved lateral transverse lines. Setae h1–h3 smooth: h1 (67–69) the longest, seta h2 (43–45) shorter than h3 (63–65); pc (37–40) serrated. Dorsal side of gnathosoma with pair of paraxial lanceolate structures –“staples” between chelicera shaft and epistome. Palpal chaetotaxy 2–5–6–13–15, palps with five free segments; palp trochanter with seta al1 long and pilose in distal third, seta al2 short and smooth; palp genu with seta al1 smooth and al2 pilose in distal third; palp tarsal claw two-tined.

Legs. ( Figs 44 View FIGURES 44–50 , 61 View FIGURES 60–61 ). Lengths: I 750–775, II 625–675, III 625–675, IV 775–790 µm. 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), 10 (2 4/2 2); tarsi I—49 (6 29/9 5), II–IV 18 (3 7/5 3). All legs with sclerotised claws and pulvillus ( Fig. 61 View FIGURES 60–61 ). Pretarsus of legs II–IV with ambulacral stalk, tarsi I with sessile claws. Coxae I with split on dorsal side, coxae IV with recesses on anterolateral side; coxae II–III with antero-dorsal spines: II with large sharp spine, III with small one; IV coxae with 1–3–tined postero-ventral spine and alveolar vestige of second av seta.

Male. ( Figs 54–59 View FIGURES 54–55 View FIGURES 56–59 , n=10).

Dorsal idiosoma. ( Fig. 56 View FIGURES 56–59 ). Dorsal idiosoma pear-shaped, 985–1000 long, 660–700 wide, ornamentation and neotrichy of dorsal shields as in female.

Ventral idiosoma. Base of tritosterum 47–50 long and 32–37 wide, pilose laciniae 108–112 long. First sternal platelet paired, divided, irregular in form, with ragged outlines, 47–50 long and 37–50 wide, with seta St1 (47–50) and slit lyrifissures iv1 on each part ( Fig. 54 View FIGURES 54–55 ). Second sternal platelets entire, with irregularly rounded anterior margin and truncated posterior one, with festoon reticulation, 45–50 long and 62–65 wide, with pair of setae St2 (43–45) and lyrifissures iv2 laterad platelet, located on soft cuticle. Truncate posterior edge of second sternal platelet is adjacent to genital opening. Third sternal platelet divided in two parts, adjacent to the genital opening on the sides, with vertical reticulation, 95–105 long, 32–37 at widest part; with setae St3, St4 (32–35), with rounded glands gv1 on anterior edge and slit lyrifissures iv 3 in central region on each side. Fourth sternal platelet (or post-genital) consists of two fragments: small anterior 25–37 x 17–25 and large subtriangular posterior 55–62 x 82–100 with pair of setae St5 (25–27), and lyrifissures iv5 inserted on soft cuticle lateral to St5 setae. Genital opening located at level between coxae II–III (50–52 x 50–55), covered by two sclerites, with a pair of eugenital setae (25–27) on anterior sclerite; with pair of inner sclerites ( Figs 54 View FIGURES 54–55 , 57–58 View FIGURES 56–59 ). Peritrematal shields similar to those of female, with smooth rx seta and six pore-like structures on each side. Arch of vertex with pair of slightly barbed setae z1 and pore po1. Peritremes similar to those of female, slightly undulating, very long (325–350). Two pairs of endopodal sclerites almost fused with each other located around coxae III–IV; extend under third sternal platelets anteriorly. Exopodal sclerites fused with peritrematal shields in region of coxae III–IV. Ventri-anal shield broad, 415–440 long and 600–650 wide, fused with metapodal platelets. Ornamentation, chaetotaxy and fusion with the opisthonotal shield as in female. Gland pores gv2 (9–15) dispersed over the surface of ventri-anal shield. Pair of glands gv3 located antero-laterally to paraanal setae. Anal opening suboval 55–57 × 47–50. Post-anal seta (30–32) longer than para-anal setae (20–25), with two lyrifissures on each valve.

Gnathosoma . ( Fig. 55 View FIGURES 54–55 ). Male chelicera with sexual dimorphism of fixed digit. Fixed digit of chelicera the same length as movable digit, with six or seven (in different specimens) medium-sized teeth and apical large outgrowth; with tubular protruding pilus dentilis; with large suboval “window” of thinner and lighter cuticle layer in paraxial side. Movable digit of chelicera 97–103 long, with four teeth in addition to apical hook, with serrate arthrodial corona at base of digit. Chelicera with dorsal seta, antiaxial and dorsal lyrifissures. Epistome, corniculi, internal malae and palpal structures as in female. Male subcapitulum without sexual dimorphism.

Legs. ( Figs 59–61 View FIGURES 56–59 View FIGURES 60–61 ). Lengths: I 700–735, II 580–600, III 580–600, IV 715–735 µm. Chaetotaxy and morphology of legs I, III–IV as in female. Legs II of male with sexual dimorphism due to some modified setae on femur II: the largest, elongated spine-like seta al2, and smaller and thinner spine-like al1 ( Fig. 60 View FIGURES 60–61 ). Other segments of legs II including genu and tibia without clearly distinct modified setae.

Deutonymph not found.

Protonymph ( Figs 62–63 View FIGURES 62–63 , n=12).

Dorsal idiosoma ( Fig. 62 View FIGURES 62–63 ). Dorsal idiosoma 550–600 long and 385–415 wide. Podonotal shield with festoon ornamentation except area between j6–j5 setae with smooth reticulation. Anterior margin of podonotum with pair of pilose setae j1 at large base. Podonotal shield with five pairs of setae in j -row (j1, j3–j6), z -row with pairs of recognisable z4 and z5 setae, with about 15 pilose setae at lateral margins from each side; three r -setae on soft cuticle on each side and four pairs of poroids po1–po4. Pygidial shield with tuberculate and festoon ornamentation except area around 5–7 posterodorsal sigillae with smooth reticulation. Pygidial region presented by one large, broad pygidial shield and two medium sized mesonotal platelets; with three pairs of pilose setae in J -row, J1 located on paired mesonotal platelets; another 12–13 pilose lateral setae and 8–9 marginal pilose curved R setae located on each side of shield. Also poroids Po1 inserted on mesonotal platelets and Po2–Po4 on pygidial shield.

Ventral idiosoma ( Fig. 63 View FIGURES 62–63 ). Sternal region with setae St1–St3 and St5 inserted in soft cuticle with slight ornamentation; seta St5 minute. Peritrematal shields not distinct. Peritremes short (62–65), with internal cell structure; with thin ducts leading from stigmata. Pair of gland pores gv2 located posteriad IV coxae. Metapodal platelets (10–12 x 18–23) present. Opisthogastric area with five pairs of simple setae inserted in soft cuticle. Anal shield subtriangular, ornamented with tubercles and folds, 105–125 long and 130–150 wide with cribrum, pair of glands gv3 at antero-lateral margins; with para-anal and post-anal setae. Opisthonotal shield curved on ventral side, not connected with anal shield; with 1–3 setae on sclerotised ornamented cuticle and eight marginal curved pilose setae from each side.

Legs. Lengths: I 465–475, II 400–425, III 400–425, IV 475–500. Chaetotaxy of legs I–IV: coxae 2, 2, 2, 1; trochanters 4, 4, 4, 4; femora 10, 8, 5, 4; genua 8, 6, 6, 5; tibiae 8, 7, 7, 7; tarsi II–IV: 17, 17, 17.

Material examined. Holotype female, Russia, Baikal Region , environs of Tankhoi village , Baikal Natural Biosphere Reserve, Khamar-Daban Ridge, 51 33’ N, 105 09’ E, 1100 m a.s.l., tall grass alpine meadow with sparse trees of Abies sibirica , in soil, 13 August 2014, coll. L. V. Petrozhitskaya GoogleMaps . Paratypes: 8 females, 4 males, same data as holotype GoogleMaps ; 2 females, 2 males, same geographical data, valley of Osinovka river , 1100 m a.s.l., 13 August 2014, coll. L. V. Petrozhitskaya ; 1 male, same geographical data, alpine tundra, 1600 m a.s.l., in litter-soil, 12 August 2014, coll. I.I. Marchenko.

Other material: 11 protonymphs, same data as holotype; 1 protonymph, same geographical data as type material, alpine tundra, 1600 m a.s.l., 12 August 2014, coll. I.I. Marchenko. GoogleMaps

Etymology. The specific name irbis refers to snow leopard in Turkic and Mongolian languages. The irbis—snow leopard inhabitant of highlands of Central Asia. New species Baikalozercon irbis also inhabits severe highlands in Siberia.

Remarks. Adults of Baikalozercon irbis differs from B. dracunculus : first species with festoon ornamentation of central part of opisthonotal shield; pair of posteriomost marginal R setae of opisthonotal shield straight and longer than others. Female of B. irbis has sack-form genital shield with constriction in anterior third. Movable digit of chelicera in both sexes of B. irbis with four teeth. Males have significant differences in sternal area, so B. irbis with first sternal platelet irregular in form, second platelet irregularly hemispherical form, fourth sternal platelet (or post-genital) fragmented, consisting of two parts: anterior smaller and posterior larger. Male gnathosoma of B. irbis without sexual dimorphism. Male II legs of B. irbis with sexual dimorphism in form of two modified enlarged setae of femur al1, al2.

Distribution. Mites of the new genus Baikalozercon are restricted in distribution to the mountains of Southern Siberia. Baikalozercon dracunculus is known from three localities: “Stolby” Nature Reserve in Eastern Sayan; Khamar-Daban Ridges in Baikal Region (Buryatia and Irkutskaya Oblast); and Sokhondinskii Nature Reserve in Zabaikalskii Krai, while B. irbis is found only in the highlands of Khamar-Daban Ridge ( Fig. 64 View FIGURE64 ). Photos of localities along altitudinal gradient of Khamar-Daban Ridge are shown in Figures 65–71 View FIGURES 65–71 . Two species of the new genus Baikalozercon coexist on the same Khamar-Daban Ridge, but inhabit different altitudes— B. dracunculus occurs at altitudes of 500–700 m a.s.l. in mountain taiga and B. irbis at 1000–1600 m in alpine sparse forest with meadow and alpine tundra ( Fig. 72 View FIGURE 72 ).