Baikalozercon dracunculus, 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 : 304-318

Baikalozercon dracunculus sp. nov.

( Figures 1–40 )

Female ( Figs 1–8 , 11–19 , n=10)

Dorsal idiosoma ( Figs 1 , 5 , 11 ). Idiosoma pear-shaped, 920–975 long, 650–700 wide, with tuberculate ornamentation, divided into two shields that cover the entire dorsal idiosoma. Anterior margin of podonotal shield curved ventrally to form a vertex. The most anterior setae j1 the longest (53–55) of all setae, pilose, inserted on anterior margin of idiosoma. Vertex with setae z1, the shortest (12–14), slightly barbed and pair of pore-like structures (glands) po1. All medial and lateral setae on dorsal shields slightly pilose (visible only with the use of oil immersion), located on rounded bases; marginal r-R setae slightly curved and feathered, inserted on rounded tubercles. Podonotal shield neotrichous, with 19–21 lateral setae of z, s -series (25–27µm), 31–36 medial setae of j -series (three pair of them longer 35–37 long, others as lateral), 18–19 setae of r -series (47–50) on each side. Podonotal shield ornamented with small tubercles forming a reticulated pattern with the exception of the midposterior region. Regions of podonotal shield between medial and lateral groups of setae with longitudinal fields of sigillae. Four pair of pore-like structures (glands) po1–po4 located in podonotum. Opisthonotal shield neotrichous, with tuberculate ornamentation except smooth reticulated regions between medial and lateral setae in anterior part and in mid-posterior region. Setae of J, Z and S -series in asymmetrical location. Medial 26–29 setae (25–27) located on raised area in the center of the shield, lateral 23–27 setae (as long as medial) located on raised ridges; and marginal 16–17 R -setae from each side (35–37); regions free of setae located in the depressions of the shield with about two pairs of sigillae. Area around five posterodorsal sigillae with smooth reticulation. Smooth reticulation radiates from the center like the petals of a flower. Four pairs of pores Po1–Po4 inserted in opisthonotum. Cribrum on the terminal end of the shield between the posteriormost marginal setae.

Ventral idiosoma. ( Figs 2–4 , 6, 7 , 12–14 ). Base of tritosternum 67–73 long and 40–45 wide; paired pilose laciniae free from each other along entire length, 105–112 long ( Fig. 3 ). First sternal platelet single, hollow inside, with sharp ragged edges along inner contour; 45–50 long (along a vertical line through setae St1) and 75–80 wide, with pair of St1 setae (45–55) and slit-form lyrifissures iv1 ( Fig. 2 , 12 ). Second sternal platelet formed by two small separate oval platelets (30–45 x 15–25) located on a larger sclerotised cuticle (35–37 x 67–75), with pair of St2 setae (35–45) and oval lyrifissures iv2 adjacent to the anterio-lateral edge. Third sternal platelet entire, the largest, 120–125 long and 117–132 wide, with convoluted structure of cuticle above level of St4 setae; 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 (40–45), St4 (45–50); with slit-form lyrifissures (iv3) and pair of large rounded poroids gv1 adjacent to the anterio-lateral edge ( Figs 4 , 13–14 ). Third sternal platelet surrounded by a hyaline membrane, inside which poroids gv1 located. Genital shield axe-shaped, expanded posteriorly, 160–175 long and 160–193 at widest part; with setae St5 (35–40), lyrifissures iv5 on shield or outside. Anterior part of the genital shield has a different cuticle structure than posterior one as shown in Fig. 4 . The genital shield is surrounded by a trapeziform membrane with mid-anterior incision opposite the same on the third sternal platelet. In the typical position, anterior part of the genital shield extends under the third sternal platelet; under pressure on the slide, the shields are displaced vertically as shown in Fig. 4 . One pair of post-genital sclerites inserted between genital and ventri-anal shields. Endopodal sclerites presented around of coxae III–IV. The anterior part of endopodal sclerite partially extends under the 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 vertex. Six pairs of poroids inserted in peritrematal shields: gp1–gp3 and ip1–ip3 and two pairs of short barbed setae: z1 and of the same length rx seta (12–14), located opposite III coxae. Peritremes slightly undulating, very long, extending from mid coxa IV to mid coxae I, 320–335 long. Metapodal platelets large, elongated in horizontal direction (17–25 x 75–95). Gland pores gv2 multiple, dispersed over surface: one pair of gland openings inserted in soft cuticle postero-laterad genital shield, other 5–7 located on ventri-anal shield from each side. Ventri-anal shield broad, 315–335 long and 550–615 wide, fused to opisthonotal shield posteriorly at level of para-anal setae, with festoon reticulation, with 11–15 opisthogastric smooth setae, setae Jv1–Jv3 the longest (30–37) and others shorter (25–30), marginal rows of opisthonotal setae pilose, slightly curved, on rounded tubercles from each side. Anterior most opisthogastric setae Jv1 can be located both on the shield or on the soft cuticle above it. Setae of Jv and Zv- rows are clearly distinguished (Jv1–Jv3, Zv1–Zv3), other setae in asymmetrical location. Anal area with smooth para-anal (25–27) and post-anal (31–37) setae; anal opening (45–50 x 40–42) with two pairs of lyrifissures on each valve; cribrum extends from ventral to dorsal sides of idiosoma between the posteriormost marginal setae. Pair of glands gv3 located anterolaterally of para-anal setae.

Gnathosoma . ( Figs 8 , 15–19 ) Movable digit of chelicera 100–105 long, with three teeth in addition to apical hook; fixed digit the same length, with seven teeth in addition to apical hook and two-pointed pilus dentilis ( Figs 15–16 ). Chelicera with long dorsal seta (40–43), lateral (antiaxial) and dorsal lyrifissures; with serrated arthrodial corona and suboval area (“window”) on paraxial side with thin cuticle. Epistome ( Fig. 17 ) 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 ( Figs 18–19 ); with smooth elongated branches, barbed at base. Deutosternal groove with seven transverse denticulate rows. Subcapitulum with 2–3 paired festoon lateral transverse lines ( Fig. 18 ). Setae h1–h3 smooth: h1 (67–69) the longest, seta h2 (37–39) shorter than h3 (55–57); pc (45–47) serrated. Dorsal side of gnathosoma with pair of paraxial lanceolate structures—“staples” between chelicera shaft and epistome in female as in male ( Fig. 27 ) and immature stages. Palpal chaetotaxy 2–5–6–13–15, palp 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 20–23 , 28–29 ). Lengths: I 660–710, II 560–600, III 550–600, IV 725–750 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 with rounded lobes ( Fig. 29 ). Pretarsus of legs II–IV with ambulacral stalk, tarsi I with sessile claws ( Fig. 28 ). 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 smaller spine; coxae IV with 1–3–tined postero-ventral spine and alveolar vestige of second av seta.

Male. ( Figs 9–10 , 24–27 , 30 , 31–36 , n=10).

Dorsal idiosoma. Dorsal idiosoma pear-shaped, 900–950 long, 625–675 wide, ornamentation and neotrichy of dorsal shields as in female.

Ventral idiosoma. ( Figs 9 , 24–25 , 31–34 ). Base of tritosterum 47–50 long and 30–32 wide, pilose laciniae 100–110 long, clamped under large subcapitular teeth ( Fig. 27 ). Pair of St1 (42–47) setae in folded soft cuticle. Lyrifissures iv1 slit-shaped, located under setae St1. Second sternal platelet entire, in the form of a narrow strip, 12– 20 long and 55–62 wide, located exactly over the genital opening, with pair of St2 setae (35–40) and lyrifissures iv2 antero-laterally to platelet. Third sternal platelet divided in two parts on sides of genital opening, 80–87 long, 37–42 wide each part; with vertical irregular folding; with St3, St4 setae (32–37), with rounded lyrifissures iv3 and slit-shaped one iv4 from each side ( Fig. 25 , 34 ). Fourth sternal platelet (or post-genital) triangular in shape with elongated apex, 100–110 long and 65–75 wide, with relief pattern above St5 setae (25–27) ( Figs 33, 34 ). Lyrifissures iv5 inserted on soft cuticle, postero-laterally of St5 setae. Genital opening located at level between coxae II–III, 45– 47 long and 47–49 wide, covered by two sclerites, with a pair of eugenital setae (25–27) on anterior sclerite; with pair of inner sclerites. Peritrematal shields similar to that female, with seta rx 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 (315–335). Pair of endopodal sclerites located at mid coxae III–IV, extends under third sternal platelets anteriorly. Exopodal sclerites fused with peritrematal shields in region of coxae III–IV. Ventri-anal shield broad, 375–380 long and 550–600 wide, fused with metapodal plates. Ornamentation, chaetotaxy and fusion with the opisthonotal shield as in female. Pair of setae Jv1 and anteriomost pair of glands gv2 inserted on anterior edge, other glands gv2 dispersed over the surface of ventri-anal shield. Pair of glands gv3 located antero-laterally to paraanal setae. Anal opening suboval (50–52 × 40–42); post-anal seta (30–32) longer than para-anal setae (22–25), with two lyrifissures on each valve.

Gnathosoma . Male chelicera with sexual dimorphism of fixed digit ( Fig. 26 ). Fixed digit of chelicera with extended distal edge; the same length as movable digit, with six medium-sized teeth and one small tooth at large apical outgrowth; with bifurcate pilus dentilis; with large suboval “window” of thinner and lighter cuticle layer in paraxial side. Movable digit of chelicera 100–105 long, tridentate 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 subcapitular structure with sexual dimorphism—one pair of massive denticles (27 x 17) protruding at an angle outward, located between h2–h3 and pc setae, laterally to deutosternal groove ( Figs 10 , 27 , 35–36 ).

Legs. ( Figs 9 , 30 , 32 ). Lengths: I 700–725, II 575–600, III 575–600, IV 725–750 µm. Chaetotaxy and morphology I, III–IV legs as in female. Legs II of male with sexual dimorphism. Femur II with three enlarged setae: the largest of all, elongated spine-like al2, and smaller spine-like al1, av1; genu II with modified spine-like al1 seta and tibia II with modified seta al1 as shown in figures 30, 32.

Deutonymph ( Figs 37–38 , n=4).

Dorsal idiosoma. Dorsal idiosoma suboval shape, 695–795 long, 500–600 wide, divided into two shields. Dorsal shields do not cover the entire body, leaving soft cuticle on the sides, with row of marginal setae. Podonotal shield does not form a vertex. Setae j1, z1 and po1 inserted on anterior margin of podonotal shield. Both shields tuberculate ornamentated over the entire surface, with neotrichy. Podonotal shield with four pairs of poroids po1– po4; opisthonotal with three pairs of poroids on shield Po1, Po3, Po4 and Po2 inserted on soft lateral cuicle. Area around five posterodorsal sigillae with smooth reticulation.

Ventral idiosoma. Sternal shield entire, slightly reticulated with setae St1–St3 and lyrifissures iv1; setae St4, St5 and lyrifissures iv5 inserted on soft cuticle. Metapodal platelets wider than long (20–25 x 40–50); pair of postgenital sclerites located posteriorly setae St5. Peritremes 265–290 long, undulated, reaching to mid coxae I. Small part of sclerotised cuticle adjoins laterally to the peritrema between coxae II and III from each side. Marginal setae rx located on soft cuticle at lateral margins of ventral idiosoma at level between coxae II–III. Opisthogastral region with four pairs of glands gv2 dispersed over surface and 12–14 simple setae on each side. Anal shield separate, wider than long (110–115 x 150–160), with pair of para-anal and post-anal setae; with cribrum and pair of glands gv3 on anterio-lateral corners of shield. Opisthonotal shield curved on ventral side postero-laterally, with nine barbed marginal setae and 2–3 setae inserted asymmetrical.

Gnathosoma . As in female.

Legs. Lengths: I 575–600, II 475–500, III 475–500, IV 585–625. Chaetotaxy and morphology of legs as in female.

Protonymph ( Figs 39–40 , n=7).

Dorsal idiosoma. Dorsal idiosoma 525–610 long and 355–425 wide, with punctate ornamentation of podonotal and pygidial shields. Anterior margin of podonotum not curved ventrally, 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 13–15 pilose setae at lateral margins from each side; two pairs of r -setae on soft cuticle and three pairs of poroids po1, po2 and po4. Pygidial region presented by one large, broad pygidial shield and two medium size mesonotal platelets. Pygidial region with three pairs of pilose setae in J -row, where J1 setae located on paired mesonotal platelets. Another lateral 19 pilose setae and 9–10 marginal curved pilose setae present on each side. Also four pairs of poroids Po1–Po4 and five or seven posterodorsal sigillae present in pygidial region.

Ventral idiosoma. Sternal region with setae St1–St3 and St5 inserted in soft folded cuticle; St5 minute. Peritrematal shields not distinct. Peritremes short (60–67), with internal cell structure; with thin ducts leading from stigmata. Two pairs of adgenital gland pores gv2 below coxae IV visible. Metapodal platelets (7–8 x 17–18) present. Opisthogastric area with five pairs of simple setae inserted in soft cuticle.Anal shield subtriangular form, ornamented with tubercles and folds, 93–95 long and 105–117 wide, with cribrum, pair of glands gv3 at antero-lateral margins; with para-anal and post-anal setae. Opisthonotal shield curved on the ventral side, not connected with anal shield; with 3–4 setae on sclerotised ornamented cuticle and eight marginal curved pilose setae on each side.

Legs. Lengths: I 465–490, II 390–415, III 390–415, IV 460–485. 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, 700 m a.s.l., Abies sibirica - Pinus sibirica taiga, in litter, 14 August 2014, coll., L.V. Petrozhitskaya. Paratypes: 6 females, 5 males, same data as holotype; 2 males, same geographical data, 1000 m a.s.l., tall grass alpine meadow with sparse trees of Abies sibirica , in soil, 13 August 2014, coll. L. V. Petrozhitskaya; 4 females, 4 males, Baikal region, environs of Vydrino village, Khamar-Daban Ridge, 51 23’ N, 104 38’ E, 500 m a.s.l., direction to Taltsinskii Peak, Abies sibirica - Pinus sibirica taiga, in litter, 23 June 2021, coll. I.I. Marchenko; 11 females, 4 males, same geographical data, 700 m a.s.l., direction to Taltsinskii Peak, Abies sibirica - Pinus sibirica taiga, in litter, 26 June 2021, coll. I.I. Marchenko; 1 males, Chitinskaya Oblast (now—Zabaikalskii Krai), Kyra District, Sokhondinskii Nature Reserve, 49 48’ N, 111 12’ E, 1600 m a.s.l., cordon Lukovoe, Larix sibirica – Pinus sibirica taiga, in litter, 12 June 1991, coll. D. V. Logunov; 2 females, Krasnoyarskii Krai, Eastern Sayan Ridge, Natural Reserve “Stolby”, mountain taiga with Pinus sylvestris , Abies sibirica , Larix sibirica , in litter, 55 56’ N, 92 44’ E, 500 m a.s.l., 30 August, 21 September 1972, coll. T.S. Sukhova.

Other material: 4 protonymphs, Russia, Baikal Region, environs of Tankhoi village, Baikal Natural Biosphere Reserve, Khamar-Daban Ridge, 51 33’ N, 105 09’ E, 700 m a.s.l., Abies sibirica - Pinus sibirica taiga, in litter, 14 August 2014, coll., L. V. Petrozhitskaya; 2 protonymphs, same geographical data, 1000 m a.s.l., tall grass alpine meadow with sparse trees of Abies sibirica , 13 August 2014, coll. Petrozhitskaya; 4 deutonymphs, 9 protonymphs, Baikal Region, environs of Vydrino village, Khamar-Daban Ridge, 51 23’ N, 104 38’ E, 500 m a.s.l., Abies sibirica - Pinus sibirica taiga, in litter, 23 June 2021, coll. I.I. Marchenko; 2 deutonymphs, 3 protonymphs, same geographical data, 700 m a.s.l., direction to Taltsinskii Peak, Abies sibirica - Pinus sibirica taiga, in litter, 26 June 2021, coll. I.I. Marchenko.

Etymology. The specific name dracunculus is Latin, little dragon: dracon (dragon) + unculus (little). This name associated with the structural features of a pair of massive subcapitular denticles in male in form of fangs like in mythical dragons.

Remarks.Adults of Baikalozercon dracunculus differs from B. irbis as follows—first species with ornamentation of central part of opisthonotal shield in the form of a network of small tubercles; pair of posteriomost marginal setae in R -row of opisthonotal shield like other R -setae in shape and length. Female of B. dracunculus with axe-form genital shield. Movable digit of chelicera in both sexes of B. dracunculus with three teeth. Males have significant differences in sternal area, so B. dracunculus without first sternal platelet, second platelet in form of a narrow strip, fourth sternal platelet (or post-genital) triangular in shape with elongated apex. Male subcapitulum of B. dracunculus with pair of massive denticles between h2–h3 and pc setae. Male legs II of B. dracunculus with sexual dimorphism in form of some modified setae: three enlarged femur setae— al1, al2 and av1; one genu seta al1 and one tibia seta al1.

Figures

FIGURE 1. Baikalozercon dracunculus sp. nov., female. Dorsal idiosoma; a—dorsal setae at higher magnification.

FIGURES 2–4. Baikalozercon dracunculus sp. nov., female. 2. Ventral idiosoma; 3. Tritosternum; 4. Region of third sternal and genital shields.

FIGURES 5–10. Baikalozercon dracunculus sp. nov., SEM photos. 5–8. Female, 9–10. Male. 5. Dorsal idiosoma; 6. Ventral idiosoma; 7 a, b. Sterno-genital region; 8. Gnathosoma and tritosternum; 9. Ventral idiosoma; 10. Subcapitulum and tritosternum, a—subcapitular denticles.

FIGURES 11–14. Baikalozercon dracunculus sp. nov., female, habitus photos. 11. Dorsal idiosoma; 12. Ventral idiosoma; 13. Sterno-genital region; 14. Second and third sternal platelets.

FIGURES 15–19. Baikalozercon dracunculus sp. nov., female. 15. Chelicera; 16. Fixed digit; 17. Epistome; 18. Gnathosoma with palp; 19. Gnathosoma with internal malae and corniculi.

FIGURES 20–23. Baikalozercon dracunculus sp. nov., female. 20. Leg I; 21. Leg II; 22. Leg III; 23. Leg IV.

FIGURES 24–27. Baikalozercon dracunculus sp. nov., male. 24. Ventral idiosoma; 25. Sterno-genital region; 26. Chelicera; 27. Gnathosoma.

FIGURES 28–30. Baikalozercon dracunculus sp. nov. 28–29. Female, male. 28. Tarsus I: a—ventral side, b—dorsal side; 29. Pretarsus III; 30. Male, leg II.

FIGURES 31–36. Baikalozercon dracunculus sp. nov., male, habitus photos. 31. Ventral idiosoma; 32. Leg II; 33. Post-genital platelet; 34. Sterno-genital region; 35–36. Gnathosoma.

FIGURES 37–40. 37. Baikalozercon dracunculus sp. nov., deutonymph, dorsal idiosoma; 38. Baikalozercon dracunculus sp. nov, deutonymph, ventral idiosoma. 39 Baikalozercon dracunculus sp. nov., protonymph, dorsal idiosoma; 40. Baikalozercon dracunculus sp. nov., protonymph, ventral idiosoma.