Orbiculobates bicornutus, Ermilov, 2023

Ermilov, Sergey G., 2023, Taxonomic contribution to the knowledge of the oribatid mite genus Orbiculobates (Acari, Oribatida, Plasmobatidae), Persian Journal of Acarology 12 (3), pp. 393-402 : 394-399

Orbiculobates bicornutus sp. nov. ( Figs. 1–14 )

http://zoobank.org/ urn:lsid:zoobank.org:act:12B42200-E81F-4C51-A466-D894860AB413

Type material

Holotype (female) and seven paratypes (four males and three females): Mexico, 20° 33' N, 87° 13' W, Quintana Roo, Municipio de Solidaridad, vicinities of Playa del Carmen, leaf litter under trees and bushes in secondary semi-evergreen tropical forest (data and collector unknown; collection of the Tyumen State University Museum of Zoology , Tyumen, Russia).

Type deposition

The holotype is deposited in the collection of the Senckenberg Museum of Natural History, Görlitz, Germany; seven paratypes are deposited in the collection of the Tyumen State University Museum of Zoology , Tyumen, Russia . All specimens are preserved in ethanol with a drop of glycerol.

Diagnosis Body length: 360–390. Rostral seta slightly phylliform (dilated in medial part); lamellar seta setiform; interlamellar seta bifurcate; bothridial seta long, bacilliform, with small, slightly visible lanceolate head. Tritonymphal exuvial scalp with anterior long band-like protrusion. Notogaster flattened, with U-shaped depression. Seven pairs of notogastral setae; h 1 and p 1 located close to each other on one tubercle. Opisthonotal gland opening slightly protruding. Epimeral region with two strong transverse opposite horn-like structures. Epimeral setal formula: 3–1–2–2. Propodolateral apophysis tubercle-like. Lateral side of body with horn-like structure directed backwards. Seven pairs of genital setae present; aggenital setae absent. Anal plate with longitudinal carina. Leg trochanters I, II and femora I–IV with triangular posterior process.

Description

Measurements – Body length: 375 (holotype), 360–390 (paratypes); notogaster width: 255 (holotype), 240–270 (paratypes). No distinct differences between males and females in body size.

Integument – Body color brown. Surface nearly smooth, covered by thick layer cerotegument including dense microgranules; cerotegument partially forming tuberculate, ridge-like and blockyshaped structures. Exuvial scalps reticulate.

anterior view; 4. Right lateral view.

Prodorsum – Rostrum incised medially. Rostral bulge large, with deep, very narrow, longitudinal furrow. Dorsolateral carina well-developed. Rostral seta (37–45) slightly phylliform (dilated in medial part), with attenuate tip, slightly barbed, located on large tubercle; lamellar seta (7–9) setiform, thin, slightly roughened, located on small tubercle; interlamellar seta (22–26) bifurcate, slightly barbed, located on large tubercle; bothridial seta (120–124) bacilliform, with small, slightly visible lanceolate head, roughened; ventral scale of bothridium excavated ( Fig. 4 ); exobothridial seta not observed.

Notogaster – Tritonymphal exuvial scalp with anterior long band-like protrusion ( Fig. 3 ). Notogaster flattened, with U-shaped depression. Seven pairs of notogastral setae present; all setae (h 1, p 1: 7–9; c, h 2, h 3, p 2, p 3: 5–7) setiform, thin, slightly roughened, located on small tubercles; h 1 and p 1 located close to each other, on one tubercle. Opisthonotal gland opening slightly protruding. All lyrifissures distinct.

Gnathosoma – Subcapitulum anarthric; size: 105–109 × 67–71; subcapitular setae (a: 30–34; m: 13–15; h: 20–22) setiform, slightly roughened; m thinnest; h located on small tubercle; adoral setae absent. Palp length: 67–71; formula: 0–2–1–3–8(+ω); solenidion long, bacilliform, slightly curved; postpalpal seta (6) spiniform, smooth. Chelicera length: 101–109; both cheliceral setae absent.

Epimeral and lateral podosomal regions – Medial region (anteriorly to genital aperture) with two strong transverse opposite horn-like structures located under oval depression. Epimeral setal formula: 3–1–2–2; setae (3a: 7–9; others: 5–7) setiform, thin, slightly roughened; 1b and 1c located on small tubercles; 3a and 3b located in basal part of horn-like structure. Propodolateral apophysis tubercle-like. Lateral side of body with horn-like structure directed backwards.

Anogenital region – Seven pairs of genital, two pairs of anal and three pairs of adanal setae (7–9) setiform, thin, slightly roughened; both aggenital setae absent. Anal plate with longitudinal carina. Adanal lyrifissure distinct.

Legs – Claw of each leg thick, with strong tooth ventrobasally, slightly barbed on dorsal side. Trochanters I, II and femora I–IV with triangular posterior process. Formulas of leg setation and solenidia: I (1–5–5–5–20) [1–2–2], II (1–5–4–4–14) [1–1–2], III (2–3–3–3–13) [0–1–0], IV (1–3– 3–3–12) [0–1–0]; homology of setae and solenidia indicated in Table 1. Solenidia ω 1, ω 2 on tarsi I, II medium-sized, bacilliform; φ 1 on tibia I very long, subflagellate; φ 2 on tibia I medium-sized, setiform; other solenidia short, slightly swollen distally.

Comparison

In having bifurcate interlamellar seta and bacilliform bothridial seta, Orbiculobates bicornutus sp. nov. is similar to O. orbiculus but differs from the latter by: the form of notogaster (flattened versus convex in O. orbiculus ); the morphology of rostral seta (dilated in median part versus setiform in O. orbiculus ); the slightly protruding opisthonotal gland opening (versus strongly protruding, tubular in O. orbiculus ); the presence of a pair horn-like structure in the epimeral region and a horn-like structure on the lateral side of body (versus absence in O. orbiculus ); and the absence of spines on anterior margin of the notogaster (versus presence in O. orbiculus ).

Etymology

The species name bicornutus (“horn” in Latin) refers to the presence of two horn- like structures in the epimeral region.

Figures

Figures 1–4. Orbiculobates bicornutus sp. nov. (adult) SEM micrographs – 1. Dorsal view; 2. Ventral view; 3. Dorso-

Figure 5. Orbiculobates bicornutus sp. nov. (adult) – Dorsal view (exuvial scalps not shown).

Figure 6. Orbiculobates bicornutus sp. nov. (adult) – Ventral view (gnathosoma and legs except trochanters not shown).

Figures 7–10. Orbiculobates bicornutus sp. nov. (adult) – 7. Right lateral view (exuvial scalps, gnathosoma and legs not shown); 8. Subcapitulum, ventral view; 9. Palp, left, paraxial view; 10. Chelicera, left, paraxial view.

Figures 11–14. Orbiculobates bicornutus sp. nov. (adult) – 11. Leg I (trochanter not shown), right, antiaxial view; 12. Leg II (trochanter and tarsus not shown), right, antiaxial view; 13. Leg III (trochanter not shown), left, antiaxial view; 14. Leg IV, left, antiaxial view.