Tritegeus tridactylus ( Woolley & Higgins, 1963 ), 2024

Ermilov, Sergey G., 2024, Taxonomic contribution to knowledge of the oribatid mite genus Tritegeus (Acari, Oribatida, Cepheusidae), Zootaxa 5556 (1), pp. 37-50 : 39-43

Tritegeus tridactylus ( Woolley & Higgins, 1963)

( Figs 1 , 2 )

Material. Two specimens (two females): USA, Utah (G.F. Knowlton). The specimens were compared to the type material for a definite identification .

All specimens (preserved in 70% solution of ethanol with a drop of glycerol) are deposited in the collection of the University of Tyumen, Museum of Zoology , Tyumen, Russia .

Supplementary description of adult. Measurements. Body length: 765, 780; notogastral width: 570, 600.

Integument ( Figs 1A–C ). Body color dark brown. Body and legs partially covered by thick gel-like layer of cerotegument, including dense microtubercles, sparsely located on notogaster and in marginal part of ventral plate. Surface with dense microtuberculate sculpturing; lamella, humeral process, pedotecta I, II, podosomal region, discidium, lateral part of prodorsum, lateral part of epimere I partially foveate; medioposterior part of notogaster (between setae lm, lp, h 2 h 3) with sparse, indistinct foveolae; lateral side of body between humeral process and acetabula II, III with dense large tubercles; additionally, podosomal region and dorsal part of pedotectum I partially rugose.

Prodorsum ( Figs 1A–C ). Rostrum pointed, observable in dorsal aspect. Rostral region with bulge. Outer tooth of lamellar cusp well developed. Translamella absent but medial parts of lamellae slightly protruding anteromedially, creating an illusion of the presence of a thin translamella. Tutorium with numerous teeth and small scales dorsally. Rostral seta (90–94) setiform, with short, flexible tip, barbed; lamellar seta (105–109) with thickened mediobasal part and flagellate distal part, barbed; interlamellar seta (217–225) thickened, acuminate, distinctly barbed; bothridial seta (124–131) with longer stalk and short expanded head bearing numerous strong spines; exobothridial seta represented by alveolus (may be broken).

Notogaster ( Figs 1A–D ). Centrodorsal region bordered by U-shaped thickening bearing dorsal notogastral setae. Setae h 1 (60–75) and p 1 (64–75) thickened, acuminate, heavily barbed; other setae (c, la, lm: 157–169; lp, h 2, h 3: 201–225; p 2, p 3: 134–146) thickened, acuminate, distinctly barbed. Opisthonotal gland opening and all lyrifissures observable.

Gnathosoma ( Figs 2A–C ). Subcapitulum size: 165–172 × 116; subcapitular setae (a: 34; m: 15–19; h: 45–52) setiform, roughened; m thinnest; both adoral setae (15–19) setiform, smooth. Palp length: 101–109; postpalpal seta (11–13) spiniform, truncate, roughened. Chelicera length: 172–184; setae (cha: 43–45; chb: 28–30) setiform, barbed.

Epimeral and podosomal regions ( Figs 1B, C ). All epimeral setae (3c, 4c: 67–75; 1b: 45–52; 3b, 4a, 4b: 34–37; 1a, 1c, 2a, 3a: 22) setiform, roughened. Discidium large, elongate triangular, rounded distally.

Anogenital region ( Figs 1B–D ). Genital (g 1, g 2: 34–37; g 3: 26–30; others: 19–22) and aggenital (26–30) setae setiform, roughened; both anal setae (22–26) setiform, barbed; all adanal setae (37–41) slightly thickened, acuminate, comparatively heavily barbed. Adanal lyrifissure distinct, oblique.

Legs ( Figs 2D–G ). All tarsi with three claws; median claw thicker than lateral claws; all claws slightly barbed on dorsal side. Trochanters III and IV with long tooth dorsoanteriorly. Formulas of leg setation and solenidia: I (1- 5-3-4-20) [1-2-2], II (1-4-3-4-16) [1-1-2], III (2-3-2-3-15) [1-1-0], IV (1-2-3-3-12) [0-1-0]; homology of setae and solenidia indicated in Table 1; comparison of morphology of some setae between T. tridactylus , T. luissantossubiasi and T. mitratus presented in Table 2.

Note: Roman letters refer to normal setae; Greek letters to solenidia (except ɛ = famulus); single quotation mark (’) marks setae on the anterior and double quotation mark (”) setae on the posterior side of a given leg segment; parentheses refer to a pair of setae.

Remarks. Based on the original description ( Woolley & Higgins, 1963) and the data presented here, the following diagnostic traits for T. tridactylus are proposed:

Adult. Body size: 720–780. Medioposterior part of notogaster (between setae la, lp, h 2 h 3) with sparse, indistinct foveolae. Rostrum pointed. Lamellar cusps separated medially; translamella absent. Rostral seta setiform, with short, flexible tip, barbed; lamellar seta with thickened mediobasal part and flagellate distal part, with slight and sparse barbs; interlamellar seta thickened, acuminate, distinctly barbed; in˃le˃ro; bothridial seta with shortly expanded head bearing numerous strong spines. Centrodorsal region of notogaster bordered by U-shaped thickening. Notogastral setae h 1 and p 1 comparatively short, slightly different in length, thickened, acuminate, heavily barbed; other setae long, thickened, acuminate, distinctly barbed; lp, h 2, h 3 ˃c, la, lm. All leg tarsi heterotridactylous; trochanters III and IV with long tooth dorsoanteriorly; seta pv’ on Ta I, II barbed (without ventral sparse spines); l” and v’ on Ti I, II thorn-like; l” on Ge I, II setiform.

Figures

FIGURE 1. Tritegeus tridactylus (Woolley & Higgins, 1963), adult: A—dorsal view (legs not illustrated); B—ventral view (legs not illustrated); C—lateral view (gnathosoma and legs not illustrated); D—posterior view (part of left half not illustrated). Scale bar 200 μm.

FIGURE 2. Tritegeus tridactylus (Woolley & Higgins, 1963), adult: A—subcapitulum, ventral view; B—palp, right, antiaxial view; C—chelicera, right, antiaxial view; D—leg I, right, antiaxial view; E—leg II, right, antiaxial view; F—leg III, left, antiaxial view; G—leg IV, left, antiaxial view. Scale bars 50 μm (A, C–G), 20 μm (B).