Ontogenetic instars of the oribatid mite Tyrphonothrus digeluensis sp. nov. (Acari Oribatida, Malaconothridae) from Ethiopia Author Ermilov, Sergey G. Tyumen State University, Institute of Environmental and Agricultural Biology (X-BIO), Tyumen, Russia. Author Rybalov, Leonid B. Institute of Ecology and Evolution, Russian Academy of Sciences, Laboratory of Soil Zoology and General Entomology, Moscow, Russia. text Zootaxa 2023 2023-08-04 5324 1 24 36 http://dx.doi.org/10.11646/zootaxa.5324.1.5 journal article 10.11646/zootaxa.5324.1.5 1175-5326 8213864 5FCE2373-0415-4B1A-8C18-6786956E58A9 Tyrphonothrus digeluensis sp. nov. Diagnosis. Adult . Body length: 705–735. Rostral, lamellar and interlamellar setae long, subflagellate, smooth ( in > le > ro ); exobothridial seta ex 1 short, setiform, barbed. Medioposterior part of notogaster slightly widening. Longitudinal notogastral ridges present. Notogastral setae e 2 , h 1 , h 2 , p 2 long, subflagellate, smooth; others medium-sized, setiform, barbed; p 2 and p 3 distant from each other. Epimeral setae 1a , 1c , 2a , 3a very short, penicillate; others short, setiform, barbed. Six pairs of genital setae setiform, slightly roughened; anal and adanal setae setiform, barbed. Heterotridactylous. Juvenile instars . Gastronotum and anogenital region typically folded. Rostral, lamellar and interlamellar setae setiform, smooth ( in > le > ro ); exobothridial seta ex 1 setiform, barbed. Notogastral setae e 2 , h 1 , h 2 , p 2 subflagellate, smooth; other setae setiform, barbed. Lateral epimeral setae comparatively short, setiform, barbed. Genital formula for nymphal instars: 1-2-4[5]. Description of adult. Measurements . Body length: 735 ( holotype , female), 705–735 ( 37 female paratypes ); notogastral width: 405 ( holotype ), 375–420 ( 37 female paratypes ). Integument ( Figs 2A, C ). Body color light brown. Body surface densely porose and covered by gel-like and sparsely microtuberculate cerotegument; lateral part of notogaster (medial to setae cp , e 2 , f 2 ) with longitudinal striate cerotegumental band. Prodorsum ( Figs 2A, C ). Rostrum broadly rounded. Lateral carina well-developed (distinctly visible in dorsal view). Rostral (64–79), lamellar (64–79) and interlamellar (123–131) setae subflagellate, smooth; exobothridial seta ex 1 (15–19) setiform, barbed. Notogaster ( Figs 2A, C ). Anterior margin slightly convex. Medioposterior part of notogaster slightly widening. Four longitudinal ridges present but often poorly observed in dorsal aspect (versus distinctly visible in dorsolateral aspect). Notogastral setae e 2 , h 1 , h 2 , p 2 (90–105) subflagellate, smooth; others (41–56) setiform, barbed; p 3 located anteriorly to p 2 , both distant from each other; alveolus of f 2 visible. Opisthonotal gland opening and all notogastral lyrifissures distinct in transmitted light. Gnathosoma ( Figs 3A–C ). Subcapitulum size: 124–127 × 105–112; subcapitular setae ( a : 15–19; m : 11–15; h : 13–15) setiform, barbed; three pairs of adoral setae (9–11) filiform, smooth. Palp (length: 142–150) formula: 0-0- 1-3-9(+ω); solenidion bacilliform; postpalpal seta (7) spiniform, roughened. Chelicera (length: 109–112) with two setae: cha (4) spiniform, barbed; chb (19–22) falciform, dorsally barbed. Epimeral region ( Fig. 2B, C ). Epimeral setal formula: 3-1-3-3(rarely 4); setae 1a , 1c , 2a , 3a (5–7) penicillate; others ( 1b , 3b , 3c , 4a , 4c : 15–19; 4b : 9–11) setiform, barbed. Anogenital region ( Figs 2B, C ). Six pairs of genital setae (52–64) setiform, slightly roughened, directed backwards; anal and adanal setae (26–34) setiform, barbed. Anal and adanal lyrifissures distinct. Legs ( Figs 4A–D ). Heterotridactylous; median claw thicker and shorter than lateral claws; all claws dorsally slightly barbed. Formulas of leg setation and solenidia: I (1-5-4-4-11) [1-1-3], II (1-5-3-4-10) [1-1-1], III (2-3-1-2- 10) [0-1-0], IV (1-2-1-2-10) [0-0-0]; homology of setae and solenidia indicated in Table 1 . Famulus of tarsus I short, spiniform; all solenidia rod-like, rounded apically. Description of juvenile instars. Measurements . Total length of larva: 315–330 (n=4), protonymph: 405–450 (n=5), deutonymph: 480–495 (n=4), tritonymph: 540–675 (n=8). Total width of larva: 150–165 (n=4), protonymph: 195–210 (n=5), deutonymph: 240–285 (n=4), tritonymph: 255–315 (n=8). Integument ( Figs 5A–C ; 6D ; 7A, B ; 8A, B ). Body color colorless to light yellowish. Body surface densely porose (especially well visible in epimeral region) and partially covered by gel-like and sparsely microtuberculate cerotegument; additionally, gastronotum, anogenital region and basal part of prodorsum folded. Prodorsum ( Figs 5A, C ; 6D ; 8A ). Relatively short, about 2/3 (in larva and protonymph) and 1/2 length (in deuto- and tritonymph) of gastronotic region. Rostrum broadly rounded. Lateral carina well-developed (distinctly visible in dorsal view). Rostral (LA: 34–37; PN: 41–45; DN: 49–52; TN: 64–75), lamellar (LA: 34–37; PN: 41–45; DN: 49–52; TN: 64–75) and interlamellar (LA: 67–75; PN: 79–90; DN: 101–109; TN: 112–131) setae setiform, smooth; exobothridial seta ex 1 (LA: 11; PN: 15; DN: 15–19; TN: 17–19) setiform, barbed. Gastronotic region ( Figs 5A, C ; 6D ; 8A ). Posteriorly rounded. Length of gastronotic setae: LA: e 2 , h 1 : 45–49, h 2 : 30–34, others: 19–22; PN: e 2 , h 1 , h 2 : 52–60, others: 22–26; DN: e 2 , h 1 , h 2 : 79–86, p 2 : 39–41, others: 26–30; TN: e 2 , h 1 , h 2 : 82–94, p 2 : 49–64, others: 34–37. Setae e 2 , h 1 , h 2 (except LA) and p 2 (except PN) subflagellate, smooth; others setiform, barbed; alveolus of f 2 not visible. Opisthonotal gland opening and all cupules distinct in transmitted light. Gnathosoma . Generally, similar to adult, except sizes and two pairs of adoral setae in larva. Subcapitulum size: LA: 60 × 49; PN: 75 × 60; DN: 86 × 75; TN: 94 × 82; length of subcapitular setae: LA and PN: 11; DN and TN: 15; length of adoral setae: LA and PN: 5; DN: 7; TN: 7–9. Palp length: LA: 41; PN: 45; DN: 49; TN: 52; length of postpalpal seta: LA, PN and DN: 4; TN: 7. Chelicera length: LA: 60; PN: 75; DN: 86; TN: 94; length of cha : LA and PN: 2; DN and TN: 4; length of chb : LA: 9; PN: 11; DN: 15; TN: 19. FIGURE 2. Tyrphonothrus digeluensis sp. nov. , adult: A—dorsal view; B—ventral view (gnathosoma and legs except trochanters not shown); C— right lateral view (gnathosoma and legs not shown). Scale bar 100 μm. Epimeral region ( Figs 5B, C ; 7A, B ; 8B ). Setal formulas for epimeres: larva: 3-1-2 ( 1c as typical scale covering Claparède’s organ); protonymph 3-1-2-1; deutonymph 3-1-2-2, tritonymph 3-1-2[rarely 3]-3. Length of setae: LA and PN: 1b , 3b : 11, others: 4; DN: 1b , 3b , 4a : 11–15, 4a : 7, others: 4; TN: 1b , 3b , 3c (if present), 4a , 4c : 15–17, 4a : 9–11, others: 4–6; setae 1a , 1c , 2a , 3a , and 4a (in larva) spiniform, roughened, others setiform, barbed. FIGURE 3. Tyrphonothrus digeluensis sp. nov. , adult: A—subcapitulum, ventral view; B—chelicera, right, antiaxial view; C—palp, right, antiaxial view. Scale bars 20 μm. Anogenital region ( Figs 5B, C ; 7A, B ; 8B ). Ontogeny of genital (PN: 22–26; DN: 26–30; TN: 37–45), anal (TN: 26–30) and adanal (DN: 19; TN: 26–30) setal formulas, proto- to tritonymphs: 1-2-4[rarely 5], 0-0-1, 0-3-3, respectively; all setae setiform, genital setae slightly roughened, anal and adanal setae barbed. Anal and adanal cupules distinct. Legs ( Figs 6A–C ). Claw of each leg dorsally slightly barbed. Formulas of leg setation and solenidia: larva I (0-2-3-4-11) [1-1-1], II (0-2-2-3-10) [1-1-1], III (0-2-1-2-10) [0-1-0]; protonymph I (0-2-3-4-11) [1-1-2], II (0-2-2- 3-10) [1-1-1], III (1-2-1-2-10) [0-1-0], IV (0-0-0-0-7) [0-0-0]; deutonymph I (1-4-3-4-11) [1-1-2], II (1-4-2-4-10) [1-1-1], III (2-2-1-2-10) [0-1-0], IV (0-1-1-2-10) [0-0-0]; tritonymph I (1-5-4-4-11) [1-1-3], II (1-5-3-4-10) [1-1-1], III (2-2[rarely 3]-1-2-10) [0-1-0], IV (1-1[rarely 2]-1-2-10) [0-0-0]; homologies of setae and solenidia indicated in Table 1 . Type material. Holotype (female), 37 paratypes (all females) and 21 juvenile instars ( four larvae , five protonymphs, four deutonymphs, eight tritonymphs): Ethiopia , Oromia Region , Arsi Zone , Arsi Mountains National Park , mountain near Digelu , 07º49′23.7′′N , 039º23′32.9′′E , 3882 m a.s.l. , mosses on the swamp at the top of the mountain, 28.11.2021 ( L.B. Rybalov ). Type deposition. The holotype is deposited in the collection of the Senckenberg Museum of Natural History, Görlitz, Germany ; 37 paratypes and juvenile instars are deposited in the collection of the Tyumen State University Museum of Zoology , Tyumen , Russia . All specimens are preserved in 70% solution of ethanol with a drop of glycerol. Etymology. The species name digeluensis refers to the Digelu town, near which the new species was collected. Differential diagnosis. Adult of Tyrphonothrus digeluensis sp. nov. is morphologically most similar to Tyrphonothrus obesus ( Yamamoto & Coetzee, 2004 ) and T. rectus ( Yamamoto & Coetzee, 2004 ) from South Africa in having large body size, smooth rostral, lamellar and interlamellar setae, slightly widening medioposterior part of notogaster, different length of notogastral setae, six pairs of genital setae, two pairs of longitudinal notogastral ridges, tridactylous legs, and in the absence of foveolate ornamentation on the notogaster. However, the new species differ from both by the barbed (versus smooth) notogastral setae c 1 , c 2 , c 3 , cp , d 1 , d 2 , e 1 , f 2 , p 1 , p 3 and exobothridial seta ex 1 , and the slightly developed (versus distinctly) notogastral ridges. Also, T. obesus has smooth (versus barbed) epimeral and anoadanal setae; T. rectus has heavily barbed (versus barbed) epimeral setae and subcapitular seta h , and smooth (versus barbed) anal and adanal setae.