Piribelba piriformis ( Mihelčič 1964 )

Miko, Ladislav, Kolesnikov, Vasiliy B., Ermilov, Sergey G. & Klimov, Pavel B., 2022, Taxonomy of European Damaeidae (Acari, Oribatida) XI. European species of the genus Piribelba Miko 2021: redescriptions of P. rossica (Bulanova-Zachvatkina 1957) and P. piriformis (Mihelčič, 1964) using morphology and DNA sequence data, Zootaxa 5187 (1), pp. 169-210 : 193-206

Piribelba piriformis ( Mihelčič 1964)

Belba piriformis Mihelčič 1964: 376 , Figs. 10–12 (holotype not designated, distribution provided by author: Austria: Carinthia, East and South Tyrol).

The species is very similar to P. rossica , but can be separated using morphology (see key to species below) and DNA sequence data: 12.0% uncorrected p-distances and 13.3% Kimura two-parameter distances (K2P). The text below, therefore focuses on measurements and diagnostic character states, without necessarily repeating all character states that are identical with P. rossica .

Adult ( Figs 21–24 , 26–29 )

Measurements. Average total body length 630 (n=8: 605–665; type 730); ventral body length 585 (n=8: 571– 605; material of Mihelčič: n=8, 537–604; type 678); length of notogaster 425 (n=8: 406–440); maximum notogaster width 355 (n=8: 345–385), maximum prodorsum width 245 (n=8: 220–270). Specimens from Slovakia are slightly more robust, with roughly same average length of body having slightly broader notogaster (363).

Integument ( Figs 23 , 24E, H , 29A ). Dark reddish-brown, whole body surface under cerotegument densely microtuberculate. Adults carrying nymphal exuvial scalps covered by thick layer of organic and inorganic debris of characteristic shape (on top of notogaster, shifted forward and not prolonged posteriad, compared to Belba species, Fig. 29C ). Most of the body covered by characteristic reticular cerotegument, including proximal segments of legs, lateral, sejugal, partly ventral parts of the body and more distal segments of legs covered by globular, columnar and amorphous cerotegument.

Prodorsum ( Figs 26A, E , 28A, D , 29A ). Rostrum broadly rounded, propodolateral apophyses absent. Dorsosejugal areas with narrow, triangular to almost linear short ridges in place of tubercles Ba (sejugal costulae, scos), in dorsal view partly over-covered by anterior edge of notogaster and sometimes difficult to observe, in some specimens doubled, with additional second, smaller, parallel ridge present laterally, prodorsal tubercles absent. Distinct prodorsal grooves present. Anterobothridial ridges (abr) almost straight, short, distinct. Prodorsal costulae (cos) present on lateral prodorsum above legs I insertions, slightly curved, usually distinct but in some populations ( Slovakia, Sivec) not well observable. Parastigmatic apophyses differently shaped, only Sa usually visible in dorsal view, relatively long, narrow, with conspicuously pointed tips, often curved slightly lateroanterad; Sp much smaller, tubercular. Rostral setae (ro) of medium length, 62–86, thin, smooth. Lamellar setae (le) longer and distinctly thicker than rostral ones, 92–106, inserted on small tubercles or cuticular thickenings, from dorsal view with more or less distinct, sometimes dark small spines or scales on majority of its length. In different aspect (mediodorsal view) they appear flattened, proximally broadened, with spines visible only partly at external curvature ( Figs 21C , 23E , 24D , 26C , 28D , 29B ). In Slovak population from Sivec, lamellar setae are flattened, broadened proximally, with more transparent lateral parts ( Fig. 26E ), with spines and scales more transparent, present on dorsal surface of setae and more difficult to observe, easily to be interchanged with covering layer of granular cerotegument. Interlamellar setae (in, 36–52) erect, straight, thick, bluntly pointed, in lateral view appearing slightly flattened ( Figs 22C , 26D , 28C ). Exobothridial setae (ex, 48–58), strong, regularly curved, attenuated at ends ( Figs 21C , 26D ). Bothridial setae (bs, 170–278) long, setiform, distally with flagellate part which may be present or broken off, proximal part may be covered with fine layer of microgranular cerotegument ( Fig 26D , 29A, F ).

Notogaster ( Figs 21A, B , 23A , 26A, E , 28A , 29A, F ). Notogaster elongated, ovoid, anteriorly narrowed, in lateral view however almost semicircular. Anterior margin of notogaster covering dorsosejugal areas in dorsal view. Notogastral setae thin, setiform, curved, distally attenuated, covered by layer of cerotegument proximally. Posterior setae more strongly curved or even curly distally, sometimes with one or two small, but distinct spines on external side of curvature. Setae medium long, their length reaching or almost reaching distance to following setal insertions, setae c 1 inserted closer to each other than other setae, distance c 1 – c 1 about twice shorter than c 2 – c 2 and shorter than c 1 – c 2. Setae of rows l slightly shorter (54–84) than rows c (60–89), h (69–91) and posterior setae (row p shorter but not observable in dorsal view).

Gnathosoma ( Figs 26B, F , 28D , 29F ). Similar to that of P. rossica , but with apparent U-shaped less-sclerotised area on mentum ( Figs 26B , 28B ). This character is less visible on specimens from Slovak population from Sivec ( Fig 26F ). Palps ( Figs 27F , 28D ) with standard setation, identical to P. rossica .

Epimeral and lateral podosomal regions ( Figs 21A , 23B–D , 26B, F , 28B , 29F ). Tecta of podocephalic fossa with short but distinct posterolateral angles, slightly projecting as short triangular projections ( Fig. 26B ). Without ventral tubercles, discidia reduced (absent or almost absent). Epimeral setal formula variable: 3-1-3or4-3or4; most of setae inserted on small tubercles or cuticular thickenings, setae rather strong, setiform or slightly flattened, attenuated towards tip ( Fig. 21A, D ). In Slovak population from Sivec, epimeral setae more distinctly flattened, with transparent margins ( Figs 26F, H , 29F ).

Anogenital region ( Figs 1B–F , 5A , 6B, C , 9B ). Anal aperture slightly narrower than genital aperture. Standard set of anogenital setae present, aggenital and adanal setae quite strongly developed, setiform, attenuated towards tip ( Fig. 21D ). Genital and anal setae thinner and slightly shorter, smooth, g 1 usually significantly longer than other genital setae ( Figs 21A , 22C , 28J ), in Slovak population from Sivec length of genital setae subequal ( Figs 26F, G , 29F ).

Legs ( Figs 22A, B, E , 23F , 24B–G , 27 , 28F–I, D–G ). All legs generally of the same form and size as in P. rossica (for lengths of leg segment see Table 3). Setae strong and distally attenuated, serrated and/or covered by spines, on proximal segments curved and dark, on distal segments (tibiae, tarsi) ventral and lateral setae finer, straight, and more transparent. Setae generally thinner and more pointed on legs I, II than on legs III, IV, where they are stronger, more flattened and more distinctly serrated (with distinct dark spinuli, scales or barbs stronger on external curvature of setae). Setae d of genua and tibiae of legs III, IV, and sometimes also on femora III, IV broadened, blunt. Specimens from Slovak population from Sivec have dorsal setae of femora III, IV, genua IV and tibiae IV less coloured, with transparent serrated margins and darker thin “core”, serrated on both sides ( Figs 27D , 29F, G ). Formulas of leg setation and solenidia same as in rossica : I (1-7-4-4-20) [1-2-2], II (1-7-4-5-17) [1-1-2], III (2-5-3-4-17) [1-1-0], IV (2-5-3-4-14) [0-1-0]; however, three setae on trochanters III were observed in one case instead of two ( Fig. 27E ). Slight difference can be observed on length of solenidia: solenidia of genua III, tibiae III (both slightly) and tibiae IV (distinctly) longer than companion setae d. However, only solenidia ϕ 1 of tibiae I, inserted on distinct apophyses, long and tactile, solenidia of tibiae IV fine, setiform, but much shorter than tibiae IV and only slightly exceeding its distal ends ( Fig 27C ).

Juvenile instars One deutonymph is available in slide D of Mihelčič ( Fig. 20D 4 ), observable only from lateral view.

Deutonymph ( Figs 22F , 25 )

Measurements. Total (maximum) body length 389, ventral body length 372; body width impossible to measure. All measurements for deutonymph should be taken as approximative, as the specimen is damaged, and some parts (such as distal parts of some setae, or whole setae bs) were difficult to observe and measure.

Integument ( Fig. 25A, B ). Body cuticle variably coloured, notogaster including anogenital region weakly sclerotized, white-coloured. Prodorsum, lateral parts of podosoma and legs with thicker cuticle, light reddish-brown. Body and legs smooth, covered with thin layer of granular cerotegument. Round or oval granules small (1.5–2.8). Prodorsal and gastronotic setae (excluding ro, le, bs) as in rossica , without cerotegument.

Prodorsum ( Figs 22F , 25A, B ). In lateral view with rather distinct prodorsal protuberances, visible straight fold or cuticular thickening above acetabula I in place of prodorsal costulae of adult. Bothridia ear-like, with elongated projections. Setae le (44) strong, barbed, setae ro finer, shorter, smooth. Interlamellar setae (18) strong, thorn-like, pointed, smooth. Exobothridial setae (19) subequal in length to in, rather strong, smooth, larger and thicker than in rossica . Bothridial setae (approx. 102) broken, very difficult to observe, long, setiform with attenuated distal part.

Gastronotum ( Figs 22F , 25B ) Gastronotic setae generally similar to rossica , appearing however generally slightly shorter and more barbed. Longer setae proximally darker, lm, lp, h 1, h 3 inserted on distinct apophyses. Setae of rows l and h (and probably also c 1, c 2 which were very difficult to observe) proximally distinctly barbed, distally flagellate, with very fine, sometimes highly curly ends. Lengths could be measured only approximately, as distal parts of some may be incomplete or broken and/or very curly, approximate measures as follows: c 2 (98), la (59), lm (56), lp (107), h 1 (180), h 2 (52), h 3 (70), p 1 (35). Setae c 3 much shorter (18), fine, smooth. Apertures of opisthonotal glands (gla) well visible, below setae lm. Cornicle (k) short, distally curly ( Fig. 22F ), positioned between setae la.

Legs ( Figs 22F , 25B, C ). Leg segments and claws similarly formed as in rossica , all legs shorter than body (legs: I—337, II—238, III—297, IV—351). Surface of femora I, trochanters and femora IV with distinct and dense punctuation (pores?) ( Fig. 22F ). Leg setae also with similar patterns to rossica , dorsal and lateral setae mostly very strong, darkly coloured, serrate or strongly barbed, ventral setae finer, on tarsi setiform, lightly coloured or transparent. Formulas of leg setation and solenidia identical to rossica : I (1-4-4-5-16) [1-2-2], II (1-4-4-4-13) [1-1- 2], III (2-3-3-4-13) [1-1-0], IV (1-2-2-3-12) [0-1-0]. Except of tibiae I and IV, solenidia of genua and tarsi difficult to observe, shorter than companion setae d, which is usually very strong, dark, distinctly serrate or barbed. Tibial solenidia φ of legs I long (over 120), tactile, solenidia φ of tibiae IV ( Fig. 25D ) much shorter (42), but clearly exceeding length of companion setae d (30). Dorsal setae of femora I (38) and genua I, and lateral setae of tibiae I (42) very strong, remarkably barbed (several rows of relatively long barbs or scales present), companion setae d on tibiae short, thin, minute but well observable. Setae ft ʺ (66) much stronger and longer than ft ʹ, proximally covered up to 2/3 of its length by layer of granular cerotegument ( Fig 25C ). Famulus of tarsi I emergent, quite fine, setiform. On legs II, lateral setae of tibiae strongly developed, long, setae ft ʺ again strong, long. Legs III with setae ev ʹ and setae d of femora, genua and tibiae very strong, curved, distinctly barbed, on genua and femora clearly overlooking the distal ends of their segments, setae ft ʺ again longer, on both sides with long hairs. Dorsal setae on femora, genua (21) and tibiae of legs IV developed similarly as on legs III, setae d on tibiae (30) particularly strong, with several rows of long spines/barbs. Setae ft ʺ (52) long, with several rows of long barbs on both sides ( Fig 25E ).

Remarks

Out of all studied P. piriformis specimens, mites collected from Sivec, Slovakia, in 1989 (two damaged specimens), show several remarkable differences, mentioned in the redescriptions above. The most conspicuous is the flattened lamellar setae with transparent lateral parts and irregular margins, and the broad, flat, partially transparent, curved dorsal setae on femora, genua and tibiae of leg IV ( Figs 26E–H , 27B, D , 29F–G ). The two specimens have also shorter and flattened epimeral setae, genital setae of subequal size (g 1 is not significantly longer than other ones), and these specimens seem to have also less developed prodorsal costulae. Given that the differences between rossica and piriformis are of similar rank or even more subtle, these specimens may represent a new species. On the other hand, the flattened lamellar setae were observed in some specimens from Austria; certain similarity also exists in the development of leg setae ( Fig. 28C ), although this similarity is intermediary between the typical piriformis and the Sivec specimens. At the same time, material collected in other locations of Slovakia ( Fig 29A, B ), not far from Sivec have a perfect match with the typical piriformis . While substantial genetic differences between rossica and piriformis were detected (see below), we could did not do molecular work for the Sivec specimens, so their status cannot be confirmed. We therefore propose to treat the Sivec material as a distinct morphotype “lanceata”, until its specific or subspecific status can be confirmed.

Figures

FIGURE 1. Piribelba rossica (Bulanova-Zachvatkina, 1957), adult from Kemerovo region: A—dorsal view (legs only partly drawn); B—ventral view (gnathosoma not shown, legs only partly drawn), C—lateral view (gnathosoma and legs not shown); D—right genital plate; E—left genital plates; F—left anal plate. Scale bar 100 μm.

FIGURE 4. Piribelba rossica (Bulanova-Zachvatkina, 1957), adultfrom Khabarovsk Krai, SEM micrograph:A, B—dorsolateral view; C—anterodorsal view; D—posterodorsal view. Scale bar 200 μm.

FIGURE 5. Piribelba rossica (Bulanova-Zachvatkina, 1957), adult from Khabarovsk Krai, SEM micrograph: A—ventral view; B—lateral view; C—gnathosoma, lateral view; D, E—cerotegument of notogaster; F—cerotegument of prodorsal region; G—femur, genua and tibia III, antiaxial view. Scale bars 200 μm (A, B), 50 μm (G), 20 μm (C, D), 5 μm (F), 2 μm (E).

FIGURE 6. Piribelba rossica (Bulanova-Zachvatkina, 1957), adult from Khabarovsk Krai, light microscope images:A—dorsal view; B—ventral view; C—lateral view; D—rostral and lamellar setae, dorsal view; E—exobothridial seta, lateral view; F— cerotegument of prodorsal region; G—prodorsum, part, dorsal view; anterior part of notogaster, dorsal view.

FIGURE 9. Piribelba rossica (Bulanova-Zachvatkina, 1957), adult from Novosibirsk (A–E) and Tuva (F–K) regions (from Bulanova-Zachvatkina collection), light microscope images:A, F—slides from the collection with type specimen; B—epimeral III–IV and anogenital plates, ventral view; C, D, I–K—notogastral setae; E—femur, genu and tibia I, antiaxial view; G— prodorsum, part, dorsal view; H—distal part of bothridial setae. Scale bars 100 μm (B, G), 50 μm (D–C, H–K).

FIGURE 10. Piribelba rossica (Bulanova-Zachvatkina, 1957), larva from Kemerovo region: A —dorsal view (legs only partly drawn); B—ventral view (gnathosoma not shown, legs only partly drawn), C—lateral view (gnathosoma and legs only partly drawn). Scale bar 100 μm.

FIGURE 11. Piribelba rossica (Bulanova-Zachvatkina, 1957), larva from Kemerovo region: A—leg I, left, antiaxial view; B—tarsus I, left, dorsal view; C—leg II, left, antiaxial view; D—leg IV, left, antiaxial view; E—genu IV, right, dorsal view. Scale bar 100 μm.

FIGURE 12. Piribelba rossica (Bulanova-Zachvatkina, 1957), protonymph from Kemerovo region:A—dorsal view (legs only partly drawn); B—ventral view (gnathosoma not shown, legs only partly drawn), C—lateral view (gnathosoma and legs only partly drawn). Scale bar 100 μm.

FIGURE 20. Piribelba piriformis (Mihelčič, 1964), collection of Mihelčič. A–E (left side) —original slides with labels of author; A1–D5—adult specimens observed in slides, with measured total length, single specimen in slide B designated as lectotype (B1), only juvenile instar (deutonymph) placed near specimen D4 on slide D.

FIGURE 21. Piribelba piriformis (Mihelčič, 1964), lectotype. A—lateral view of the body (total length 678 µm); B—view of notogaster from adverse side; C—detail of prodorsal setae le, ro and ex; D—detail of selected setae of the body (C and D scale is increased).

FIGURE 22. Piribelba piriformis (Mihelčič, 1964), paralectotypes (originally syntypes of author). A—solenidion φ1; B— setation of genu III (GeIII), genu and tibia IV (GeIII, TiIV); C—aggenital seta and genital setae, lateral view; D—details of selected setae (all in same scale); E—details of leg setation of another specimen, genu III and IV (GeIII, GeIV), tibia and proximal part of tarsus I (TiI, TsI); F—deutonymph in lateral view (dashed area represents crack in medium where observation is more difficult). Scale bar 100 μm.

FIGURE 23. Piribelba piriformis (Mihelčič, 1964), lectotype. A—lateral view with indication of areas depicted in detail; B—detail of sejugal area; C—ventral side, detail of epimeres; D—ventral side, anogenital area; E—detail of lamellar and rostral seta; F—parts of legs II-III-IV. Scale bars 200 μm (A), 100 μm (C, D), 50 μm (E), 20 μm (B).

FIGURE 24. Piribelba piriformis (Mihelčič, 1964), paralectotypes (syntypes of the author, specimens marked according to Fig 20). A—ventral side, anogenital area (specimen A1); B—leg IV and part of notogastral setae (C1); C—leg I (C1); D—seta le (C1); E—parts of leg I and II and distal part of bothridial seta (A1); F—leg IV (D2); G—detail of setae and cerotegument on proximal part of leg IV (D3); H—reticular cerotegument of notogaster (C1). Scale bars 200 μm (F), 50 μm (A–E, G, H).

FIGURE 25. Piribelba piriformis (Mihelčič, 1964), deutonymph from Mihelčič collection. A—lateral view of the body; B— detail of legs IV and posterior part of the body; C—leg I; D—detail of dorsal seta and solenidion of tibia IV; E—detail of seta ftʺ of tarsus IV. Scale bars 100 μm (B), 50 μm (C).

FIGURE 26. Piribelba piriformis (Mihelčič, 1964), adult. Specimen fromAustria (Dörfertal):A—dorsal view; B—ventral view; C—seta le in different aspects (left: dorsal to dorsolateral view, right: dorsomedial view); D—bothridial complex. Specimen from Slovakia (Sivec), form “lanceata”: E—dorsal view, F—ventral view, G—anal and genital shields; H—seta of ventral and dorsal parts of the body. Scale bars 100 μm (A, B, E, F), 50 μm (D, G, H).

FIGURE 27. Piribelba piriformis (Mihelčič, 1964), legs. A—leg I of specimen from Austria (Virgental); B—part of leg I, specimen from Slovakia (Sivec), form “lanceata”; C—leg IV of specimen from Slovakia (Dreveník); D—part of leg IV, specimen from Slovakia (Sivec), form “lanceata”; E—trochanter with additional seta and femur of leg III, specimen from Austria (Dörfertal); F—palp of specimen from Slovakia (Sivec). Scale bars 100 μm (A–E), 25 μm (F).

FIGURE 28. Piribelba piriformis (Mihelčič, 1964), adult specimen from Austria (Dörfertal).A —dorsal view; B—ventral view, C—lateral view, D—rostrum and mouthparts in lateral view; E—seta le in dorsal view; F—leg IV, G—detail of femur and genu IV; H—detail of tibia III and IV; I—detail of femur and genu I; J—anterior genital setae in lateral view.

FIGURE 29. Piribelba piriformis (Mihelčič, 1964), adult specimens from Slovakia (A–E: Dreveník, F–G: Sivec). A—dorsal view of the body; B—seta le; C—general view of the body with carried load of debris on notogaster, lateral view; D—legs I–III in lateral view, E—leg IV in lateral view; F—form “lanceata”, lateral view; G—form “lanceata”, detail of seta d of femur IV.