The morphological ontogeny of Platynothrus troendelagicus A. et S. Seniczak sp. nov. is described and illustrated. This species was found in two Atlantic raised bogs in Trøndelag, Norway, and based on comparison of cytochrome oxidase I (COI) nucleotide sequences, it also occurs in Ireland and Canada. It is the most similar to P. punctatus (L. Koch, 1879) as adult, but differs from it mainly by having more genital setae, longer seta f2, alveolar seta exp and only one pair of hypostomal setae m. In all juveniles of P. troendelagicus, the bothridial seta and exobothridial seta exa are short, and exp is alveolar. In the larva, seta f1 is setiform, but in the nymphs it is alveolar. Most prodorsal and gastronotal setae are short and smooth, except for longer and barbed f2 and h1 in the larva, and longer and finely barbed f2, and h- and p-series in the nymphs. In all instars, one pair of hypostomal setae m is present, and palp femur has one seta. In the ontogeny of this species, many l setae appear on trochanter III and femora I–III, and l and v setae on tarsi, and the number of setae on femora of deutonymph to adult is diagnostic. Both species differ also by COI nucleotide sequence.
Introduction
While working on the oribatid mites from two Atlantic raised bogs in Trøndelag, Central Norway, we found one species of Platynothrus Berlese, 1913, which is similar, but slightly smaller than P. punctatus (L. Koch, 1879) and is new to science. Systematic problems of Platynothrus were discussed by Seniczak et al. (2022), which also gave the diagnosis of this genus as follows: species of medium size to large (595–1220), with bacilliform bothridial seta and thickened head; number of hypostomal setae m varies within species and developmental stages; notogaster with 1–3 longitudinal ridges and 15 pairs of setae (f1 absent, only alveolus of this seta remains), posterior setae without distinct apophyses; epimeres IV separated from each other and epimeres III separated from each other in half of diameter; epimere IV with three or four setae, 11–38 pairs of genital setae present, leg tarsi with one or three claws. Seniczak and Seniczak (2022) also gave the diagnosis of juveniles of Platynothrus: prodorsal setae ro, le and in of medium size or long, exa short and exp alveolar. Bothridium small, rounded, bothridial seta short or minute. Number of hypostomal setae m and length of gastronotal setae varies between species and developmental stages, seta f1 setiform in larva, and alveolar in nymphs. Posterior gastronotal setae of nymphs without distinct apophyses. Number of genital setae and setae on femora of deutonymph and tritonymph varies between nymphs and species. According to Subías (2004, updated electronic version 2022), Seniczak et al. (2022) and Seniczak and Seniczak (2022), Platynothrus comprises 26 nominative species and two subspecies, from which one is considered by Subías (2004, updated electronic version 2022) species inquirenda.
The morphology of juveniles of Platynothrus is insufficiently known. According to Norton and Ermilov (2014) and further literature (Seniczak et al. 2022; Seniczak & Seniczak 2022), the full morphological ontogeny of P. altimontanus Hammer, 1958, P. bicarinatus (Jacot, 1938), P. coulsoni A. et S. Seniczak, 2022, P. peltifer C.L. Koch, 1839 and P. punctatus (L. Koch, 1879) is only known, which constitutes 21% of Platynothrus species.
This paper aims to describe the morphological ontogeny of Platynothrus troendelagicus A. et S. Seniczak sp. nov. and compare it with congeners.
Material and methods
The adults and juveniles of P. troendelagicus A. et S. Seniczak sp. nov. used in this study were collected on June 29th and 30th 2020 by A. Seniczak, K.I. Flatberg and K. Hassel from Sphagnum mosses in two Atlantic raised bogs located in Trøndelag, Central Norway (Hitra, 63°29′20.4″N, 8°52′26.4″E, 49 m a. s. l. and Høstadmyra 63°24′18.0″N, 10°07′12.0″E, 107 m a. s. l.).
The Hitra island is characterised by mild oceanic climate, with the following data in the year of study (2020): a mean annual temperature of 8.1°C, annual precipitation of 1436.2 mm, the lowest temperature was -4.9°C, and the highest was 31.3°C. Høstadmyra has slightly colder and drier climate, comparing to Hitra, with a mean annual temperature of 6.6°C and annual precipitation of 1192.8 mm (both in 2020). The minimum temperature was -13.2°C and the maximum temperature was 30.8°C. Climatic data were taken from Norwegian Centre for Climate Services (available at https://seklima.met.no/).
In total 64 samples of Sphagnum mosses, each of 500 cm3 were collected, including 28 samples in Hitra and 36 in Høstadmyra. Samples were transported in plastic bags in cool boxes for four days and extracted with Tullgren funnels in the Department of Natural History (University Museum of Bergen, University of Bergen, Norway) for ten days. The type specimens originate from a sample of Sphagnum compactum Lam. et DC. collected in a poor fen carpet site in Høstadmyra.
We investigated the density and stage structure of mites and based on 20 randomly selected adults we measured the body length and width, determined the sex ratio and number of gravid females and carried eggs. We measured total length (tip of rostrum to posterior edge of notogaster) in lateral aspect and width (widest part of notogaster) of mites in dorsal aspect, and size of anal and genital openings and setae perpendicularly to their length in µm. In a similar way we measured the morphological characters given in Table 1. Apical part of notogastral and gastronotal setae of P. troendelagicus is fragile, so we measured these setae, which looked undamaged.
The illustrations are limited to the body regions that show substantial differences between instars and were prepared from individuals mounted temporarily on slides in lactic acid. We used the following abbreviations in the text and figures: rostral (ro), lamellar (le), interlamellar (in) and exobothridial (exa, exp) setae, bothridium (bo), bothridial seta (bs), notogastral or gastronotal setae (c-, d-, e-, f-, h-, p-series), lyrifissures or cupules (ia, im, ip, ih, ips, iad, ian), cheliceral setae (cha, chb), Trägårdh organ (Tg), palp setae (sup, d, l, cm, acm, lt, ul, su) and solenidion ω, epimeral setae (1a–c, 2a, 3a–c, 4a–d), genital setae (g), aggenital setae (ag), adanal and anal setae (ad-, an-series), leg solenidia (σ, φ, ω), famulus (ε) and setae (bv, ev, d, l, v, ft, tc, it, pv, pl, a, s, p, u). The leg setae l on femora, and l and v on tarsi were labelled according to their appearance in the ontogeny. Terminology used follows that of Grandjean (1939, 1953, 1971, 1972, 1974) and Norton and Behan-Pelletier (2009). The species nomenclature follows partly Subías (2004) and Norton and Ermilov (2014).
TABLE 1.
Some morphological characters of instars of Platynothrus troendelagicus A. et S. Seniczak sp. nov., (mean measurements of 2–10 specimens in µm); nd—not developed.
For scanning electron microscopy (SEM), the mites were air-dried and coated with Au/Pd in a Polaron SC502 sputter coater and placed on Al-stubs with double-sided sticky carbon tape. Observations and micrographs were made with a QUANTA FEG 450 scanning electron microscope.
DNA barcoding
Six specimens of P. troendelagicus (three from Hitra and three from Høstadmyra) were used in this study. They were compared with P. punctatus from two sites: submerged mosses growing at the edge of a pool in Finse (Vestland, Western Norway, 60°34′48.0″N, 7°28′19.2″E, 1341 m a. s. l., 22.09.2019, leg. Anna Seniczak) and from Sphagnum mosses in peatland on Lydehorn (Bergen, Vestland, Western Norway, 60°22′12.0″N, 5°14′38.4″E, 293 m a. s. l., 05.10.2018, leg. Anna Seniczak). We used species of putatively close genera as outgroups, Capillonothrus thori (Berlese, 1904) (collected in peatland Borreguil de la Virgen in Sierra Nevada, Spain, 37°05′13.2″N, 3°22′26.4″W, 2494 m a. s. l., 18.08.2017, leg. Anna Seniczak and Emilia F. Ondoño), Heminothrus targionii (Berlese, 1885) (collected in Hitra together with P. troendelagicus, see above for details), and Camisia foveolata Hammer, 1955 (collected in Vestland, Hardanger, Finse, 60°35′34.8″N, 7°25′55.2″E, 1356 m a. s. l., 07.09.2018, leg. Anna Seniczak) (Table 2).
TABLE 2.
Information about specimens used in this study; labels correspond to specimen numbers in BOLD database; ad—adult, juv—juvenile, NA—not available.
Each specimen was photographed, and the photos are the vouchers that are available at Barcode of Life Data System (BOLD, http://boldsystems.org). The specimens were subsequently placed in a well containing 50 ml of 90% ethanol in a 96-well microplate and send to the Canadian Centre for DNA Barcoding (CCDB 2021). Mites were sequenced for the barcode region of the COI gene according to standard protocols at CCDB ( www.ccdb.ca 34), using either LepF1/LepR1 (Hebert et al. 2003) or LCO1490/HCO2198 (Folmer et al. 1994) primer pairs. The DNA extracts were placed in archival storage at -80°C at the Canadian Centre for DNA Barcoding. The sequences are available in GenBank (accessions numbers in Table 2).
COI sequences (sequence length ≥ 407 bp) were blasted against GenBank in order to detect and exclude possible contaminations. In blast search two sequences of Platynothrus from other countries turned out to be very similar to those of P. troendelagicus, so they were included in the analyses. One of them was from Ireland (Leinster, Lullymore, 53°16′48.0″N, 6°57′00.0″W, 80 m a. s. l., 09.12.14, leg. Anna Seniczak and Thomas Bolger) and another one from Canada (Fundy National Park, New Brunswick, (45°37′30.0″N, 65°03′36.0″W, 336 m a. s. l., GenBank Accession number MF911250, Young et al. 2019). Sequence variation within P. troendelagicus specimens and between-species was calculated in BOLD using Kimura 2 Parameter distance model, pairwise deletion, and BOLD Aligner (Amino Acid based HMM). The sequences were aligned by eye and Neighbor joining trees were constructed using MEGA6 (Tamura et al. 2013). Joint neighborhood topologies were visualized in FigTree 1.4.2 (available at http://tree.bio.ed.ac.uk/software/figtree).
Platynothrus troendelagicus A. et S. Seniczak sp. nov.
(Figs. 1–21)
Diagnosis
Adult of medium size (length 663–722), with characters of Platynothrus given by Seniczak et al. (2022). Prodorsal setae in thin and of medium size, alveolar seta exp present. Bothridial seta of medium size, bacilliform, with thickened, barbed head. Notogastral setae (15 pairs) of medium size, setae f2 longer than e2. Adult with one pair of hypostomal setae m, palp femur with one seta. Three pairs of adanal setae and two pairs of anal setae present. Leg tarsi with one claw.
Juveniles with characters of Platynothrus given by Seniczak and Seniczak (2022). Most prodorsal and gastronotal setae short and smooth, except for longer and barbed f2 and h1 in larva, and longer and finely barbed f2 and h- and p-series in nymphs. All juveniles with one pair of hypostomal setae m, palp femur with one seta.
Formula of genital setae of species 2-4-9-14 (protonymph to adult), and segments AD (protonymph to adult)—0333 and AN (deutonymph to adult) – 022. Formula of setae on femora I–IV of deutonymph 6-6-3-2, tritonymph 7-8-3-2 and adult 8-9-5-3.
Morphology of adult
Measurements: body length (and range) of females 693.6±20.0 (663–722, n= 20) and width 418.9±12.2 (377–436), males absent.
Cerotegument. Brown with light spots and microporose.
Prodorsum. Rostrum rounded, with rostral setae short (ro, 39–41) and smooth (Figs. 1a, 2, 3a, 4, 5a, 6a, 6b, 7c, 7d), lamellar setae longer (le, 77–82) and finely barbed, inserted posterior to setae ro on large apophyses and transverse ridge; interlamellar setae in longest (in, 91–95), but thinner than le and smooth. Setal pair ro inserted close to each other, mutual distance between setal pair le about two times longer than between setal pair ro, and between setal pair in about four times longer than between setal pair ro. Bothridium (bo) small and rounded, located on large tubercle, bothridial seta (bs) of medium size (99–105), bacilliform, with thickened, barbed head (Figs. 1a, 1b, 3a, 4a–c, 5a, 5b, 6, 7a). Exobothridial seta exa short (18) and smooth, inserted lateral to bo, alveolar exp present. Central and anterior part of prodorsum with foveae (Figs. 1a, 4a–c, 5a, 5b, 6a–c).
Notogaster. Longer (444–484) than wide (377–436), with three pairs of longitudinal ridges, inner ridges better formed and longest, medial ridges shortest (Figs. 1a, 4a–c, 5c, 5d). Most notogastral setae (15 pairs, excluding alveolar f1) relatively short or of medium size (38–86, Table 1) and smooth. Seta f2 longer than e2. Opisthonotal gla opening posteromedial to seta f2 (Figs. 1a, 1c, 5c, 5d, 7b). Transverse ridge present posterior to setal pair h3, alveolar seta f1 anteromedial to seta h3. Lyrifissure ia posterolateral to seta c3, im posterolateral to seta cp, ip anterolateral to seta h2, ian anterior to seta an2, iad lateral to anterior part of anal plate, ips and ih displaced anterolateral to seta ad3 (Figs. 2, 3a).
Gnathosoma. Subcapitular setea h, m and a short (5) and smooth, one pair of setae m present (Figs. 2, 7c, 7d). Chelicera (length 149, width 53) with short (23–25), barbed setae, cha slightly longer and thicker than chb (Fig. 3b). Palp short (length 61–63), with most setae short and smooth, except for slightly longer d and cm (Fig. 3c). Formula of palp setae (trochanter to tarsus + solenidion ω): 0-1-0-3-7(1).
Ventral aspect. All epimeral setae short (7–10) and smooth (Figs. 2, 4d, 7c, 8a, 8b), formula of epimeral setae 3-1-3-4. Aggenital setae (2 pairs) longer (17–19) than epimeral setae, genital setae (14 pairs) longest (38–42) and inserted on inner part of genital plates (Figs. 2, 8a, 8b); all smooth. Adanal setae (3 pairs) and anal setae (2 pairs) short (16–19), all smooth (Figs. 2, 8a, 8c).
Legs. Femora with reticulate integument (Figs. 4, 5, 6a, 6b, 7c, 8d, 9a, 10b). Most leg setae relatively thick, finely barbed, or smooth, except for longer setae on distal part of tarsi (Figs. 4, 5a, 5c, 5d, 6a, 6b, 7c, 8a, 8b, 8d, 9, 10). Seta d coupled to solenidion present on all genua and tibiae. Formulae of leg setae (and solenidia), trochanter to tarsus: I—1-8-5(1)-5(2)-23(3); II—1-9-5(1)-5(1)-21(2); III—5-5-4(1)-4(1)-21; IV—1-3-4(1)-4(1)-18 (Table 3). Leg tarsi monodactylous.
Description of juvenile stages
Larva stocky (Figs. 11, 12a, 13a), unpigmented, prodorsum, epimeres and legs light brown. Prodorsum subtriangular, central part punctate, with small pits. Prodorsal setae ro inserted close to each other on rostrum, pair le inserted posterior to ro on transverse ridge, pair in inserted in central part, posteromedial to bothridial setae (bs); ro and exa short, le and in of medium size (Table 1), seta exp alveolar, le finely barbed, other setae smooth. Ridge present anterior to seta exa in direction of seta le and posterior to seta exa in direction of seta c1. Mutual distance between setal pair le about five times longer than between setal pair ro, and between setal pair in about eight times longer than between setal pair ro, setae le inserted closer to ro than to in (Figs. 11, 13a). Opening of bothridium small, rounded, bothridial seta minute. One pair of hypostomal setae m present.
Gastronotum of larva with transverse folds and lateral tubercles and 12 pairs of setae, including f1 placed anterior to seta h1, and h2 inserted lateral to posterior part of anal valves (Figs. 11, 12a, 13a); most setae of medium size and smooth, except for longer and barbed f2 and h1 (Table 1). Cupule ia posterior to seta c3, im anterior to seta e2, ip not observed between folds, ih lateral to anterior part of anal valves (Figs. 12a, 13a). Opisthosomal gland opening anteromedial to seta f2. Anal valves of larva (segment P) glabrous. Leg segments relatively thick, and most leg setae relatively thick and short or conical, except for longer apical setae on tarsi (Fig. 14). Seta d coupled to solenidion present on all genua and tibiae.
Shape and color of protonymph and prodorsal setae of nymphs as in larva, but in central part of prodorsum pits denser than in larva. Bothridium weakly developed, rounded, bothridial seta short, exa short and exp alveolar. One pair of hypostomal setae m present. Gastronotum of protonymph with folds and small pits and 15 pairs of setae because seta f1 lost and alveolus of seta remaining and present in other instars, and setae h3 and p-series appearing and remaining in deutonymph and tritonymph, most setae relatively short and smooth, except for longer finely barbed f2 and h- and pseries, but in protonymph p3 short and smooth (Fig. 12b, Table 1). In protonymph, two pairs of setae appearing on genital valves, and two pairs added in deutonymph and five pairs in tritonymph (Figs. 12b, 15a, 15b). In deutonymph, one pair of aggenital setae appearing, and one pair added in tritonymph, all short and smooth. Anal valves of protonymph (segments AD) and deutonymph (segments AN) glabrous, in tritonymph two pairs of short and smooth setae present (Figs. 12a, 15a, 15b). In all nymphs, posterior setae on small apophyses. In tritonymph, cupules ia and im placed as in larva, ip not observed between folds, cupule ian anterior to seta an2, iad lateral to anterior part of anal valves, cupules ips and ih pushed anterolateral to seta ad3 (Figs. 15b, 16). Opisthonotal gland opening medial to seta f2 and alveolus of seta f1 anterior to seta h1. In all nymphs, central and anterior part of prodorsum with foveae (Figs. 16, 17a, 17b, 18b). Leg segments relatively thick (Figs. 17a–c, 18–20), and femora with reticulate integument (Figs. 17a, 17b, 20b). Most leg setae of tritonymph short or of medium size, relatively thick and smooth, except for longer apical setae on tarsi (Fig. 20). Seta d coupled to solenidion present on all genua and tibiae.
Remarks. Neighbor-joining tree based on cytochrome oxidase I (COI) nucleotide sequences confirmed morphological observations that P. troendelagicus differs from P. punctatus also on the molecular level (Fig. 21). The sequences of P. troendelagicus were identical (distance 0%), the maximum mitochondrial DNA variation within P. punctatus was 2.62%, while the minimum distance to compared representatives within the genus was 28.69%.
Summary of ontogenetic transformations
In all instars of P. troendelagicus, the prodorsal setae ro, le and in are short or of medium size, and exp is alveolar. In all juveniles, the bothridium is weakly developed, and the bothridial seta is short, whereas in the adult the bothridium is large, located on large tubercle, with small, rounded opening, and bothridial seta is bacilliform, with thickened, barbed head. The larva has 12 pairs of gastronotal setae, including f1 and h2, whereas the nymphs and adult have 15 pairs (in protonymph f1 is lost and only alveolus of this seta remains, and setae h3 and p-series are added). Formula of gastronotal setae of P. troendelagicus is 12-15-15-15-15 (larva to adult, excluding alveolar f1). Formulae of epimeral setae are 3-1-2 (larva, including scaliform 1c), 3-1-3-1 (protonymph), 3-1-3-3 (deutonymph) and 3-1-3-4 (tritonymph and adult). In all instars, one pair of hypostomal setae m is present. Formula of genital setae is 2-4-9-14 (protonymph to adult), aggenital setae is 1-2-2 (deutonymph to adult), and setae of segments PS–AN is 03333-0333-022. The ontogeny of leg setae and solenidia is given in Table 3.
Distribution, ecology and biology
Platynothrus troendelagicus was found in ten samples (out of the total of 64 samples) collected in Hitra and Høstadmyra, only in the moist habitats. It was the most abundant and represented by all developmental stages in a sample of Sphagnum compactum Lam. et DC. collected in a poor fen carpet site in Høstadmyra, where the density of this species was 69 individuals/500 cm3. The adults dominated in extracted sample, constituting 51% of population. The stage structure of P. troendelagicus was the following: 3 larvae, 10 protonymphs, 19 deutonymphs, 2 tritonymphs and 35 adults. Among 20 individuals investigated, 50% of females were gravid, carrying 1–5 large eggs (each 155 x 80), constituting 22% of the length of females.
The species was also found in samples collected from lawns and carpets in Hitra and Høstadmyra: in Sphagnum medium Limpr., S. cuspidatum Ehrh. ex Hoffm., S. rubellum Wilson, and at the pond with a mixture of Sphagnum species [S. inundatum Russow, Sphagnum papillosum Lindb. and Sphagnum tenellum (Brid.) Brid.]. Based on COI nucleotide sequences, the species also occurs in the peatlands in Ireland (Lullymore, Leinster) and Canada (Fundy National Park, New Brunswick, Young et al. 2019) (Table 2, Fig. 21).
Type material
The holotype (female) and five paratypes (females) with the above collection data are deposited in the University Museum of Bergen, University of Bergen, Bergen, Norway (ZMUB).
Etymology
This species is named after the county Trøndelag in the central part of Norway where it was discovered.
FIGURE. 1–2.
Platynothrus troendelagicus A. et S. Seniczak sp. nov., adult, legs partially drawn, scale bars 50 µm. 1. (a) Dorsal aspect, (b) bothridial seta, (c) region of gla opening (b, c, enlarged). 2. Ventral aspect.
FIGURE 3.
Platynothrus troendelagicus A. et S. Seniczak sp. nov., adult. (a) Lateral aspect, legs partially drawn, scale bar 50 µm; mouthparts, scale bars 20 µm, (b) chelicera, right side, antiaxial aspect, (c) palp, lateral aspect.
FIGURE 4.
Platynothrus troendelagicus A. et S. Seniczak sp. nov, adult, SEM micrographs. (a) Dorsal view, (b) lateral view, (c) frontolateral view, (d) ventral view.
FIGURE 5.
Platynothrus troendelagicus A. et S. Seniczak sp. nov., adult, SEM micrographs. Dorsal view, (a), (b) anterior part, (c) posterior part; (d) posterior part, lateral view.
FIGURE 6.
Platynothrus troendelagicus A. et S. Seniczak sp. nov., adult, SEM micrographs. Dorsal view, (a), (b) anterior part, (c), (d) bothridium and bothridial seta, dorsal view.
FIGURE 7.
Platynothrus troendelagicus A. et S. Seniczak sp. nov., adult, SEM micrographs. Bothridium and bothridial seta, dorsal view; (b) opisthonotal gla opening, dorsal view; (c), (d) anterior part, ventral view.
FIGURE 8.
Platynothrus troendelagicus A. et S. Seniczak sp. nov., adult, SEM micrographs. Posterior part of body, ventral view (a), (b) genital plates, (c) anal plates; (d) legs I and II, lateral view.
FIGURE 9.
Platynothrus troendelagicus A. et S. Seniczak sp. nov., adult, SEM micrographs. (a) Femora II and III, lateral view; leg I, (b) lateral view, (c) tarsus, frontolateral view, (d) claw I, lateral view.
FIGURE 10.
Platynothrus troendelagicus A. et S. Seniczak sp. nov., leg segments of adult (part of femur to tarsus), right side, antiaxial aspect, setae on the opposite side not illustrated are indicated in the legend, scale bar 20 µm. (a) Leg I, femur (l′, v′), genu (v′), tibia (v′), tarsus (v′, pv′); (b) leg II, femur (v′), genu (v′), tibia (v′), tarsus (v′, pv′); (c) leg III, genu (v″), tibia (v″), tarsus (pv″); (d) leg IV, genu (v″), tibia (v″), tarsus (v″); (e) connection of femur I with genu I, (f) part of tarsus I (e, f enlarged).
FIGURE. 11–12.
Platynothrus troendelagicus A. et S. Seniczak sp. nov., legs partially drawn, scale bars 20 µm. 1. Larva, dorsal aspect. 2. Ventral aspect of hysterosoma, (a) larva, (b) protonymph.
TABLE 3.
Ontogeny of leg setae (Roman letters) and solenidia (Greek letters) in Platynothrus troendelagicus A. et S. Seniczak sp. nov.
Comparison of morphology of Platynothrus troendelagicus A. et S. Seniczak sp. nov. with congeners and remarks
Seniczak and Seniczak (2022) compared the morphology of adults of Platynothrus species with most gastronotal setae short or of medium size, and P. troendelagicus is the most similar to P. punctatus but differs from it mainly by slightly smaller body size, larger number of genital setae, presence of alveolar seta exp, which in P. punctatus is absent, presence of only one pair of hypostomal setae m (vs. 1, 2, 3, 4, 5 pairs of this setae in larva, protonymph, deutonymph, tritonymph and adult of P. punctatus, respectively). It differs also by COI nucleotide sequence.
FIGURE 14.
Platynothrus troendelagicus A. et S. Seniczak sp. nov., leg segments of larva (part of femur to tarsus), right side, antiaxial aspect, setae on the opposite side not illustrated are indicated in the legend, scale bar 20 µm. (a) Leg I, tibia (pl′); (b) leg II, tarsus (pv′); (c) leg III.
FIGURE. 15–16.
Platynothrus troendelagicus A. et S. Seniczak sp. nov., legs partially drawn, scale bars 50 µm. 15. Ventral aspect of hysterosoma, (a) deutonymph, (b) tritonymph. 16. Tritonymph, dorsal aspect.
FIGURE 17.
Platynothrus troendelagicus A. et S. Seniczak sp. nov., deutonymph, SEM micrographs. (a) Dorsal view, (b) frontal view, (c), (d) anterior part, ventral view.
FIGURE 18.
Platynothrus troendelagicus A. et S. Seniczak sp. nov., deutonymph, SEM micrographs. Anterior part, (a) ventral view, (b) dorsal view; (c) leg I and II, frontal view; (d) leg I, lateral view.
In the juveniles of P. troendelagicus, the number, shape and distribution of setae are similar to those of other species of Camisiidae (Seniczak 1990a, b, 1991a–c; Seniczak & Klimek 1990; Seniczak & Seniczak 2022; Seniczak et al. 2022). In all species, the larva has seta f1, but this seta is lost in the protonymph and only alveolus of this setae remains. However, in the nymphs of Platynothrus, the posterior gastronotal setae are inserted on small apophyses (Seniczak 1990a; Seniczak & Klimek 1990; Seniczak & Seniczak 2022; Seniczak et al. 2022), whereas in the other genera of this family, such as Heminothrus Berlese, 1913 and Camisia Heyden, 1826 these apophyses are clearly larger (Seniczak 1990b; Seniczak 1991a–c). In the nymphs of other genera of Crotonioidea, such as Hermannia Nicolet, 1855, Phyllhermannia Berlese, 1916 and Nothrus C.L. Koch, 1836, seta f1 is present (Seniczak 1992; Seniczak & Żelazna 1992; Seniczak & Norton 1993; Colloff 2011; Seniczak et al. 2017a, b).
The morphology of successive developmental instars of P. troendelagicus is generally similar to those of P. coulsoni and P. punctatus, but the morphological ontogeny of these species differs by formulae of hypostomal setae, genital, adanal, and anal setae and the number of leg setae on femora and tarsi (Table 4). Moreover, the successive developmental instars of these species differ in the body size (P. coulsoni is larger than other species) and length of some setae. Generally, these species are most similar to each other in the larva, and their differentiation of morphology increases during the ontogeny (Table 4, Seniczak & Seniczak 2022; Seniczak et al. 2022). Based on Table 4, the larvae of compared species differ clearly in one morphological character, protonymphs in two characters (formulae of hypostomal and genital setae) and deutonymphs, tritonymphs and adults at least in six morphological characters, on the main body (number of hypostomal, palpal, genital, adanal and anal setae), and on leg segments (the number of setae on femora and tarsi, at least on legs I–III). In the adults, the cuticle is better sclerotized than in the juveniles, with more morphological characters.
FIGURE 19.
Platynothrus troendelagicus A. et S. Seniczak sp. nov., deutonymph, leg I, SEM micrographs. (a) Dorsal view, (b) ventral view, (c), (d) lateral view.
FIGURE 20.
Platynothrus troendelagicus A. et S. Seniczak sp. nov., leg segments of tritonymph (part of femur to tarsus), right side, antiaxial aspect, seta on the opposite side not illustrated are indicated in the legend, scale bar 20 µm. (a) Leg I, femur (v′), genu (v′), tibia (v′), tarsus (pl′, v′); (b) leg II, femur (v′), genu (v′), tibia (v′); (c) leg III, genu (v″), tibia (v″), tarsus (pv″); (d) leg IV, genu (v″), tibia (v″); (e) connection of femur and genu I.
The ontogeny of leg setae and solenidia of P. troendelagicus differs from that of P. coulsoni and P. punctatus, but in all species many l setae are present on trochanter III and at least on femora I–IV, and setae l and v on tarsi. In these species, typical tarsal setae (ft, pl, tc, p, u, a, s, pv) are inserted on 1/3 apical part of tarsi, but nevertheless in P. troendelagicus fewer setae v appear on all tarsi than in other species.
The chelicera of the adult of P. troendelagicus is similar to that of P. punctatus, by having well-developed Trägårdh organ that protrudes beyond the line of chelicera in lateral aspect. In both species, cheliceral setae are of similar length and barbed, as in other species of Platynothrus (Trägårdh 1910; Lee 1985; Olszanowski 1996). The palp of adult of P. troendelagicus is similar to that of P. punctatus, except for absence of seta inf on femur, which in P. punctatus is present.
TABLE 4.
Comparison of some morphological characters of Platynothrus troendelagicus A. et S. Seniczak sp. nov., P. coulsoni and P. punctatus.
Acknowledgements
We express our gratitude to Dr. Steffen Roth (University Museum of Bergen, Bergen, Norway) for assistance with field work, to anonymous reviewers for helpful comments and suggestions that improved the quality of this paper, and to Mr. Jian-Feng Liu for nice editorial work. The study was partly supported by the grant to the University Museum of Bergen from the Norwegian Taxonomy Initiative "Mites of Atlantic Raised Bogs" (Grant No. 6-20, 70184243). The sequencing was financed by Norwegian Barcode of Life (NorBOL).
