Nanhermannia sellnicki Forsslund, 1958

Seniczak, Anna, Seniczak, Stanisław, Hagen, Snorre B. & Klütsch, Cornelya F. C., 2023, Morphological ontogeny of Nanhermannia sellnicki (Acari, Oribatida, Nanhermanniidae), and comments on Nanhermannia Berlese, Zootaxa 5324 (1), pp. 110-132 : 111-129

Nanhermannia sellnicki Forsslund, 1958

( Figs 1–14 )

Diagnosis

Adult of medium size (length 507–540), with characters of Nanhermannia given by Sitnikova (1975) and Weigmann (2006). Body colour brown. Prodorsal seta in thin, approximately as long as bothridial seta, protuberances on posterior part of prodorsum highly sclerotized, with 3–4 small posterior tubercles, and 4–5 pairs of light spots between setal pair in. Ratio of body length/width 2.2:1. Seta exp short, setae c 1, d 2, and e 1 reaching insertions of setae d 1, e 1 and h 1 respectively. Formula of epimeral setae 3-1-3-4. Seta d accompanying solenidion σ on all genua, φ 1 on tibia I and φ on other tibiae present.

Juveniles elongated, unpigmented; hysterosoma cylindrical with cuticular tubercles, but prodorsum, epimeres and legs light brown. Bothridium small, bothridial seta minute, seta exp short, setiform, exa reduced to its alveolus. Larva with 12 pairs of gastronotal setae, including f 1 and h 2, nymphs with 15 pair, f 1 not observed between cuticular tubercles. Most prodorsal and gastronotal setae of larva short, of nymphs of medium size; all smooth. Seta in and all gastronotal and adanal setae inserted in small individual depressions. Leg segments relatively thick and oval in cross section, most leg setae relatively short, thick or conical. Seta d accompanying solenidion σ on all genua, φ 1 on tibia I and φ on other tibiae present.

Formula of genital setae 1-4-6-9 (protonymph to adult); formulae of femoral setae of deutonymph 4-4-2-2 (leg I–IV), tritonymph 5-6-3-2 and adult 5-6-3-2.

Supplementary description of adult

Adult elongated ( Figs 1a , 2 , 4a ), similar to that described by Forsslund (1958), but see Remarks. Mean length (and range) of females 526.5±11.2 (507–540, n= 20), mean width (and range) 226.2±4.9 (221–234), males absent. Body colour brown. Prodorsal seta in thin, slightly longer than bothridial seta, protuberances on posterior part of prodorsum highly sclerotized, with 3–4 pairs of small posterior tubercles ( Figs 1a , 3a , 4a, 4b, 4d , 5a ), and 4–5 pairs of light spots present between setal pair in ( Fig. 1a ). Ratio of body length/width 2.2:1. Seta exp short, setae c 1, d 2 and e 1 reaching insertions of setae d 1, e 1 and h 1 respectively. Lyrifissure ia lateral to seta c 3, im anterior to seta e 2, ip posterior to seta f 2, ian anterior to seta an 2, iad lateral to anterior part of anal plates, ips and ih pushed anterolateral to iad ( Figs 2 , 3a ). Opisthonotal gland opening medial to seta f 2. Chelicera chelate-dentate, seta cha long, chb short and inserted posterior to cha, both smooth ( Figs 3c , 6a ). Most palpal setae relatively short and smooth ( Figs 3d , 6a ), eupathidia short, formula of setae (trochanter to tarsus + solenidion ω): 1-0-2-7(1). Hypostomal setae h and a slightly longer than m, all smooth ( Figs 2 , 3b , 5b , 6a ). Most epimeral setae short and smooth except for longer 4b and 4d ( Figs 2 , 4c , 5d ). Aggenital setae (2 pairs) and genital setae (9 pairs) long, all smooth ( Figs 2 , 3a , 4c , 5c, 5d ). Adanal setae (3 pairs) long, anal seta (2 pairs) short. Ovipositor relatively thick ( Fig. 3a ). Legs relatively thick, all femora oval in cross section with cuticular ornamentation ( Figs 4 , 5 , 6b–d , 7 ). Seta l on trochanter II and d on all femora barbed, other leg setae smooth or finely barbed. Solenidion ω 1 on tarsus I located between seta ft’ and ft’’, whereas solenidia ω 2 and ω 3 located anterior to seta a’’. Solenidia ω 1 and ω 2 on tarsus II located close to seta ft’. Seta d accompanying solenidion σ on all genua, φ 1 on tibia I and φ on other tibiae present ( Figs 6b–d , 7 ). In all tarsi, hypertichy occurs; setae on basal and medial part conical, those on distal part normal ( Table 2 ). Formula of femora (leg I–IV) 5-6-3-2. Formulae of leg setae (and solenidia), trochanter to tarsus: I—1-5-5(1)-5(2)-24(3); II—1-6-5(1)- 5(1)-23(2); III—4-3-3(1)-4(1)-19; IV—1-2-3(1)-4(1)-17. Leg tarsi monodactylous.

Remarks. The mean body size of individuals studied herein was slightly smaller than of that described by Forsslund (1958) —length 530 (495–610), width was 245 (225–270) and investigated by Sitnikova (1975) —length 530, width 245, and Weigmann (2006) —length 495–610.

Description of juvenile stages

Larva elongated in dorsal and ventral view ( Figs 8a , 9a ), hysterosoma cylindrical, unpigmented with cuticular tubercles, but prodorsum, epimeres and legs light brown. Prodorsum subtriangular, central part punctate, lateral parts reticulate. Prodorsal setae ro and le short, in slightly longer ( Table 1 ), all smooth, seta in in small individual depression; seta exp short, exa reduced to its alveolus. Mutual distance between setal pair le slightly longer than that between setal pair ro, and mutual distance between setal pair in about 2.5 times longer than that between setal pair ro. Setal pair le inserted closer to pair ro than to pair in. Opening of bothridium small, rounded, bothridial seta minute.

Gastronotum of larva with cuticular tubercles and 12 pairs of setae, including dorsal f 1 and ventral h 2, inserted lateral to posterior part of anal valves ( Figs 8a , 9a , 10a ); all short ( Table 1 ) and smooth, and inserted in small individual depressions. Cupules ia, im and ip not observed between cuticular tubercles, cupule ih lateral to anterior part of anal valves. Opisthosomal gland opening medial to seta f 2. Anal valves of larva (segment P) glabrous. Leg segments relatively thick, and most leg setae short, thick and conical, except longer apical setae on tarsi ( Fig. 11 ). On dorsal part of genu I alveolus of second solenidion σ visible ( Fig. 11d ). Seta d accompanying solenidion σ on all genua, φ 1 on tibia I and φ on other tibiae present.

Shape and colour of protonymph and prodorsal setae as in larva, but seta in relatively longer than in larva. Bothridium weakly developed, bothridial seta minute, seta exp short, exa reduced to its alveolus. Gastronotum of nymphs with cuticular tubercles and 15 pairs of setae because seta f 1 lost in protonymph (alveolus of this seta not observed between tubercles of nymphs), and setae h 3 and p -series appearing and remaining in deutonymph and tritonymph ( Figs 9b , 10b , 12 , 13 ). Most gastronotal setae of medium size ( Table 1 ), and smooth. In protonymph one pair of seta appearing on genital valves, and three pairs added in deutonymph and two pairs in tritonymph ( Figs 9b , 12 ). In deutonymph three pairs of adanal setae and one pair of aggenital setae appearing, and one pair of aggenital setae added in tritonymph ( Fig. 12 ). Anal valves of protonymph and deutonymph (segments AD and AN respectively) glabrous, and those of tritonymph with two pairs of short and smooth setae. All gastronotal and adanal setae inserted in small individual depressions. In protonymph cupule ips present lateral to anterior part of anal valves, in deutonymph and tritonymph cupule iad observed in the same place, whereas other cupules not observed between cuticular tubercles. Opisthonotal gland opening located medial to seta f 2 ( Fig. 10b ). Leg segments relatively thick, and most leg setae short, thick or conical, except for longer apical setae on tarsi ( Fig. 14 ). Seta d accompanying solenidion σ on all genua, and φ 1 on tibia I and φ on other tibiae present.

Summary of ontogenetic transformations

In the larva of N. sellnicki , the prodorsal setae ro and le are short and seta in is slightly longer, but in the nymphs and adult seta in is clearly longer than setae ro and le. In all juveniles, seta exp is short and seta exa is reduced to its alveolus, whereas the adult loses alveolar seta exa. In all juveniles, the bothridium is weakly developed, and the bothridial seta is minute, whereas in the adult the bothridium is well developed, with small, rounded opening, and the bothridial seta is setiform, with narrow barbed head. The larva has 12 pairs of gastronotal setae, including f 1 and h 2, whereas the nymphs and adult have 15 pairs (in protonymph f 1 is lost and h 3 and p -series are added). The formula of gastronotal setae of N. sellnicki is 12-15-15-15-15 (larva to adult). Formulae of epimeral setae are 3-1-2 (larva, including scaliform 1c), 3-1-3-2 (protonymph), 3-1-3-3 (deutonymph) and 3-1-3-4 (tritonymph and adult). The formula of genital setae is 1-4-6-9 (protonymph to adult), of aggenital setae is 1-2-2 (deutonymph to adult), and of setae of segments PS−AN is 03333-0333-022. The ontogeny of leg setae and solenidia is given in Table 2 .

Distribution, ecology, and biology

Nanhermannia sellnicki is known from the Palearctic region (Euro Siberia, Tibet, Caucasus) according to Subías (2004, 2022). In Norway, it has been reported from numerous birch stands (especially with understory formed by Vaccinium and Empetrum ) and from a pine stand in Trøndelag, Nordland, and Troms and Finnmark ( Karppinen 1971). It was also found in ornithogenous soils in Svalbard (Spitsbergen: Barentsburg, Longyearbyen) ( Lebedeva et al. 2006; Seniczak et al. 2020b). In the study concerning wetlands in Norway, it was mistaken with N. coronata ( Seniczak et al. 2020a) . Nanhermannia sellnicki is usually found in drier habitats ( Forsslund 1958). For example, it was associated with the dwarf shrub tundra on the Kola Peninsula, Russia ( Leonov 2020). One specimen was also found in the feathers of great egret ( Ardea alba L.) ( Krivolutsky & Lebedeva 2004).

In the present study, N. sellnicki was found abundantly in a sample collected from a birch forest with Vaccinium and Ledum understory. Its abundance was 212 individuals per 500 cm 3, and the juveniles dominated in the population (66%). We found 15 larvae, 24 protonymphs, 51 deutonymphs, 49 tritonymphs, and 73 adults.Among 30 individuals investigated all were females and 7% were gravid, carrying one large egg (215 x 142), constituting about 41% of the total body length of females.

1

Comparison of morphology of Nanhermannia sellnicki with congeners and remarks

Among the adults of Nanhermannia species, the longest is N. comitalis Berlese, 1916 , and the shortest is N. dorsalis ( Banks, 1896) ; the body size of N. himalayensis Chakrabarti & Raychaudhuri, 1978 (in Chakrabarti et al. 1978) is unknown ( Table 3 ). The body length of most species overlaps including N. sellnicki . The stockiest species is N. elegantissima Hammer, 1958 (ratio of body length to width is 2.0), while the slimmest are N. fenneri Balogh, 1970 and N. pectinata Strenzke, 1953 (ratio of body length to width is 2.5); this ratio of body of N. gladiata Balogh, 1985 and N. tenuisetosa Balogh, 1985 is unknown. Nanhermannia sellnicki can be distinguished from other species known in Norway, e.g., N. coronata by having a lighter body color (brown vs dark brown in other species). The Nanhermannia species differ from one another in the shape of the posterior prodorsal protuberances and tubercles (from prominent tubercles to small tubercles of different size), and the length of some setae on the prodorsum and notogaster ( Table 3 ). In some species, only the anterior part of the body was illustrated, and the length of most notogastral setae is unknown. In most species, the ventral part of body is insufficiently known, including the number of epimeral, genital, aggenital, adanal and anal setae, which makes it difficult to summarize diagnosis of Nanhermannia . Weigmann (2006) separated Nanhermannia from Masthermannia by the formula of epimeral setae (3-1-3-3 and 3-1-3-4, respectively), but this difference needs revision because in Nanhermannia species both formulae of epimeral setae are noted and, in some species, the hypertichy of epimeral setae occurs.

Based on the morphological characters (see Table 3 ) and earlier diagnoses of Nanhermannia , the diagnosis of this genus is as follows:—medium sized (450–660), elongated, brown to dark brown and narrow species, with bothridia and bothridial setae situated on top of prodorsum; protuberances on posterior part of prodorsum with sclerotized teeth, often extending above anterior part of notogaster. Notogaster cylindrical, with coarse structure of pits and 15 pairs of long setae, curved and appressed to body, extended ventrally and connected ventro-median, arched suture delimits genital and aggenital area laterally (diagastry). Aggenital plate fused with epimere, adanal plate fused with notogaster, but still recognizable; formula of epimeral setae usually 3-1-3-3 or 3-1-3-4, but in some species hypertichy on some epimeres occurs; 7–10 pairs of genital setae, 2 pairs of aggenital setae, 3 pairs of adanal setae, and 2 pairs of anal setae present. Legs with one claw.

The juveniles of N. sellnicki are similar to those of N. cf. coronata , N. comitalis , and N. nana and differ from one another mainly in the length of some prodorsal and gastronotal setae, and the shape of posterior prodorsal protuberances and tubercles ( Table 4 ). In the juveniles of N. nana , the prodorsal and gastronotal setae are clearly longer than in other species. In the nymphs of N. sellnicki , N. comitalis , and N. nana the posterior prodorsal protuberances are present, with different number of tubercles, whereas in those of N. cf. coronata these protuberances are not evident ( Ermilov & Łochyńska 2008). In the larvae of N. nana and N. comitalis the posterior prodorsal protuberances are present, with different number of tubercles ( Seniczak 1991), whereas in other species these protuberances are absent.

1 1 1

The larva of N. sellnicki has the seta f 1 and two pairs of exobothridial setae (including exa reduced to its alveolus), which are common in other species of Crotonioidea ( Seniczak et al. 2017a), to which Nanhermannia belongs. The nymphs of this species lost the seta f 1 in the protonymph, as is most genera of Crotonioidea, except for Hermannia Nicolet, 1855 , Phyllhermannia Berlese, 1916 and Nothrus C.L. Koch, 1836 , in which this seta is retained in all instars (Seniczak 1992; Seniczak & Żelazna 1992; Seniczak & Norton 1993; Colloff 2011; Seniczak et al. 2017a, b).

In the larva of N. sellnicki there is a pit on dorsal part of genu I which Grandjean (1940) considered an alveolus of the second solenidion σ. Two solenidia on genu I occur in some groups of lower Oribatida , for example in Lohmanniidae ( Seniczak et al. 2018, 2021).

In Nanhermannia species, the leg segments, setae and solenidia are poorly known. Lee (1985) drew all legs of N. grandjeani Lee, 1985 , whereas Fujikawa (1990, 2003) drew all legs of N. bifurcata Fujikawa, 1990 , genu II of N. triangula Fujikawa, 1990 , and genu, tibia and tarsus I of N. angulata Fujikawa, 2003 . In all species, most leg setae are short, thick or conical, and most solenidia are blunt, as in N. sellnicki . Lee (1985) used his own system of labelling of the leg setae, which is difficult to compare, whereas in Fujikawa (1990, 2003) the leg setae are unlabelled. In N. grandjeani and N. bifurcata , the hypertrichy of setae l occurs on the trochanter III, and l and v on tarsi I and II and v on other tarsi, as in N. sellnicki . On the tarsus II of N. grandjeani and N. bifurcata , the seta l is visible close to the solenidion ω 2 and posterior to the seta tc, and in N. bifurcata there are also additional setae l on the femur II, as in N. sellnicki . Interestingly, Fujikawa (2003) drew in N. grandjeani solenidia ω 2 and ω 3 in the anterior position, close to the claw I, as in N. sellnicki .

The pattern of leg setae and solenidia of N. sellnicki is in a certain degree similar to that of Platynothrus species, which also have additional setae l on femora II and III, and l and v on most tarsi (Seniczak et al. 2022, Seniczak & Seniczak 2022a, b). However, in N. sellnicki setal pair l 1 and l 2 on tarsus II are separated by solenidia ω 1 and ω 2 and setae ft, whereas in Platynothrus species solenidia ω 1 and ω 2 are located in the anterior position, and all setae l are added posterior to them. In all species, the number of setae on femora of deutonymph, tritonymph and adult, and number of setae on tarsi of adult are species-specific.

The shape of chelicera and palp is known in N. dorsalis , N. grandjeani Lee, 1985 and N. verna ( Fujikawa 1990) . Their chelicerae are chelate-dentate with a short and thick seta chb located posterior to the longer seta cha, as in N. sellnicki . In these species, the palp setae are short and thick; the femur has one seta and the genu has no seta, as in N. sellnicki . In N. bifurcata Fujikawa, 1990 , N. grandjeani , N. milloti Balogh, 1961 , and N. verna , the hypostomal setae are drawn. Only in N. grandjeani these setae are relatively short, thick and smooth, as in N. sellnicki , whereas in most other species they are longer, pliable and smooth. The exception is N. milloti in which the seta h is clearly longer than other setae and barbed, whereas other setae look smooth. In N. sellnicki studied herein, the hypostomal setae were drawn from the light microscopy ( Fig. 3a ) and are well complemented by the SEM micrographs ( Figs 5b , 6a ).

Figures

FIGURE 1. Nanhermannia sellnicki, female. (a) Dorsal aspect, legs I−III partially drawn, scale bar 50 μm; (b) apical part of bothridial seta (enlarged).

FIGURE 2. Nanhermannia sellnicki, female, ventral aspect, legs partially drawn, scale bar 50 μm.

FIGURE 3. Nanhermannia sellnicki, female. (a) Lateral aspect, ovipositor rejected, legs partially drawn, (b) hypostomal setae; mouthparts, right side, (c) chelicera, (d) palp. Scale bars in μm (a) 50, (b, c) 20, (d) 10.

FIGURE 4. Nanhermannia sellnicki, female, SEM micrographs. (a) Dorsal view; (b) lateral view; (c) ventrolateral view; (d) medial part of body, dorsal view.

FIGURE 5. Nanhermannia sellnicki, female, SEM micrographs. (a) Bothridial seta, dorsal view; ventrolateral view; (b) anterior part of body, (c) posterior part of body, (d) medial part of body.

FIGURE 6. Nanhermannia sellnicki, female, SEM micrographs. (a) Mouthparts, ventral view; lateral view, (b) leg I and II, (c), (d) leg I.

FIGURE 7. Nanhermannia sellnicki, leg segments of female (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; (b) leg II; (c) leg III, tibia (v’’); (d) leg IV, tibia (v’’); (e) seta d on leg I; (f) seta l1 ’’ on femur I (e, f enlarged).

FIGURE 8. Nanhermannia sellnicki, larva. (a) Dorsal aspect, legs I and II partially drawn, scale bar 20 μm; (b) shape of seta in and bothridial seta (enlarged).

FIGURE 9. Nanhermannia sellnicki, ventral part of hysterosoma, legs III and IV partially drawn, scale bar 50 μm. (a) Larva, (b) protonymph.

FIGURE 10. Nanhermannia sellnicki, lateral aspect, legs partially drawn, scale bars 50 μm. (a) Larva, (b) tritonymph.

FIGURE 11. Nanhermannia sellnicki, leg segments of larva (part of femur to tarsus), scale bar 20 μm. Right side, antiaxial aspect; (a) leg I, tarsus (pl’ not illustrated); (b) leg II; (c) leg III; (d) genu and tibia I, dorsal aspect.

FIGURE 12. Nanhermannia sellnicki, ventral part of hysterosoma, legs IV partially drawn, scale bar 50 μm. (a) Deutonymph, (b) tritonymph.

FIGURE 13. Nanhermannia sellnicki, tritonymph. (a) Dorsal aspect, legs I and II partially drawn, scale bar 50 μm; (b) basal part of seta d1 (enlarged).

FIGURE 14. Nanhermannia sellnicki, leg segments of tritonymph (part of femur to tarsus), scale bar 10 μm. Right side, antiaxial aspect; (a) leg I, tarsus (pl’ not illustrated); (b) leg II; (c) leg III; (d) leg IV; (e) region of solenidia ω1 and ω2 on tarsus II, dorsal aspect.