Zachvatkinibates svanhovdi A. Seniczak & S. Seniczak, 2023

Seniczak, Stanisław, Seniczak, Anna, Hagen, Snorre B. & Klütsch, Cornelya F. C., 2023, Morphological ontogeny of Zachvatkinibates svanhovdi (Acari, Oribatida, Punctoribatidae), Zootaxa 5324 (1), pp. 66-82 : 70-81

Zachvatkinibates svanhovdi A. Seniczak & S. Seniczak, 2023

( Figs 1–12 )

Zachvatkinibates svanhovdi A. Seniczak & S. Seniczak , in Seniczak et al., 2023; p. 44

Diagnosis

The diagnosis of adult of this species was given by Seniczak et al. (2023, their figures 2–11). Herein only diagnosis of juveniles is given.

Juveniles light brown with slightly darker prodorsum, gastronotal shield, surrounding of gla opening and legs. Larva with 12 pairs of gastronotal setae, most of medium size, barbed and inserted on unsclerotized integument, nymphs with 15 pairs, most short and smooth; setae of c -series inserted on unsclerotized integument. In larva pygidial shield absent, in nymphs gastronotal shield present, with 10 pairs of setae (c -, d -, l -, h -series, p 1), p 2 and p 3 inserted on unsclerotized integument. In larva porose humeral organ absent but in nymphs present.

Description of juveniles

Larva oval in dorsal and ventral views, light brown with slightly darker prodorsum, posterior part of gastronotum, surrounding of gla opening and legs. Prodorsum subtriangular, prodorsal setae ro, le and in of medium size and barbed, ro longest, le shortest, all barbed; seta ex short and smooth ( Figs 1 , 2a , 3a , 4a, 4b , Table 1 ). Mutual distance between setal pair le about 1.5 times longer than that between setal pair ro, and mutual distance between setal pair in more than three times longer than that between setal pair ro, pair le inserted closer to pair in than ro. Opening of bothridium rounded, with small posterolateral ridge, bothridial seta clavate, with barbed head.

Gastronotum of larva with 12 pairs of setae including h 3 inserted lateral to anterior part of anal valves, most setae of medium size and barbed except for smooth h 2 and short and smooth h 3; setae dp, lp and h 1 slightly longer than other gastronotal setae ( Figs 1a , 2a , 3a , 4 , Table 1 ). Pygidial shield not observed but posterior part of gastronotum slightly darker than other parts, length setae of d - and l -series slightly increasing from anterior to posterior. Cupule ia posterior to seta c 3, cupule im posterior to seta lm, cupule ip between setae h 1 and h 2, cupule ih lateral to anterior part of anal opening. Opisthonotal gland opening posterolateral to seta lm, with dark sclerotized surrounding. Humeral organ not observed. Paraproctal valves (segment PS) glabrous. Chelicera chelate-dentate ( Fig. 5a ). Leg segments relatively thick ( Figs 4a, 4d , 6 ), most leg setae with short barbs, seta ft" on tarsus I relatively long.

Shape and colour of protonymph and other nymphs, prodorsal setae and bothridium as in larva but seta in longer than ro and bothridial setae slimmer ( Figs 3b , 5b–d , 8 ) than in larva. Gastronotum of protonymph with 15 pairs of setae (p -series added, Fig. 2b ) and retaining in subsequent nymphs ( Figs 7a,7b ), setae of p -series short and smooth. In all nymphs gastronotal shield with 10 pairs of setae (d -, l -, h -series, p 1), setae p 2 and p 3 inserted on unsclerotized integument; all setae relatively short and smooth or with short barbs ( Figs 2b , 3b , 5b–d , 7 , 8 , 9a–c , 10d , 11a ). Setae of c -series of medium size with small barbs and inserted on unsclerotized integument, c 3 longest, c 2 shortest ( Table 1 ). In protonymph one pair of genital setae appearing on genital valves and two pairs added in each, deutonymph and tritonymph ( Figs 2b , 7a, 7b ), all short and smooth. In deutonymph one pair of aggenital setae and three pairs of adanal setae appearing and remained in tritonymph; all short and smooth. In protonymph and deutonymph anal valves glabrous, in tritonymph two pairs of short and smooth anal setae present. In tritonymph, cupules ia and im as in larva, cupule ip between setae p 1 and h 2, cupule iad lateral to anterior part of anal valves, cupules ips and ih displaced posterolateral to iad ( Figs 3b , 7 ). Humeral organ rounded, porose, located anteroventral to seta c 3, opisthonotal gland opening anteroventral to seta lp, with dark sclerotized surrounding ( Fig. 3b ). Leg segments of tritonymph relatively thick ( Figs 3b , 5b–d , 9a, 9c, 9d , 10b–d , 11 , 12 ), most leg setae barbed but barbs on setae v on tibia and pv on tarsi slightly longer than on other setae, seta ft" on tarsus I relatively long.

Summary of ontogenetic transformations

In all juveniles the prodorsal setae ro, le and in are of medium size or long and seta ex is short, but in the larva ro is longer than in and in the nymphs in is longer than ro. The bothridium is rounded in all instars, and the bothridial seta is clavate with barbed head but in the larva the head is thicker than in the nymphs. The larva has 12 pairs of gastronotal setae including h 3, the nymphs have 15 pairs (p -series added in the protonymph). The notogaster of adult loses five pairs of setae (c 1, c 3 and d -series), such that 10 pairs of notogastral setae remain ( Seniczak et al. 2023). The formula of gastronotal setae in Z. svanhovdi is 12-15-15-15-10 (from larva to adult), the formulae of epimeral setae are 3-1-2 (larva, including scaliform 1c), 3-1-2-1 (protonymph), 3-1-2-2 (deutonymph) and 3-1-3-3 (tritonymph and adult). The formula of genital setae is 1-3-5-6 (protonymph to adult), and formula of aggenital setae is 1-1-1 (deutonymph to adult), and setal formula of segments PS–AN is 03333-0333-022. The ontogeny of leg setae and solenidia of Z. svanhovdi , including data on the adult ( Seniczak et al. 2023) is shown in Table 2 .

Distribution, ecology, and biology

Zachvatkinibates svanhovdi is known only from Sør-Varanger community and Gr. Jakobselv locality (Troms and Finnmark county, Northern Norway). In the sample (volume unknown) collected at the end of August, 119 individuals of Z. svanhovdi were found, and the adults dominated constituting 68% of all individuals. The stage structure of this species was: 19 larvae, 7 protonymphs, 10 deutonymphs, 2 tritonymphs and 81 adults. Among the 30 individuals investigated, the sex ratio (females to males) was 1:1, and no females were gravid and carried eggs ( Seniczak et al. 2023). In the sample collected in October (volume 500 cm 3), 123 specimens of Z. svanhovdi were found, and the juveniles predominated making 92% of all individuals. The stage structure in this sample was: 6 larvae, 61 protonymphs, 26 deutonymphs, 20 tritonymphs and 10 adults.

Comparison of morphological ontogeny of Zachvatkinibates svanhovdi with that of some species of Punctoribatidae and remarks

Seniczak et al. (2020b) considered the morphology of juveniles of Zachvatkinibates highly differentiated, compared to other genera of Punctoribatidae which is well-observed on the example of species of Zachvatkinibates ( Z. latilamellatus , Z. svanhovdi , and Z. tetrasklerosis ), Minunthozetes Hull, 1916 [ M. pseudofusiger ( Schweizer, 1922) , M. semirufus (C.L. Koch, 1841) ], Mycobates Hull, 1916 [ M. sarekensis ( Trägårdh, 1910) ] and Punctoribates Berlese, 1908 ( P. astrachanicus Shaldybina, 1973 and P. ghilarovi Shaldybina, 1969 ) with known morphological ontogeny, including leg setae and solenidia ( Table 3 ; Behan-Pelletier 1988; Seniczak et al. 2015, 2018, 2020a, b, 2022; Seniczak & Seniczak 2018). For example, the larva of Z. svanhovdi studied herein lacks a humeral organ but it is present in most species of Punctoribatidae , both in the larva and nymphs, except for juveniles of Punctoribates sellnicki Willmann, 1928 ( Seniczak & Seniczak 2008). The larvae of Zachvatkinibates lack a pygidial sclerite, similarly as members of Mycobates and Punctoribates but in Minunthozetes this sclerite is present ( Table 3 , Palacios-Vargas & Vasquez 1988; Behan-Pelletier & Eamer 2005, 2008). The juveniles of Z. latilamellatus have small, sclerotized depressions on the gastronotum ( Seniczak et al. 2020b), which are absent in other species of Punctoribatidae . The nymphs of Z. svanhovdi have setae of c -series inserted on unsclerotized integument, as those of Mycobates , Punctoribates , and M. semirufus but in other species of Zachvatkinibates these setae originate from basal microsclerites. The nymphs of Z. svanhovdi have setae p 2 and p 3 inserted on unsclerotized integument, as in Z. latilamellatus and members of Minunthozetes , Mycobates and Punctoribates but in Z. tetrasklerosis these setae arise on basal microsclerites. The juveniles of Z. svanhovdi have a dark sclerite around gla opening, as those of Z. tetrasklerosis and members of Punctoribates but in Z. latilamellatus and other species given in Table 3 this sclerite is absent. The juveniles of species compared also differ from one another by the length of setae and some leg characters which can be used for identification of species in ecological investigations. The presence of humeral organ in the juveniles is an important morphological character typical of larger groups of mites ( Norton & Behan-Pelletier 2009) but other characters are probably species-specific. In the light of this comparison the diagnosis of juveniles of Zachvatkinibates given by Behan-Pelletier & Eamer (2005) should be modified as follows: humeral organ present at least in tritonymph, gastronotal shield present at least in tritonymph, opisthonotal gland opening with or without surrounding sclerite. The adults of these species differ from one another by the length, shape and location of setae including bothridial setae, location of porose area A1 and some leg characters ( Table 3 ).

1 According to Seniczak et al. (2020b), 2 Behan-Pelletier (1988), 3 Seniczak et al. (2018), 4 Seniczak & Seniczak (2018), 5 Seniczak et al. (2015), 6 Seniczak et al. (2020a), 7 Seniczak et al. (2022), 8 sacculi present, 9 length slightly shorter than distance between setae c 1 and c 2

The ontogeny of leg setae of Z. svanhovdi differs slightly from other species of Zachvatkinibates and other genera of Punctoribatidae compared in Table 3 . The formulae of leg setae (and solenidia) of tarsi, genua and trochanters I–IV are similar in all species [20(2)-15(2)-15-12; 4(2)-4(2)-3(1)-3(1) and 1-1-2-1 respectively] but differences concern femora and genua. For example, in the adult of Z. svanhovdi seta v'' on femora I and II is absent, but in other species of Zachvatkinibates and other genera of Punctoribatidae it is present. In the tritonymph of Z. svanhovdi seta l on femur III is present, as in other species of Zachvatkinibates and members of Punctoribates but in Minunthozetes and Mycobates this seta is absent both in the tritonymph and adult. In the tritonymph of Z. svanhovdi seta v' on genua I and II is present, as in species of Mycobates , Punctoribates and M. pseudofusiger but in M. semirufus this seta is absent. In the light of this comparison, the presence of seta v'' on femora I and II, l' on femur III and v' on genua I and II is species specific.

Figures

FIGURE 1. Zachvatkinibates svanhovdi, larva. (a) Dorsal aspect, legs I and II partially drawn, scale bar 20 μm; (b) shape of seta c3 (enlarged).

FIGURE 2. Zachvatkinibates svanhovdi, ventral part of hysterosoma, legs III and IV partially drawn, scale bar 20 μm. (a) Larva, (b) protonymph.

FIGURE 3. Zachvatkinibates svanhovdi, lateral aspect, legs partially drawn, scale bars 50 μm. (a) Larva, (b) tritonymph.

FIGURE 4. Zachvatkinibates svanhovdi, larva, SEM micrographs. Lateral view, (a) habitus, (b) prodorsum, (c) gla opening; (d) habitus, ventral view.

FIGURE 5. Zachvatkinibates svanhovdi, SEM micrographs. (a) Larva, mouthparts; tritonymph, (b) dorsal view, (c) lateral view, (d) anterior part of body, lateral view.

FIGURE 6. Zachvatkinibates svanhovdi, leg segments of larva (part of femur to tarsus), right side, antiaxial aspect, scale bar 10 μm. (a) Leg I, tarsus (pl' not illustrated); (b) leg II; (c) leg III.

FIGURE 7. Zachvatkinibates svanhovdi, ventral part of hysterosoma, legs IV partially drawn, scale bar 50 μm. (a) Deutonymph, (b) tritonymph.

FIGURE 8. Zachvatkinibates svanhovdi, tritonymph. (a) Dorsal aspect, legs I and II partially drawn, scale bar 50 μm; (b) seta c3 (enlarged).

FIGURE 9. Zachvatkinibates svanhovdi, tritonymph, SEM micrographs. Lateral view, (a) medial and posterior part, (b) gla opening; ventral view, (c) habitus, (d) anterior and medial part of body.

FIGURE 10. Zachvatkinibates svanhovdi, tritonymph, SEM micrographs. Bothridial seta, (a) lateral view, (b) dorsal view; dorsal view, (c) anterior part of body, (d) medial and posterior part of body.

FIGURE 11. Zachvatkinibates svanhovdi, tritonymph, SEM micrographs.Ventral view, (a) posterior part of body, (b) mouthparts; lateral view, (c) legs I–III, (d) legs III and IV.

FIGURE 12. Zachvatkinibates svanhovdi, leg segments of tritonymph (part of femur to tarsus), right side, antiaxial aspect, scale bar 20 μm. (a) Leg I, tarsus (pl' not illustrated); (b) leg II; (c) leg III; (d) leg IV.

Tables

TABLE 2. Ontogeny of leg setae (Roman letters) and solenidia (Greek letters) in Zachvatkinibates svanhovdi.

Leg	Trochanter	Femur	Genu	Tibia	Tarsus
Leg I
Larva	-	d, bv''	(l), σ	(l), v', φ1	(ft), (tc), (p), (u), (a), s, (pv), (pl), ε, ω 1
Protonymph	-	-	-	-	ω2
Deutonymph	-	(l)	-	φ2	-
Tritonymph	v'	-	v'	v''	(it)
Adult	-	v''	-	-	v', l''
Leg II
Larva	-	d, bv''	(l), σ	l', v', φ	(ft), (tc), (p), (u), (a), s, (pv), ω1
Protonymph	-	-	-	-	-
Deutonymph	-	(l)	-	l"	ω 2
Tritonymph	v'	-	v'	v''	(it)
Adult	-	v"	-	-	-
Leg III
Larva	-	d, ev'	l', σ	v', φ	(ft), (tc), (p), (u), (a), s, (pv)
Protonymph	-	-	-	-	-
Deutonymph	l'	l'	-	l'	-
Tritonymph	v'	-	-	v''	(it)
Adult	-	-	-	-	-
Leg IV
Protonymph	-	-	-	-	ft'', (p), (u), (pv)
Deutonymph	-	d, ev'	d	v', φ	(tc), (a), s
Tritonymph	v'	-	l'	l', v''	-
Adult	-	-	-	-	-