Punctoribates astrachanicus Shaldybina, 1973

Seniczak, Stanisław, Ivan, Otilia, Marquardt, Tomasz & Seniczak, Anna, 2020, Morphological ontogeny of Punctoribates astrachanicus (Acari: Oribatida Punctoribatidae), and comments on Punctoribates Berlese, Zootaxa 4900 (1), pp. 43-61 : 48-59

Punctoribates astrachanicus Shaldybina, 1973

Punctoribates astrachanicus: Krivolutsky and Lebedeva 2004 .

Semipunctoribates astrachanicus: Mahunka1987 , Andrievskij et al. 2002, Subías 2004, Smelyansky 2006, Bayartogtokh 2010.

Punctoribates (Semipunctoribates) astrachanicus: Subías 2012 .

Diagnosis

Adult of medium size (415–488), with characters of Punctoribates . Bothridial seta fusiform, anterior tectum of notogaster straight. Most notogastral setae alveolar, except for short p -series. Four pairs of saccules present. Aggenital, adanal and anal setae short. Trochanter IV and femur IV with transverse folds, tarsus I with dorsal projection.

Juveniles light brown, prodorsal seta ex short and thin, humeral organ relatively large, especially in nymphs. Gastronotal setae of larva of medium size and pointed, in nymphs short.

Morphology of adult

Adults ( Figs. 1–5a, 5b ) similar to those investigated by Shaldybina (1973), but see Remarks. Mean length (and range) of females 458.9±12.8 (440–488, n= 19) and males 432.5±10.4 (415–446, n= 11), mean width (and range) of females 327.8±11.2 (307–343) and males 303.2±7.2 (295–319). Pedotectum I strongly convex dorsally ( Fig. 3a ). Hypostomal setae h, m and a short and smooth, m slightly longer than other setae ( Fig. 2 ). Cheliceral seta cha longer and thicker than chb, both barbed ( Fig. 3b ). Most palp setae relatively long, sup, inf and l” on tibia finely barbed, other setae smooth ( Fig. 3c ), formula of palp setae 0-2-1-3-9(1). Trochanters III and IV and all femora flattened, trochanter IV and femur IV with transverse folds, tibiae II–VI and tarsus I with dorsal projections ( Fig. 4 ). Formulae of leg setae [trochanter to tarsus (+ solenidia)]: I – 1-5-3(1)-4(2)-20(2); II – 1-5-3(1)-4(1)-15(2); III – 2-3-1(1)-3(1)-15; IV – 1-2-2-3(1)-12. Leg tarsi heterotridactylous.

Remarks. The adults investigated herein are wider, and slightly longer than those investigated by Shaldybina (1973; length 430–473, width 258–301, sex not investigated). In our individuals, the epimeral setae 1b, 1c and 4a are slightly longer than in those studied by Shaldybina (1973; setae 3c and 4c not drawn).

Description of juveniles

Larva oval in dorsal view ( Fig. 6 ), light brown. Prodorsum subtriangular, prodorsal seta ro long, in and le of medium size ( Table 1 ), all barbed; seta ex short and smooth. Mutual distance between setal pair le about 2.5 times longer than between pair ro, between setal pair in about three times longer than between pair ro, pair le inserted approximately midway between pairs ro and in. Opening of bothridium rounded, bothridial seta clavate, with barbed head.

Gastronotum of larva with 12 pairs of setae, including h 3 inserted lateral to medial part of anal valves ( Figs. 6 , 7a , 8a ), most setae of medium size and barbed, except for short and smooth h 3. Pygidial shield absent, all setae inserted on unsclerotized integument, length of setae of d - and l -series slightly increasing from anterior to posterior ( Table 1 ). 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. Porose humeral organ relatively large, anterior to seta c 3 ( Fig. 8a ). Paraproctal valves (segment PS) glabrous. Most leg setae barbed, seta ft” relatively long ( Fig. 9 ).

Shape and colour of protonymph, prodorsal setae and bothridium as in larva; gastronotum with 15 pairs of setae because p -series added ( Fig. 7b ), and retained in subsequent nymphs ( Figs. 10a, 10b ). In protonymph, setae of p -series longer than other posterior setae. In all nymphs, gastronotal shield present, with 10 pairs of setae (d -, l -, h -series, p 1), setae p 2 and p 3 inserted on unsclerotized integument; all short and smooth. Setae of c -series of medium size and barbed, c 3 longest, c 2 shortest ( Table 1 ). In protonymph, one pair of genital setae appearing on genital valves, two pairs added in deutonymph and tritonymph each ( Figs. 7b , 10a, 10b ), all short and smooth. In deutonymph, one pair of aggenital setae and three pairs of adanal setae appear, 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 p 2, cupule iad lateral to anterior part of anal valves, cupules ips and ih displaced posterolateral and anterolateral to iad, respectively ( Figs. 8b , 10b , 11 ). Humeral organ large, rounded, porose, located posterolateral to seta c 3 ( Figs. 5f , 8b ), opisthonotal gland opening lateral to seta lp, with dark sclerotized surrounding. Legs of tritonymph stocky ( Figs. 5d, 5e , 12 ), without dorsal projections and setae pv on tarsi with shorter barbs than in adult ( Fig. 4 ).

Summary of ontogenetic transformations

In the larva, the prodorsal seta ro is longer than setae le and in, whereas in the other instars seta in is longer than ro and le. Seta ex is short in all instars. The bothridium is rounded in all instars, but in the adult it is covered by anterior tectum of notogaster. In all juveniles, the bothridial seta is clavate, with barbed head, whereas in the adult it is fusiform and smooth. The larva has 12 pairs of gastronotal setae, including h 3, the nymphs have 15 pairs (p -series appears in the protonymph), whereas the notogaster of adult loses five pairs of setae (c 1, c 3 and d -series), so the 10 pairs of notogastral setae remain. The formula of gastronotal setae in P. astrachanicus 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 P. astrachanicus is shown in Table 2 .

Distribution, ecology and biology

According to Subías (2020), Punctoribates astrachanicus is known only in South European Russia, but it was also collected in Romania ( Ivan 2005). This species prefers steppe habitats ( Shaldybina 1973, Andrievskij et al. 2002, Smelyansky 2006), and the upper soil horizon ( Smelyansky 2010). Smelyansky (2006) investigated some population characters of this species in steppe habitat in South-East of the European part of Russia, and this species was not abundant, females were more abundant than males (mean sex ratio 1:0.48), and gravid females carried usually three large eggs ( Smelyansky 2010). This species was also found in feathers of chaffinch ( Krivolutsky & Lebedeva 2004).

In this study, P. astrachanicus was found in two habitats in Mânzăteşti ( Romania), with salty soils. In facies with Camphorosma annua , this species was distinctly more abundant (148.6 indiv./ 500cm 3) than in ruderal stand with Lolium perenne and Cynodon dactylon (3.2 indiv./ 500cm 3). In both habitats, the adults dominated the juveniles. In the former habitat, the juveniles comprised 31% of all individuals, whereas in the later habitat they comprised 13% of all individuals. In facies with Camphorosma annua , the stage structure of P. astrachanicus was the following: nine larvae, 27 protonymphs, 136 deutonymphs, 59 tritonymphs and 512 adults (total number from five replicates). In this habitat, the sex ratio (females to males) was 1:0.6, 48% females were gravid, carying 3–7 large eggs (185 x 90), which comprised 40% of the length of females.

Comparison of morphology of Punctoribates astrachanicus with congeners and remarks

Among Punctoribates adults, the largest species is P. tschernovi Shtanchaeva & Subías, 2014 , and smallest species is P. conjunctus ( Subías et al., 1990) , and the body length of several species overlaps ( Table 3 ). In most species, the bothridial seta is clavate, whereas in other species it is fusiform. Most species have alveolar notogastral setae, whereas in other species they are short or minute (unknown in some species). In most species, the medial part of anterior tectum of notogaster is straight, whereas in other species is convex or has incision. In most species, adanal and anal setae are short, whereas in few species they are alveolar or in some species are unknown. All these species also differ from one another by the form of octotaxic system and the shape of porose areas ( Table 3 ).

Seniczak and Seniczak (2008) compared the morphological ontogeny of P. punctum , P. hexagonus and P. sellnicki , and the juveniles of P. astrachanicus are most similar to those of P. hexagonus , in having a humeral organ and thin prodorsal seta ex. In the larva of P. hexagonus , most gastronotal setae are of medium size and pointed, and in the nymphs these setae are short, as in P. astrachanicus . However, the larva of P. astrachanicus is stockier than that of P. hexagonus and has the gastronotal seta h 2 barbed, whereas in P. hexagonus it is smooth. The nymphs of P. astrachanicus have relatively shorter seta c 1 and longer seta c 2 than in P. hexagonus , and seta c 2 is barbed, whereas in P. hexagonus it is smooth. By contrast, the larva of P. punctum has the prodorsal seta ex barbed and gastronotal setae blunt, and the nymphs have setae c 1 and c 2 short and smooth, which in P. astrachanicus are barbed. Moreover, a humeral organ of nymphs of P. astrachanicus is larger than in P. hexagonus and P. punctum . The juveniles of P. sellnicki differ from those of P. astrachanicus , P. hexagonus and P. punctum mainly by the absence of humeral organ and longer and thicker gastronotal setae. Generally, the juveniles of species compared differ from one another by specific characters, and no generic character was observed in them, which argue against dividing these species in subgenera, proposed by Subías (2004).

The juveniles of P. astrachanicus are also similar to those of other species of Punctoribatidae . For example, the larva of P. astrachanicus is similar to those of Minunthozetes pseudofusiger ( Schweizer, 1922) and M. semirufus (C.L. Koch, 1841) , except for absence of the pygidial shield, which in other species is present (Seniczak & Seniczak 2018, Seniczak et al. 2018). The nymphs of all species have a large gastronotal shield, with 10 pairs of short setae (d -, l -, h -series and p 1), but P. astrachanicus has larger humeral organ than other species, located posterolateral to seta c 3, as in P. punctum ( Seniczak & Seniczak 2008) , whereas in other species it is placed anterior to seta c 3. The juveniles of P. astrachanicus are also similar to those of Zachvatkinibates latilamellatus Bayartogtokh & Aoki, 1998 , except for presence of small, sclerotized depressions on the gastronotum, which in the former species are absent. The juveniles of Mycobates sarekensis ( Trägårdh, 1910) are more stocky than those of P. astrachanicus , have longer gastronotal setae, and the nymphs have the gastronotal shield divided in two parts by transverse furrow ( Seniczak et al. 2015), which in P. astrachanicus is absent.

The ontogeny of leg setae and solenidia of P. astrachanicus is similar to that of Z. latilamellatus , except for seta v’ on genua I and II, which in the latter species appears in the tritonymph (Seniczak et al. 2018), and in the former species is delayed to the adult. The ontogeny of leg setae and solenidia of P. astrachanicus differs more from that of M. pseudofusiger and M. semirufus mainly by the appearance of pair l on femora I and II in the deutonymph (versus in the two latter species this pair is delayed to tritonymph), and setae l’ and v’’ on tibia IV in the tritonymph (versus in two latter species they are delayed to adult, Seniczak & Seniczak 2018, Seniczak et al. 2018). The ontogeny of leg setae and solenidia of Mycobates Hull, 1916 differs more from that of P. astrachanicus , and differentiates particular species ( Behan-Pelletier et al. 2001, Seniczak et al. 2015).

Figures

FIGURE 1. Punctoribates astrachanicus, female, dorsal aspect, legs partially drawn, scale bar 50 μm.

FIGURE 2. Punctoribates astrachanicus, female, ventral aspect, legs partially drawn, scale bar 50 μm.

FIGURE 3. Punctoribates astrachanicus, adult. (a) Lateral aspect, legs partially drawn, scale bar 50 μm; mouthparts, right side, scale bars 20 μm; (b) chelicera (Trägårdh organ in transparent area), (c) palp.

FIGURE 4. Punctoribates astrachanicus, 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, genu (l’), tarsus (pl’); (b) leg II; (c) leg III; (d) leg IV.

FIGURE 5. Punctoribates astrachanicus, transmitted-light photomicrographs. Adult, (a) whole body, dorsal view, (b) anterior part, dorsal view; (c) larva, dorsal view; tritonymph, (d) whole body, dorsal view, (e) anterior part, dorsal view, (f) humeral organ, lateral view. Scale bars (um): (a), (d) ‾ 100, (b), (c), (e), (f) ‾ 50.

FIGURE 6. Punctoribates astrachanicus, larva. (a) Dorsal aspect, legs partially drawn, scale bar 20 μm, (b) shape of seta lp (enlarged).

FIGURE 7. Punctoribates astrachanicus, ventral part of hysterosoma, legs partially drawn, scale bar 20 μm. (a) Larva, (b) protonymph.

FIGURE 8. Punctoribates astrachanicus, lateral aspect, legs partially drawn, scale bars 50 μm. (a) Larva, (b) tritonymph.

FIGURE 9. Punctoribates astrachanicus, leg segments of larva (part of femur to tarsus), right side, antiaxial aspect, seta on the opposite side not illustrated is indicated in the legend, scale bar 20 μm. (a) Leg I, tarsus (pl’); (b) leg II; (c) leg III.

FIGURE 10. Punctoribates astrachanicus, ventral part of hysterosoma, legs partially drawn, scale bar 50 μm. (a) Deutonymph, (b) tritonymph.

FIGURE 11. Punctoribates astrachanicus, tritonymph, dorsal aspect, legs partially drawn, scale bar 50 μm.

FIGURE 12. Punctoribates astrachanicus, leg segments of tritonymph (part of femur to tarsus), right side, antiaxial aspect, seta on the opposite side not illustrated is indicated in the legend, scale bar 20 μm. (a) Leg I, tarsus (pl’); (b) leg II; (c) leg III; (d) leg IV.

Tables

TABLE 1. Measurements of some morphological characters of juvenile stages and adult of Punctoribates astrachanicus (mean measurements of 2–10 specimens in μm); Nd – not developed.

Morphological characters	Larva	Protonymph	Deutonymph	Tritonymph	Adult
Body length	185	251	323	416	460
Body width	96	146	191	254	329
Length of prodorsum	61	65	67	126	86
Length of seta ro	25	26	27	32	43
Length of seta le	14	21	24	27	30
Length of seta in	21	33	36	40	79
Length of seta bs	33	37	40	42	64
Length of seta c 1	16	18	16	14	Lost
Length of seta c 2	6	6	5	5	0
Length of seta c 3	19	19	30	27	Lost
Length of seta da	18	5	5	5	Lost
Length of seta dp	20	5	5	5	Lost
Length of seta la	15	5	5	5	0
Length of seta lp	16	5	5	5	0
Length of seta h 1	19	5	5	5	0
Length of seta h 3	4	5	5	5	0
Length of seta p 1	Nd	9	5	5	5
Length of seta p 3	Nd	8	5	5	5
Length of genital opening	Nd	26	33	54	62
Length of anal opening	46	50	55	101	86