Sellnickia caudata ( Michael, 1908 )

Ermilov, Sergey G. & Salavatulin, Vladimir M., 2024, Juvenile instars of Sellnickia caudata (Michael, 1908) (Acari, Oribatida, Sellnickiidae), Zootaxa 5485 (1), pp. 38-48 : 39-41

Sellnickia caudata ( Michael, 1908)

( Figs 1–8 )

Description of juvenile instars

Measurements. Total length of larva: 225–240 (n=5), protonymph: 285–300 (n=4), deutonymph: 375–420 (n=4), tritonymph: 465–540 (n=5). Total width of larva: 142–150 (n=5), protonymph: 180–195 (n=4), deutonymph: 240– 285 (n=4), tritonymph: 300–365 (n=5).

Integument ( Fig. 8M ). Body color of larva, proto- and deutonymphs colorless to light brownish but legs and dorsal side of prodorsum intensely pigmented; body color of tritonymph brown but legs, gnathosoma, epimeres, and dorsal side of prodorsum usually intensely pigmented. Body surface densely microporose (distinctly visible on dorsal side of prodorsum and in epimeral region; Fig. 8M ); additionally, anogenital region partially slightly folded.

Prodorsum ( Figs 1A ; 2A ; 3A ; 4A ; 5A, B ; 8A–C ). Relatively short, about 1/2 length of gastronotic region. Rostrum broadly rounded. Dorsal side of prodorsum with large sclerite bordered by lateral carinae. Rostral (LA: 30– 34; PN: 34–37; DN: 45–52; TN: 49–60), lamellar (LA: 41–49; PN: 52–61; DN: 82–90; TN: 112–116), interlamellar (LA: 60–64: PN: 90–94; DN: 120–131; TN: 161–169), and exobothridial (LA: 22–26; PN: 34–37; DN: 120–131; TN: 161–169) setae setiform (in blunt), barbed ( Fig. 8C ); bothridial seta (LA: 15; PN: 19; DN, TN: 22–26) with short stalk and globular, slightly barbed head ( Figs 8A, B ). Transverse lineate ridge located anteriorly to rostral setae.

Gastronotic region ( Figs 1A ; 2A ; 3A ; 4A ; 5A, B ; 8D–G ). Gastronotic macrosclerite (shield) not observed. Gastronotum (and adanal region in tritonymph) with scattered poorly visible pit-like structures ( Fig. 8F ), posteriorly rounded. Larva with 13 pairs of setae (c 3 absent) including two pairs of paraproctal setae p 1 and p 2; setae c 1, c 2, da, la, dm, lm stiff, blunt, barbed ( Fig. 8D ), others setiform, smooth; all setae except h 2 and h 3 with excentrosclerite at the base ( Fig. 8D ). Nymphal instars with 14 pairs (c 3 absent) of setiform, smooth setae; all setae with excentrosclerite at the base ( Fig. 8E ). Length of gastronotic setae: LA: c 1, c 2, da, la, dm, lm: 22–26, dp, lp, h 1: 5, h 2: 9–11, h 3: 7, p 1, p 2: 5; PN: 7–11; DN, TN: 5–7. Opisthonotal gland opening and all cupules distinct.

Gnathosoma (6A–C; 7A–C; 8H). Subcapitulum size: LA: 37–39 × 49–56; PN: 52 × 67; DN: 67 × 86; TN: 82–90 × 101–109; length of subcapitular seta a: LA: 9–11; PN: 15; DN: 15–17; TN: 19; length of subcapitular setae m and h: LA: 9–11; PN: 15; DN: 19–22; TN: 22–26; all subcapitular setae setiform, a barbed, m and h roughened; length of adoral setae: LA: 7; PN: 7–9; DN: 9–11; TN: 13–15; all adoral setae setiform, barbed. Palp length: LA: 37–41; PN: 49; DN: 64; TN: 75–82; palp formula: 0-2-1-3-9(+ω); solenidion attached with eupathidium; length of postpalpal seta: LA: 2; PN, DN: 4; TN: 6. Chelicera length: LA: 49–52; PN: 60; DN: 75; TN: 97–112; length of cha: LA: 19; PN: 22; DN: 26–30; TN: 37; length of chb: LA: 13; PN: 15; DN: 19; TN: 26; both cheliceral setae setiform, barbed.

Epimeral region ( Figs 1B ; 2B ; 3B ; 4B ; 5A, B ). Setal formulas for epimeres: larva: 3-1-2 (1c as typical scale covering Claparède’s organ); protonymph: 3-1-2-1; deutonymph: 3-1-2-2, tritonymph: 3-1-3-3; length of setae: LA: 1b, 3b: 9–11, others: 6; PN: 1b, 3b: 13–19, 1c: 9–11, others: 7–9; DN: 1b, 3b: 22–26, 1c: 15–17, others: 11–15; TN: 1b, 3b: 22–26, 3c, 4c: 11, others: 17–19; all setae setiform, smooth.

Anogenital region ( Figs 1B ; 2B ; 3B ; 4B ; 5A, B ). Ontogeny of genital (PN: 7–11; DN: anterior and posterior setae: 7–9, median seta: 11; TN: anterior and posterior setae: 11, median three setae: 15), aggenital (DN: 9–11; TN: 17–19), anal (TN: 11), and adanal (DN: 9–11; TN: 15) setal formulas, proto- to tritonymph: 1-3-5, 0-1-1, 0-0-2, 0-3-3, respectively; all setae setiform, smooth, without excentrosclerite at the base; paraproctal segment with two gastronotic setae p in larva, without setae in protonymph and deutonymph. Adanal cupule distinct; anal cupule not observed.

Legs ( Figs 6D–F ; 7D–G ; 8I–L ). Claw of each leg dorsally slightly barbed. Tarsal pulvillus well developed ( Fig. 8I, J ). Tarsi I–IV with elongate oval ventrobasal porose area ( Fig. 8K ); femora I–IV with large ventrolateral (including antiaxial and paraxial sides) porose area ( Fig. 8L ). Formulas of leg setation and solenidia: larva I (0-2- 2-3-16) [1-1-1], II (0-2-2-2-13) [1-1-1], III (0-2-1-1-13) [1-1-0]; protonymph I (0-2-2-3-16) [1-1-2], II (0-2-2-2-13) [1-1-1], III (0-2-1-1-13) [1-1-0], IV (0-0-0-0-7) [0-0-0]; deutonymph I (0-3-2-3-16) [1-2-2], II (0-3-2-2-13) [1-1-1], III (1-2-1-1-13) [1-1-0], IV (0-2-1-1-12) [0-1-0]; tritonymph I (1-3-2-3-18) [1-2-2], II (1-3-2-3-15) [1-1-1], III (1- 2[3]-1-1-15) [1-1-0], IV (0-2-2-1-12) [0-1-0]; homologies of setae and solenidia indicated in Table 1 ; solenidia ω 1 on tarsus I, ω on tarsus II and σ on genu II slightly bacilliform, others rod-like or setiform.

Figures

FIGURE 1. Sellnickia caudata (Michael, 1908), larva: A—dorsal view; B—ventral view (gnathosoma and legs except trochanters not shown). Scale bar 50 μm.

FIGURE 2. Sellnickia caudata (Michael, 1908), protonymph: A—dorsal view; B—ventral view (gnathosoma and legs except trochanters not shown). Scale bar 50 μm.

FIGURE 3. Sellnickia caudata (Michael, 1908), deutonymph: A—dorsal view; B—ventral view (gnathosoma and legs except trochanters not shown). Scale bar 100 μm.

FIGURE 4. Sellnickia caudata (Michael, 1908), tritonymph: A—dorsal view; B—ventral view (gnathosoma and legs except trochanters not shown). Scale bar 100 μm.

FIGURE 5. Sellnickia caudata (Michael, 1908), larva (A) and deutonymph (B): right lateral view (gnathosoma and legs except trochanters not shown). Scale bars 50 μm (A), 100 μm (B).

FIGURE 6. Sellnickia caudata (Michael, 1908), larva: A—subcapitulum, ventral view; B—palp, right, antiaxial view; C—leg III, left, paraxial view; D—leg I, right, antiaxial view; E—leg II, right, antiaxial view; F—leg III, right, paraxial view. Scale bars 20 μm (A, C–F), 10 μm (B).

FIGURE 7. Sellnickia caudata (Michael, 1908), tritonymph: A—subcapitulum, ventral view; B—palp, right, antiaxial view; C—leg III, left, paraxial view; D—leg I, right, antiaxial view; E—leg II, right, antiaxial view; F—leg III, left, antiaxial view; G—leg IV, left, antiaxial view. Scale bars 20 μm (A–C), 50 μm (D–G).

FIGURE 8. Sellnickia caudata (Michael, 1908), larva (A, D) and deutonymph (B, C, E–L), microscope images: A, B— bothridial seta; C—lamellar seta; D—gastronotic setae la and lm; E—gastronotic seta la; F—gastronotic pit-like structures; G—opisthonotal gland opening; H—gnathosoma; I, J—claw and pulvillus of leg tarsus III; K, L—porose area on tibia I and femora III, respectively; M—microporose integument in interlamellar region. Magnification: 10 × 100.