Lepidacarus maafushiensis, Bayartogtokh & Ermilov & Joharchi, 2022

Bayartogtokh, Badamdorj, Ermilov, Sergey G. & Joharchi, Omid, 2022, Ontogenetic instars of Lepidacarus maafushiensis sp. nov. from the Maldives, with remarks on morphological ontogeny of Lohmanniidae (Acari, Oribatida), Zootaxa 5187 (1), pp. 7-29 : 9-16

Lepidacarus maafushiensis sp. nov.

( Figs 1–12 )

Diagnosis. Adult. Body length: 531–581. Prodorsum, notogaster, partially subcapitular mentum and epimeres III, IV heavily tuberculate. Rostrum broadly concave, with median triangular tooth. Rostral, lamellar, interlamellar, anterior exobothridial, posterior exobothridial, notogastral, and adanal setae widely phylliform, rounded distally, heavily barbed. Bothridial seta long, narrowly elongate fusiform, with sparsely ciliate one side and densely serrate opposite side. Notogaster with numerous oval depressions in medioposterior part. Eighteen pairs of notogastral setae present including two pairs of additional setae. Dorsal transverse bands present. Subcapitulum with four pairs of widely phylliform, rounded distally, ciliate setae (m 2, m 3, m 4, and h). Palp setation: 0–1–0–2–9(+ω). Epimeral setal formula: 10–7–3–4; all setae widely phylliform, rounded distally, ciliate. One pair of genital setae widely phylliform, rounded distally, ciliate; other setae as well as anal setae setiform, shortly ciliate. Tarsus II with two solenidia. Many leg setae widely phylliform, rounded distally, ciliate. Juvenile instars. Prodorsum and gastronotum sparsely microtuberculate. Rostrum broadly concave, with median triangular tooth. Rostral, lamellar, interlamellar, anterior exobothridial, posterior exobothridial, true gastronotic, and true adanal setae widely phylliform, rounded distally, heavily barbed. Bothridial seta long, narrowly elongate fusiform, with sparsely ciliate one side and densely serrate opposite side. Gastronotum with numerous oval depressions in medioposterior part. Larva with 16 pairs of gastronotic setae including three pairs of p 1 – p 3 on pseudoanal plates; protonymph with 17 pairs (added n 1), deuto- (added n 2) and tritonymph with 18 pairs of gastronotic setae. Palp setation of larva and protonymph: 0–0–0– 2–9(+ω); seta on femur added in deutonymph. Setal formulas for epimeres: larva: 3–1–2; protonymph: 4–2–2–1; deutonymph: 6–4–3–3, tritonymph: 8–5–3–4; seta 1c in larva setiform, shortly ciliate; other setae widely phylliform, rounded distally, ciliate. Deutonymph and tritonymph with one pair of lateral, widely phylliform, rounded distally, ciliate setae.

Adult

( Figs 1–5 )

Description. Measurements. Medium sized species as compared to other species of the genus. Body length: 564 (holotype), 531–581 (six paratypes); notogaster width: 282 (holotype), 249–298 (six paratypes).

Integument. Body colour yellowish-brown. Surface of body and legs densely microreticulate (micropolygonal ornamentation).Also, prodorsum, notogaster, partially subcapitular mentum and epimeres III, IV heavily tuberculate (diameter of tubercle up to 12) and partially densely microgranulate. Macroreticulate (macropolygonal) pattern on body absent.

Prodorsum. Roughly triangular in dorsal view, occupying about 2/3 of dorsal length. Rostrum broadly concave, with median triangular tooth. Lateral side of rostrum with some slight barbs and partially undulate. Rostral, lamellar, interlamellar, anterior exobothridial, and posterior exobothridial setae widely phylliform, rounded distally, heavily barbed. Bothridial seta (77–82) with short stalk and narrowly elongate fusiform head having sparsely ciliate one side and densely serrate opposite side. Lateral tubercle of prodorsum (close and anterolateral to anterior exobothridial seta) well developed. Region between lamellar and interlamellar setae with some depressions. Postbothridial band present, very broad.

Notogaster. With numerous oval depressions in medioposterior part. Eighteen pairs of notogastral setae present (sixteen pairs of basic setae and two pairs— n 1, n 2 —of additional setae); all setae widely phylliform, rounded distally, heavily barbed. Five transverse bands (others not visible) present dorsally; S 2 complete, S 3 – S 6 interrupted medially. Lyrifissures ia, im, ih, and ip distinct; ips not observed. Ventral bands close to adanal region indistinct.

Gnathosoma. Subcapitulum size: 139–147 × 110–114. Six pairs of subcapitular setae developed including four pairs of m; a (41–45) setiform, smooth; m 1 (49–53) setiform, slightly barbed; m 2, m 3, m 4, and h widely phylliform, rounded distally, ciliate. Adoral seta or 1 lobe-shaped, slightly roughened distally; or 2 (28–32) setiform, bluntended, with one small barb in distal part; or 3 (22–24) setiform, with attenuate tip, smooth. Palp length: 49–53; palp setation: 0–1–0–2–9(+ω); second tarsal—posterior—seta lt” absent; three distal setae of tarsus— ul’, ul”, su —connected basally. Postpalpal seta (12) stick-like, roughened. Chelicera length: 168–176. Cheliceral seta cha (10–12) needleform, smooth; chb (36–41) setiform, roughened.

Epimeral and lateral podosomal regions. Epimeral setal formula: 10–7–3–4. All setae widely phylliform, rounded distally, ciliate.

Anogenital region. Lateral pair of genital setae larger than others, widely phylliform, rounded distally, ciliate; other setae setiform, shortly ciliate (of these, five pairs of medial setae shorter, 20–24; four pairs of mediolateral setae longer, 28–32). Transverse furrow of genital plate distinct. Two pairs of anal setae (28–32) setiform, shortly ciliate. Four pairs of adanal setae widely phylliform, rounded distally, barbed. Anal and adanal lyrifissures not observed.

Legs. Claw of each leg smooth on dorsal side, with tooth proximoventrally. Formulas of leg setation and solenidia: leg I (0–5–3–5–17) [2–1–2], leg II (0–5–3–5–13) [1–1–2], leg III (2–4–2–3–10) [1–1–0], leg IV (2–3–2– 3–10) [1–0–0]; homology of setae and solenidia indicated in Table 1 . Solenidion ω 1 on tarsus I, ω 1, ω 2 on tarsus II and φ on tibia III bacilliform; other solenidia setiform. Solenidion ω 2 and seta ft” on tarsus I inserted close to each other. Famulus tubercle-like, inserted anterolateral to solenidion ω 1. Some leg setae widely phylliform, rounded distally, ciliate.

Juvenile instars

( Figs 2 , 6–12 )

Description. Measurements. Body length:larva:265–273(three specimens), protonymph:315–365(four specimens); deutonymph: 415–431 (11 specimens), tritonymph: 464–514 (14 specimens). Body width: larva: 149–166 (three specimens), protonymph: 182–199 (four specimens); deutonymph: 215–232 (11 specimens), tritonymph: 249–282 (14 specimens).

Integument. General body cuticle colourless, rarely slightly yellowish in some nymphs. Surface of body and legs densely microreticulate (micropolygonal ornamentation). Also, prodorsum and gastronotum sparsely microtuberculate in larva, proto- and deutonymph versus tubercles usually large in tritonymph. Macroreticulate (macropolygonal) pattern on body absent.

Prodorsum. Roughly triangular in dorsal view, occupying about 2/3 of dorsal length. Rostrum broadly concave, with median triangular tooth. Lateral side of rostrum with some slight barbs and partially undulate. Rostral, lamellar, interlamellar, anterior exobothridial, and posterior exobothridial setae widely phylliform, rounded distally, heavily barbed. Bothridial seta (La: 49–57; Pn: 53–61; Dn: 61–69; Tn: 69–77) with short stalk and narrowly elongate fusiform head having sparsely ciliate one side and densely serrate opposite side. Lateral tubercle of prodorsum (close and anterolateral to anterior exobothridial seta) well developed. Region between lamellar and interlamellar setae with some depressions. Postbothridial band distinct in larva and protonymph versus slightly visible in deuto- and tritonymph.

Gastronotic region. With numerous oval depressions in medioposterior part (poorly visible in larva and protonymph versus clearer visible in deuto- and tritonymph). Larva with 16 pairs of gastronotic setae including three pairs of p 1 – p 3 on pseudoanal plates; seta h 4 not developed. Protonymph with 17 pairs (added n 1), deutonymph with 18 pairs (added n 2), tritonymph with 18 pairs of gastronotic setae. All gastronotic setae—except setiform, smooth setae h 3 (12–14) and p 1 – p 3 (8–10) in larva—widely phylliform, rounded distally, heavily barbed. Some transverse bands present dorsally, usually slightly visible or indistinct.

Gnathosoma. Generally, similar in adult. Larva with three pairs of subcapitular setae (a, m 1, h); m 2 added in protonymph, m 3 in deutonymph, m 4 in tritonymph. Larva with two pairs of adoral setae (or 1, or 2); or 3 added in protonymph. Palp setation of larva and protonymph: 0–0–0–2–9(+ω); seta on femur added in deutonymph.

Epimeral region. Setal formulas for epimeres: larva: 3–1–2; protonymph: 4–2–2–1; deutonymph: 6–4–3–3, tritonymph: 8–5–3–4. Seta 1c in larva setiform, shortly ciliate; other setae widely phylliform, rounded distally, ciliate. Claparède’s organ distinct.

Anogenital region. Genital valves divided in deuto- and tritonymph (undivided in protonymph). Larva without genital, anal and adanal setae; protonymph without anal setae, but with one pair of genital (18–20; setiform, shortly ciliate) and four pairs of adanal (8–10, setiform, smooth) setae; deutonymph with five pairs of genital (four pairs of medial setae: 12, setiform, shortly ciliate; one pair of lateral setae: widely phylliform, rounded distally, ciliate), two pairs of anal (12, setiform, smooth) and four pairs of adanal (widely phylliform, rounded distally, heavily barbed) setae; tritonymph with eight pairs of genital (three pairs of medial setae: 12, setiform, shortly ciliate; four pairs of mediolateral setae: 20, setiform, shortly ciliate; one pair of lateral setae: widely phylliform, rounded distally, ciliate), two pairs of anal (20–24, setiform, shortly ciliate) and four pairs of adanal (widely phylliform, rounded distally, heavily barbed) setae. Pseudoadanal (in protonymph) and pseudoanal (in deutonymph) plates with paraproctal setae. Cupules ih and ips appearing in normal ontogenetic pattern; adanal and anal cupules not observed.

Legs. Claw of each leg smooth on dorsal side, with tooth proximoventrally. Formulas of leg setation and solenidia: larva: I (0–2–3–4–15) [2–1–1], II (0–2–3–3–13) [1–1–1], III (0–2–2–3–10) [1–1–0]; protonymph: I (0– 2–3–4–16) [2–1–2], II (0–3–3–3–13) [1–1–1], III (1–3–2–3–10) [1–1–0], IV (0–0–0–0–6) [0–0–0]; deutonymph: I (0–5–3–4–16) [2–1–2], II (0–5–3–3–13) [1–1–2], III (2–3–2–3–10) [1–1–0], IV (1–2–2–2–10) [1–0–0]; tritonymph: I (0–5–3–5–17) [2–1–2], II (0–5–3–5–13) [1–1–2], III (2–4–2–3–10) [1–1–0], IV (2–3–2–3–10) [1–0–0]; homology of setae and solenidia indicated in Table 1 .

Material examined. Holotype and six paratypes : Maldives, Maafushi Island, 3°56'40.5"N, 73°29'35.2"E, soillitter samples under the Indian Almond Tree near the coast, 25.XII.2021 (leg O. Joharchi). Three larvae, four proto-, 11 deuto-, and 14 tritonymphs: the same data as for the holotype and paratypes.

Type deposition. The holotype is deposited in the collection of the Senckenberg Museum of Natural History, Görlitz, Germany; six paratypes, three larvae, four proto-, 11 deuto-, and 14 tritonymphs are deposited in the collection of the Tyumen State University Museum of Zoology, Tyumen, Russia. All specimens are preserved in 70% solution of ethanol with a drop of glycerol.

Etymology. The species name maafushiensis refers to the place of origin, Maafushi Island.

Differential diagnosis. In having elongate fusiform bothridial seta and numerous notogastral depressions, adult of Lepidacarus maafushiensis sp. nov. is similar to Lepidacarus ennarpi Haq & Ramani, 1997 from India. However, the new species can be distinguished from the later by the size of rostral setae (comparatively very large, connected medially versus medium-sized, distinctly separated), the morphology of rostrum (broadly concave, with median triangular tooth versus rounded) and bothridial setae (head sparsely ciliate on one side and densely serrate opposite side versus both sides of head ciliate), and the number of setae on epimere IV (four pairs versus three pairs).

Ontogenetic transformations

The juveniles are colourless or slightly yellowish in some nymphs, adult of yellowish-brown colour. In both juveniles and adult, cuticle of body and legs densely microreticulate, prodorsum and gastronotum sparsely microtuberculate. Rostrum broadly concave, with median triangular tooth, in both juveniles and adult. Form of the prodorsal and gastronotic/notogastral setae is the same throughout ontogenetic instars: larva with 13 pairs of gastronotic setae (larval seta h 4 absent), protonymph with 17 pairs (setae of p -series newly appeared), deuto-, tritonymphs and adult with 18 pairs of gastronotic/notogastral setae. Larva with three pairs of subcapitular setae (a, m 1, h), seta m 2 appeared in protonymph, m 3 in deutonymph and m 4 in tritonymph. Larva with two pairs of adoral setae (or 1, or 2), and seta or 3 added in protonymph. Palp femur with no seta in larva and protonymph, but femoral seta added in deutonymph. Larva with six pairs of epimeral setae (1a, 1b, 1c, 2a, 3a, 3b), seta 1d, 2b and 4a newly appeared in protonymph, while 3c, 4b, 4c added in deutonymph, seta 4d developed in tritonymph, seta 4e added in adult. Number of anogenital setae gradually increasing from larva to adult: larva without anogenital setae; one pair of genital and four pairs of anal setae appeared in protonymph; four pairs of genital and two pairs of anal setae formed in deutonymph; three pairs of genital setae added in tritonymph, and one more pair of genital setae added in adult. Paraproctal valves of larva (segment PS) with three pairs of setae, protonymph (segment AD) without seta, and deutonymph (segment AN) with two pairs of setae. Leg setation increasing from instar to instar as shown in Table 1 .

Figures

FIGURE 1. Lepidacarus maafushiensis sp. nov., adult: A—dorsal view; B—ventral view (gnathosoma and legs except trochanters not shown). Scale bar 100 μm.

FIGURE 2. Lepidacarus maafushiensis sp. nov., adult (A, C, E) and larva (B, D, F): A, B—subcapitulum, ventral view; C, D—palp, left, paraxial view; E—chelicera (basal part not shown), left, paraxial view; F—chelicera, left, paraxial view. Scale bar 20 μm (A–C, E, F), 10 μm (D).

FIGURE 3. Lepidacarus maafushiensis sp. nov., adult:A—leg I, without trochanter, right, antiaxial view; B—femur, genu and tibia of leg II, right, antiaxial view; C—femur, genu and tibia of leg III, left, antiaxial view; D—leg IV, without trochanter, left, antiaxial view. Scale bar 20 μm.

FIGURE 4. Lepidacarus maafushiensis sp. nov., adult, SEM micrographs: A—dorsal view; B—ventral view; C—ventrolateral view; D—anterodorsal view.

FIGURE 5. Lepidacarus maafushiensis sp. nov., adult, SEM micrographs: A—posterior view; B—gnathosoma, lateral view; C—genital region, ventrolateral view; D—anoadanal region, lateral view.

FIGURE 6. Lepidacarus maafushiensis sp. nov., larva: A—dorsal view; B—ventral view (gnathosoma and legs except trochanters not shown); C—part of prodorsum and notogaster, lateral view. Scale bar 50 μm.

FIGURE 7. Lepidacarus maafushiensis sp. nov., dorsal view of juvenile instars: A –protonymph; B—tritonymph. Scale bar 50 μm (A), 100 μm (B).

FIGURE 8. Lepidacarus maafushiensis sp. nov., epimeral region of juvenile instars: A –protonymph; B—deutonymph; C— tritonymph. Scale bar 50 μm.

FIGURE 9. Lepidacarus maafushiensis sp. nov., anogenital region of juvenile instars: A –protonymph; B—deutonymph; C— tritonymph. Scale bar 50 μm.

FIGURE 10. Lepidacarus maafushiensis sp. nov., larva (A–C) and protonymph (D):A—leg I, without trochanter, left, paraxial view; B—leg II, without trochanter, left, paraxial view; C—leg III, without trochanter, left, antiaxial view; D—leg IV, without trochanter, right, antiaxial view. Scale bar 20 μm.

FIGURE 11. Lepidacarus maafushiensis sp. nov., tritonymph, SEM micrographs: A—dorsal view; B—part of gastronotic region, dorsal view; C—ventral view; D—anterodorsal view; E—part of prodorsum, dorsal view.

FIGURE 12. Lepidacarus maafushiensis sp. nov., deuto- (A–D; F) and tritonymph (E), microscope images: A—part of prodorsum, lateral view; B—part of ventral side, ventral view; C—subcapitulum and palp, ventral view; D—part of epimeral region, ventral view; E—genital plate, right, ventral view; F—leg III, right, antiaxial view.