Eremella (Eremella) ryabinini, Ermilov & Abramov, 2023

Ermilov, Sergey G. & Abramov, Vladimir V., 2023, Eremella ryabinini (Acari, Oribatida, Eremellidae), a new oribatid mite species phoretic on Amphotis marginata (Coleoptera, Nitidulidae) from Russia, Persian Journal of Acarology 12 (2), pp. 189-197 : 190-194

Eremella (Eremella) ryabinini sp. nov. ( Figs. 1–13 )

http://zoobank.org/ urn:lsid:zoobank.org:act:366F2BCB-B966-408D-B678-2A18DA3A1CF3

Diagnosis

Body length: 300–330. Notogaster and anogenital region with cerotegumental tubercles connected by cerotegumental strands, forming reticulate pattern. Costulae long, fused by two transcostulae (of them, the first is located behind lamellar setae; the second is located anteriorly to interlamellar setae). Rostral, lamellar and interlamellar setae medium-sized, slightly thickened, barbed; bothridial seta long, clavate, barbed. Dorsomedial part of notogaster hump-like; dorsolateral and posterior parts of notogaster depressed. All notogastral setae medium-sized, slightly thickened, barbed. Axillary saccule present. All epimeral and anogenital setae short, setiform, thin, roughened. Leg tarsi with three claws; tarsus II with one solenidion.

Description

Measurements – Body length: 330 (holotype, female), 300, 315 (two paratypes, two females); notogaster width: 180 (holotype), 165 (two paratypes).

Integument – Body brown. Surface microgranulate sculpturing; prodorsum, epimeral region and legs partially covered by layer of thin blocky cerotegument including dense granulate components; notogaster and anogenital region with larger sparse cerotegumental tubercles connected by cerotegumental strands, forming reticulate pattern.

Prodorsum – Rostrum rounded. Costula about 2/3 length of prodorsum, thin, slightly divergent distally; two transcostulae present: the first is located behind lamellar setae; the second is located anteriorly to interlamellar setae. Basal part of prodorsum between insertions of interlamellar setae hump-like. Tutorium well developed, simple. Rostral (30–34), lamellar (30–34) and interlamellar (22–26) setae slightly thickened, barbed; le slightly thicker than ro and in, inserted on strong tubercles; exobothridial seta (7) setiform, thin, roughened; bothridial seta (49–52) clavate, barbed.

Notogaster – Elongate oval, anterior and posterior notogastral margins rounded. Dorsomedial part of notogaster hump-like; dorsolateral and posterior parts of notogaster depressed. Notogastral setae (p 1 – p 3: 26–30; others: 37) slightly thickened, barbed. Opisthonotal gland opening and lyrifissure ia not observed; lyrifissures im, ip, ih, and ips well visible.

Gnathosoma – Subcapitulum size: 60–64 × 45–49; all subcapitular setae (m, h: 17–19; a: 11) setiform, roughened; all adoral setae (4) setiform, thin, smooth. Palp (length: 41–45) setation: 0–2– 1–3–9(+ω); postpalpal seta (4) spiniform. Axillary saccule present. Chelicera (length: 64–67) with two setiform, barbed setae (cha: 15–19; chb: 11–13).

Epimeral and lateral podosomal regions – Epimeral setal formula: 3–1–2–2; all epimeral setae (15) setiform, thin, roughened. Discidium well-developed, rounded distally.

Anogenital region – Genital (g 1: 13–15; others: 11), aggenital (11), anal (5–7), and adanal (11) setae setiform, thin, roughened. Adanal lyrifissure small, located close and parallel to anal plate.

Legs – Tridactylous; median claw thicker than lateral claws, all slightly barbed on dorsal side. Dorsoparaxial porose area on femora I–IV slightly visible. Formulas of leg setation and solenidia: I (1–5–3–4–17) [1–2–2], II (1–5–3–4–15) [1–1–1], III (2–3–1–3–15) [1–1–0], IV (1–2–2–3–12) [0–

1–0]; homology of setae and solenidia indicated in Table 1. Solenidion φ 1 of tibia I very long, subflagellate; other solenidia rod-like to slightly thickened.

Comparison

In having setiform interlamellar and notogastral setae, and reticulate notogastral cerotegument, E. (E.) ryabinini sp. nov. is similar to E. (E.) pulchella ( Balogh, 1959) from central and southern Europe and phoretic (on elaterid beetles) E. (E.) reticulatus ( Woolley, 1969) from the U.S.A. (Louisiana). However, the new species differs from both species by the larger body size (length: 300–330 versus 240–275 in E. (E.) pulchella , 186–204 in E. (E.) reticulatus ), the number and localization of transcostulae (two transcostulae developed, the first is located behind lamellar setae, the second is located anteriorly to interlamellar setae versus one transcostula developed, equally removed from lamellar and interlamellar setae in E. (E.) pulchella ; transcostulae absent in E. (E.) reticulatus ), and the similar length of lamellar and rostral setae (versus ro longer than le in E. (E.) pulchella and E. (E.) reticulatus ). Also, E. (E.) pulchella has monodactylous legs (versus tridactyllous in E. (E.) ryabinini ).

Type material

Holotype (female) and two paratypes (two females): Russia, Tula District, 54° 07' 20'' N, 36° 29' 47'' E, forest in the vicinity of the village of Matyukhinsky , from the edge of the right elytron of the beetle Amphotis marginata (Fabricius) , 12.05.2022 (leg. V. V. Abramov).

Type deposition

The holotype and two paratypes 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 is dedicated to our colleague Dr. Nikolay A. Ryabinin, the acarologist from the Institute of Water and Ecological Problems, Far Eastern Branch, Russian Academy of Sciences, Khabarovsk, Russia, for his extensive contributions to our knowledge of fauna and taxonomy of oribatid mites.

Remarks

1. Specimens of the new species located on the edge of the right elytron of Amphotis marginata (Nitidulidae) . They did not have specific phoretic morphological structures (e.g., Norton 1980; Ermilov and Frolov 2019b; Ermilov and OConnor 2020), however, due to the tight fit (adhesion) with the beetle, there is no doubt about phoresy.

2. The phoretic oribatid mites remains still poorly studied; available literature suggests that they prefer to use beetles of the family Passalidae for phoresy (e.g., Norton 1980; Ermilov 2019; Ermilov and Frolov 2021). The new species was found on the beetle of Nitidulidae ; it is the first record of using members of this family for phoresy.

Figures

Figures 1–2. Eremella (Eremella) ryabinini sp. nov. (adult, microscope images) – 1. Dorsal view; 2. Ventral view.

Figures 3–5. Eremella (Eremella) ryabinini sp. nov. (adult) – 3. Dorsal view (legs not shown); 4. Ventral view (gnathosoma and legs not shown); 5. Lateral view (gnathosoma and legs not shown).

Figures 6–13. Eremella (Eremella) ryabinini sp. nov. (adult) – 6. Posterior view; 7. Subcapitulum, ventral view; 8. Palp, right, antiaxial view; 9. Chelicera, left, antiaxial view; 10. Leg I, right, antiaxial view; 11. Leg II, right, antiaxial view; 12. Leg III, left, antiaxial view; 13. Leg IV, left, antiaxial view.