# A new species of Adactylidium (Acari: Heterostigmata: Acarophenacidae) associated with Phlaeothrips sp. (Thysanoptera: Phlaeothripidae) from European Russia

Alexander A Khaustov, Vladimir V Abramov

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Alexander A Khaustov, Vladimir V Abramov. A new species of Adactylidium (Acari: Heterostigmata: Acarophenacidae) associated with Phlaeothrips sp. (Thysanoptera: Phlaeothripidae) from European Russia. Acarologia, 2021, 61 (2), pp.356-364. 10.24349/acarologia/20214435. hal-03211950v2

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# A new species of *Adactylidium* (Acari: Heterostigmata: Acarophenacidae) associated with *Phlaeothrips* sp. (Thysanoptera: Phlaeothripidae) from European Russia

Alexander A. Khaustovª, Vladimir V. Abramovᵇ

## Original research

### ABSTRACT

A new species, *Adactylidium europaeum* n. sp. (Acari: Acarophenacidae), is described based on phoretic females collected on thorax of larvae of *Phlaeothrips* sp. (Thysanoptera: Phlaeothripidae) in European Russia. An updated key to the species of *Adactylidium* is provided.

**Keywords** Heterostigmatina; Pyemotoidea; systematics; morphology; phoresy; parasitoids

**Zoobank** http://zoobank.org/E77F0742-DF53-4704-AA60-B17FFEBBBF6C

## Introduction

The family Acarophenacidae includes species that are parasitoids of eggs of various insects, including beetles from the families Cerambycidae, Erotylidae, Tenebrionidae, Nitidulidae, Der-mestidae, Curculionidae (Scolytinae), Mycetophagidae and thrips (Thysanoptera) (Goldarazena et al. 2001; Katlav et al. 2015; Ardjomandi et al. 2017; Walter and Seeman 2017; Khaustov and Abramov 2018; Xu et al. 2018). At present, the family includes about 40 described species (including three extinct species) from eight genera (Khaustov et al. 2021). Khaustov et al. (2021) provided the latest key to the genera of Acarophenacidae. Currently six species of acarophenacid mites have been recorded from Russia: *Aethiophenax ipidarius* (Rediko-rtzev, 1947), *Paracarophenax scolyti* Khaustov, 1999 (both associated with bark beetles), *P. bambergensis* (Krczal, 1959) (associated with Nitidulidae), *P. triplaxophilus* Khaustov and Abramov, 2018 (associated with Erotylidae), *Paradactylidium pyemotoformis* Khaustov, 2007 and *Adactylidium absurdum* Khaustov, 2007 (both from unknown hosts) (Khaustov 1999, 2007; Khaustov and Abramov 2018, 2019).

The genus *Adactylidium* Cross, 1965 comprises 16 described species distributed in Europe, North and South Americas, and northern Africa (Goldarazena *et al.* 2001; Antonatos *et al.* 2011). All *Adactylidium* species are egg parasitoids of various thrips species (Thysanoptera). Therefore, they have been suggested to be potential biological control agents of thrips pests in agricultural systems (Antonatos *et al.* 2011).

During the study of insect associated mites, a new species of *Adactylidium* associated with *Phlaeothrips* sp. was revealed from the European Russia. The aim of this article is to describe this new species and provide an updated key to world species of *Adactylidium*.

Received 05 February 2021

Accepted 25 April 2021

Published 29 April 2021

Corresponding author
Alexander A. Khaustov:
alex1973khaustov@gmail.com

Academic editor
Baumann, Julia

DOI
10.24349/acarologia/20214435

ISSN 0044-586X (print)

ISSN 2107-7207 (electronic)

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Copyright

Khaustov A. A. and Abramov V. V.

Distributed under
Creative Commons CC-BY 4.0

OPEN ACCESS

<footnote>ªTyumen State University, Tyumen, Volodarskogo 6, 625003 Russia.</footnote>

<footnote>ᵇGagarin str. 12, Suvorov, Tula Region, 301430, Russia.</footnote>
**Material and methods**

Mites were collected from thorax of larvae of *Phlaeothrips* sp. by the junior author. The mites were mounted in Hoyer’s medium. The terminology follows that of Lindquist (1986). All measurements are given in micrometers (µm) for the holotype and two female paratypes (in parentheses). For leg chaetotaxy the number of solenidia is given in parentheses. Differential interference contrast (DIC) micrographs were taken using the Carl Zeiss Axio Imager A2 compound microscope and Hitachi KP-HD20A and Olympus OM-D Em-10 digital cameras.

**Abbreviations** — ap1-ap5 – apodemes 1-5; appr – prosternal apodeme; appo – poststernal apodeme; apsej – sejugal apodeme; apgn – gnathosomal apodeme.

**Results**

**Systematics**

**Family Acarophenacidae Cross, 1965**

**Genus Adactylidium Cross, 1965**

Type species: *Adactylidium beeri* Cross, 1965, by original designation

<figure><img src="image_8.png" /><figcaption>**Figure 1** *Adactylidium europaeum* n. sp., female (holotype): A – dorsum of body, B – venter of body. Legs omitted.</figcaption></figure>
<figure><img src="image_9.png" /><figcaption>**Figure 2** *Adactylidium europaeum* n. sp., female (holotype): A – right leg I, dorsal aspect, B – right leg II, dorsal aspect.</figcaption></figure>

**Adactylidium europaeum n. sp.**

Zoobank: 227447D6-8908-4C9C-8555-E92E102DC85A

(Figures 1–6)

**Diagnosis** — Apgn with median projections; genua I and III with three and one setae, respectively; tibiotarsus I with ventral subapical indentation; setae (tc) and (ft) of tibiotarsus I subequal in length; dorsal idiosomal setae with similar shape, elongate; apsej not fused with appr; setae 1b absent.

**Description**

**Female** – Length of idiosoma 130 (130, 135), width 100 (98, 105).

**Gnathosoma** – Apgn with distinct median projections (Fig. 6 A). Gnathosoma concealed dorsally by prodorsum, ventrally indistinguishable from idiosoma; dorsum with one pair of setae anterolaterally, probably representing postpalpal seta *pp*; venter with mouth flanked by paired, semi-ovular smooth membranous areas; one pair of rod-like ventral setae of unknown homology situated at anterior ends of membranous areas; one pair of blunt-ended subcapitular setae *m* located posteriad membranous areas. Pharynx large, slightly oval, thin walled, distinctly punctate (Fig. 6B).

Idiosomal dorsum (Figs 1A, 4A, 5A) – Ovate. Prodorsal shield delineated into primary plate and prodorsal projection, encapsulating gnathosoma. Stigmata on prodorsal projection; tracheal trunks long, with small atria located posteriad posterior margin of apgn. Prodorsal shield and plates C, D, EF, H distinctly punctate (Fig. 5A). Alveolar pits *sc*₁ situated anterolaterad bases of setae *v*₂. Setae *v*₂, *sc*₂, *c*₁ and *c*₂ thin, smooth and pointed; setae *d*, *e* and *f* with few weak barbs in basal half; setae *h*₁ and *h*₂ located ventrally, slightly thickened, blunt-ended and weakly barbed. Cupuli *ia* small, round, located laterad or anterolaterad bases of setae *d*; cupuli *im* situated anteromesad bases of setae *e*; cupuli *ih* not evident. Lengths of dorsal setae: *v*₂ 38 (38,
<figure><img src="image_10.png" /><figcaption>**Figure 3** *Adactylidium europaeum* n. sp., female (holotype): A – right leg III, dorsal aspect, B – right leg IV, dorsal aspect.</figcaption></figure>

43), *sc*₂ 18 (18, 19), *c*₁ 17 (18), *c*₂ 17 (18), *d* 17 (18, 20), *e* 15 (17, 18), *f* 17 (18), *h*₁ 7 (8, 9), *h*₂ 6 (7, 8). Distances between setae: *v*₂–*v*₂ 34 (34, 38), *sc*₁–*sc*₁ 43 (42, 47), *v*₂–*sc*₂ 17 (16–18), *sc*₂–*sc*₂ 66 (65, 71), *c*₁–*c*₁ 43 (42, 45), *c*₁–*c*₂ 22 (23, 24), *d*–*d* 52 (49, 58), *e*–*f* 16 (15, 16), *f*–*f* 20 (19, 26), *e*–*e* 52 (48, 52), *h*₁–*h*₁ 13 (11), *h*₂–*h*₂ 8 (11, 12).

Idiosomal venter (Figs 1B, 4B, 5B) – Ventral plates smooth; small subtriangular areas posteriad trochanters II with rough microsculpture; coxisternal fields IV with weak longitudinal striation (Fig. 5B). All ventral setae smooth and pointed; setae 1b absent. Aggenital plate with deep incision posteriorly. Ap1 weakly sclerotized, fused with well sclerotized appr; ap2 well sclerotized and fused with appr; apsej well sclerotized, not fused with appr; ap3 well developed, fused with well-developed appo; ap4 well sclerotized, not fused with appo; ap5 absent. Lengths of ventral setae: 2*a* 11 (12–13), 3*a* 11 (12, 13), 3*c* 11 (12), 4*b* 276 (7, 8), 4*c* 9 (8, 10), *ag* 7 (7, 8).

Legs (Figs 2, 3) – Leg I (Fig. 2A) distinctly shorter than other legs. Leg setation: Tr 0, Fe 3, Ge 3, TiTa 15(1). Tibiotarsus with ventral subapical indentation. Solenidion ω 4 (3, 4) clavate, situated in the middle of segment. Seta k bifurcate; eupathidia (tc) and (ft) subequal in length. At least setae *l''*, *v''* and *pv''* of tibiotarsus weakly barbed, other leg setae smooth; setae *d*, *l'* of femur and eupathidia (tc) and (ft) blunt-ended, other leg setae pointed. Leg II (Fig. 2B). Leg setation: Tr 0, Fe 3, Ge 3, Ti 4, Ta 6(1). Solenidion ω 4 (4, 5) digitiform. Setae *l'* of femur and (*u*) of tarsus blunt-ended, other leg setae pointed; at least setae *l'* of tibia and (*pv*) of tarsus weakly barbed, other leg setae smooth. Leg III (Fig. 3A). Leg setation: Tr 0, Fe 2, Ge 1, Ti 4, Ta 4. Setae (*u*) of tarsus blunt-ended, other leg setae pointed; at least setae *v'* of femur, *v'* of genu, *l'*, *v''* of tibia and *pv'* of tarsus weakly barbed, other leg setae smooth. Leg IV (Fig.
<figure><img src="image_11.png" /><figcaption>**Figure 4** DIC micrographs of *Adactylidium europaeum* n. sp., female (holotype): A – general view dorsally, B – general view ventrally.</figcaption></figure>

3B). Leg setation: Tr 0, Fe 1, Ge 1, Ti 4, Ta 4. Setae (u) of tarsus blunt-ended, other leg setae pointed; at least setae v' of genu, l', v'' of tibia weakly barbed, other leg setae smooth; seta tc'' of tarsus ultralong.

**Type material** — Female holotype, slide ZISP T-Acaroph-001, Tula Region, vicinity of Suvorov town, 54°07′ N, 36°30′ E, 10 November 2020, on thorax of larva of *Phlaeothrips* sp. on the bark of thin dead branches of birch, coll. V.A. Abramov. Paratypes: two females, same data, 14 November 2020.

**Type deposition** — The holotypes of the new species is deposited in the acarological collection of the Zoological Institute of RAS, St. Petersburg, Russia; two female paratypes are deposited in the mite collection of the Tyumen State University Museum of Zoology, Tyumen, Russia.

**Etymology** — The name of the new species refers to distribution in European part of Russia.

**Differential diagnosis** — The new species is most similar to *Adactylidium ficorum* Goldarazena and Ochoa, 2001, described from Puerto Rico and Egypt (Goldarazena *et al.* 2001) in having three setae on genu I, one seta on genu III, and well developed appo. The new species differs from *A. ficorum* in having apsej not fused with appr (apsej fused with appr in *A. ficorum*), setae 1b completely absent (alveoli of setae 1b present in *A. ficorum*) and median projections present on apgn (absent in *A. ficorum*).
<figure><img src="image_12.png" /><figcaption>**Figure 5** DIC micrographs of *Adactylidium europaeum* n. sp., female (holotype): A – left parts of prodorsum and tergite C, B – hysterosoma, ventral aspect.</figcaption></figure>
<figure><img src="image_13.png" /><figcaption>**Figure 6** DIC micrograph of *Adactylidium europaeum* n. sp., female (holotype): A – gnathosomal apodeme and tracheae, B – pharynx.</figcaption></figure>
Key to world species of Adactylidium (females)

1. Tibiotarsus I with solenidion..................................................2
— Tibiotarsus I without solenidion...........................................A. absurdum Khaustov, 2007

2. Tarsus III without solenidion..................................................3
— Tarsus III with solenidion..................................................A. nicolae (Krczal, 1959)

3. Setae 4b present.................................................................5
— Setae 4b absent.................................................................4

4. Genu I with three setae; genu II with two setae; dorsal hysterosomal setae short, thickened and distinctly barbed ....................................A. brasiliensis Goldarazena and Ochoa, 2001
— Genu I with four setae; genu II with three setae; dorsal hysterosomal setae long, thin and weakly barbed in basal part ........................A. flechtmanni Goldarazena and Ochoa, 2001

5. Genu I with three setae.........................................................6
— Genu I with four setae.........................................................8

6. Poststernal apodeme well developed........................................7
— Poststernal apodeme absent...........................................A. irregularis Goldarazena and Ochoa, 2001

7. Sejugal apodeme fused with prosternal apodeme; setae 1b present ....................................................A. ficorum Goldarazena and Ochoa, 2001
— Sejugal apodeme not fused with prosternal apodeme; setae 1b completely absent ............A. europaeum n. sp.

8. Genu III with one seta.........................................................9
— Genu III with two setae ......................................................10

9. Coxisternal fields I with tiny setae 1b..................A. morazae Goldarazena and Ochoa, 2001
— Coxisternal fields I without setae ....................................A. beeri Cross, 1965

10. Femur II with three setae..................................................11
— Femur II with two setae...........................................A. rumanicus Jordana and Goldarazena, 2001

11. At least setae *f* similar in shape and length to *d*........................................12
— Setae *e* and *f* short, thick and distinctly barbed, much shorter than *d*......A. gynaikothripsi Antonatos *et al.*, 2011

12. Setae *e* much shorter than *f*............................................14
— Setae *e* and *f* subequal....................................................13

13. Bases of setae *e* located distinctly anteriad setae *f*............................................A. lindquisti Jordana and Goldarazena, 2001
— Bases of setae *e* located slightly posteriad setae *f*......A. moundi Goldarazena *et al.*, 1997

14. Aggenital plate striated ....................................................15
— Aggenital plate smooth......................................................16

15. Gnathosomal apodeme with a distal notch; tergite C longer than wide; setae *h*₁ as long as *h*₂ ............................................A. costarricensis Goldarazena *et al.*, 1997
— Gnathosomal apodeme smooth distally; tergite C wider than long; setae *h*₁ three times longer