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A new species of Paracarophenax (Acari: Heterostigmata: Acarophenacidae) associated with Triplax scutellaris (Coleoptera: Erotylidae) from European Russia

Khaustov, Alexander A.1 and Abramov , Vladimir V.2

1✉ Tyumen State University, Tyumen, Semakova 10, 625003 Russia.
2Gagarin str. 12, Suvorov, Tula Province, 301430, Russia.

2018 - Volume: 58 Issue: 2 pages: 332-341

DOI: 10.24349/acarologia/20184245
ZooBank LSID: E23C6E9C-0E42-4DF8-B263-C0C9BCADB2AF

Keywords

Heterostigmatina Pyemotoidea systematics morphology phoresy

Abstract

A new species, Paracarophenax triplaxophilus n. sp. (Acari: Acarophenacidae), is described based on phoretic females collected under the elytra of a mycophagous beetle Triplax scutellaris Charpentier, 1825 (Coleoptera: Erotylidae) in European Russia. An updated key to species of Paracarophenax is provided. Homologies of some gnathosomal structures of acarophenacid mites are re-evaluated.

Introduction

The family Acarophenacidae currently includes one fossil genus Protophenax Magowski, 1994 and six extant genera: Acarophenax Newstead and Duval, 1918, Adactylidium Cross, 1965, Aegyptophenax Rady, 1992, Aethiophenax Mahunka, 1981, Paracarophenax Cross, 1965 and Paradactylidium Mahunka, 1975 and about 36 described species (Magowski 1994; Ardjomandi et al. 2017; Walter & Seeman 2017). Members of the family are parasitoids of eggs of various insects, including beetles from the families Cerambycidae, Tenebrionidae, Nitidulidae, Dermestidae, Curculionidae, Mycetophagidae and thrips (Thysanoptera) (Goldarazena et al. 2001; Katlav et al. 2015; Ardjomandi et al. 2017; Walter & Seeman 2017). The genus Paracarophenax Cross, 1965 includes six described species: P. dybasi Cross, 1965 from USA (Cross 1965), P. bambergensis (Krczal, 1959) from Germany (Krczal 1959), P. undosus Mahunka, 1975 from New Guinea (Mahunka 1975), P. paucisetosus Mahunka and Rack, 1977 from Hungary (Mahunka & Rack 1977), P. scolyti Khaustov, 1999 from Crimea (Khaustov 1999), and P. myzognathus Walter and Seeman, 2017 from Canada (Walter & Seeman 1917). Katlav et al. (2015) discussed distribution and host range of Paracarophenax species and Walter & Seeman (2017) redefined the genus and described the phenomenon of pre-phoresy, when adult females of P. myzognathus attached to larvae of the host beetle. During the study of insect associated mites, a new species of Paracarophenax was revealed from European Russia. This is the first record of a species of Acarophenacidae associated with fungus beetles of the family Erotylidae.

The aim of this article is to describe this new species associated with the mycophagous beetle Triplax scutellaris from European Russia and to re-evaluate homologies of some gnathosomal structures.

Materials and methods

Mites were collected from under the elytra of a single specimen of Triplax scutellaris that was captured by the junior author on rotten oyster mushroom Pleurotus sp.. 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 five female paratypes (in parentheses). For leg chaetotaxy the number of solenidia is given in parentheses. DIC micrographs were taken using the Carl Zeiss Axio Imager A2 compound microscope and digital Cameras Hitachi KP-HD20A. For SEM microscopy, alcohol-preserved mites were dried in a freeze drying device JFD 320 (JEOL, Japan), dusted by silver and scanned with the aid of a JEOL–JSM-6510LV SEM microscope. The holotypes and most paratypes of the new species are deposited in the mite collection of the Tyumen State University Museum of Zoology, Tyumen, Russia; two female paratypes of the new species are deposited in the acarological collection of the Zoological Institute of RAS, St. Petersburg, Russia.

Results
Systematics
Family Acarophenacidae Cross, 1965

Genus Paracarophenax Cross, 1965

Type species: Paracarophenax dybasi Cross, 1965

Paracarophenax triplaxophilus n. sp. (Figures 1–5)

ZOOBANK: 73D3924C-5DEB-4F99-B151-3D9608B35095

Diagnosis — Gnathosoma ventrally with pair of smooth membranous areas. Setae e and ps absent. Setae h 2 present. Aggenital setae present. Trochanter I with seta, trochanter II without seta. Apodemes 1 and 3 absent. Femur III with 2 setae, femur IV with 1 seta. Genua I and II with 2 setae each. Seta pl” of tarsus II spine-like.

Description

Female — Length of idiosoma 260 (280–290), width 190 (195).

Figure 1. Paracarophenax triplaxophilus n. sp., female: A – dorsum of the body, B – venter of the body. Legs omitted.

Figure 2. Paracarophenax triplaxophilus n. sp., female: A – right leg I in dorsal view, B – right leg II in dorsal view.

Figure 3. Paracarophenax triplaxophilus n. sp., female: A – right leg III in dorsal view, B – right leg IV in dorsal view.

Figure 4. DIC micrographs of Paracarophenax triplaxophilus n. sp. female: A – central part of prodorsum, B – lateral part of tergite D, C – gnathosoma and anterior part of anterior sternal plate, D – lateral part of posterior sternal plate, E – opisthosoma in ventral view, F – ducts (arrows) of unknown homology located above pharynx.

Figure 5. SEM micrographs of Paracarophenax triplaxophilus n. sp. female: A – general view, B – anterior part of prodorsum, C – stigma, D – setae of tergite H, E – left tibiotarsus I in dorsal view, F – right tarsus II in dorsal view.

Gnathosoma (Figures 1B, 4C, F) — Concealed dorsally by prodorsum, indistinguishable ventrally from idiosoma; palps absent. One pair of setae laterally, probably representing postpalpal seta pp (Figure 5C) (see Discussion). Venter with mouth flanked by paired, semi-ovular smooth membranous area (Figure 4C); one pair of rod-like ventral setae 4 (3–4) of unknown homology situated at anterior ends of membranous areas. Pharynx large, narrowly oval, thin walled. One pair of very thin ducts leads from mouth into propodosoma above pharynx (Figure 4F).

Idiosomal dorsum (Figures 1A, 4A, B, 5A-D) — Ovate. Prodorsal shield delineated into primary plate and prodorsal projection encapsulating gnathosoma. Stigmata on prodorsal projection; tracheal trunks broad, expanding after ca. 15–25 μm (into cylindrical atrium), becoming obsolete ca. 30–50 μm into body. Prodorsal shield and plates C, D, EF, H weakly punctate (Figures 4A, B). Pits sc 1 situated anterolaterally to bases of setae v 2. Setae e absent. All dorsal setae weakly barbed and blunt-ended (Figures 4A, B, 5D). Cupules small, round; ia and im situated anterolaterad bases of setae d and f respectively; cupules ih situated just laterad bases of setae h 1. Lengths of dorsal setae: v 2 37 (32–37), sc 2 34 (30–34), c 1 36 (34–37), c 2 36 (33–36), d 40 (39–41), f 44 (39–44), h 1 43 (39–43), h 2 34 (28–34). Distances between setae: v 2 –v 2 30 (30–34), sc 2 –sc 2 99 (99–105), v 2-sc 2 35 (35–39), c 1c 1 77 (69–77), c 1c 2 37 (37–39), dd 100 (98–105), ff 68 (65–67), h 1h 1 40 (32–36), h 2h 2 34 (29–34).

Idiosomal venter (Figures 1B, 4C-E) — Ventral plates punctate (Figures 4C-E), punctations coarser than on dorsal shields. Ventral setae 4b, 4c and ag weakly barbed, attenuate; other ventral setae smooth and attenuate. Setae 2a, 3a, 3c, and 4c with slightly thickened base (Figures 4C, D). Pseudanal setae absent. Apodemes 1 absent, apodemes 2 (ap2) well developed, just reaching prosternal apodeme (appr); sejugal apodeme (apsej) well developed and joined with prosternal apodeme; apodemes 3 absent; apodemes 4 (ap4) and 5 (ap5) well developed, but not joining each other medially. Lengths of ventral setae: 1a 12 (12–13), 2a 26 (24–27), 3a 21 (21–24), 3c 28 (27–31), 4a 19 (19–20), 4b 26 (25–27), 4c 29 (28–30), ag 38 (34–38).

Legs (Figures 2, 3, 5E, F) — Leg I (Figures 2A, 5E) much thicker than other legs. Leg setation: Tr 1, Fe 3, Ge 2, TiTa 17(2). Tibiotarsus with massive claw and structure opposing to claw. Solenidia ω 9 (7–9) and φ 8 (6–8) weakly clavate. Seta k thickened and flattened in middle part. Setae (pl), d and v” of tibiotarsus very long, smooth; seta l’ of femur slightly thickened, blunt-ended, smooth; seta d of femur blunt-ended and weakly barbed; seta pv” blunt-ended and smooth; other leg setae (except eupathidia) pointed and weakly barbed. Leg II (Figures 2B, 5F). Leg setation: Tr 0, Fe 3, Ge 2, Ti 4(1), Ta 7(1). Solenidia ω 10 (8–10) and φ 6 (5–6) weakly clavate. Tarsus with pair of simple claws and tongue-like empodium. Setae pl” and pv” spine-like, smooth; setae (tc) and (u) smooth, pointed; other leg setae weakly barbed and pointed. Leg III (Figure 3A). Leg setation: Tr 1, Fe 2, Ge 2, Ti 4, Ta 6. Claws and empodium as on tarsus II. Seta pv” spine-like, smooth; setae (tc) and (u) smooth, pointed; other leg setae weakly barbed and pointed. Leg IV (Figure 3B). Leg setation: Tr 1, Fe 1, Ge 1, Ti 4, Ta 5. Claws and empodium as on tarsus II. Seta pv” spine-like, smooth; setae tc” and (u) smooth, pointed; other leg setae weakly barbed and pointed.

Male unknown.

Type material — Female holotype, slide VA140616, Tula Province, vicinity of Suvorov town, 13 April 2016, under elytra of Triplax scutellaris Charpentier, 1825, coll. V.A. Abramov. Paratypes: 9 females, same data.

Etymology — The specific epithet of the new species is derived from the name of its phoretic host genus Triplax and Greek $hiotaambdaotalpha$ (philia), meaning ``friendship" or ``fondness".

Differential diagnosis — The female of the new species is most similar to P. myzognathus Walter and Seeman, 2017 described from Canada and P. paucisetosus Mahunka and Rack, 1977 described from Hungary because it lacks the body setae e and ps and also seta v′ on trochanter II. It can be distinguished from both species by the presence of aggenital setae (vs. absent in both other species), presence of seta on trochanter I (vs. absent in both other species), absence of apodemes 3 (vs. present in both other species), and well developed medially sejugal apodeme (vs. weak medially in P. myzognathus, but well developed in P. paucisetosus).

Key to species of Paracarophenax (based on Walter & Seeman (2017) with modifications)

1. Setae e and ps absent; trochanter II without seta
...... 2

— Setae e and ps present; trochanter II with seta
...... 4

2. Trochanter I without seta, aggenital setae absent
...... 3

— Trochanter I with seta, aggenital setae present
...... P. triplaxophilus n. sp.

3. Tracheal atria bulbous, narrowing distally; sejugal apodeme fully developed; apodemes I moderately well developed
...... P. paucisetosus Mahunka and Rack

— Tracheal atria cylindrical, not narrowing distally; sejugal apodeme weakly developed medially; apodemes I weakly developed or obsolete
...... P. myzognathus Walter and Seeman

4. Setae ag absent, tegula present
...... 5

— Setae ag present, tegula absent
...... 6

5. Tracheae with atrium terminating in brush-like extensions; setae h 2 present
...... P. scolyti Khaustov

— Tracheae without obvious atrium extensions; setae h 2 absent
...... P. undosus Mahunka

6. Prosternal and poststernal apodeme absent; setae h 2 as long as h 1
...... P. dybasi Cross

— Prosternal apodeme present; poststernal apodeme present as remnant; setae h 2 about twice as long as h 1
...... P. bambergensis (Krczal)

Discussion

Homologies of some gnathosomal structures. Paracarophenax triplaxophilus and some closely related species, such as P. myzognathus, retain two pairs of gnathosomal setae. One pair of setae is situated anterolaterally to stigmata, which Katlav et al. (2015) considered to be palpal femoral (dFe). Another pair of setae is located near to the anterior margin of the paired membranous areas. Walter & Seeman (2017) considered this pair of setae as subcapitular (su). We compared the gnathosomal structures of P. triplaxophilus with those of Pyemotes dryas (Vitzthum, 1923) (Figure 6), which is a representative of a closely related and more early-derivative family of the superfamily Pyemotoidea. In our opinion the ventrolateral pair of setae found in P. triplaxophilus is homologous to the gnathocoxal (or postpalpal) (pp) setae of P. dryas, because they are located in similar position and even have a similar shape (blade-like and appressed to the gnathosoma). A pair of membranous areas, which is located laterally to the mouth and is found in some Paracarophenax species is probably the remnants of the palps. In Pyemotes dryas, the palps are also weakly sclerotized, membranous and bearing setae dGe anteriorly (Figure 6). In our opinion the setae designated by Walter and Seeman (2017) as su could not be subcapitular because they are located anteriorly to mouth and on the anterior margin of the membranous areas (vestigial palps). Most probably this pair of setae is homologous with dGe of P. dryas, but it also could be cheliceral setae (ch) moved close to vestigial palps.

Figure 6. DIC micrograph of Pyemotes dryas (Vitzthum, 1923) female: gnathosoma in ventral view.
We also recorded paired thin ducts leading almost from the mouth to just above the pharynx (Figure 4F). These ducts are probably homologous to those recently found in females of some Petalomium (Pygmephoroidea: Neopygmephoridae) species (Silva et al. 2017).

Notes on phylogenetic relationships among some species of Aethiophenax and Paracarophenax. At present three species of acarophenacid mites are known as associates of mycophagous beetles: Paracarophenax myzognathus and Aethiophenax mycetophagi are associated with Mycetophagus sp., (Mycetophagidae) (Walter amd Seeman 2017; Arjomandi et al. 2017), and Paracarophenax triplaxophilus associated with Triplax scutellaris (Erotylidae) (present study). All host beetles were collected in oyster mushrooms. The above mentioned acarophenacid species are characterized by several synapomorphic characters: 1) absence of setae e on tergite EF, 2) absence of pseudanal setae, 3) spiniform setae pl” on tarsus II. All of these synapomorphies are also known in Paracarophenax paucisetosus and Aethiophenax luteoli Katlav et al. 2015. Phylogenetic relationships among the species of the genera Aethiophenax and Paracarophenax are unknown. Synapomorphies 1 and 2 are setal reductions and could be a result of homoplasy; synapomorphy 3 potentially could be a good evidence of close relationships between some species of Aethiophenax and Paracarophenax. It is still not clear are this group of species represents a single generic-level taxon (Aethiopenax potential synonym of Paracarophenax) or synapomorphic characters independently appeared in the genera Aethiophenax and Paracarophenax. The phylogenetic analysys of the genera Aethiophenax and Paracarophenax is necessary to clarify this taxonomic problem.

Acknowledgements

The authors thank A.N. Bobylev (Tyumen State University) for preparing SEM photos.

References

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Article editorial history

Date received:
2017-10-11
Date accepted:
2017-10-17
Date published:
2018-02-22

Edited by:
Bertrand, Michel

(CC BY 4.0)
© 2018 Khaustov, Alexander A. and Abramov , Vladimir V.

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