A new species Paracarophenax alternatus Xu and Zhang sp. nov. is described and illustrated based on phoretic females. The mites were found attached to the adult of Monochamus alternatus Hope (Coleoptera: Cerambycidae) collected from traps set in Minhou county, Fuzhou city, Fujian province, China. The new species is the eighth representative of the genus and also the first record of the Paracarophenax associated with the host family Cerambycidae. An updated the key to species of Paracarophenax is provided.
The family Acarophenacidae currently consists of 7 genera (six extant and one fossil) and about 37 described species worldwide (Arjomandi et al. 2017; Walter & Seeman 2017; Khaustov & Abramov 2018). Only one species of this family, Acarophenax mahunkai Steinkraus and Cross, 1993, was recorded from China (Gao & Zou 1994). Acarophenacid mites are known as egg parasitoids of various insects, including beetles (Cerambycidae, Tenebrionidae, Nitidulidae, Dermestidae, Curculionidae, Mycetophagidae and Erotylidae) and thrips (Thysanoptera) (Goldarazena et al. 2001; Katlav et al. 2015; Arjomandi et al. 2017; Walter & Seeman 2017; Khaustov & Abramov 2018), and considered as potential biological control agents due to its non-toxicity to people or domesticated animals (Krantz & Walter, 2009).
The genus Paracarophenax resembles Aethiophenax, but can be easily distinguished by stigmatal openings dorsal, atria membranous; one or two pairs of setae on tergite EF, setae e present or absent; and setae ps present or absent (stigmatal openings lateral, atria sclerotized; one pair of setae on tergite EF, setae e absent; and setae ps absent in Aethiophenax) (Walter & Seeman 2017). Paracarophenax comprises 7 described species: P. dybasi Cross, 1965, P. bambergensis (Krczal, 1959), P. undosus Mahunka, 1975, P. paucisetosus Mahunka and Rack, 1977, P. scolyti Khaustov, 1999, P. myzognathus Walter and Seeman, 2017 and P. triplaxophilus Khaustov and Abramov, 2017. In this paper, we describe and illustrate a new species associated with Monochamus alternatus Hope (Coleoptera: Cerambycidae). This is the second report of the family Acarophenacidae from China. An updated key to species of Paracarophenax is also provided.
Materials and methods
The beetle hosts Monochamus alternatus were captured in trap devices set up in Minhou county, Fuzhou city, Fujian province, China. The trapped beetles were examined and then the phoretic mites were transferred into 70% ethanol under a stereo microscope. All acarophenacid mites removed and cleared in lactic acid, and mounted in Hoyer's medium. Specimens were examined at 400x and 1000x magnification by using differential interference contrast of a Leica DM5000B compound microscope.
All measurements in micrometers (µm) were taken from slide-mounted specimens using a stage-calibrated ocular ruler. Measurement data are presented for holotype, followed by ranges for paratypes in parentheses. Body length was measured from the anterior margin of the idiosoma (including gnathosoma) to the posterior margin of the opisthosoma, and body width was measured as the greatest distance posterior to coxae II. Setal lengths were measured from the center of the setal base to the tip of the seta; distances between setae were measured as the distance from the center of one setal base to that of the other. Legs were measured from the basal end of trochanter to the distal end of tarsus (excluding pretarsus). Terminology follows Katlav et al. (2015) and Walter & Seeman (2017) who adapted from Lindquist (1986).
Family Acarophenacidae Cross, 1965
Genus Paracarophenax Cross, 1965
Type Species: Paracarophenax dybasi Cross, 1965
Paracarophenax alternatus Xu and Zhang sp. nov.
Diagnosis. Adult female. Each tracheal trunk with a brush-like atrium; two pairs of setae on tergite EF, two pairs of setae on tergite H; lacking setae ag; apodemes 1, 2 and sejugal apodeme well developed and fused, apodeme 3 not extending beyond setae 3c, apodeme 4 well developed but separated; tegula present; trochanters 1-1-1-1, femora 3-3-2-0, genua 4-1-1-1; setae v′ on genu II, v″ on tibia II, pv″ and pl″ on tarsus II spine-like.
Type material. Holotype Female, China, Minhou county, Fuzhou city, Fujian province, 27 Aug. 2018, by Meng-Ling Cai and Feng Xia, ex. Monochamus alternatus Hope (Coleoptera: Cerambycidae). Paratypes: 56 females, same data as holotype.
Type deposition. The holotype and 9 paratypes will be deposited in the National Zoological Museum of China, Institute of Zoology, Chinese Academy of Sciences, Beijing; 37 paratypes are deposited in the Department of Plant Protection, Fujian Agriculture and Forestry University, China; 10 paratypes are deposited in the New Zealand Arthropod Collection (NZAC), Landcare Research, Auckland, New Zealand.
Adult female (n=25).
Gnathosoma (Fig. 2). Rounded, fused with idiosoma. Palps fused with gnathosomal capsule, one pair of setae laterally, length 3 (3–4). Cheliceral stylets 12 (12–14) strong and curved. Pharynx enlarged and almost elliptical, length 50 (46–52), width 14 (12–15).
Idiosomal dorsum (Fig. 1). Ovate, length 255 (225–255), width 115 (100–115). Prodorsal shield trapezoidal, with two pairs of setae (v2 and sc2) thickened and blunt-ended; Lengths of setae: v2 50 (40–50), sc2 39 (33–40); distances between setae: v2–v2 30 (27–30), v2–sc2 30 (25–31), sc2–sc2 77 (72–77). Stigmata on prodorsal projection, associated with tracheal system and atria, tracheal trunks with a brush-like atrium. Cupules ia, im and ih situated on tergites D, EF and H, respectively. One pair of crescent-shaped ornamentation located near posterior margin of tergites C and middle of tergites D, respectively. Tergite C with two pairs of setae (c1 and c2); tergite D with one pair of setae d; tergite EF with two pairs of setae (e and f); tergite H with two pairs of setae (h1 and h2); all dorsal setae thickened and blunt-ended except h2 thinner and pointed. Setae f about twice as long as e; setae v2, c1 and f subequal, setae sc2, c2 and d subequal in length, and about four-fifths as long as setae f; setae h2 about two-thirds of h1 and located very close to h1. Setal lengths: c1 48 (43–50), c2 37 (30– 37), d 37 (35–43), e 22 (17–26), f 45 (36–49), h1 30 (20–30), h2 17 (13–18); distances between setae: c1–c1 50 (45–50), c2–c2 115 (100–115), c1–c2 40 (35–40), d–d 60 (55–60), e–e 56 (47–56), f–f 22 (20–26), e–f 15 (12–17), h1–h1 32 (25–32), h2–h2 40 (33–40), h1–h2 5 (3–5).
Idiosomal venter (Fig. 2). Ventral plates smooth. All ventral setae thin and smooth, lengths of setae: 1a 7 (5–7), 2a 12 (11–15), 3a 21 (20–28), 3c 12 (10–15), 4a 10 (8–12), 4b 8 (7–10), 4c 8 (8–10); distances between setae: 1a–1a 58 (50–58), 2a–2a 40 (38–42), 3a–3a 42 (33–42), 4a–4a 26 (23–30). All ventral apodemes well developed except for apodemes 3 (ap3) which are short and reach the bases of setae 3c. Apodemes 1 (ap1), apodemes 2 (ap2) and sejugal apodeme (apsej) joined with prosternal apodeme (appr); ap1 fused with appr to form a Y-shaped structure with anterior branches surrounding the base of gnathosoma. Posterior margin of posterior ventral plate with well developed tegula. Aggenital plate without setae ag; plate PS with one pair of setae ps, 6 (4–6).
Legs (Figs. 3–4). Lengths of legs I–IV: 75 (70–77), 72 (70–75), 87 (85–95), 100 (92–100). Tibiotarsus I length 39 (35–40), width 22 (20–23). Setal counts for legs I–IV (trochanter to tarsus): 1-3-4-17 +ϕ+ω+tarsal-claw complex, 1-3-1-4+ϕ-6+ω, 1-2-1-4-6, 1-0-1-4-6.
Leg I (Fig. 3A): Trochanter: seta v′ comparatively short. Femur: setae l′ and v″ setiform, d weakly barbed and blunt-ended, 48 (45–50). Genu: setae l′ and l″ thickened and blunt-ended, v′ and v″ setiform. Tibiotarsus: 6 of 17 tibiotarsal setae are tibial (d, k, l′, l″, v′, v″) and 11 setae are tarsal (p′, p″, pl′, pl″, pv′, pv″, s, tc′, tc″, ft′, ft″); solenidion ϕ 10 (8–9), ω 8 (7–8); eupathidial setae p′, p″,ft′, ft″ tc′ and tc″ blunt-ended; seta d attenuated and whip-like, 87 (78–90); seta pl′ 53 (48–53) about twice as long as pl″ 27 (23–28); eupathidial seta k, 15 (13–15); seta v″ whip-like, 54 (48–55), almost 3.5 times as long as v′ 15 (14–16); setae l′, l″, pv′ and pv″ smooth and setiform.
Leg II (Fig. 3B): Trochanter: seta v′ slender and short. Femur: setae l″, v″ and d setiform. Genu: seta v′ spine-like, 8 (7–8). Tibia: solenidion ϕ 3 (3–5); setae d, v′ and l′ attenuated and whip-like, 70 (65–72), 50 (46–51) and 41 (38–44), respectively; seta v″ spine-like, 8 (7–8). Tarsus: solenidion ω 4 (3–5); seta tc″ attenuated and whip-like, 35 (30–38); setae pl″ and pv″ spine-like, 8 (7–8) and 10 (9–10), respectively; setae u′ and u″ slender and hard to discern.
Leg III (Fig. 4A): Trochanter: seta v′ slender and pointed. Femur: setae d and v″ slender and pointed. Genu: setae v′ slender and pointed. Tibia: seta d attenuated and whip-like, 87 (80–87); setae v′ v″ and l′ slender and pointed. Tarsus: seta pv″ spine-like, 7 (6–7); seta tc″ attenuated; setae pv′ pointed and pl″ blunt-ended; setae u′ and u″ as on tarsus II.
Leg IV (Fig. 4B): Trochanter: seta v′ slender and pointed. Femur: nude. Genu: seta v′ slender and pointed. Tibia: setae d, v′ and v″ attenuated and whip-like, 94 (83–96), 42 (39–43) and 46 (40–46) respectively; seta l′ slender and pointed. Tarsus: seta pv″ spine-like, 8 (7–8); seta tc″ attenuated; setae pv′ and pl″ pointed; setae u′ and u″ as on tarsus II.
Etymology. The species name refers to the specific name of the host beetle, Monochamus alternatus Hope (Coleoptera: Cerambycidae) on which it was collected.
Remarks. On live specimens, the body of Paracarophenax alternatus Xu and Zhang sp. nov., looks yellowish-brown with a shiny appearance; phoretic mites were found distributed around the coxal cavity of the adult of Monochamus alternatus, cramping the host setae by hook-like claws on legs I (Fig. 5). It was observed feeding on the eggs of the host beetles (Fig. 6).
Differential diagnosis: Paracarophenax alternatus Xu and Zhang sp. nov. is most similar to P. scolyti Khaustov, 1999 in having two pairs of setae on tergite EF; lacking setae ag; and trochanters I–II with a seta (v′ present); tracheae with atrium terminating in brush-like extensions; but mainly differs in the following characters: setae f about twice as long as e (setae e slightly longer than f in P. scolyti); setae v2, c1 and f subequal in length, sc2, c2 and d subequal in length, and about four-fifths as long as seta f (setae v2, sc2, d and e subequal in length, c1, c2 and f subequal in length in P. scolyti); setae h2 located proximate to h1, about one fifth of the distance between setae e and f (the distance between setae h2 and h1 equal to the distance between setae e and f in P. scolyti); femora I–IV with 3, 3, 2, 0 setae (femora I–IV with 3, 3, 1, 0 setae in P. scolyti); setae v′ on genu II spine-like (setae v′ on genu II setiform in P. scolyti); on tibia II, setae v′ longer than l′ (setae l′ about twice as long as setae v′ in P. scolyti).
Key to species of Paracarophenax (based on Khaustov & Abramov (2017) with modifications)
1. Tergite EF with one pair of setae f (setae e absent); setae ps absent; trochanter II nude 2
-Tergite EF with two pairs of setae e and f; setae ps present; trochanter II with seta v′ 4
2. Aggenital setae ag present, trochanter I with seta v′ P. triplaxophilus Khaustov and Abramov
- Aggenital setae ag absent, trochanter I nude 3
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. Opisthogaster with one pair of setae ps, setae ag absent; tegula present 5
- Opisthogaster with two pairs of setae (ag and ps); tegula absent 7
5. Setae h2 present; tracheae with atrium terminating in brush-like extensions 6
- Setae h2 absent; tracheae without obvious atrium extensions P. undosus Mahunka
6. Setae e slightly longer than f; the distance between setae h2 and h1 equal to the distance between setae e and f (according to the Fig. 3 in Khaustov 1999); femur III with 1 seta; genu II with 1 setiform seta (according to the Fig. 4 in Khaustov 1999). P. scolyti Khaustov
Setae f about twice as long as e; setae h2 located very close to h1, and about one fifth of the distance between setae e and f; femur III with 2 setae; genu II with 1 spine-like seta. P. alternatus Xu and Zhang sp. nov.
7. Prosternal and poststernal apodeme absent; setae h2 as long as h1 P. dybasi Cross
- Prosternal apodeme present; poststernal apodeme present as remnant; setae h2 about twice as long as h1 P. bambergensis (Krczal)
We are very grateful to Prof. Qing-Hai Fan (Ministry for Primary Industries, Auckland, New Zealand) for review and comments on the draft of this paper; to Associate Prof. Mei-Xiang Wu (Fujian Agriculture and Forestry University, China) for her continued support in providing lab space to Yun Xu; to the student Feng Xia (Fujian Agriculture and Forestry University, China) for sample collection. This project was supported by the National Key Research and Development Program (2017YFD0600105), and by the National Natural Science Foundation of China (31702044) and China Postdoctoral Science Foundation (2017M612113).