Xu, Yun¹ ; Zhu, Yu-Zhen² ; Wu, Jie-Qin³ and Zhang, Fei-Ping⁴

¹College of Forestry, Key Laboratory of Integrated Pest Management in Ecological Forests, Fujian Province University, Fujian Agriculture and Forestry University, Fuzhou 350002, China.
²College of Forestry, Key Laboratory of Integrated Pest Management in Ecological Forests, Fujian Province University, Fujian Agriculture and Forestry University, Fuzhou 350002, China.
³College of Forestry, Key Laboratory of Integrated Pest Management in Ecological Forests, Fujian Province University, Fujian Agriculture and Forestry University, Fuzhou 350002, China.
⁴✉ College of Forestry, Key Laboratory of Integrated Pest Management in Ecological Forests, Fujian Province University, Fujian Agriculture and Forestry University, Fuzhou 350002, China.

2020 - Volume: 60 Issue: 2 pages: 481-487

ZooBank LSID: BC239A46-D75A-4812-952E-3A60CDD725D9

Original research

Keywords

Abstract

Introduction

The family Pediculochelidae has been associated with two mite suborders Prostigmata and Astigmata. It was erected by Lavoipierre (1946) and placed in the family Tarsonemidae (Prostigmata), and then proposed to be a member of Astigmata by Baker and Wharton (1952). Krantz (1978) suggested that it belonged to the primitive Pachygnathoidea but didn't provide supportive discussion. Norton et al. (1983) proposed based on a cladistic analysis that it represented a sister-group of the Haplochthoniidae and belonged to the superfamily Cosmochthonioidea (Oribatida). To date, one genus and seven species have been described (Schatz et al. 2011): Paralycus chongqingensis Fan, Li & Xuan, 1996 from Auricularia sp. in China, P. lavoipierrei (Price, 1973) from soil in California, P. longior Fan, Li & Xuan, 1996 from lily fruits in China, P. parasiti Zhang & Li, 2001 from Coccinella septempunctata in China, P. parvulus (Price, 1973) from soil in California, P. pyrigerus (Berlese, 1905) from soil in Italy, and P. raulti (Lavoipierre, 1946) from bees in South Africa (Norton et al. 1983). In this paper, we describe and illustrate a new species of this family, which is the fourth record in Chinese fauna. An updated key to the species of the genus Paralycus is also provided.

Materials and methods

Barks of Pinus massoniana Lamb. attacked by Monochamus alternatus were collected in Minhou country, Fuzhou city, Fujian province, China. The specimens were extracted from the barks using a Berlese funnel and separated under a stereomicroscope. All mites removed were cleared in lactic acid, and afterwards mounted in Hoyer's medium. Specimens were examined at 400x magnification by using differential interference contrast of a Leica DM5000B compound microscope. The studied materials were deposited in the National Zoological Museum of China, Institute of Zoology, Chinese Academy of Sciences, Beijing, China (NZMC) and the Department of Plant Protection, Fujian Agriculture and Forestry University (FAFU), Fuzhou, China (Zhang 2018). All measurements are given in micrometers (μm). The morphological terminology used in this paper is mostly based on that developed by Norton & Behan-Pelletier (2009).

Family Pediculochelidae Lavoipierre, 1946

Genus Paralycus Womersley, 1944

Paralycus Womersley, 1944. Type species: Alicus pyrigerus (Berlese, 1905); Norton, OConnor & Johnston, 1983.

Pediculochelus Lavoipierre, 1946. Type species: Pediculochelus raulti Lavoipierre, 1946; Price, 1973.

Paralycus nortoni sp. nov.

ZOOBANK: CCED3053-E61E-484C-8161-BD3F45F11020

(Figures 1–3)

Diagnosis — Adult female. Minute and elongate, weakly sclerotized. Idiosoma with a distinct humeral sulcus; propodosoma with 5 pairs of setae and a single pair of clavate bothridial organs; notogaster divided into 4 regions by 3 transverse dorsal sutures, covered with fine longitudinal striae. Venter each with one pair of setae between coxae I, coxae II, coxae III and without setae between coxae IV. Genital region with 2 pairs of discs and five pairs of genital setae. Setae g₁, g₂ and g₃ minute and subequal in length, g₄ and g₅ subequal in length and about twice as long as g₁. Claws absent on all tarsi, each tarsus with a minute empodial remnant and caruncle-like membrane.

Type material — Holotype Female, China, Minhou county, Fuzhou city, Fujian province, 17 Apr. 2019, by Yu-Zhen Zhu, Jie-Qin Wu and Yun Xu, ex. the barks of Pinus massoniana Lamb attacked by Monochamus alternatus. Paratypes: 1 female, same data as holotype.

Type deposition — The holotype and paratype were deposited in the National Zoological Museum of China, Institute of Zoology, Chinese Academy of Sciences, Beijing (NZMC) and the Department of Plant Protection, Fujian Agriculture and Forestry University (FAFU), respectively.

Female (n=2)

Gastronotic region (Fig. 1A): Body minute and elongate, colorless when alive. Length of gastronotic region 210–215, width 55–65. Prodorsum covered with shield-shaped plate in middorsal region, bearing 2 pairs of setae (ro and le); 3 pairs of setae (exa, exp and in) and one pair of clavate bothridial organs ss in the dorsolateral area of prodorsum. Setae le about twice as long as ro, in about twice as long as exa, and exp minute, lengths ro 13–14, le 30–31, exa 22–23, exp 5, in 42–44, ss 17. Notogaster divided into 4 regions by 3 transverse dorsal sutures. Notogaster covered with fine longitudinal striae, bearing 4 pairs of setae (c₁, c₂, c₃ and cp) in the region of segment C, 4 pairs of setae (d₁, d₂, e₁ and e₂) in the region of segment DE, 2 pairs of setae (f₁ and f₂) in the region of segment F, and 6 pairs of setae (h₁, h₂, h₃, ps₁, ps₂ and ps₃) in the region of segment H and PS. Lengths of notoastral setae c₁ 22–24, c₂ 28–29, c₃ 34–35, cp 29–34, d₁ 17–18, d₂ 24–26, e₁ 22–23, e₂ 24–27), f₁ 32–34, f₂ 32–39, h₁ 32–39, h₂ 37–39, h₃ 32–35, ps₁ 27, ps₂ 53–56, ps₃ 14–15.

Gnathosoma (Figs. 1B, 2A). Gnathobase with rutella and 4 pairs of setae along midventral line plus one seta proximal to trochanter on coxal base of palp. Palp simple, with 4 free segments, setal formula: 0, 2, 1, 7.

Ventral region (Figs. 1B, 2B). Venter each with one pair of setae between coxae I, coxae II, coxae III and without setae between coxae IV; setae between coxae II about twice as long as setae between coxae I, setae between coxae III minute. Venter of opisthosoma with 2 pairs of acetabula, 5 pairs of genital setae (g₁, g₂, g₃, g₄ and g₅), 3 pairs of adanal setae (ad₁, ad₂ and ad₃). Setae g₁, g₂, g₃ minute and subequal in length, g₄, and g₅ subequal and about twice as long as g₁. Lengths: g₁ 3, g₂ 3–4, g₃ 3–4, g₄ 7–8, g₅ 8, ad₁ 14–15, ad₂ 53–58, ad₃ 11–13.

Legs (Fig. 3). Legs relatively short, measurements (total length from trochanter to tarsus, pretarsus excluded): I 50–55, II 45–48, III 45–48, and IV 50–52. Leg structure simple with highly visible segments, as shown in the Fig. 3. Claws absent on all tarsi, each tarsus with a minute empodial remnant and caruncle-like membrane. Setation of legs I–IV (from trochanter to tarsus, solenidia in brackets): leg I 0-2-4-3 (1)-8 (1); leg II 0-2-3-3 (1)-7 (1); leg III 1-2-0-3(1)-5 and leg IV 0-2-0-2-5. Dorsal, ventral and lateral setae on trochanter, femora, genua and tibiae I–IV simple and filiform. Solenidion φ on tibiae I–II elongate, attenuate, on tibia III baculiform. Unguinal setae u and proral setae p on tarsus I–IV simple. Only p’’ on tarsus I; seta s on tarsus I simple. Solenidion ω on tarsi I–II baculiform, ω on I about twice the length of that on II.

Male unknown.

Etymology — The species is named after Dr. Roy A. Norton, a distinguished acarologist who made significant contributions to the systematics of Oribatida.

Remarks — Paralycus nortoni sp. nov. is easily distinguishable from other species by the following features: Venter without setae between coxae IV (vs. with one pair of setae between coxae IV in P. chongqingensis, P. lavoipierrei, P. longior, P. parasiti and P. raulti); venter of opisthosoma with 5 pairs of genital setae (vs. with 3 pairs of genital setae in P. chongqingensis, P. lavoipierrei and 4 pairs of genital setae in P. parasiti, P. parvulus and P. raulti); trochanters 0-0-1-0 (vs. 0-0-0-0 in P. parvulus); genua 4-3-0-0 (vs. 4-2-0-0 in P. lavoipierrei and P. parvulus); tarsi 7+ω-6+ω-5-5 (vs. 9+ω-6+ω-5-5 in P. chongqingensis and P. longior). The identification characters of P. pyrigerus are not listed because the morphological details were not given by Berlese (1905), but the differences in size (213 μm for P. nortoni sp. nov. vs. 170 μm for P. pyrigerus), habitat (barks of pine for P. nortoni sp. nov. vs. soil for P. pyrigerus) and collection locality (China for P. nortoni sp. nov. vs. Italy for P. pyrigerus) suggest that P. nortoni sp. nov. and P. pyrigerus are distinct species.

The known species of Paralycus are described from soil, bees, Auricularia sp., lily fruits, and Coccinella septempunctata. Among them, two species are described as phoretic mites: P. parasiti and P. raulti (Berlese, 1905; Lavoipierre, 1946; Price, 1973; Fan et al. 1996; Zhang and Li, 2001). Despite of being collected from the barks of beetle-infested pines, the new mite species P. nortoni sp. nov. was not detected on the eggs, instars or mature beetles at the site, nor obvious interaction was noted between them. Up to date, there are five species of mesostigmatid mites, including Dendrolaelaps fukikoae, D. unispinatus, Proctolaelaps hystrix, Mucroseius nipponensis and M. squamosus, which were found to coexist in the pupal chambers of the beetle M. alternatus (Tamura and Enda, 1980; Kinn, 1987; Lindquist and Wu, 1991); and one species of prostigmatid mite Paracarophenax alternatus distributed around the coxal cavity of the adult and feeding on the egg of M. alternatus (Xu et al. 2018). No significant morphological body adaptations to aid in phoresy, such as attachment devices (hook-like claws on legs), were found neither on this new species, nor on P. parasiti and P. raulti. With that said, it remains an interesting topic whether this new species is phoretic on beetles or share the same host preference with beetles.

Notes — In the holotype, one seta h₃ was duplicated (h₃ and h_3x in Fig. 1B and 2B)

Key to species of the genus Paralycus

The incompletely described species P. pyrigerus (Berlese, 1905) is not included.

1. Venter without setae between coxae IV
...... 2

— venter with one pair of setae between coxae IV
...... 3

2. Venter of opisthosoma with 5 pairs of genital setae; trochanters with 0-0-1-0 setae; genua with 4-3-0-0 setae
...... Paralycus nortoni sp. nov.

— Venter of opisthosoma with 4 pairs of genital setae; trochanters with 0-0-0-0 setae; genua with 4-2-0-0 setae
...... P. parvulus (Price, 1973)

3. Tarsi with 9+ω-6+ω-5-5 setae
...... 4

— Tarsi with 7+ω-6+ω-5-5 setae
...... 5

4. Venter of opisthosoma with 3 pairs of genital setae, without setae g₁ and g₃; setae g₂ about half of the length of g₄ and g₅
...... P. chongqingensis Fan, Li & Xuan, 1996

— Venter of opisthosoma with 5 pairs of genital setae; setae g₂ about half of the length of g₄ and two-thirds of g₅
...... P. longior Fan, Li & Xuan, 1996

5. Venter of opisthosoma with 3 pairs of genital setae, without setae g₁ and g₃; genua with 4-2-0-0 setae
...... P. lavoipierrei (Price, 1973)

— Venter of opisthosoma with 4 pairs of genital setae, without setae g₃; genua with 4-3-0-0 setae
...... 6

6. Setae 2a between coxae II elongate, reaching the base of setae 1a between coxae I; setae 2a about twice as long as 1a
...... P. parasiti Zhang & Li, 2001

— Setae 2a between coxae II short, not reaching the base of setae 1a between coxae I; setae 2a as long as 1a
...... P. raulti (Lavoipierre, 1946)

Acknowledgements

We are very grateful to Prof. Qing-Hai Fan (Plant Health & Environment Laboratory, Ministry for Primary Industries, Auckland, New Zealand) for help with references, to Associate Prof. Mei-Xiang Wu (Fujian Agriculture and Forestry University, China) for her continued support in lab facility; to the master student Ci-Ding Lu (College of Forestry, Fujian Agriculture and Forestry University, China) for sample collection. This project was supported by The National Key Research and Development Program (2017YFD0600105) and China Postdoctoral Science Foundation (2017M612113).

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