Acarologia

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in Acarology

# A new species of Rhinonyssidae (Mesostigmata) nasal mite (*Ptilonyssus simplex* n. sp.) from the Bohemian waxwing in Denmark.

Simon Haarder<sup>id a</sup>, Ivan Dimov<sup>id b</sup>

## Original research

### ABSTRACT

A new species of nasal mite, *Ptilonyssus simplex n. sp.* is described and illustrated based on material from Bohemian waxwing, *Bombycilla garrulus* (Linnaeus, 1758) (Bombycillidae). The bird host was collected in a residential area in Hirtshals, Denmark, in October 2022. A set of diagnostic characters is presented in order to differentiate the new species from the overall similar species *Ptilonyssus bombycillae* Pence, 1973 which has been recorded from *Bombycilla* spp. in Europe and Northern America.

**Keywords** Rhinonyssidae; *Ptilonyssus*; nasal mites; *Bombycilla garrulus*; birds; new species

**Zoobank** http://zoobank.org/ED947B7E-28DD-4EE7-9880-D6DB8025A2EC

### Introduction

Mites of the family Rhinonyssidae Trouessart, 1895 (Parasitiformes: Mesostigmata) are a highly specialized group of gamasids, the representatives of which are permanent endoparasites of birds. The mites of this family have a worldwide distribution and are known from the majority of known recognized bird orders but are absent from, for example, ratites (Palaeognathae) (Giebel 1871; Hirst 1921; Vitzthum 1935; Fain 1957; Gretillat *et al.* 1959; Domrow, 1969; Kadosaka 1987; Dimov and Mironov 2012; Mascarenhas *et al.* 2018; Beron 2020). The world fauna of rhinonyssids presently includes more than 600 species arranged in 11 genera (Dimov 2018; de Rojas *et al.* 2020). Rhinonyssid mites parasitize the respiratory system of birds, where they are localized mainly in the nasal cavity, less often in the trachea and pulmonary sacs. The majority parasitize in the nasal cavities, though some species occupy the lungs, tracheal tissues and even body cavity (Porter and Strandtmann 1952). Moving along the surface of the epithelial tissue of these parts of the respiratory system, rhinonyssids feed on the blood or lymph of the host (Vitzthum 1935; Bell 1996). When fed, rhinonyssids injure the nasal epithelium and blood vessels (de Rojas *et al.* 2002), causing a bird disease called Rhinonyssoidosis avium (Dimov 2011). Host specificity of rhinonyssid genera is variable: some genera are constrained to one host family, while others parasitize hosts from different orders (Bregetova 1956; Pence 1975; Butenko 1984; Dimov and Spicer 2013; Vanstreels *et al.* 2018).

The genus *Ptilonyssus* is the most specious in the family Rhinonyssidae. Today, there is no consensus among experts about its taxonomic boundaries and the number of species which should be included. To date, more than 170 species of the genus *Ptilonyssus* have been described, all of which are associated with birds of the order Passeriformes (Domrow 1969; Pence 1975; Butenko 1984; Knee 2008; Dimov and de Rojas, 2012; Dimov 2020).

Received 14 July 2024
Accepted 27 August 2024
Published 09 September 2024

Corresponding author
Simon Haarder<sup>id</sup>:
simon.haarder@gmail.com

Academic editor
Faraji, Farid

https://doi.org/10.24349/57ia-6ley

ISSN 0044-586X (print)
ISSN 2107-7207 (electronic)

<figure><img src="image_1.png" /></figure>

Haarder S. and Dimov I.

Licensed under
Creative Commons CC-BY 4.0

OPEN ACCESS

<footnote><sup>a</sup> Ornebjergvej 43, 4760 Vordingborg, Denmark.</footnote>

<footnote><sup>b</sup> Laboratory of Parasitology, Zoological Institute, Russian Academy of Science, Universitetskaya embankment 1, Saint Petersburg, 199034, Russia.</footnote>
**Material and methods**

Nasal mites were recovered by placing the bird specimen (*Bombycilla garrulus* L, from Hirtshals, Denmark – see “Type Materials”) in a container with 30% ethanol and shaking vigorously for one minute. All found mites were preserved in 70% ethanol. Then mites were cleared in 75% lactic acid for 2 hrs, put again in 70% ethanol for 2 min and finally mounted on slides with Hoyer’s medium. Description is based upon the holotype and paratypes (female holotype and six paratypes). The description of the new species follows the modem format used for rhinonyssid mites (Dimov 2018). The chaetotaxy of idiosoma used in the present work is based on the system proposed by Lindquist and Evans (1965) and Butenko (1984). Abbreviations for terms and measurements provided in descriptions of species are adapted from Fain and Hyland (1962) and Dimov (2018). The chaetotaxy of tarsal complex and palpal complex is based on the system proposed by Leonovich (2005) and Leonovich and Dimov (2012).

In species descriptions, with the following abbreviations for standardly measured structures are used:

LB, length of body including palps; WID, width of idiosoma; LPS, length of podosomal shield; WPS, width of podosomal shield; LPgS – the length of the pygidial shield; WPGS – the width of the pygidial shield; LSS, length of sternal shield; WSS, width of sternal shield; LGS, length of genital shield; WGS, width of genital shield; LAS, length of anal shield; WAS, width of anal shield; LG, length of gnathosoma, ventral view, including palps; WG, width of gnathosoma; Lleg, length of leg, including coxa, excluding ambulacrum (LLeg I to LLeg IV). All measurements are in µm.

Holotypes and paratypes are deposited in the Zoological Institute of the Russian Academy of Sciences collection in St. Petersburg, Russia (RASP 1–7). Six additional unmounted specimens are kept in 70% ethanol in the collection of the first author. They will eventually be deposited in the Acari collection of the Natural History Museum in Copenhagen, Denmark.

**Results**

**Genus *Ptilonyssus* Berlese and Trouessart 1889**

*Ptilonyssus* Berlese and Trouessart 1889: 128; Vitzthum 1935: 578; Cooreman 1946: 4; Castro 1948: 260; Pereira and Castro, 1949: 218; Zumpt and Patterson 1951: 77; Strandtmann 1951: 129; Zumpt and Till 1955: 69; Domrow 1969: 333; Pence 1975: 11; Butenko 1984: 156; Knee et al. 2008: 350; Dimov 2018: 74.

**Type species** — *Ptilonyssus echinatus* Berlese and Trouessart 1889.

**Diagnosis** — Mites with oblong body, length 380–760. Dorsal side of podosoma only with podosomal shield. Dorsal side of opisthosoma with only one of shields, either opisthosomal or pygidial one. Stigma with oblong peritremes and located dorsolaterally. Mesosomal shield present or absent. Poststigmal shield absent. Gnathosoma located terminally. Deutosternal denticles present or absent. Tritosternum absent. Sternal shield present or absent. Genital and anal shields present. Anus with anal shield located ventrally. Aspero present. Convexitas and spina coxae absent. Female setae are microchetes, male setae needle-shaped.

**Ptilonyssus simplex** Dimov n. sp.

Zoobank: 96ACD67D-D8BB-49F1-9D65-4E291D132FF3

**Female**

Female (based on holotype and 4 paratypes): LB 435–550; WID 182–210; LPS 70–85; WPS 62–79; LPgS 16–18; WpgS 49–58; LSS 57–62; WSS 27–32; LGS 43–47; WGS 31–36; LAS 52–67; WAS 34–36; LG 74–86; WG 48–63; Lleg I 175–190; Lleg II 150–162; Lleg III 146–161; Lleg IV 150–169.
<figure><img src="image_2.png" /><figcaption>**Figure 1** *Ptilonyssus simplex* n. sp., female. A – dorsum; B – venter.</figcaption></figure>

**Dorsum** — (Figure 1A) Podosomal shield poorly sclerotized; anterior margin slightly concave, lateral margins widely concave, posterior margin slightly sinuous; surface with six pairs of setae (j2-5, z2-4). Two pairs of mesosomal shieldlets of irregular shape located posterior to podosomal shield. Cuticle of dorsal podosoma with six pairs of setae: one setal pair (j6) behind the podosomal shield. Five pairs of mesolateral setae of the same length (r3,4,6, s5-6) arranged lateral to the podosomal shield. Soft cuticle of dorsal opisthosoma with six pairs of setae (Z1-3, J1-3). Pygidial shield with rounded lateral margins and convex anterior margin; surface with one pair of setae (J4) and one pair of big pore. A couple of mites have a slightly different pygidial shield shape; here, the anterior border of the shield is slightly wavy and sharply convex (Figure 2A). Stigmata with peritremes, located dorsolaterally.

**Venter** — (Figure 1B) sternal shield long and wide, with three pairs of sternal setae located on the shield border and two pairs of big pores at the level of *St1* and *St2*. Genital shield oblong with one pair of genital setae (*he4*). Soft cuticle of ventral opisthosoma with six pairs of setae (*Jv1*/*3*, *Zv3*/*5*/*6*, *Ur3*). Anal shield large, pear-shaped, situated ventral, anus situated in central part of this shield, surface with one pair of adanal setae (*Ad*) and a single unpaired postanal seta (*PA*) posterior to anus. Anal formula (*Ad*=$PA$). Aspero present. Gnathosoma inserted ventrally with nine deutosternal denticles (*Dd*). Gnathosomal formula (*hyp1*, *hyp2*, *hyp3*, *cs*) = 2-2-2.

**Legs** — all legs six-segmented. Chaetotaxy of legs: Coxa: 2-2-2-1, trochanter 4-4-4-5, femur 8-6-4-5, genu 5-5-7-3, tibia 7-7- 6-6. Tarsus 22-17-17-17. Claws straight, tapering.

**Tarsal receptor complex** — (Figure 2B). Topography and types of sensilla – two chemo-mechanoreceptor sensilla with apical pore (up), five olfactory porous single-cavity sensilla (sw) and five chemoreceptor sensilla with peripheral cavities (dw).

**Palpal receptor complex** — (Figure 2C). Topography and types of sensilla – one pair of big
<figure><img src="image_3.png" /><figcaption>**Figure 2** *Ptilonyssus simplex* n. sp., female. A – alternative shape of pygidial shield; B – tarsal receptor complex; C – palpal receptor complex.</figcaption></figure>

<figure><img src="image_4.png" /><figcaption>**Figure 3** *Ptilonyssus simplex* n. sp., male. A – dorsum; B – venter.</figcaption></figure>

tactile sensilla and three pair of little tactile sensilla with apical pore (np), three double-waled with apical pore sensilla (dw-up) and five single-waled with apical pore sensilla (sw-up).

Larva, nymphs

Unknown.
<figure><img src="image_5.png" /><figcaption>**Figure 4** Host bird specimen (*Bombycilla garrulus*) of *Ptilonyssus simplex* n. sp., from Hirtshals, Denmark. Photo: Marianne Nors.</figcaption></figure>

**Male**

Male: (2 paratypes): LB 430-546; WID 173-195; LPS 64-71; WPS 52-61; LPgS 15-16; WpgS 41-45; LSS-48-52; WSS 22-26; LGS 39-41; WGS 28-31; LAS 48-55; WAS 28-33; LG 67-74; WG 42-49; Lleg I 171-184; Lleg II 149-153; Lleg III 143-156; Lleg IV 148-158.

**Dorsum** — (Figure 3A) Podosomal shield poorly sclerotized; anterior margin slightly concave, lateral margins widely concave, posterior margin the posterior margin is strongly convex in the central part; surface with five pairs of setae (j2-4, z3,4). Two pairs of mesosomal shieldlets located posterior to podosomal shield. Soft cuticle of dorsal podosoma with eight pairs of setae: one pair of setae (j5) disposed posterior to podosomal shield, three mesolateral pairs of setae (r3-5) arranged lateral to this shield, setae (j1, z1) anteriorly the podosomal shield. Soft cuticle of dorsal opisthosoma with 19 setae; of them, setae Z1-3, R1-3, J1-5. One seta J3 moved to the shield. Pygidial shield with rounded lateral margins and convex anterior margin; surface with one pair of setae (J4) and one seta J3 with two big pores. Stigmata with peritremes, located dorsolaterally.

**Venter** — (Figure 3B) sternal shield ovoid shape, with 3 pairs of sternal setae, sternal formula (St1=St2=St3). Genital shield located on the basis of gnathosoma. Soft cuticle of dorsal opisthosoma with six pairs of setae (St4, Jv1,2,4, Zv2-3). Anal shield large, triangular shape, situated ventral, anus situated most anteriorly of this shield, surface with two adanal setae (Ad) anterolateral to anus and a single unpaired postanal seta (PA) posterior to it, anal formula (Ad<PA). Aspero present.

**Type materials**

Female holotype (RASP 1), and six paratypes (RASP 2-7) from *Bombycilla garrulus* (Linnaeus, 1758) (Bombycillidae) (Figure 4). Location: Hirtshals, Denmark. Residential area (57°35′23.0″N 9°57′22.3″E). Date: 19th October 2022. Bird was found by Marianne Nors. Window collision was the most probable cause of death.

**Etymology**

The specific epithet “simplex” refers to the overall fewer body and shield setae when compared to *P. bombycillae*.
<table><caption>**Table 1** Differential characters of *Ptilonyssus simplex* n. sp. and *Ptilonyssus bombycillae* Pence, 1973.</caption><thead><tr><th>Character</th><th>Ptilonyssus simplex n.sp.</th><th>Ptilonyssus bombycillae</th></tr></thead><tbody><tr><td>Setal pairs on podosomal shield</td><td>6</td><td>7</td></tr><tr><td>Posterior margin of podosomal shield is trilobed</td><td>yes</td><td>no</td></tr><tr><td>Mesolateral setal pairs</td><td>5</td><td>4</td></tr><tr><td>Setation of dorsal opisthosoma (pairs)</td><td>6</td><td>7</td></tr><tr><td>Big pores of dorsal idiosoma</td><td>2</td><td>4</td></tr><tr><td>Gnathosomal formula</td><td>2-2-2</td><td>2-0-2</td></tr><tr><td>Setation of ventral opisthosoma (pairs)</td><td>6</td><td>7</td></tr><tr><td>Setae on the sternal shield</td><td>no</td><td>yes</td></tr><tr><td>Coxal setae equal in length</td><td>no</td><td>yes</td></tr><tr><td>Tarsal receptor complex</td><td>12</td><td>16</td></tr><tr><td>Palpal receptor complex</td><td>16</td><td>13</td></tr></tbody></table>

## Discussion

*Ptilonyssus simplex* n. sp. is most similar to *Ptilonyssus bombycillae* Pence, 1973. The latter species was described from the cedar waxwing (*Bombycilla cedrorum*) Vielliot 1808 in New Orleans, USA, and has since been reported from this host in Canada as well as from *B. garrulus* in Belgium, Spain and Canada (Knee and Proctor 2010; Beron 2020). Shared characters include the presence of the podosomal shield, four mesosomal shields and one pygidial shield. The differential characters between the species are as follows (Table 1):

*Ptilonyssus simplex* n. sp.

Posterior margin of podosomal shield is trilobed. 6 pairs of podosomal setae. 5 pairs of mesolateral setae. 6 pairs of setae on dorsal opisthosoma. 2 big pores on dorsal idiosoma. Gnathosomal formula 2-2-2. 6 pairs of setae on ventral opisthosoma. Setae absent on sternal shield. Coxal setae not equal in length. Tarsal receptor complex 12. Palpal receptor complex 16.

*Ptilonyssus bombycillae* Pence, 1973:

Posterior margin of podosomal shield is not trilobed. 7 pairs of podosomal setae. 4 pairs of mesolateral setae. 7 pairs of setae on dorsal opisthosoma. 4 big pores on dorsal idiosoma. Gnathosomal formula 2-0-2. 7 pairs of setae on ventral opisthosoma. Setae present on sternal shield. Coxal setae equal in length. Tarsal receptor complex 16. Palpal receptor complex 13.

## Acknowledgements

We are grateful to Marianne Nors for providing us with the bird specimen. We thank Sergey Mironov (Zoological Institute, Russian Academy of Science) for his advice and assistance. One anonymous reviewer is thanked for giving useful comments which improved the manuscript.

## ORCID

Simon Haarder https://orcid.org/0000-0001-5981-738X

Ivan Dimov https://orcid.org/0000-0001-9155-1155

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