Feather mites (Acariformes, Astigmata) from marine birds of the Barton Peninsula (King George Island, Antarctica), with descriptions of two new species

Abstract We report on the first investigation of feather mites associated with birds living on the Barton Peninsula (King George Island, Antarctica). We found seven feather mite species of the superfamily Analgoidea from four host species. Two new species are described from two charadriiform hosts: Alloptes (Sternalloptes) antarcticussp. nov. (Alloptidae) from Stercorariusmaccormicki Saunders (Stercorariidae), and Ingrassiachionissp. nov. (Xolalgidae) from Chionisalbus (Gmelin) (Chionidae). Additionally, we provide partial sequences of the mitochondrial cytochrome c oxidase subunit I (COI), which was utilized as a DNA barcode, for all seven feather mite species.


Introduction
Feather mites (Astigmata, Analgoidea and Pterolichoidea) are a vast group of highly specialized parasites or mutualistic ectosymbionts that spend their entire life cycle on their bird hosts (Gaud and Atyeo 1996;Dabert and Mironov 1999;Proctor 2003). Most of these mites occupy various microhabitats in the plumage of birds; however, representatives of a few families are parasites located on the skin and in the respiratory tract of their avian hosts. Owing to their specialization to particular microhabitats on birds and dispersal mainly by a direct contact of host individuals, feather mites usually show a high level of host-specificity Proctor and Owens 2000;Dabert 2005).
Antarctica is the fifth largest and most isolated continent on our planet (Peck 2018;Sancho et al. 2019). On this 14 million km 2 continent, less than 0.35% of the territory remains seasonally free of ice and snow (Bockheim 2015). Many endemic species inhabit these ice-free terrestrial areas, where birds and marine mammals breed in the coastal zones (Chown and Convey 2007;Hughes 2010). Approximately 400 species of birds have been recorded from the Antarctic continent and oceanic waters north to approximately 40°S (Shirihai 2007). Vanstreels et al. (2020) recently summarized data on the biodiversity of ectoparasites associated with Antarctic and Subantarctic birds and reported 30 feather mite species from 28 bird species in this region.
King George Island is the largest of the South Shetland Islands at the northwest tip of the Antarctic Peninsula (Potapowicz et al. 2020). This island has six areas designated as the Antarctic Specially Protected Areas (ASPA), one of which is ASPA No. 171, located on the southeast coast of the Barton Peninsula. Approximately 5,000 pairs of two penguin species, Pygoscelis antarcticus (Forster) and P. papua (Forster) (Kim et al. 2005(Kim et al. , 2014. To date, no studies have been conducted on feather mites associated with birds living on the Barton Peninsula. In the present work, we report seven analgoid feather mites, including descriptions of two new species from the genera Alloptes and Ingrassia, found on four bird species on the Barton Peninsula of King George Island. Additionally, we provide DNA barcodes for the mitochondrial cytochrome c oxidase subunit I (COI) from these seven analgoid feather mite species.

Material sampling
Mite samples were obtained from the Antarctic Shag (L. bransfieldensis), South Polar Skua (S. maccormicki), Wilson's Storm Petrel (O. oceanicus), and three Snowy Sheatbills (Ch. albus) in the Barton Peninsula. The birds were captured using a hand net or loop according to 'SKUAS Manual for Fieldworkers' (PBEG 2003), and all birds were re-leased after collecting the mites. Feather mites were collected using 3M ScotchMag-icTape (3M, St. Paul, Minnesota, USA) from the wing, down, and tail feathers, and then immediately preserved in 70% ethanol for 3 h. The preserved samples were separated from Scotch tape under a dissecting microscope with a dissecting needle and then preserved in 95% ethanol. The collected mite specimens were cleared in 10% lactic acid for 24 h at room temperature and then mounted on microscope slides using PVA mounting medium (BioQuip, Rancho Dominguez, California, USA).
Descriptions of two new species are given according to standard formats used for the corresponding feather mite taxa (Mironov and Palma 2006;Mironov and Proctor 2008;Stefan et al. 2013;Hernandes et al. 2017). Terminology, idiosomal, and leg chaetotaxy follow Gaud and Atyeo (1996), with minor corrections for the coxal chaetotaxy by Norton (1998). All measurements are in micrometers (μm). All examined specimens are deposited at the National Institute of Biological Resources (NIBR), Korea. The classification and scientific names of birds follow Gill et al. (2021).

DNA sequencing
Before preparing the microscopic slides, genomic DNA was extracted from one leg of each specimen using a Tissue DNA Purification Kit (Cosmogenetech Inc., Seoul, Korea) according to the manufacturer's instructions. The COI barcode fragment was amplified using two universal primers: bcdF05 (5′-TTTTCTACHAAYCATAAAGA-TATTGC-3′) and bcdR04 (5′-TATAAACYTCDGGATGNCCAAAAAA-3′) under the following conditions: 2 min at 94 °C; 40 cycles at 98 °C for 15 s, 50 °C for 30 s, and 68 °C for 60 s; and a final extension at 68 °C for 5 min (Dabert et al. 2008). The amplified products were sequenced using an ABI3100 automated sequencer (Perkin Elmer, Foster City, California, USA). Sequence assembly, alignment, and trimming were performed using Geneious 8.1.9 software (Kearse et al. 2012). We obtained a 654 bp fragment sequence of the COI gene from two individuals per mite species.

Superfamily Analgoidea Trouessart & Mégnin, 1884
Family Alloptidae Gaud, 1957 Genus Alloptes Canestrini, 1879 Notes. Alloptes is one of the most specious genera of the family Alloptidae and currently includes about 50 described species (Gaud 1972;Vasyukova and Mironov 1991;Kivganov and Mironov 1992;Mironov and Palma 2006). All representatives of this genus are associated with birds of the order Charadriiformes, with exception of a questionable host association of Alloptes tubinarii Dubinin, 1949 reported from several procellariiform hosts (Dubinin 1949). Gaud (1972) subdivided the genus into the three subgenera, Alloptes s. str., Apodalloptes Gaud, 1972, andConuralloptes Gaud, 1972. Further, nearly a half of species of the subgenus Conuralloptes was arranged into a fourth subgenus, Sternalloptes Mironov, 1992 (in Kivganov andMironov 1992). Three Alloptes species found on marine birds of the Barton Peninsular belong to three different dubgenera. Below we provide descimination features for these subgenera.

Subgenus Alloptes Canestrini, 1879
Notes. The subgenus Alloptes s. str. currently includes three species and is characterized by the following features (Gaud 1952(Gaud , 1972Mironov 1996): in both sexes, seta mG of genu II is spiculiform; in males, the opisthosoma is roughly shaped as an equilateral triangle with terminal part strongly enlarged, setae h3 are present, setae ps2 are well developed (half as long as f2); in females, the opisthosoma is rounded, the opisthosomal lobes are not developed, idiosomal setae ps1 and f2 are present. Representatives of the subgenus are known from birds of the families Scolopacidae and Chionidae (Gaud 1952(Gaud , 1957(Gaud , 1972Vasyukova and Mironov 1991). Five Alloptes species described by Dubinin (1952) from auks (Alcidae) could also belong to this subgenus, because these mites have filiform genual setae mGII and females have the opisthosoma rounded or with strongly abbreviated lobes, but all these species need re-investigation.
Molecular data. The COI sequences were obtained from two individuals and deposited in GenBank with accession numbers MZ489637 and MZ489638. Gaud, 1972 Notes. The subgenus Conurlloptes currently includes 23 species and is characterized by the following features (Gaud 1972;Vasyukova and Mironov 1991): in both sexes, seta mG of genu II is short spine-like with widely rounded apex; in males, the opisthosoma is triangular, gradually narrowed posteriorly and without posterior enlargement, idiosomal setae h3 are absent, setae ps2 are strongly reduced (barely distinct); in females, opisthosoma with well-developed opisthosomal lobes, setae ps1 and f2 are present. This subgenus is known from birds of the families Chionidae, Pedionomidae, Recurvirostridae, and Scolopacidae in the order Charadriiformes (Gaud 1972;Vasyukova and Mironov 1991;Mironov and Palma 2006).

Alloptes (Conuralloptes) chionis Atyeo & Peterson, 1967
Alloptes chionis Atyeo & Person, 1967: 98, figs 1-4;1970: 129-130 Remarks. Alloptes (Conuralloptes) chionis was described from specimens collected from Ch. minor (type host) on Heard Island and was also found on Ch. albus from the Gaston Islands (Atyeo and Person 1967). When this mite was described, the genus Alloptes had not yet been subdivided into subgenera. Gaud (1972) established three subgenera in this genus but did not consider the taxonomic position of this species. Mironov (2007) placed this mite in the subgenus Conuralloptes based on the following characters: in both sexes, genual setae mGII are shaped as short and thick spines with bluntly rounded apices; in males, the opisthosoma is not enlarged apically, and idiosomal setae h3 are absent; in females, the idiosomal setae ps1 and f2 are present. The males of A. (C.) chionis can be distinguished from other species of the subgenus Conuralloptes by the following combination of features: the anterior margin of the hysteronotal shield is slightly convex, the pregenital sclerites are free from each other and almost parallel, the adanal shields are C-shaped, and macrosetae h2 are flattened and slightly widened in the medial part Peterson 1967, 1970).
Molecular data. The COI sequences were obtained from two individuals and deposited in GenBank with accession numbers MZ489639 and MZ489640. Mironov, 1992 Notes. The subgenus Sternalloptes includes about 20 species and is characterized by the following features (Kivganov and Mironov 1992;Mironov 1996): in both sexes, seta mG of genu II is shortspine-like with widely rounded apex; in males, the opisthosoma is triangular, gradually narrowed posteriorly and with noticeable terminal enlargement, idiosomal setae h3 are present or absent, setae ps2 are strongly reduced; in females, the opisthosoma with well-developed opisthosomal lobes, idiosomal setae ps1 and f2 are absent. Common hosts of the subgenus Sternalloptes are birds of the families Laridae and Stercorariidae in the order Charadriiformes (Gaud 1976;Vasyukova and Mironov 1991;Kivganov and Mironov 1992;Mironov and Kivganov 1993).  tibia IV with small spine. Tarsus IV 54 (49-55) long, with claw-like apex; setae d and e small spine-like, seta e situated near tarsal apex, seta d at level of seta f, setae r and w in basal one-third of the segment (Fig. 3A-C).
Remark. The comparative material of A. (S.) catharacti used here to illustrate morphological differences was collected from the same host species, S. maccormicki, at Jangbogo station, Terra Nova Bay, Antarctica, in 2016, by Ji-Yong Lee.
Molecular data. The COI sequences were obtained from two individuals and deposited in GenBank with accession numbers MZ489641 and MZ489642.
Etymology. The specific name refers to the geographical range of the type host. Remarks. Mites of the genus Scutomegninia, collected from the Imperial Shag, Leucocarbo atriceps (King) (= Phalacrocorax atriceps) in Maipo Island (Buls Bay on Brabant Island, Palmer Archipelago, Antarctica) by Atyeo and Peterson (1967), were originally identified as S. phalacrocoracis (Dubinin and Dubinina, 1940). Furthermore, Atyeo and Peterson (1970) reported S. (S.) phalacrocoracis from Leucocarbo georgianus (Lönnberg) (= P. atriceps georgianus) from Bird Island, South Georgia. Later, Mironov (1990Mironov ( , 2000 described specimens from the Palmer Archipelago as a separate species, S. (S.) subantarctica. According to the present taxonomic view, Phalacrocorax atriceps belongs to the genus Leucocarbo and is split into several separate species restricted to particular areas of the Antarctic and subantarctic regions (Gill et al. 2021). Taking into consideration this concept, S. (S.) subantarctica reported by previous researchers Peterson 1967, 1970) were collected from the Antarctic Shag, L. bransfieldensis (Antarctic Peninsula and Palmer Archipelago), and the South Georgia Shag, L. georgianus (South Georgia).
Scutomegninia (S.) subantarctica belongs to the phalacrocoracis group (species associated with Phalacrocoracidae and Anhingidae), and it is most similar to S. (S.) pygmaea Mironov, 1990. It differs from S. (S.) pygmaea and other species of the phalacrocoracis group by the following combination of characters in males: the terminal ends of the interlobar membrane have a small spine-like process; the lateral adanal shields have acute posterior ends, while the medial adanal shields have the posterior ends bluntly rounded; the anteromedial ends of adanal apodemes are rounded; setae s of tarsus III are spine-like, strongly attenuate apically, and bear two small denticles; the terminal cleft is 1.8-2 times longer than wide; and the incision in the interlobar membrane extends to the level of setae h2 (Mironov 1990(Mironov , 2000.
Molecular data. The COI sequences were obtained from two individuals and deposited in GenBank with accession numbers MZ489643 and MZ489644.
Molecular data. The COI sequences were obtained from two individuals and deposited in GenBank with accession numbers MZ489645 and MZ489646.
Although Z. stercorarii and Z. isolata are associated with birds in the order Charadriiformes, these mite species belong to the puffini species group, which is characterized by a single dorsobasal spine on tarsus IV in males and setae d1 situated off the lateral hysteronotal shields in females (Mironov 1989). All remaining species of the puffini group are associated with Procellariiformes, while other representatives of the genus Zachvatkinia associated with Charadriiformes belong to the sternae species group. It was hypothesized that the common ancestors of Z. stercorarii and Z. isolata were probably transferred from some procellariiform hosts to the ancestor of the family Stercorariidae .
Zachvatkinia stercorarii can be clearly distinguished from Z. isolata in having the following features: in males, the bases of genital setae g are adjacent (vs distant from each other); in females, the posterior margin of the prodorsal shield is just slightly convex (vs strongly convex), and the lateral margins of this shield have small incisions posterior to the bases of setae se (vs smooth and without incisions) (Mironov 1989).

Molecular data.
The COI sequences were obtained from two individuals and deposited in GenBank with accession numbers MZ489647 and MZ489648.
Legs I, II as in the male. Legs IV with tarsus extending beyond posterior end of opisthosoma. Tarsi III, IV without apical spines, length of tarsi III, IV 60-61 and 72-74, respectively. Setae sRIII subequal to combined length of corresponding femur, genu, and tibia. Seta w of tarsus III and setae r, w of tarsus IV spiculiform (Figs 6, 7).
Differential diagnosis. The new species Ingrassia chionis sp. nov. belongs to a group of species associated with the Charadriiformes and is characterized by a retrograde spine-like apophysis on femorogenu II in both sexes (Gaud 1972;Vasyukova and Mironov 1991). Among this species grouping, the new species is most similar to I. tringae Vitzthum, 1922(= I. minuta Gaud, 1972 described from Calidris minuta (Leisler) (Scolopacidae) in having the following features: in males of both species, the opisthosomal lobes are relatively short, equal to or slightly longer than wide at the bases, and the supranal concavity is completely separated from the terminal cleft; in females, the hysteronotal shield is shaped as a large longitudinal plate occupying the median area of the hysterosoma. Ingrassia chionis is distinguished from I. tringae by the following features: in both sexes, the prodorsal shield is narrow, parallel-sided, with the width about one-third the distance between setae se, and the posterior end of this shield is tapering; in males, the terminal cleft is semi-ovate, narrowed only in the anterior end, and tibia III bears a small apical spine of rectangular shape; in females, the anterior margin of the hysteronotal shield is right-angled and extends to the level of setae c2, and the posterior margin of this shield is truncate and extends to the level of setae e2. In both sexes of I. tringae, the prodorsal shield is a longitudinal plate widened posteriorly, with its greatest width equal to or larger than the halfway between setae se, and the posterior margin is widely rounded; in males, the anterior half of the terminal cleft is strongly narrowed, and tibia III bears a pointed apical spine; in females, the anterior margin of the hysteronotal shield is semi-ovate and does not extend to the level of setae c2, and the posterior margin of this shield is concave and extends beyond the level of setae e2. Molecular data. The COI sequences were obtained from two individuals and deposited in GenBank with accession numbers MZ489649 and MZ489650.
Etymology. The specific name is taken from the generic name of the type host and is a noun in apposition.
National University, Korea) for sample collection. The permit for catching birds was officially approved the Korean Ministry of Foreign Affairs and Trade through the Korea Polar Research Institute.