Alloptidae

Vanstreels, Ralph Eric Thijl, Palma, Ricardo L. & Mironov, Sergey V., 2020, Arthropod parasites of Antarctic and Subantarctic birds and pinnipeds: A review of host-parasite associations, International Journal for Parasitology: Parasites and Wildlife 12, pp. 275-290 : 283

3.6. Feather mites ( Alloptidae , Avenzoariidae , Freyanidae and Xolalgidae )

There is debate on whether feather mites should be considered parasites or mutualistic ectosymbionts, because representatives of most families live in different microhabitats of the plumage of their host and normally do not cause any visible damage to birds. While there is evidence that in rare cases feather-inhabiting mites may cause itching, discomfort and premature breakage of feathers ( Proctor, 2003), some authors have argued that they might benefit their hosts by contributing to the cleaning of their feathers ( Blanco et al., 2001; Jovani, 2003). In this context, the relationship between feather mites and their hosts may depend on the species involved, infestation intensity and environmental conditions ( Proctor, 2003). Feather mites complete their entire life cycle on the skin and feathers of their host, and as in the Psoroptidia they lack a phoretic deutonymphal stage, that is present in other Astigmata ( Proctor, 2003) . This condition, in combination with their relatively limited mobility, implies that direct animal-to-animal contact (e.g. chick-rearing and mating) is the primary means of transmission between feather mites and their hosts ( Proctor, 2003), which is reflected on their close co-evolutionary relationships ( Dabert and Mironov, 1999). Nevertheless, it should be noted that some taxa of feather mites are transmitted by phoresis through hippoboscid flies and chewing lice ( Harbison et al., 2009).

Feather mites have been recorded from all orders of Antarctic birds except penguins ( Spheniscidae ) and the South Georgia pipit ( Anthus antarcticus ). It is worth noting that although it was previously believed that penguins could not host feather mites due to their strongly modified plumage and highly aquatic lifestyle ( Atyeo and Peterson, 1970; Proctor, 2003), a more recent study demonstrated the occurrence of feather mites on penguins in Australia ( Mironov and Proctor, 2008). Forty species of feather mites have been recorded from Antarctic birds ( Table 1): Alloptidae (Analgoidea) was represented by 18 species from five genera, Avenzoariidae (Analgoidea) was represented by 10 species from five genera and Xolalgidae (Analgoidea) and Freyanidae (Pterolichoidea) were represented by one species each. Additionally, immatures of Freyana sp. have also been recorded in the Antarctic region ( Atyeo and Peterson, 1970), adding one more genus of the family Freyanidae .

Among the four families of feather mites recorded on birds of Antarctica, species of three families ( Alloptidae , Avenzoariidae and Freyanidae ) are restricted to orders of aquatic birds, while species of Xolalgidae infest a wider range of hosts and occur both on aquatic and terrestrial birds ( Gaud and Atyeo, 1996; Proctor, 2003). Members of the families Alloptidae and Avenzoariidae stand out as particularly frequent parasites of Antarctic seabirds, with species of Alloptidae infesting Charadriiformes and Procellariiformes , whereas those of Avenzoariidae have been recorded on these orders but also on Suliformes and Anseriformes . Despite such a broad range of hosts at the family level, at the species level these mites are generally limited to infesting hosts of the same genus, corroborating the interpretation that they have coevolved and cospeciated along with their hosts ( Dabert and Mironov, 1999).

Members of the families Xolalgidae and Freyanidae were not as frequent among Antarctic hosts. Species of Ingrassia ( Xolalgidae ) have been recorded from several species of Procellariiformes and Sphenisciformes ( Mironov and Proctor, 2008) and, in the Antarctic region, Ingrassia antarctica ( Gaud, 1952) was described from South Georgia diving-petrels ( Pelecanoides georgicus ) at Kerguelen Island ( Gaud, 1952). Unidentified specimens of Ingrassia have also been recorded on snowy sheathbills ( Chionis albus ) and Salvin's prions ( Pachyptila salvini ) ( Atyeo and Peterson, 1970; Bishop and Heath, 1998), suggesting that the diversity and prevalence of these mites in the Antarctic region has been underreported. Diomedacarus gigas (Trouessart, 1895) ( Freyanidae ) was recorded on black-browed albatrosses ( Thalassarche melanophris ) at South Georgia Islands ( Atyeo and Peterson, 1970). Considering the wide host and geographic distribution of this parasite on albatrosses ( Diomedeidae ) in the northern hemisphere, it seems probable that the occurrence of D. gigas in albatrosses in the Antarctic region has also been underreported.

It should be noted that although quill mites (Cheyletoidea: Syringophilidae ) have not been recorded on Antarctic birds, they are relatively frequent parasites of other species of the families Anatidae , Diomedeidae , Laridae , Motacillidae , Phalacrocoracidae and Procellariidae ( Schmidt and Skoracki, 2007; Glowska et al., 2015; Zmudzinski et al., 2016). It is therefore plausible that these parasites occur in the Antarctic region but were not yet recorded due to insufficient research effort.