An unexpected finding of mammal mites (Psoroptidia: Sarcoptoidea) on a bird

The psoroptidian mite Myocoptes musculinus (Koch, 1844) is the most common species of the family Myocoptidae (Sarcoptoidea), along with its main host, the house mouse Mus musculus Linnaeus. The present article reports the first recorded confirmation of M. musculinus on a bird – the tropical screech-owl Megascops choliba (Vieillot). Finding myocoptid mites on a non-rodent host is an additional case of predator-prey contamination.

In the present study we report the finding of M. musculinus on a bird, the tropical screechowl Megascops choliba (Vieillot, 1817) (Aves: Strigidae) in Brazil.

Materials and methods
During September of 2015 a tropical screech owl Megascops choliba was kept in captivity after being attacked and injured by a dog in Mogi Mirim, São Paulo State, Brazil. The owl was fed daily with live white mice (Mus musculus). After a month, the bird died and was taken to the Acari laboratory of the São Paulo State University (UNESP) in Rio Claro, where it was washed for ectoparasites following the technique described by Clayton and Walther (1997). The recovered mites were put in 30% lactic acid for 24 hours, then mounted on microscopic slides using Hoyers medium and heated at 50°C for 5 days. The slides were then sealed with varnish and labeled. The mites were identified by means of a light microscope with differential interference contrast following Fain (1970).

Results and discussion
A total of 5 males, 7 females, 3 nymphs and 1 larva of Myocoptes musculinus (Figure 1) were recovered from Megascops choliba. The bird had no evidence of any harmful effects, such as mange or plucking behavior.
Similar cases of horizontal transfer between psoroptidian mites to new host species often result in severe and harmful effects by the mites (Andriantsoanirina et al. 2015;Hernandes et al. 2014;Mironov 2013;Skerratt et al. 1998).
The fact that only myocoptid mites were found on the owl might indicate that the bird was previously free of typical bird mites (Astigmata: Analgoidea, Pterolichoidea) and therefore there was no competition between mammalian (Astigmata: Sarcoptoidea) and avian mites. Notwithstanding, the owl's condition (injured, stressed and caged) probably facilitated colonization by the atypical mites.
Other cases in which potential mite transfer can occur involve interspecific interaction between birds, such as feather mites on obligatory brood parasite birds. However, in most of these cases, mites are not transmitted from foster parents to the bird parasitic nestling, but instead are acquired from a conspecific host later in life, probably during copulation or other intraspecific interaction (Atyeo and Gaud 1983;Gaud 1992). Birds of prey (e.g. falcons, hawks and owls), which prey on many bird species, and thus could have a higher probability of acquiring mites from their prey, were rarely reported with mites other than their typical associated taxa. Proctophyllodes polyxenus Atyeo & Braasch, 1966 (Analgoidea: Proctophyllodidae), a typical passerine-associated feather mite, was also recorded on three owl species, which certainly represent predator-prey contamination (Atyeo and Braasch 1966;Philips 2000).
On the other hand, a recent cophylogenetic study on feather mites of the genera Proctophyllodes Robin, 1877 and Trouessartia Canestrini, 1899 (Analgoidea: Proctophyllodidae and Trouessartiidae) concluded that horizontal transfer -i.e. between different host species -is probably the main cause for speciation in these mites, suggesting that interspecific transfer can occur more commonly in nature than what was previously estimated (Doña et al. 2017).
The present finding represents the first record of a mammal mite on a bird; the opposite situation was recorded by Gaud (1992), who reported a few specimens of Ciconiacarus Gaud, 1973 (Pterolichoidea: Vexillariidae), typically associated with hornbills (Aves: Bucerotiformes), on two old-world monkey skins of the genera Colobus and Cercopithecus. The author later discovered that the monkeys and the bird were placed on the same table during the taxidermy process in the field.
Discovering M. musculinus on an atypical host like a strigid bird is obviously a case of predator-prey contamination. Still, despite the phylogenetic distance between the hosts, the similarity of their symbiotic mites is remarkably close, and it might suggest a possible route from which the lineage of mammal associated psoroptidians (Astigmata: Sarcoptoidea) successfully colonized these new hosts by evolving from bird associated mites (Analgoidea) (Klimov and OConnor 2008;2013).