Ixodidae

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 : 282

3.4. Ticks ( Ixodidae )

Although both soft ticks ( Argasidae ) and hard ticks ( Ixodidae ) are frequent parasites of seabirds ( Dietrich et al., 2011), only hard ticks have been recorded as parasites of Antarctic seabirds. These parasites can exploit up to three different host individuals during their life cycle (larva, nymph and adult stages), with intervals between hosts ranging from weeks to years ( Randolph, 1998). Although they may remain attached to their seabird hosts when they forage at sea and potentially ‘hitchhike’ over great distances, seabird ticks are believed to be predominantly nest-dwelling during the wintering period ( Olsen et al., 1995; Dietrich et al., 2011). These characteristics, combined with relatively low host specificity, make hard ticks highly effective vectors for pathogens of seabirds between hosts within the same site and between distant sites ( Olsen et al., 1995; Dietrich et al., 2011; Muñoz-Leal and González-Acuña, 2015).

Four species/subspecies of ticks were recorded in the Antarctic region, all hard ticks of the Ixodes genus. Ixodes uriae White, 1852 has the most extensive geographical distribution and one of the greatest host ranges of all ticks, having been recorded on almost 100 avian and mammalian hosts in all continents (including the northern hemisphere) ( Muñoz-Leal and González-Acuña, 2015). This species has a remarkable resistance to dehydration and cold-hardiness, being able to tolerate temperatures as low as −30 ̊C ( Lee and Baust, 1987), and is able to become established in rocky areas without any vegetation ( Barbosa et al., 2011). These characteristics help explain why it is the only tick species able to survive in the Antarctic Peninsula, and why it also scores the highest host range of the external parasites recorded from Antarctic hosts, with 27 avian hosts.

Ixodes kerguelenensis André & Colas-Belcour, 1942 might not be as widely distributed as I. uriae , but it is a common parasite of seabirds in the Southern Ocean ( Arthur, 1960; Wilson, 1970a), having been recorded from 12 Antarctic species. It is worth noting that Wilson (1970a) found that several records of seabird ticks ( I. auritulus , I. percavatus and I. zumpti ) were based on misidentified specimens of I. kerguelenensis , and also concluded that Ixodes pterodromae was a synonym of I. kerguelenensis . Ixodes kerguelenensis has not yet been recorded in Subantarctic island groups with scarce vegetation (e.g. Bouvet, South Orkney, South Sandwich); however, it is difficult to ascertain whether this is due to a dependency of plant substrate to provide protection from desiccation, to differences in avian community composition (e.g. absence of albatrosses and several species of burrowing petrels), or if it is reflective of the relatively lower sampling effort conducted at those locations.

The distribution of Ixodes auritulus zealandicus Dumbleton, 1953 extends close to the margins of the Southern Ocean, with records at Macquarie, Antipodes and Auckland Islands, as well as on mainland New Zealand and the Chatham Islands ( Nuttall, 1916; Dumbleton, 1953; Heath et al., 2011). Considering that it has been recorded from 12 Antarctic bird species that were sampled outside of the Antarctic region, it seems likely that this tick species could also be established within the region. Ixodes auritulus sensu lato was recorded infesting “penguins” at the Antarctic Peninsula; however, the subspecies was not determined ( Gressitt and Weber, 1959). Considering the locality, this record probably corresponds to Ixodes auritulus auritulus Neumann, 1904 , which is common in South America ( Kohls and Clifford, 1966), rather than I. a. zealandicus. It is worth noting that although I. a. auritulus is generally considered a parasite of terrestrial birds, it is also capable of infesting seabirds such as the Magellanic diving-petrel ( Pelecanoides magellani ) ( González-Acuña et al., 2005). Both I. auritulus and I. kerguelenensis are members of the Ixodes auritulus-percavatus group, for which the phylogeny and nomenclature are unclear ( Arthur, 1960; Wilson, 1970a); it seems likely that future reviews might change the taxonomy of these parasites, which in turn will reflect on our knowledge of their ecology in the Antarctic region.

Lastly, Ixodes laridis Heath and Palma, 2017 has only been recorded on Antarctic hosts outside of the Antarctic region. This species infests a broad variety of seabirds, including four species of Antarctic seabirds, but its records are restricted to Australia, mainland New Zealand and the Chatham Islands ( Heath and Palma, 2017), and therefore to date it does not appear to have established in the Antarctic region. It is worth noting that it has been speculated that I. a. zealandicus and I. laridis might be capable of producing neurotoxins, leading to muscle paralysis ( Heath, 2006).