Tuatara: Volume 23, Issue 1, July 1977
Zoogeography of the New Zealand Tick Fauna
Zoogeography of the New Zealand Tick Fauna
It is characteristic of an oceanic island that its fauna, in comparison with that of an adjacent continent, is an impoverished one (Falla, 1953). Thus Australia (including Papua/New Guinea) has 66 species of ticks, 52 of which are indigenous whereas the New Zealand sub-region has only 9 named species of ticks. 3 of which are endemic and 6 of which also occur in Australia. One further species, an as yet unnamed argasid from a native bat (Mystacina tuberculata), was collected recently from North Auckland (G. W. Ramsay, pers. comm.).
The origins of New Zealand's tick fauna and its affinities with those of other countries in the Pacific region have received little attention. The aim of this paper is to investigate the possible origins and means of dispersal of our tick fauna and to place the New Zealand Ixodidae and Argasidae within the framework of current biogeographical knowledge. The data used for this purpose come from a large number of host and locality records, and from publications on bird migration, geology and vertebrate palaeontology.
Tick Biology and Dispersal
Ticks are blood-feeding, obligate ectoparasites of vertebrates and are related to spiders and mites. There are two families — the Ixodidae or hard ticks, so called because of the presence of an inflexible dorsal scutum, and the Argasidae, or soft ticks that have a leathery cuticle and no scutum.
Ticks can cause anaemia, paralysis and death of their hosts and, in addition, are among the most successful of those arthropods that transmit viral, protozoan and rickettsial organisms to man and other animals.
Members of both tick families pass through egg, larval, nymphal and adult stages. The Argasidae can have 2 to 7 nymphal instars whereas the Ixodidae have a single nymph stage. Some Ixodidae are 1 or 2-host ticks but most utilise 3 hosts. In other words, each of the 3 feeding stages is punctuated by a free-living phase. During this latter period, the engorged tick moults (if a larva or nymph) or oviposits (if a female) and the ensuing unfed stage later becomes parasitic on another host. Feeding times range from 4 to 21 days (Balashov, 1972) with larvae feeding more rapidly than adults or nymphs.
The Argasidae are mainly multihost ticks and contrast with Ixodidae in that the feeding times of nymphs and adults vary from page 27 minutes to, at most, a few hours. At the same time, the larvae of some Argasidae may remain attached to the host for some days but in view of their short feeding periods, widespread dispersal of the feeding stages of Argasidae by land or sea birds seems unlikely. In contrast, the Ixodidae remain attached to the host for long periods while feeding and could be dispersed by bird hosts. Nevertheless, carriage of the eggs of both families in mud or similar material on the feet of birds could occur and a phoretic association between an unfed tick and a vertebrate is another likely means of dispersal.
The time spent off the host by members of both families depends upon the stage of development reached, the ambient temperature and humidity, and the availability of hosts. The unfed, questing stages of some species of Ixodidae can live without food for at least one year. Some Argasidae have been known to survive for 10 years without a blood meal. Such survival ability would be of considerable value to ticks on isolated, infrequently visited islands or in generally inhospitable areas where hosts only appear sporadically.
The duration of the incubation and premoulting periods can range from days to months, depending upon the temperature and humidity within the immediate environment (Heath, 1974). Generally, low temperatures and low humidities can retard moulting or incubation to the extent that eggs or engorged stages of ticks could be carried over long distances stuck to birds' feathers or feet. Ticks carried on sea-birds face the problem of immersion in sea water but there is evidence (Murray and Vestjens, 1967; Sutherst, 1971) to show that tickets are capable of withstanding prolonged immersion in fresh as well as exceedingly stagnant water, thus periodic immersion in sea water may not disadvantage them.
The Endemic New Zealand Tick Species
There are three endemic species of ticks occurring in New Zealand: Aponomma sphenodonti Dumbleton, the tuatara tick, Ixodes anatis Chilton, the kiwi tick, and I. jacksoni Hoogstraal, the cormorant tick.
Aponomma sphenodonti Dumbleton
The genus Aponomma contains about 25 species (Roberts, 1970). Five species are found in Africa, 8 in the Australian-New Guinea-Indonesian region and 4 in the Americas (Hoogstraal, 1956). The genus is unknown in Europe. Most species occur on reptiles and exhibit remarkable host and geographic specificity, factors which could indicate considerable antiquity.
The first rhyncocephalid reptiles, forerunners of the tuatara, appear in the fossil record in the Lower Triassic (Fleming, 1962a). They are known also from East Africa and South America, but probably became extinct, except in New Zealand, in the late Cretaceous or Tertiary (Robb, 1973). This geographical distribution page 28 could be explained in terms of the continental drift hypothesis (Keast, 1971; Hallam, 1975). Darlington (1965) offers the opinion that New Zealand has been isolated from all habitable continents at least since the beginning of the Tertiary, and this could have ensured the isolation of the tuatara on the early New Zealand land mass.
The reptile and its tick are known to occur together only on Stephens Island (I. G. Crook, pers. comm.). One could speculate that if the tick is found on any of the other offshore islands, it will possibly show a pattern of subspeciation due to the long isolation of these separate tick populations.page 29
When the systematics of the genus Aponomma are finally unravelled, it may be possible to show whether A. sphenodonti has African or South American affinities, especially since its host has at least tenuous links with those continents.
Ixodes anatis Chilton
This species was first described from the North Island kiwi, Apteryx mantelli, and occurs in both islands (Fig. 1). It is chiefly regarded as a kiwi tick, the only other recorded hosts being the grey duck, Anas superciliosa, a colonist from Australia, and the Canada goose, Branta canadensis, which was introduced from North America. The earliest known kiwi dates from the Quaternary although Reid and Williams (1975) are inclined to accept Fleming's (1962b) hypothesis that the ancestor or ancestors of the kiwis and moas colonised New Zealand during the Upper Cretaceous.
The affinities of I. anatis are not clear, although Dumbleton (1963) felt that the tick may be contemporaneous with the kiwi and could be included in the subgenus Sternalixodes which occurs on land mammals in Australia. However, I find little agreement between Dumbleton's (1953) description of I. anatis and Roberts's (1970) definition of Sternalixodes.
There still remains the possibility of an Australian origin for the tick, as Reid and Williams (1975) infer that the New Zealand and Australian ratites are more closely related to one another than to those in South America or Africa. Unfortunately, no ticks are known from Australian ratites with which comparisons can be made.
Ixodes jacksoni Hoogstraal
This species was only recently described from New Zealand by Hoogstraal (1967) and its affinities are not yet clear. It is held that I. jacksoni and I. uriae share a relationship within the subgenus Ceratixodes (Dumbleton, 1973), a group which, until now, had had I. uriae as its sole representative. Hoogstraal (1967) does not share Dumbleton's (1973) view but these differences of opinion do not clarify the degree of relationship between the species.
Indigenous New Zealand Species
Ixodes eudyptidis Maskell
This species occurs commonly on penguins in New Zealand and there are also records of the tick from Australia on a penguin, a gull and a gannet (Roberts, 1970). Because the tick appears to be so common in New Zealand and because there are so few Australian records (Fig. 2) I suggest that we have ‘exported’ I. eudyptidis to Australia. This could have been effected by the little blue penguin (Eudyptula minor) or by gannets (Sula bassana serrator). The latter are known to make east to west Tasman crossings (Stein and Wodzicki, 1955). Although a proportion of New Zealand's plant and animal life appears to have come from Australia, a modest flow of organisms to Australia from New Zealand is a distinct possibility (Fleming, 1976).
Ixodes eudyptidis is very similar to, but distinguishable from I. kohlsi, a tick which is restricted to Australian waters. The latter species is common on the Australian race of the little blue penguin and has also been found on gannets (Roberts, 1970). Dumbleton (1961) felt that because of the absence of significant overlap in the distribution of I. eudyptidis and I. kohlsi, the home range of the hosts did not interdigitate. He was also of the opinion that the page 31 penguin ticks of Australia and New Zealand did not arise and evolve from the same stock in parallel with the subspeciation of the host. Without going into the origins and relationships of penguins in detail, it would appear as though ticks from two different stocks have adopted the same hosts in both New Zealand and Australia (Dumbleton, 1961). This thesis, however, does not preclude colonisation of Australia by an endemic New Zealand tick.
Ixodes auritulus-percavatus groups
All the species within these complex groups appear to be closely related although they are different in form.
The relationships and localities of the various species as presently accepted, are set out below using data from Zumpt (1952), Arthur (1953), Roberts (1970) and Dumbleton (1973). The question marks serve to emphasise Arthur's (1953) contention that I. percavatus is synonymous with I. auritulus and that I. rothschildi deserves specific ranking instead of its earlier status as a variety of I. percavatus.
In addition to the above species, I. kerguelenensis, Kerguelen Island (Arthur, 1960b), I. kohlsi, Australia, and I. diomedeae, Tristan da Cunha (Murray, 1967), are other sea-bird ticks of the south circumpolar region which may one day be found in the New Zealand subregion.
There is a likelihood that the New Zealand subspecies of I. auritulus has been derived from a North American parent stock but the different host preference tends to contradict this view. In fact Arthur (1960a) expresses the doubt that I. auritulus is a sea-bird tick at all.
The auritulus and percavatus complexes along with I. kerguelenensis, I. kohlsi and I. diomedeae may be a recently evolved group of species, with origins in the southern oceans and having no affinities with the Northern Hemisphere at all. The parent form(s) can only be speculated upon but the stock(s) could presumably have become isolated during the break-up of Pangaea.
Ixodes uriae White
Study of this species has generated some interesting theories because of its bipolar distribution (Fig. 3). Schulze (1938) discussed the distribution of I. uriae and suggested that this could have been achieved either by land bridges or by dissemination of the tick's eggs by migratory sea-birds. Conversely, the tick could be a relic of a Tertiary fauna separated by continental drift (Pfeffer's hypothesis).
There is no morphological evidence of subspeciation in either the Northern or Southern Hemiphere populations and Schulze (1938) attributes this to the similarity of the two polar environments. page 33 However, no attempt has been made to interbreed representatives of the two populations and this would be a more certain method of clarifying the situation.
The distribution of I. uriae could be explained by birds carrying tick eggs on their feet from their breeding grounds to their overwintering regions. The ticks themselves do not appear to remain attached to the host for long enough to ensure that another hemisphere could be reached (Murray and Vestjens, 1967). On the other hand, Amerson (1968) found an I. pterodromae which was believed to have remained attached to a bird which had flown a distance of 4800 km, so the feeding stages of some ticks may become widely dispersed.
A number of birds, including the sooty shearwater Puffinus griseus (Fig. 3) and Wilson's storm petrel, Oceanites oceanicus, are transequatorial migrants (Serventy, 1953; Palmer, 1962) but only the former species has been found infested with I. uriae.
Circumpolar distribution in both the Northern and Southern Hemispheres could be accounted for by a large range of hosts including penguins, albatrosses, skuas and puffins (Nuttall, Warburton, Cooper and Robinson, 1911; Nuttall, 1912, 1916; Johnston, 1937; Senevet, 1937; Cooley and Kohls, 1945; Hoogstraal, 1954; Gregson, 1956; Dumbleton, 1961; Arthur, 1963; Gressitt, 1964; Wilson, 1964, 1967; Theiler, 1971). In addition, Falla's (1960) comments on oceanic birds as dispersal agents support the view that many sea-birds fly considerable distances and do regularly visit oceanic islands. On the other hand, there is some doubt (G. van Tets and C. J. R. Robertson, pers. comm.) that the distribution of I. uriae in the circum-south-polar region is related to bird movement in this area (see Fig. 2). The birds on which the tick has been found apparently do not normally indulge in ‘island hopping’, although it is possible that heavily tick-infested birds are forced to rest on islands and so disseminate I. uriae. Arthur (1963) records the debilitating effect of heavy I. uriae infestations and affected birds could have their flying ability reduced.
There are no indications as to which hemisphere is the ancestral home of I. uriae although the possibility cannot be discounted that two separate stocks of ticks evolved in parallel or converged.
Ornithodoros capensis Neumann
This species is essentially a tropical and subtropical species with a wide distribution throughout the Pacific (Fig. 4).
Until recently this was the only argasid tick known to occur in New Zealand (G. W. Ramsay, pers. comm.). The species has now been found on both the east and west coasts of the South Island and on the Kermadec Islands (Ramsay, 1967; Dumbleton, 1973) and throughout its range is mainly associated with sea-birds (Amerson, 1968; Theiler, 1971).page 34
On present evidence the tick's presence in New Zealand can be linked with two species of birds. One is a turnstone, Arenaria interpres, a land bird from the Holarctic region. The other is the brown booby Sula leucogaster which does not range further than 40° S (Fig. 4). Both species commonly visit New Zealand and spend some time here (Baker, 1963; Kinsky, 1970). Both birds have been found infested with O. capensis (Amerson, 1968).
An Introduced Tick
Haemaphysalis Iongicornis Neumann
The genus Haemaphysalis contains a world-wide total of about 150 species with representatives in Africa, Russia, Europe, the Americas and Asia which has the majority of species (Hoogstraal, 1956).
Haemaphysalis longicornis is the only tick of economic importance in New Zealand. It feeds on sheep and cattle and also infests many mammalian and avian hosts (Myers, 1924). The tick occurs on both islands as shown in Fig. 1 and is particularly abundant in the northern half of the North Island (Heath, 1973).
The species is found in a number of countries in the Western Pacific (Hoogstraal, Roberts, Kohls and Tipton, 1968) and probably came from Japan, reaching New Zealand via Australia (Hoogstraal et al., 1968). Because H. longicornis has been in this country for a relatively short time and with cattle as the generally accepted introductory agent, there is no need to invoke other theories for its presence. Nevertheless, Myers (1924) suggests a number of alternatives.
As Fleming (1963) suggests, Australia is well placed to supply New Zealand with animal and plant colonists. In fact, the bulk of New Zealand's plant and animal life appears to be closely related to the Australian biota. Many northern and southern elements are shared by Australia and New Zealand and could have come to New Zealand via Australia or directly from the north or south. However, New Zealand's endemic tick fauna appears to have no close affinity with extant Australian species and indeed there appears to be no single country of origin for any of its components. The zoogeographic associations of the tick fauna indicate introductions from areas remote from New Zealand's present faunal boundaries. Thus, there are affinities with the Central Pacific (O. capensis), the Atlantic (I. uriae) and the circumpolar region (many species). Alternatively, some species may have arisen from an ancestral stock which has evolved to varying degrees since the break-up of Gonwanaland (I. auritulus-percavatus group).
There is every likelihood that additional sea-bird ticks will be discovered in and around New Zealand. Other potential colonists such as Argas (Persicargas) robertsi (Hoogstraal, Kaiser and McClure, 1975) and H. (Ornithophysalis) doenitzi (Hoogstraal and Wassef, 1973) which are known from Australia on birds that frequently reach our shores, may be added to our tick fauna in the future.
In addition, Haemaphysalis spp. could be introduced to New Zealand by migrating birds from Asia, a major source of members of this genus (Hoogstraal and Wassef, 1973).
Tick Collection and Preservation
Very little detailed knowledge exists regarding the biology of any New Zealand ticks except H. longicornis. A keen collector could help greatly by adding to host lists and locality records. The larger the number of known hosts and localities, the more likely a common factor may become apparent which will clarify some point about the life cycle or biology of a tick.
Ticks can be found in a variety of habitats and are easily removed from the host or from places of concealment with a small paint brush or fine forceps. Gentle traction with the forceps grasping the base of the mouthparts should easily remove feeding ticks. In sea-bird colonies, ticks are frequently found under stones or timber or at the base of plants in the close vicinity of nests. Nests and burrows are also a good source of ticks and material from kiwi nests would be of particular value. Living and freshly-dead sea-birds are frequently found infested with ticks and anyone having the opportunity to examine ‘wrecked’ birds driven ashore by gales is sure to find some tick specimens.
When examining a bird-host, pay careful attention to the head, vent, and webbing of the feet; and when examining mammals, look in the ears, around the eyes and axillae and groin as these are sites preferred by ticks. Do not confine your collecting to the bloated, easily-seen female ticks. Careful searching is likely to reveal pin-head sized larvae and slightly larger nymphs as well. Nest material from birds and mammals can be shaken up in water and sieved, or exposed in a Tullgren funnel.
Ticks are best preserved in 70% ethanol but if a study of living engorged stages or eggs is desired, moist sand or tissue paper in the bottom of a covered container should be sufficient to maintain a suitable humidity at room temperatures.
I wish to thank Mr H. St. J. Burden for considerable assistance in preparation of the figures.
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