Tuatara: Volume 11, Issue 2, June 1963
A Synopsis of the Ticks — (Acarina: Ixodoidea) of New Zealand
A Synopsis of the Ticks
(Acarina: Ixodoidea) of New Zealand
The ticks are the largest of all Acarina. They may be distinguished by the presence of a movable capitulum, distinct from the fused thorax and abdomen and visible dorsally in most genera, and the prominent barbed hypostome. Unfed ticks in all stages are dorso-ventrally flattened but the bodies of engorged females may be spherical and up to 10 mm. in diameter, when the sclerotized parts which provide the main taxonomic characters become relatively inconspicuous. The basis capituli may bear cornuae postero-laterally or auriculae ventrally and in the females has two dorsal porose areas. The mouth parts are borne in the median line anteriorly and consist of a dorsal cheliceral sheath and a ventral toothed hypostome which enclose the chelicerae and are apposed to form a sucking tube. This structure is flanked on each side by a labial palp which is four-segmented, though the fourth segment is small and often not visible dorsally. The scutum is a flat shield-shaped plate on the dorsum of the thorax immediately behind the capitulum. The legs are six-segmented and bear a sensory organ (Haller's organ) on the distal tarsal segment of the first pair of legs. The spiracular plates are sub-circular and are situated ventro-laterally behind the fourth coxae. The integument of the remainder of the body, except in the males, has a thin unsclerotized integument which is capable of great extension during engorgement. The eyes, when present, are situated on the sides of the scutum but they are not present in New Zealand species.
The females are oviparous and the development of individuals of both sexes includes a larval and a nymphal stage. The larvae have only three pairs of legs and the nymphs lack the genital opening of the males and females. The males and females of Ornithodoros differ only in the form of the genital opening, but in the Ixodidae the males have the scutum covering the dorsum and more numerous ventral plates, while the females have porose areas on the dorsum of the basis capituli.
All stages except the males are blood-sucking. The skin of the host is pierced by the cutting chelicerae and the recurved teeth of the hypostome, which is inserted into the wound, act as a holdfast. The argasid ticks such as Ornithodoros feed quickly and leave the host at once, and all stages are commonly found in the nest, where they shelter, and not on the host. All stages page 73 of the ixodids, except the males, remain on the host for long periods and leave it only to moult or lay eggs. The males, however, are commonly found only in the nest material. In the course of feeding the individuals of many tick species feed on more than one host individual, dropping to the ground for each moult and later regaining another host individual.
This habit is of significance in the transmission of the diseases of man and animals, especially in tropical countries, which are caused by the pathogenic viruses, rickettsiae, and protozoans which the ticks may carry. In some cases the pathogenic agent is transmitted to the progeny of the infected female tick through the eggs, and ticks which have never fed on an infective host may thus carry infection. Apart from their role as vectors of disease the ticks inject salivary secretions when feeding and in some species these have a neurotoxic constituent which causes ‘tick paralysis’ in man and animals, especially when the feeding site is near the brain or spinal cord.
The eggs, which are spherical and about half a millimeter in diameter, are extruded in large masses containing as many as 1000 eggs. They are found in the nest of the host, or on the ground where the female has dropped from the host. Host finding is easy for the larval ticks hatching from eggs laid in a nest, burrow, or lair which is constantly used or periodically reoccupied. The tick species infesting free-ranging mammals may drop from the host anywhere, though they would tend to be concentrated in favoured camping places. The larvae or newly moulted individuals of such species ascend grasses or other vegetation and wait for the passing hosts to brush against them.
Ticks have been known to survive unfed for very long periods but there is no doubt that a large part of the mortality amongst larvae and nymphs awaiting a host is due to adverse climatic factors. One small hymenopterous (chalcid) parasite of ticks is known elsewhere, but invertebrate predators may take a greater toll of ticks on the ground. Birds such as the starling may take the ticks not only from the ground but from the host also. Two unusual cases are known of a sea-bird tick taken from the faeces of a tuatara and a kiwi tick from the faeces of a cat. On the hosts the ticks aggregate in positions where they are not readily dislodged by self-cleaning or scratching.
Because of their medical and veterinary importance considerable work has been done on the physiology, ecology, and control, of ticks. In New Zealand the cattle tick (Haemaphysalis) is the only species which has been studied (Myers, 1924).
Recent taxonomic work on New Zealand ticks is accessible in previous papers (Dumbleton 1943, 1953, 1958, 1961), and detailed host lists are given in two of these (1953, 1961), A generalised host list is combined with the list of the species in the New page 74 Zealand fauna which is given below. Three other species, Haemaphysalis leachi Audouin, Hyalomma aegyptium Linnaeus, and Ixodes ricinus Linnaeus, have been recorded as present in New Zealand. They were considered (1953) as doubtfully established and are now omitted from the list as they have not been collected since that date.
Little can be said regarding the origin of the tick fauna. The single species of Aponomma, a genus largely restricted to reptiles, would appear to have been contemporaneous with Sphenodon.
The same may be true of Ixodes anatis Chilton the only New Zealand species confined to land birds, more especially the kiwi. This appears to belong to a group differing from that of the other New Zealand species. While there are few or no Australian species confined to land birds I. anatis has some affinities with the species of Ixodes (Sternalixodes) which occur there on land animals.
The species occurring on sea birds are either cosmopolitan or belong to species-groups which are widespread in the Subantarctic or in Australia.
|Aves||Spotted Shag.||South Island, S. Hemisphere and N. Pacific.||Ornithodoros capensis Neumann.|
|Aves||Land birds; esp. Kiwi.||Both Islands, Endemic.||Ixodes anatis Chilton.|
|Land birds; various.||North Island, Introduced.||Haemaphysalis bispinosa Neumann.|
|Sea birds; esp. Penguin, also Black Shag.||Both Island, Endemic. (Also Australia?).||Ixodes eudyptidis Maskell.|
|Sea birds; esp. burrow-nesting spp.||South Island, Endemic; also N.Z. Subantarctic.||Ixodes auritulus zealandicus Dumbleton.|
|Sea birds; various.||South Island, Cosmopolitan.||Ixodes uriae White.|
|Mammalia||Various; esp. cattle.||North Island, Introduced.||Haemaphysalis bispinosa Neumann.|
|Reptilia||Tuatara.||South Island (Stephen Is.), Endemic.||Aponomma sphenodonti Dumbleton.|
Keys to the families, genera, and the males and females of the genus Ixodes are given below. Nymphs, and usually larvae, are identifiable by association with adults and similarities in morphology.
Key to Families of the Superfamily Ixodoidea in New Zealand
Scutum absent in all stages; capitulum ventral, visible dorsally in larva but not in nymphs and adults; integument mamillated, with symetrical pattern of smooth plaques on dorsal surface; sexes differing only in form of genital orifice (figs. 1 and 2) . . Argasidae.
Scutum always present, covering all (males) or not more than anterior half (females, nymphs, larvae) of dorsum; capitulum anterior, visible dorsally and with prominent basis capituli; integument smooth; females with porose areas on basis capituli, males with median and ad-anal plates (figs 3, 4, 5 and 6). Ixodidae.
Without a marginal sutural line, separating the dorsal and ventral surfaces and differing in sculpture from both …. Ornithodoros.
Key to Genera of Ixodidae
|(1)||Posterior body margin not divided into sections or festoons; anal groove contouring the anus in front||Ixodes.|
|Festoons present; anal grove contouring the anus behind (fig. 7)||(2).|
|(2)||Capitulum short, palps short and stout, second segment angulate postero-laterally||Haemaphysalis.|
|(One species. Third segment of palp with an erect dorsal spur; at least 4 files of teeth on each side of hypostome [4/4]; scutum as wide as long [fig. 8]||H. bispinosa).|
|Capitulum long, palps long and slender, no processes on second and third segments||Aponomma.|
|(One species. Second palpal segment longer than third; dentition of hypostome 2/2: scutum wider than long [fig. 9]||A. sphenodonti).|
Key to Males of Genus Ixodes
|(1)||Posterior margin of body with five hair brushes; all coxae without spurs; third segment of palp pointed and upturned apically (fig. 10)||I. uriae|
|Not as above||(2).|
|(2)||Pre-genital plate transverse, jugular plates absent (fig. 11)||I. anatis.page 76|
|Pre-genital plate sub-pentagonal, jugular plates present (fig. 12)||(3).|
|(3)||Dentition of hypostome 4/4, toothed area long; second palpal segment gradually narrowed basally; capsule of Haller's organ on first tarsus superficial; anal grooves slightly diverging (fig. 13)||I. auritulus zealandicus.|
|Dentition of hypostome 2/2. toothed area short; second palpal segment abruptly narrowed basally; capsule of Haller's organ concave: anal grooves arcuate, converging (fig. 14)||L. eudyptidis.|
Key to Females of Genus Ixodes
|(1)||All coxae without spurs; third palpal segment swollen mesad at apex (fig. 15)||I. uriae.|
|At least some coxae with spurs: third segment of palpus not swollen apically||(2).|
|(2)||Scutum broader than long, sub-angulate laterally at midlength; spurs present on first three coxae; second palpal segment longer than third; dentition of hypostome 2/2 (fig. 16)||I. anatis.|
|Scutum longer than broad, rounded laterally; spurs present on all coxae; second and third palpal segments sub-equal in length; dentition of hypostome 4/4||(3).|
|(3)||First segment of palp with anterior mesal margin produced into a spur; basis capituli with cornua posterolaterally on dorsum and retrograde auriculate ventrally, porose areas ovoid (fig. 17)||I. auritulus zealandicus|
|First palpal segment without anterior spur; basis capituli without cornua. auriculae with transverse posterior margin, porose areas pear-shaped, widest internally (occasionally fused in median line) (fig. 18)||I. eudyptidis.|
Fig. 1: Ornithodoros capensis, dorsal. Fig. 2: Ornithodoros capensis, ventral; capitulum, hood (h), cheeks (c), and genital opening (go). Fig. 3: Ixodid male, dorsal; scutum (s). Fig. 4: Ixodid female, dorsal. Fig. 5: Ixodid male, ventral; coxae (ex), spiracle (sp). Fig. 6: Ixodid female, ventral; anus (a), anal groove (ag). Fig. 7: Aponomma sphenodonti ventral; festoons (f). Fig. 8: Haemaphysalis bispinosa, female capitulum, ventral (L) and dorsal (R); chelicera (ch), hypostome (hy), sheath (sh), palpal segments (2, 3). Fig. 9: Aponomma sphenodonti, female capitulum. Fig. 10: Ixodes uriae male, posterior margin, ventral. Fig. 11: Ixodes anatis male, genital opening, pre-genital plate (pg), coxal spur (cs). Fig. 12: Ixodes auritulus zealandicus male; pre-genital and jugal (j) plates. Fig. 13: Ixodid male, ventral; diverging anal groove. Fig. 14: Ixodid male, ventral; converging anal groove. Fig. 15: Ixodes uriae, female capitulum. Fig. 16: Ixodes anatis, female capitulum. Fig. 17: Ixodes auritulus zealandicus female capitulum; auricua (au), cornua (co), palpal spur (ps). Fig. 18: Ixodes eudyptidis, female capitulum; porose area (po).
Dumbleton, L. J., 1943. A New Tick from the Tuatara (Sphenodon punctatus) N.Z. J. Sci. & Tech. 24B: 185-190.
Dumbleton, L. J., 1953. The Ticks (Ixodoidea) of the New Zealand Sub-region. N.Z. Cape Exped. Ser. Bull. 14: 1-28.
Dumbleton, L. J., 1958. The Occurence of an Argasid Tick in New Zealand. N.Z. J. Sci. 1: 570-578.
Dumbleton, L. J., 1961. The Ticks (Acarina: Ixodoidea) of Sea-birds in New Zealand Waters. N.Z. J. Sci., 4: 760-769.
Myers, J. G., 1924. The Cattle Tick (Haemaphysalis bispinosa) N.Z. Dep. Agric. Bull. 116: 1-105.