''Archaeocroton sphenodonti'', or the tuatara tick, is a species of

tick Ticks are parasitic arachnids of the order Ixodida. They are part of the mite superorder Parasitiformes. Adult ticks are approximately 3 to 5 mm in length depending on age, sex, and species, but can become larger when engorged. Ticks a ...

that parasitises only the

tuatara The tuatara (''Sphenodon punctatus'') is a species of reptile endemic to New Zealand. Despite its close resemblance to lizards, it is actually the only extant member of a distinct lineage, the previously highly diverse order Rhynchocephal ...

New Zealand New Zealand () is an island country in the southwestern Pacific Ocean. It consists of two main landmasses—the North Island () and the South Island ()—and List of islands of New Zealand, over 600 smaller islands. It is the List of isla ...

. It is found on just four of the twelve island groups where tuatara survive, preferring islands where the reptiles live in high densities. Larvae, nymphs, and adults all feed exclusively on tuatara blood, and ticks can survive for up to a year without a host. When tuatara are translocated, the tick has been lost or survives only in low densities in the new population. It is the only living species in the genus ''Archaeocroton''.

Description

Adult tuatara ticks are nearly circular, light brown and long. They were first described by

Lionel Jack Dumbleton Lionel Jack Dumbleton (1905 – 25 September 1976) was a New Zealand entomologist. He was born in Hampden, New Zealand and was a founding member of the Entomological Society of New Zealand. Dumbleton was one of the entomologists studying inse ...

in 1943. The

holotype A holotype (Latin: ''holotypus'') is a single physical example (or illustration) of an organism used when the species (or lower-ranked taxon) was formally described. It is either the single such physical example (or illustration) or one of s ...

male specimen was collected from Stephens Island by E. J. Tillyard in January 1922 and later deposited in the New Zealand Arthropod Collection.

Taxonomy

Originally, this species was placed in the genus ''Aponomma'', as members of this genus mostly parasitise reptiles. More primitive ''Aponomma'' were placed into the genus ''

Amblyomma ''Amblyomma'' is a genus of hard ticks. Some are disease vectors, for example the Rocky Mountain spotted fever in United States or ehrlichiosis in Brazil. This genus is the third largest in the family Ixodidae, with its species primarily ...

'' in 2002. Phylogenetic analyses suggest that this tick is not closely related to other ticks in the genus ''Amblyomma,'' being more closely related to genus ''

Bothriocroton ''Bothriocroton'' is a genus of hard ticks. There are seven extant member species, native to Australia and Papua New Guinea. ''Bothriocroton'' species typically parasitise monotremes, marsupials, and reptiles. ''Bothriocroton'' ticks have a limi ...

'' and it should to be placed in its own genus, ''Archaeocroton''. A fossil species of the genus, ''Archaeocroton kaufmani'' was described in 2023 from

Burmese amber Burmese amber, also known as Burmite or Kachin amber, is amber from the Hukawng Valley in northern Myanmar. The amber is dated to around 100 million years ago, during the latest Albian to earliest Cenomanian ages of the mid-Cretaceous period. Th ...

from Myanmar, dating to the mid-

Cretaceous The Cretaceous ( ) is a geological period that lasted from about 143.1 to 66 mya (unit), million years ago (Mya). It is the third and final period of the Mesozoic Era (geology), Era, as well as the longest. At around 77.1 million years, it is the ...

, around 100 million years ago. The host of this species is unknown.

Distribution

Like its host, this species has populations living on islands off the coast of the

North Island The North Island ( , 'the fish of Māui', historically New Ulster) is one of the two main islands of New Zealand, islands of New Zealand, separated from the larger but less populous South Island by Cook Strait. With an area of , it is the List ...

and

South Island The South Island ( , 'the waters of Pounamu, Greenstone') is the largest of the three major islands of New Zealand by surface area, the others being the smaller but more populous North Island and Stewart Island. It is bordered to the north by ...

of New Zealand. However, its distribution is confined to only four of the twelve island groups: the Mercury and Aldermen Islands off the coast of the North Island, and Stephens Island and the

Trios Trio may refer to: Music Groups * Trio (music), an ensemble of three performers, or a composition for such an ensemble ** Jazz trio, pianist, double bassist, drummer ** Minuet and trio, a form in classical music ** String trio, a group of three ...

Cook Strait Cook Strait () is a strait that separates the North Island, North and South Islands of New Zealand. The strait connects the Tasman Sea on the northwest with the South Pacific Ocean on the southeast. It is wide at its narrowest point,McLintock, ...

. Islands with a high density of tuatara, with increased association between hosts, are more likely to have ticks present, as the parasite has limited mobility and would find it difficult to disperse where tuatara densities are lower or fluctuate.

Life cycle

The tick has a three-stage life cycle, with all stages parasitising the tuatara. Females that have fed on the host's blood detach from the tuatara and lay eggs. This occurs in the tuatara's burrow. When the eggs hatch, the larvae attach to a tuatara, feed and detach. After moulting, the resulting nymph also attaches and repeats the cycle of feeding, detaching and moulting to become an adult tick. This life cycle may take 2–3 years. Increased temperatures may cause an increase in copulation on adult ticks and faster development rates of all life cycle stages.

Ecology

Tuatara are reptiles that use burrows for shelter. Their ticks can spend over one year off their host and prefer the moist and dark habitats provided by these burrows. Their preference for humid and dark conditions may be an adaptive feature for remaining inside or finding burrows where the host resides. If copulation takes place off the host, ticks may use pheromones to locate a mate. Tuatara live in a variety of habitats and are parasitised by ticks in all of them. The density of ticks on tuatara are higher when the host lives in pasture than in canopy forest. Tuatara ticks mirror the nocturnal activity of tuatara. They are more mobile at night, which could increase the chance of unattached ticks finding a host. It could also reduce the likelihood of desiccation due to the increased humidity at night. They prefer attaching in positions on the back of the host, folds in the skin of the rear legs and the side of the body. Once attached, they feed on the host's blood. Unfed adult ticks have been observed to survive for over one year without their host.

Conservation

This species is less widespread than its host. When translocation of tuatara has occurred, tick densities are lower or absent in the new population. Some tuatara have had the parasite removed before translocation and other populations of tuatara have lost the parasite afterwards. Its conservation status is relict, as – like its host – it once occupied a wider distribution.

References

External links

* ''Amblyomma sphenodonti'' discussed on RNZ ''

Critter of the Week ''Critter of the Week'' is a weekly RNZ National programme about endangered and neglected native plants and animals of New Zealand. Beginning in 2015, ''Critter of the Week'' is an approximately 15-minute discussion between Nicola Toki (origi ...

''

{{DEFAULTSORT:Amblyomma sphenodonti Animals described in 1943 Acari of New Zealand Endemic fauna of New Zealand Taxa named by Lionel Jack Dumbleton Endemic acari of New Zealand Ixodidae Monotypic arachnid genera