Tuatara tick
Amblyomma sphenodonti on a tuatara

Relict (NZ TCS)[1]
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Arthropoda
Subphylum: Chelicerata
Class: Arachnida
Order: Ixodida
Family: Ixodidae
Genus: Archaeocroton
Dumbleton, 1943
Species:
A. sphenodonti
Binomial name
Archaeocroton sphenodonti
(Dumbleton, 1943)[2]
Synonyms
  • Aponomma sphenodonti Dumbleton, 1943
  • Amblyomma sphenodonti

Archaeocroton sphenodonti, or the tuatara tick, is a species of tick that parasitises only the tuatara of New Zealand. 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 2 millimetres (0.079 in) long.[3] They were first described by Lionel Jack Dumbleton in 1943.[4] The holotype 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 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 and it should to be placed in its own genus, Archaeocroton.[5][6][7][8]

A fossil species of the genus, Archaeocroton kaufmani was described in 2023 from Burmese amber from Myanmar, dating to the mid-Cretaceous, around 100 million years ago. The host of this species is unknown.[9]

Distribution

Like its host, this species has populations living on islands off the coast of the North Island and South Island 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 in Cook Strait. 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.[7]

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.[10] 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.[11]

Ecology

Tuatara ticks on the body of their host, Sphenodon punctatus

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.[12] 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.[10] Once attached, they feed on the host's blood.[12] Unfed adult ticks have been observed to survive for over one year without their host.[6]

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.[13] Its conservation status is relict,[14] as – like its host – it once occupied a wider distribution.[15]

References

  1. ↑ "Archaeocroton sphenodonti. NZTCS". nztcs.org.nz. Retrieved 3 April 2023.
  2. ↑ "NZOR". New Zealand Organisms Register. Retrieved 26 June 2018.
  3. ↑ "Amblyomma (Aponomma) sphenodonti". Retrieved 3 July 2018.
  4. ↑ Dumbleton, L.J. (1943). "A new tick from the tuatara (Sphenodon punctatus)". New Zealand Journal of Science and Technology. 24 (4): 185B–190B. Retrieved 3 July 2018.
  5. ↑ Heath, Allen; Rolfe, Jeremy; Michel, Pascale. "Conservation status of parasitic mites and ticks (Acari) in New Zealand, 2021. NZTCS". nztcs.org.nz. New Zealand Threat Classification Series 37. Department of Conservation, Wellington. 23 p. Retrieved 3 April 2023. PDF
  6. 1 2 "New Zealand BioSecure" (PDF). Southern Monitoring Services Limited. Retrieved 3 July 2018.
  7. 1 2 Miller, Hilary C.; Conrad, Ailis M.; Barker, Stephen C.; Daugherty, Charles H. (January 2007). "Distribution and phylogenetic analyses of an endangered tick, Amblyomma sphenodonti". New Zealand Journal of Zoology. 34 (2): 97–105. doi:10.1080/03014220709510068.
  8. ↑ Burger, Thomas D.; Shao, Renfu; Barker, Stephen C. (June 2013). "Phylogenetic analysis of the mitochondrial genomes and nuclear rRNA genes of ticks reveals a deep phylogenetic structure within the genus Haemaphysalis and further elucidates the polyphyly of the genus Amblyomma with respect to Amblyomma sphenodonti and Amblyomma elaphense". Ticks and Tick-borne Diseases. 4 (4): 265–274. doi:10.1016/j.ttbdis.2013.02.002. PMID 23602360.
  9. ↑ Chitimia-Dobler, Lidia; Dunlop, Jason A.; Pfeffer, Timo; Würzinger, Felix; Handschuh, Stephan; Mans, Ben J. (February 2023). "Hard ticks in Burmese amber with Australasian affinities". Parasitology. 150 (2): 157–171. doi:10.1017/S0031182022001585. ISSN 0031-1820. PMC 10090639. PMID 36341553.
  10. 1 2 Heath, A.C.G. (2006). "A reptile tick, Aponomma sphenodonti Dumbleton (Acari: Ixodidae), parasitic on the tuatara, Sphenodon punctatus Gray (Reptilia: Rhyncocephalia), in New Zealand: observations on its life history and biology". Systematic and Applied Acarology. 11: 3–12. doi:10.11158/saa.11.1.1. S2CID 88425035.
  11. ↑ Godfrey, S. S.; Bull, C. M.; Nelson, N. J. (2008). "Seasonal and spatial dynamics of ectoparasite infestation of a threatened reptile, the tuatara (Sphenodon punctatus)". Medical and Veterinary Entomology. 22 (4): 374–385. doi:10.1111/j.1365-2915.2008.00751.x. PMID 19120965. S2CID 20718129.
  12. 1 2 Godfrey, Stephanie S.; Nelson, Nicola J.; Bull, C. Michael (2011). "Microhabitat choice and host-seeking behaviour of the tuatara tick, Amblyomma sphenodonti (Acari: Ixodidae)" (PDF). New Zealand Journal of Ecology. 35 (1): 52–60. Retrieved 4 July 2018.
  13. ↑ Pawson, Steve (Mar–Apr 2008). "Nervous Tick". New Zealand Geographic. Retrieved 4 July 2018.
  14. ↑ Buckley, T. R.; Palma, R. L.; Johns, P. M.; Gleeson, D. M.; Heath, A. C.G.; Hitchmough, R. A.; Stringer, I. A.N. (2012). "The conservation status of small or less well known groups of New Zealand terrestrial invertebrates". New Zealand Entomologist. 35 (2): 137–143. Bibcode:2012NZEnt..35..137B. doi:10.1080/00779962.2012.686319. S2CID 55135775.
  15. ↑ Townsend, Andrew J.; de Lange, Peter J.; Duffy, Clinton A.J.; Miskelly, Colin M.; Molloy, Janice; Norton, David A. "New Zealand Threat Classification System manual" (PDF). Department of Conservation. Retrieved 4 July 2018.
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