Ixodiphagus hookeri

Ixodiphagus hookeri, the tick wasp, is a chalcid wasp which lays its eggs into ticks.[3] It seems to use a symbiotic bacteria, Wolbachia pipientis, to weaken the tick's immune system.

Ixodiphagus hookeri
adult hatched from an nymph of Ixodes ricinus
Scientific classification
Kingdom: Animalia
Phylum: Arthropoda
Class: Insecta
Order: Hymenoptera
Family: Encyrtidae
Genus: Ixodiphagus
Species:
I. hookeri
Binomial name
Ixodiphagus hookeri
(Howard, 1908)
Synonyms[1]
  • Habrolepis caniphila Risbec, 1951
  • Hunterellus hookeri Howard, 1908[2]
  • Ixodiphagus caniphila Risbec, 1951
  • Ixodiphagus caucurtei Buysson, 1912

Description

Ixodiphagus hookeri is a small wasp which has the typical morphology of a chalcid wasp and is blackish in colour, it measures 0.8-0.9mm in length and has a wing length span of 1.5mm. Its head is dorsally flattened with very large compound eyes. In females, the antennae have eleven segments and the antennae are club shaped; while in males they have ten segments and are thread-like.[4]

Biology

Ixodiphagus hookeri has a short flight period in the summer in Europe. The female normally oviposits an egg into the body of an unfed nymph of Ixodes ricinus, but has been recorded ovipositing in the adults of Rhipicephalus sanguineus. The egg remains in diapause until the nymph engorges on vertebrate blood, at which point the egg becomes active. Some eggs are not successful, as the tick's immune system can encapsulate the egg, which results in the egg becoming melanised and dying. The bacteria Wolbachia is symbiotic with the wasp, and its presence in ticks is a possible indicator of infestation by tick wasps; Wolbachia may have a role in suppressing the host's immune system response to the wasp. The wasp larvae then exist as koinobiont parasitoids in the tick for 28 to 70 days before emerging.

Ticks from the genera Ornithodoros, Amblyomma, Dermacentor, Haemaphysalis, Hyalomma, Ixodes and Rhipicephalus are recorded as having been infected by I. hookeri. In Europe, Ixodes ricinus appears to be the preferred species and the marsh tick Dermacentor reticulatus is not used as a host. Because of the potential importance of I. hookeri as a natural enemy of ticks, it has been extensively researched.[5] Different populations of I. hookeri around the world show different host preferences, complicating attempts to use this species as a biological control for ticks.[3][6]

A Female habitus. B Female ovipositing in an engorged nymph of Ixodes ricinus (ovipositor indicated by the arrow). C Adults of I. hookeri around the dead body of an engorged nymph of I. ricinus. D Emergence hole from which parasitoids exit the dead body of the engorged nymph.

Distribution

I. hookeri occurs worldwide, except in Antarctica.

References
  1. "Ixodiphagus hookeri (Howard, 1908)". GBIF.org. Retrieved 29 May 2017.
  2. Howard, L. O. (1908). "Another chalcidoid parasite of a tick". The Canadian Entomologist. 40 (7): 239–241. doi:10.4039/Ent40239-7.
  3. Plantard O; Bouju-Albert A; Malard M-A; et al. (2012). "Detection of Wolbachia in the tick Ixodes ricinus is due to the presence of the hymenoptera endoparasitoid Ixodiphagus hookeri". PLOS ONE. 7 (1): e30692. doi:10.1371/journal.pone.0030692. PMC 3266912. PMID 22292021.
  4. M. S. Quaraishi (1958). "Morphology of Two Chalcidoid Parasites of Ticks, Hunterellus hookeri Howard, 1908, and Ixodiphagus texanus Howard, 1907". The American Midland Naturalist. 59 (2): 489–504. doi:10.2307/2422494. JSTOR 2422494.
  5. Renjie Hu; K. E. Hyland; J. H. Oliver (1998). "A review on the use of Ixodiphagus wasps (Hymenoptera: Encyrtidae) as natural enemies for the control of ticks (Acari: Ixodidae) (abstract)". Systematic and Applied Acarology. 3 (1): 19–28. doi:10.11158/saa.3.1.3.
  6. J. Collatz; P. Selzer; A. Fuhrmann; et al. (2010). "A hidden beneficial: biology of the tick-wasp Ixodiphagus hookeri in Germany". Journal of Applied Entomology. 135 (5): 351–358. doi:10.1111/j.1439-0418.2010.01560.x.
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