X-ray microscopy (micro-CT) is used for the 3D visualization and analysis of arachnids, including ticks, spiders, and mites. Ticks are external parasites that survive by feeding on the blood of mammals, birds, and sometimes reptiles and amphibians. The oldest known tick fossils are from the Cretaceous period, around 100 million years old; today there are about 850 documented tick species, only some which transmit diseases. Because tickborne diseases – including Lyme disease, anaplasmosis, Rocky Mountain spotted fever, babesiosis, and ehrlichiosis – increasingly threaten human health, researchers study ticks to aid in developing prevention and treatments. Scientists also study their insertion mechanics, means of attachment, and unique mechanics for sucking blood.
3D model obtained from X-ray projection images illustrating female tick mouthpart topography. “Three-dimensional reconstruction of the feeding apparatus of the tick Ixodes ricinus (Acari: Ixodidae),” Vancová, Marie, et al, Scientific Reports, January 13, 2020.
Three-dimensional reconstruction of the feeding apparatus of the tick Ixodes ricinus (Acari: Ixodidae): a new insight into the mechanism of blood-feeding
Ticks are pool feeders, utilizing their mouthparts to cut and tear into the skin, secreting saliva to silence the host’s awareness of their presence, cementing themselves to the skin, and gorging themselves on the blood oozing around their mouthparts. These actions have been the subject of intense study for many years but the mechanics of pool feeding without a strong pulsing current surging into their mouthparts are quite different from those presented by mosquitoes or other insects that suck directly from host blood vessels. Micro-CT makes it “possible to reveal fundamental details of insect and tick microanatomy, not previously recognized by 2-dimensional transmission electron microscopy.”
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A novel approach to imaging engorged ticks: Micro-CT scanning of Ixodes ricinus fed on blood enriched with gold nanoparticles
Micro-CT is an exceptional imaging modality but it is limited in visualizing soft biological tissues that need pre-examination contrasting steps, which can cause serious deformation to sizable specimens such as engorged ticks. “The aim of this study was to develop a new technique to bypass these limitations and allow the imaging of fed ticks in their natural state. According to this pilot study, micro-CT of ticks engorged on blood supplemented with contrasting agents in vitro may reveal additional information regarding the engorged ticks’ anatomy.”
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Ticks parasitised feathered dinosaurs as revealed by Cretaceous amber assemblages
“Direct evidence herein proves that hard ticks fed on blood from feathered theropods (non-avialan or avialan) during the latest Early Cretaceous, showing that the parasitic relationship that today binds ticks to birds was already established among early representatives of both lineages and has persisted for at least 99 million years.” This study presents the fossil record of a hard tick entangled in a pennaceous feather preserved in ca. 99 million-year-old Burmese amber. Ticks today are among the most prevalent blood-feeding ectoparasites, but the feeding habits and hosts of their ancestors have been speculative. This investigation demonstrates that “hard ticks and ticks of the extinct new family Deinocrotonidae fed on blood from feathered dinosaurs, non-avialan or avialan excluding crown-group birds.”
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Microtomography of the Baltic amber tickIxodes succineusreveals affinities with themodern Asian disease vectorIxodes ovatus
Lyme disease is strongly associated with the Ixodes tick species today. This study confirms that at least one anatomically modern species of Ixodes was present during the Eocene. Closely related to a modern disease vector, it can be placed in the same sub-genus (Partipalpiger) as the Asian tick Ixodes ovatus. This leads the researchers to believe that the amber fossil they studied may have acted as a vector as well. “Molecular estimates of origination dates suggest that at least piro-plasmids and the Rickettsia and Anaplasma bacteria should have been present around 50 million years ago as well. This begs a further question whether evolution and radiation events among the pathogens are more closely tied to the ticks –as one of their carriers –or to the mammals as their principal hosts and reservoirs.”
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X-ray Microscopic Examination of Ticks
Learn more about how micro-CT is used for phenotyping research.