A surprising discovery has emerged from the depths of the collections at Harvard University’s Museum of Comparative Zoology. Two ticks were found attached to an electric eel collected from northern Brazil in 1872. This is the first-ever instance of ticks found attached to a fish.
A paper recently published in the Journal of Medical Entomology describes a specimen of Electrophorus varii into which two ticks of the species Amblyomma cajennense are embedded – seeking blood from a seemingly atypical source.
The specimen was initially flagged by a researcher working in the collections in 2009 but not formally described until a colleague told Kaylin Chong – the paper’s author – that there were ticks in the ichthyological collection.
“When I started working on ticks, I became fascinated by the idea that they might exist not only in the invertebrate collections but remain still attached to their hosts. Previous to finding the electric eel, I was looking at ticks on iguanas,” says Chong. Andrew Williston, curatorial associate of ichthyology at MCZ, informed her that an electric eel in the collection had ticks attached to it.
With his assistance, Chong located the specimen – indeed, two ticks were embedded in its shrivelled side. She pulled one out for closer examination and identification.
Until now, A. cajennense has been thought to parasitise mostly mammals, such as capybaras and horses, with some records of the juveniles parasitising birds. Other species of Amblyomma tick have been found attached to cold-blooded vertebrates – reptiles and amphibians. One species in the same genus has even been recorded feeding on sea snakes, indicating an ability to survive underwater.
“Ticks are obligate blood feeders and at the end of the day, blood (even if not from the preferred host) is food,” says Chong. “Many ticks have a broad host range allowing them to feed on a variety of mammals, birds and reptiles.”
Ticks have been known to survive in water for up to 70 days so their attachment to an aquatic creature is not entirely surprising. They are able to capture a thin layer of air using hydrophobic hairs and use it to respirate for surprisingly long periods.
The records attached to the specimen are sparse, making it impossible to determine the circumstances of the attachment of the ticks.
They may have located their host while it was traversing the land between two waterways. Or they may have latched on after the eel was captured by Charles Linden, the high school teacher who collected it over a century ago. The eel was one of around 100 specimens Linden donated to the Museum of Comparative Zoology following his 1872 expedition.
“Since both ticks don’t appear to be engorged, this could suggest that they weren't attached for very long: perhaps 1–2 days,” Chong adds.
The discovery indicates the resilience and adaptability of these arachnids – which recent research has indicated can even fly through the air using static electricity. Sharknados may be fictional but scuba-diving and paragliding ticks are real – and that may actually be even more impressive.
Top image: ticks on eel. Credit: Chong 2025, Journal of Medical Entomology
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