A Shocking Host: Museum Specimen Reveals First-Ever Tick Parasitizing a Fish

Parasites may be among the most diverse organisms on Earth, yet many remain undocumented—often hiding in plain sight. Now, a surprising discovery tucked away in a museum collection has revealed an entirely new kind of host–parasite relationship: ticks feeding on a fish.

In a study published by the Entomological Society of America, Ph.D. candidate Kaylin L. Chong (Brian Farrell, Advisor) reports the first known instance of ticks associated with a fish host. Two female hard ticks were found embedded in the skin of a preserved electric eel (Electrophorus varii) from the Amazon Basin. One of the specimens was identified as Amblyomma cajennense sensu stricto, a tick species previously known to feed only on terrestrial vertebrates.

Ticks are notorious generalists, parasitizing mammals, birds, and reptiles worldwide—but fish had never appeared on their host list. The newly documented interconnection likely reflects opportunistic feeding, yet it dramatically expands what scientists thought possible in tick ecology.

While reviewing digital records from the Museum of Comparative Zoology, Chong noticed a 2009 note attached to an electric eel specimen mentioning “two ticks burrowed in the skin.” When examined more than a decade later, the preserved eel still bore the ticks, allowing detailed imaging and identification.

Beyond its novelty, the finding underscores the untapped scientific value of natural history collections. By preserving organisms—and their unexpected companions—museums can reveal rare ecological interactions that challenge long-standing assumptions. In this case, a forgotten specimen has rewritten part of the story of how parasites find and exploit new hosts, reminding scientists that biodiversity’s greatest surprises may already be cataloged, waiting to be noticed.