Unusual fossil flea in 15-20 million-year-old amber

Fossilized fleas in amber are exceptionally rare, with only a handful of specimens discovered to date. All of these have been referred to modern groups still alive today, including (initially), a remarkable specimen in Dominican amber with unique features that warrant new tribal status. These properties are five-segmented maxillary palps and a pair of cerci-like organs positioned on tergite-X near the tip of the abdomen.

The new species Atopopsyllus cionus was described by Dr. George Poinar, Jr., an entomologist from Oregon State University who published his findings in the latest edition of the Journal of Medical Entomology.

Atopopsyllus cionus in Miocene Dominican amber

In addition to the flea’s unusual morphology, Poinar was struck by the microbes found in the amber fossil, which provides a palaeontological snapshot of the connection between insects and pathogenic microorganisms.

“I’ve spent a lot of time looking for pathogens that are vectored by insects in amber,” he said. “I was quite excited when we found pathogens inside the flea in the anal area. We found bacteria that have the characteristics of plague bacteria. We can’t say they’re plague bacteria. All we can say is their morphology is similar to that which is shown to be associated with plague.”

He also found trypanosomes in the specimen.

“So we know that this flea was vectoring at least two pathogens,” he said. “It shows that even back at that time, pathogens were established in fleas in the West Indies. They could have affected rodents because we found rodent hair in the amber. This shows the antiquity of the relationship between vector, host, and pathogen.”

The open access article can be read for free by clicking here. To find out more about the remarkable fossil record of fleas and other arthropods in amber check out our related titles: