Parasites have a disturbingly deep history. Many of the sneaky little hitchhikers around today – from feather lice to fungi that control the behavior of ants – have been around for millions and millions of years. Tapeworms, amoebas, and their kind are some of evolution’s greatest success stories.
Finding ancient parasites is no easy task, though. The ancient critters are difficult to detect, and their discovery is often an accident. Nevertheless, a scattered record of prehistoric parasites is starting to come together, and the latest find may be the earliest known record of tapeworms infesting a vertebrate.
The fossil in question is a shark coprolite – feces that were buried on a lakebed 270 million years ago, in a deposit now preserved in southern Brazil. And while an adult tapeworm wasn’t found in the peculiar specimen, it does contain a cluster of “93 small oval-elliptical smooth-shelled structures.” According to paleontologist Paula Dentzien-Dias and coauthors, who identified the eggs in a thin section made of the coprolite, these pips are tiny tapeworm eggs.
Dentzien-Dias and collaborators base their identification on the shape of the eggs, similar to those of more recent tapeworms, and what appears to be a tapeworm larva in one of the eggs. The density of the minifossils suggests that the eggs were part of a tapeworm body segment that breaks off and passes out of the body with feces, a standard part of the tapeworm life cycle that is still in place today. The strategy relies on some unlucky consumer coming along and eating the parasite-laden poop, giving the eggs a new home and starting the process anew.
Exactly what kind of tapeworm inhabited the shark is unknown. The identity of the shark, too, is unclear. The coprolite is the standard spiral shape expected for sharks, but the ancient dung is a trace fossil which contains further trace fossils. Still, if Dentzien-Dias and colleagues are correct, tapeworms have been exploiting the bodies and behavior of other organisms for at least 270 million years. The parasites are wonderful, disgusting survivors.
Dentzien-Dias, P., Poinar, G., de Figueiredo, A., Pacheco, A., Horn, B., Schultz, C. 2013. Tapeworm Eggs in a 270 Million-Year-Old Shark Coprolite. PLoS ONE. 8, 1: e55007. doi:10.1371/journal.pone.0055007