Ancient Tapeworm Eggs Found in Shark Coprolite

Researchers have found a cluster of tapeworm eggs preserved in 270-million-year-old fossilized shark feces in southern Brazil. The new discovery suggests that intestinal parasites are older than previously thought.

Tapeworms are intestinal parasites that are found in vertebrates - creatures that have backbones such as fish and humans. Tapeworms release the eggs through the feces of their hosts. Finding fossil remains of prehistoric intestinal parasites belonging to the age of dinosaurs is very rare.

Interestingly, researcher Paula Dentzien-Dias and colleagues from the Federal University of Rio Grande, Brazil, have discovered the spiral shark coprolite (fossilized dung) bearing a cluster of 93 small oval-elliptical tapeworm eggs. The fossil dates back to the Paleozoic era (251 million to 542 million years ago), even before dinosaurs had roamed the Earth.

"This discovery shows that the fossil record of vertebrate intestinal parasites is much older than was previously known and occurred at least 270-300 million years ago," the researchers said.

Of the 500 samples examined from this era, only one revealed the tapeworm eggs. This new discovery predates other ancient intestinal parasites found in vertebrates, dating back to 140 million years. The fossilized cluster of eggs looks similar to the eggs laid by modern tapeworms that occur in foods like pork, fish and beef.

Each egg is about 150 microns long and about one-and-a-half times the average width of a human hair, reports LiveScience. Some of the eggs were un-hatched and one egg contained what appeared to be a developing larva.

Researchers also found the mineral pyrite in the coprolite, suggesting that the region was depleted of oxygen, conditions which helped to preserve the fossilized shark coprolite for millions of years, the LiveScience report said.

The findings of the study, "Tapeworm Eggs in a 270 Million-Year-Old Shark Coprolite", appear in the journal PLOS ONE.