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Ancient tapeworm eggs found in 270-million-year-old shark poop

Researchers from the Federal University of Rio Grande, Brazil, have discovered a cluster of ancient tapeworm eggs in 270-million-year-old fossilized shark feces. This findings suggests that intestinal parasites in vertebrates are much older than previously thought.

LiveScience reports that tapeworms attach to the inner walls of the intestines of vertebrates. When tapeworms mature, they let loose their eggs in the feces of their hosts.

According to a news release from the Public Library of Science, remains of such parasites in vertebrates from this era are extremely rare- of 500 samples analyzed, only one contained the tapeworm eggs.

“Luckily in one of them, we found the eggs,” paleontologist Paula Dentzien-Dias told LiveScience. “The eggs were found in only one thin section.”

Researchers believe that their findings helps develop a timeline for the evolution of present-day parasitic tapeworms that can be found in foods like pork, fish and beef.

According to researchers, the fossilized tapeworm eggs were discovered in a cluster very similar to those laid by modern tapeworms. One of the unhatched eggs even contains what looks like a developing larva.

“The eggs were found in a thin section of an elasmobranch coprolite. Most of the eggs are filled by pyrite and some have a special polar swelling (operculum), suggesting they are non-erupted eggs. One of the eggs contains a probable developing larva. The eggs are approximately 145–155 µm in length and 88–100 µm in width and vary little in size within the cluster,” write the researchers in the abstract discussing their study.

The 270-million-year-old fossilized shark poop is from the Middle-Late Permian times. Shortly after this period, approximately 90 percent of marine species and 70 percent of terrestrial species went extinct.

“While it is impossible to state what vertebrate group served as the original hosts to tapeworms, the present study shows that elasmobranchs (neoselachians), were hosts of tapeworms some 270 million years ago. The lacustrine environment could well have been the ancestral habitat of cestodes, with elasmobranchs as their primitive final hosts,” add the researchers.

The study’s findings were described in detail in the open access journal PLOS ONE by Dentzien-Dias and her colleagues at the Federal University of Rio Grande, Brazil.