Parasite eggs found in fossil feces of more than 125 million years in Cuenca

Parasite eggs found in fossil feces of more than 125 million years in Cuenca

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The exceptional preservation of fossil feces, called coprolites, from the Las Hoyas deposit in Cuenca, has allowed the identification of parasite eggs in two remains attributed to fish and crocodiles. The find also documents the ancient connection between fishGonorynchiformes basal and trematode parasites.

Thecoprolites They are fossilized animal feces that can provide a lot of information about ancient ecosystems, not only about predator-prey relationships, but also about parasite-host interactions.

"Parasites generally need different hosts in order to complete their biological cycle, and these are sometimes very specific", explain the authors of a work published in the journalScientific Reports which describes the finding of parasite eggs in fossilized feces from the Las Hoyas site in Cuenca.

The discovery "gives us clues about the trophic relationships of the animals that lived in Las Hoyas: depending on the type of parasite we find and its biological stage, we can establish with precision the possible producer of the coprolite, as well as its possible prey" , the scientists continue.

The work, led by the Paleontology Unit and the Center for Integration in Paleobiology of the Autonomous University of Madrid (UAM), and which has had the participation of the Department of Parasitology of the University of Granada (UGR), has described the presence of helminth eggs (parasitic worms) in coprolites between 129 and 126 million years old.

Intermediate guests

Scientists found flatworms (worm-shaped parasites) of the classTrematoda, which are a type of parasites that need several intermediate hosts to complete their biological cycle.

"For trematodes, the first host must necessarily be a mollusk, for example a snail, and in this case, it needs a second intermediate host (generally a fish), although it can also be a crustacean", the authors emphasize. what is foundAntonio Osuna Carrillo de Albornoz, Professor of the Department of Parasitology of the UGR and director of the University Institute of Biotechnology.

"TheGuest The definitive parasite of the parasite becomes infected when it ingests the fish or crustacean where the metacercaria of the parasite has developed (one of the stages of its biological cycle), reaching maturity in the digestive system of the definitive host, which can be animals such as reptiles, birds, mammals (including humans, currently) or larger fish ”, describe the experts.

"It is in the definitive host - they add - where the parasite arrives as an adult and will deposit the eggs, which will be expelled in its faeces, starting the biological cycle of this type of parasite again", they emphasize.

In the case of Las Hoyas, a trematode egg has been found in a coprolite attributed to a fish, probably an adult teleost fish or an amiiform, as well as fossil remains of intermediate hosts such as snails, crustaceans, and smaller fish.

In fact, the coprolite where this egg was found shows remains of crustaceans in its interior, which corresponds to the life cycle of fluke parasites. The producer of the coprolite would ingest crustaceans infected with the larvae of the parasite in their diet, and once adults, they produced the eggs that have been found in the feces.

The study also shows that gonorynchiform fish, close relatives of siluriformes, could have played a relevant role in the life cycle of these parasites, acting as hosts for the flukes of this ancient ecosystem.

“This is just one example of all the information that can be gleaned from this type of research. In the study, we also evaluated the life cycle of two nematodes, belonging to the genus Anisakis, whose eggs were found in the same coprolite as the trematode, and in another coprolite attributed to a reptile, probably a crocodile ”, the researchers conclude.


Barrios-De Pedro, S. et al. 2020. "Helminth eggs from early cretaceous faeces"Scientific Reports10, 18747.
Source: Sinc, UGR, UAM
Rights: Creative Commons.

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