31 January 2013, 13:42 BST
The oldest-ever evidence of tapeworms has just been discovered in fossil shark feces that are more than 270-million-years-old. The fossil coprolite was discovered in southern Brazil, and is offering a rare insight into what sorts of parasites were in existence that far back in time, predating any other fossils of intestinal parasites by 140 million years.
The eggs in question are tiny, only slightly thicker than a human hair, and hard to locate. Out of the 500 samples examined, tapeworm eggs were only discovered in one. Researchers are excited about the discovery because it gives new insight into a major human health problem. Present-day parasitic tapeworms are common in foods like pork, freshwater fish and beef, were it not for cooking, the parasite would have a significant impact on human populations.
As the new research shows, these animals have been around for a very long time, and survived multiple extreme extinction events that have killed off most of the other life that was on the Earth at the time. The researchers note that the discovery shows that parasitism has likely been around nearly as long as life itself has.
“The fossilized eggs were found in a cluster very similar to those laid by modern tapeworms. Some of them are un-hatched and one contains what appears to be a developing larva. According to the study, 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 Permian Extinction Event occurred only 20 or million years after the time period that these fossils date to. That event lead to the extinction of over 90% of all marine species and over 70% of terrestrial species, and left the world in a state where no new species emerged for over 5 million years, known as a dead zone.
Here’s some more background on tapeworms:
“Cestoda (Cestoidea) is the name given to a class of parasitic flatworms, commonly called tapeworms, of the phylum Platyhelminthes. Its members live in the digestive tract of vertebrates as adults, and often in the bodies of various animals as juveniles. Over a thousand species have been described, and all vertebrate species can be parasitised by at least one species of tapeworm. Several species parasitise humans after being consumed in underprepared meat such as pork (Taenia solium), beef (T. saginata), and fish (Diphyllobothrium spp.), or in food prepared in conditions of poor hygiene (Hymenolepis spp. or Echinococcus spp.).”
“T. saginata, the beef tapeworm, can grow up to 20 m (65 ft); the largest species, the whale tapeworm Polygonoporus giganticus, can grow to over 30 m (100 ft).”
The new research was just published January 30th in the open access journal PLOS ONE.
Source: Public Library of Science and Wikipedia