Tapeworms may have been upsetting intestines for around 99 million years, as experts believe they have discovered the first-ever partial-body fossil of the parasite.
A Notable Discovery
The partial worm was discovered by an international team of researchers led by experts from the Nanjing Institute of Geology and Paleontology (NIGPAS). It was found preserved in mid-Cretaceous Kachin amber from the Hukawng Valley of northern Myanmar, assumed to have formed on a prehistoric coastline.
The body appears to be a tentacle, with features consistent with the kinds of living parasites known to infect elasmobranch fish such as sharks and rays. The discovery details are discussed in the paper "Preservation of a marine tapeworm tentacle in Cretaceous Amber." It was undertaken by paleontologist Bo Wang of NIGPAS and his colleagues.
The research team believes the specimen had infected a host stranded on a beach by a falling tide or storm. The creature was then bitten by a scavenger or a land-based predator, causing the tapeworm's tentacle to be pulled free and stuck in resin from a nearby plant.
Trypanorhyncha, the most diverse group of marine tapeworms, is believed to have evolved around 200 million years ago. However, no fossil record of the parasites has ever been found. According to Wang, the fossil record of tapeworms is very sparse because of their soft tissues and endoparasitic habitats, which prevents understanding of their early evolution.
Until now, the closest paleontologists have come to an actual tapeworm fossil are the little circles of hooks and sucking disks which were discovered on fossil fish from Latvia dating back to the Devonian Period. In these cases, the arrangement of the hooks is consistent with living parasitic worms, but no other bodily structures were found to support this interpretation.
Meanwhile, a body fossil of a disc worm was reported from Baltic amber dating back to the Eocene period. However, this has been reinterpreted as air bubbles within the prehistoric resin. Tapeworm eggs have also been reported from pieces of fossilized shark feces dating back to the Carboniferous and Permian periods. Although an embryo has been allegedly discovered inside one such egg, it has never been confirmed.
According to paper author Cihang Luo, this makes the current discovery the most convincing body fossil of a flatworm ever found. The morphology of this fossil tapeworm resembles the surviving trypanorhynch tapeworms Nybelinia and Dollfusiella. These modern parasites are known for infecting rays, nurse sharks, and hound sharks.
Morphology of Modern Tapeworms
Today, tapeworms are found in almost all freshwater, marine, and terrestrial ecosystems, infecting all major groups of vertebrates, including humans and livestock. Tapeworms are considered endoparasites, which means that they live inside their hosts. They do not have a mouth or digestive tract, and they absorb nutrients directly from their victims' guts. They do this by clinging on using a grasping head that has either suckers, hooks, or hooked tentacles.
Each tapeworm usually infects two or three hosts across its lifespan. They are spread as eggs or larvae consumed through contaminated food, water, or soil. Adult tapeworms grow with long segmented bodies, varying in size from less than 0.039 inches to 98 feet (29.87 meters) long. Tapeworm infection does not result in any symptoms, although it can cause diarrhea, abdominal pain, weight loss, and tiredness in human hosts.
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