Widespread Parasite Is Actually ‘Micro jellyfish,' New Study Shows

Many people are familiar with the common, stinging sea pests known as jellyfish, which are also important food for certain predators and serve a further role in their ecosystems by minimizing population explosions of some small fish, despite their nettling reputation. But researchers recently uncovered a new "micro jellyfish" that changes the way we see animals. The recent finding also suggests the sea creatures have evolved rather diversely over time, into microscopic organisms made of only a few cells that can live inside other animals.

In a recent study, researchers from the University of Kansas (KU) sequenced the genomes of myxozoans, which are a diverse group of microscopic parasites that infect invertebrate and vertebrate hosts. This revealed that the parasites are actually shrunken cnidarians, or jellyfish, according to a news release.

"This is a remarkable case of extreme degeneration of an animal body plan. First, we confirmed they're cnidarians. Now we need to investigate how they got to be that way." Paulyn Cartwright, lead researcher and an associate professor of ecology and evolutionary biology at KU, explained in the university's release. "These were 20 to 40 times smaller than average jellyfish genomes. It's one of the smallest animal genomes ever reported. It only has about 20 million base pairs, whereas the average Cnidarian has over 300 million. These are tiny little genomes by comparison." (Scroll to read more...)

Despite the microorganism's drastic simplification, it retained the essential characteristics of a jellyfish, including its stinger. Not only does this finding shed light on the diversity of animals, but it could help researchers understand why myxozoa plagues commercial fish such as trout and salmon.

"They're a very diverse group of parasites, and some have been well-studied because they infect fish and can wreak havoc in aquaculture of economic importance," Cartwright added. "They cause whirling disease in salmon. The fish start swimming in circles -- it's a neurological problem caused by a myxozoan."

Essentially, the transition from a marine animal to a microscopic parasite could reveal a unique strategy in nature and redefine what it means to be an animal. Their study was recently published in the Proceedings of the Nation Academy of Sciences. 

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