Organism Once Thought To Be Single-Celled Were Once Jellyfish

Myxozoans are a complex parasite that retain jellyfish stinger genes.

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Myxozoans retain the genes of a jellyfish stinger and were once thought to be single- celled organisms
John Virata

Researchers with Tel Aviv University have discovered that a close cousin of jellies or jellyfish have over time, evolved into a microscopic parasite, and this development marks for the first time that an organism devolved, in what the scientists call “extreme evolutionary degeneration of an animal body.”

The researchers, led by  Prof. Dorothée Huchon of TAU’s Department of Zoology and Prof. Paulyn Cartwright of the University of Kansas and working with Prof. Arik Diamant of Israel’s National Center for Mariculture and Prof. Hervé Philippe of the Centre for Biodiversity Theory and Modelling, CNRS, France, employed genome sequencing and found that myxozoans are actually degenerated cnidarians, which in the underwater world include jellies, corals and sea anemones. These microscopic parasites infect invertebrate and vertebrate hosts.

“These micro-jellyfish expand our basic understanding of what makes up an animal,” Prof. Huchon said in a statement. “What’s more, the confirmation that myxozoans are cnidarians demands the re-classification of myxozoa into the phylum cnidaria.”

The scientists point out that in spite of the change in body structure and genome over millions of years, the myxozoa still look like jellyfish and retain the genes to produce the stinger that jellyfish are known to possess. These organisms are just 10 to 20 microns across, which gave biologists the notion that they ere single-celled organisms. The researchers sequenced the DNA of these organisms and discovered that they were actually a more complex macroscopic marine animal.

“Some myxozoa cause a neurological problem in salmon called ‘whirling disease,'” said Prof. Huchon. “These fish parasites cause tremendous damage to the fish industry, and unfortunately there is no general treatment against them. We hope that our data will lead to a better understanding of the biology of these organisms and the development of more effective drugs to fight against myxozoa.”

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Fish · Lifestyle