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What The Fish! Parasites That Infect Salmon Are Actually Jellyfish

Update Date: Nov 19, 2015 03:43 PM EST

What was earlier believed to be a microscopic parasite has turned out to be jellyfish, much to the astonishment of scientists.

According to Discovery News, myxozoa which infect salmon and other fish were studied extensively given the commercial implications of their infestations. However their evolutionary origins remained less revealed until scientists sequenced DNA. The exercise revealed myxozoans are in fact microscopic jellyfish.

"This is a remarkable case of extreme degeneration of an animal body plan," Paulyn Cartwright, principal investigator of the research, said.

Researchers are yet to explain the shrinking. The DNA of myxozoans is just about 20 million base-pairs long compared to 300 million base-pairs of average Cnidarian which include jellyfish.

At just about 20 microns in size, myxozoa stand classified as parasites and were thought to be single-cellular. Absence of traits that classify other species as animals could have led to misclassification of myxozoans.

"Hox genes are one example, which are important to development of all animals, and these lack them. But Myxozoa is definitely an animal because its evolutionary origin is shared with jellyfish, and we use species' ancestry to define them. But animals are usually defined as macroscopic multicellular organisms, and this is not that. Myxozoa absolutely redefines what we think of as animal," Cartwright said.

One of the traits that myxozoa share with the cnidarian family is the existence of a stinging mechanism, that jellyfish are notoriously known for. The reclassification indicates there could more such instances of a macroscopic to microscopic transformation where evolutionary of species is not clearly known, researchers believe.

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