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Sometimes, scientists get things wrong. There have been reported cases of zookeepers mistaking male animals for females. There was even that time a famous Asian elephant turned out to be African. The most recent incident of wrongful classification involves jellyfish.

According to the Proceedings of the National Academies of Sciences, myxozoans, tiny parasites composed of a few cells that are known to burrow themselves in both vertebrate and invertebrate animals, are actually microscopic jellyfish. Using genome sequencing and DNA analysis, researchers were able to verify that the tiny bug belongs to the phylum of cnidarians. Previously, researchers thought myxozoans were macroscopic multicellular organisms. But now, under the new category and despite their misleading size, the creatures are definitely animals.


“Hox genes are one example, which are important to development of all animals, and these lack them,” said Paulyn Cartwright, a researcher on the project and an evolutionary biologist at the University of Kansas. “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.”

Another dead giveaway is the structure of the jellyfish. Under a microscope, it can be seen to have the same circular body, eerie transparent skin and set of stingers. The cnidarian group is a diverse bunch of 10,000 species that includes sea anemones and corals. Myxozoans are considered to be one of the simplest forms in their broad class. Because of this, scientists were unsure about their previous findings. Unlike most jellyfish, it is also missing a functional mouth and gut.

The new classification shines light on numerous unanswered questions about the strange parasite. Myxozoans are known to attach themselves onto fish, like trout and salmon. They don’t actually kill their hosts, but they do inflict “whirling disease” which is a neurological issue that causes fish to swim in circles uncontrollably. The infection is a huge problem for hatchery quarters and facilities that tend to keep the animals in tight pens. There is currently no cure for the disease, and humans, as well as other mammals, cannot get infected.


“This is a remarkable case of extreme degeneration of an animal body plan,” highlighted Cartwright. “First, we confirmed they’re cnidarians. Now we need to investigate how they got to be that way. Their biology was well-known, but not their evolutionary origins. They’re microscopic, only a few cells measuring 10 to 20 microns.”

Another application for the researchers’ findings is 3D printing. Lately, there has been a growing fascination in the medical field for microscopic vessels that can perform basic functions, ranging from transporting medicine to probing. Because myxozoans have been so successful at penetrating hosts through cartilage and other complex pathways, scientists could easily replicate their design without scaling issues (since they’re already tiny). Most scientists adopt the structure of large animals like fish and sharks, but when used in microscopic environments, the pods lose their efficiency. Myxozoans could prove to be the breakthrough researchers have been searching for in the creation of functional microscopic vessels.

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