Whirling Disease

Most infected rainbow trout die from whirling disease at a very young age. Those that do survive usually have deformed skeletons and skulls, bulging eyes, and black tails, like the ones pictured above.  Photo by Sascha L. Hallett Under a microscope, a Myxobolus cerebralis triactinomyxon looks like a grappling hook. At this stage, the parasite is ready to attach to a fish. When it does, three coiled springs in the tip (the dark portion on the right) shoot into the skin, providing a secure entrance route for the germ capsule.  Photo by Vicki Blazer, U.S. Geological Survey The whirling disease parasite, Myxobolus cerebralis, forms small spores like this one, photographed with an electron microscope. The spores remain viable for dozens of years in the mud, until they are eaten by a small worm known as Tubifex tubifex. When the worms die, they release another phase of the parasite known as a triactinomyxon (TAM) that is ready to infect another fish and complete the life cycle.  Photo by Ronald P. Hedrick Colorado Division of Wildlife biologists examine a stunned rainbow in the Gunnison Gorge to gather population data and evidence of whirling disease. The department released a strain of rainbows resistant to whirling disease into the river the previous year, this was probably one of them.  Photo by Anders Halverson Barry Nehring, a Colorado Division of Wildlife biologist, stands in front of the Gunnison Gorge, where whirling disease nearly wiped out a legendary rainbow trout fishery.  Photo by Anders Halverson A Colorado Division of Wildlife crew electrofishing in the Gunnison Gorge in September 2006. Some of the crew hold wands that send out a small electric shock, while others wait to net the stunned fish. Photo by Anders Halverson A Colorado Division of Wildlife crew electrofishing in the Gunnison Gorge. For bigger fish, a boat like this is used.  Photo by Anders Halverson A Colorado Division of Wildlife crew electrofishing in the Gunnison Gorge. Some of the crew hold wands that send out a small electric shock, while others wait to net the stunned fish.  Photo by Anders Halverson

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