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Name of disease: Tetrahymena

Type of disease: Ciliated protozoan

Occurrence: A regular inhabitant of ponds , lakes and slow moving streams.

Symptoms include: Similar to a chilodonella infection. Flashing, rubbing or scratching on ornaments or gravel. Pacing along glass, spinning out in corners, rapid fin shaking or head shaking and coughing.

Background: Little is known about these guys and the aquatic industry. There are numberous reports of it causing fatalities by infecting the skin and gill of small or weakened fish. They have even been found invading the soft tissues of the organs and eyes of fish. However, this is MUCH less common than the skin/fin/gill infestation. Most likely, the way they invade the body cavity and organs is either by penetrating the egg yolk before birth OR by entering through ulcers and the like. Again, internal tetrahymena is a rarity.

These guys normally subsist on organic matter at the bottom of the pond, tank, filters and other spots where detritus accumulates. Nobody REALLY knows what causes them to become parasitic but it could have to do with too much organic matter causing the populations of them to explode. Conversely, if their normal food source (mulm, algaes and bacterias, is reduced, they can become parasitic. Both of these scenarios would cause competition. As good a reason as any, if you ask me.

It has been commonly said that Tetrahymena is nothing to worry about. But, if there is another parasite or pathogen present, they can and will use the necrosis and/or stress caused by other parasites and pathogens to invade. In short, they are probably a secondary invader rather than the source of a problem. In a sense, they are part of the "clean-up crew" and they dont care if their "next big job" is dead or alive, they just get started. So, be well and sure to rule out other pathogens (VIA microscopic exams) if you think that Tetrahymena may be bothering your fish.

Interesting facts: Tetrahymena multiplies by binary fission. Essentially, it splits into two organisms. Believe it or not, Tetrahymena is basically immortal. By this statement, I mean that if nothing consumes it or no chemical destroys it (an individual organism), it can go on living and multiplying indefinitely. This is made possible by the fact that the micro and/or macronucleus can regenerate (replace) DNA lost to binary fission. Most other ciliates lose portions of their DNA as they divide into two. This causes available DNA "pool" for fission to become weaker and weaker until the individual cannot go on dividing. Tetra is an exception. This is my understanding of it. I could be wrong. Some of the papers I've read can be pretty darn hard to fully comprehend.

Treatments: Multiple, daily, 0.3% salt dips with transfers to sterile tanks or containers (non-cycled with daily waterchanges to control ammonia). Then medicating with malachite green/formalin combos OR Acriflavin/salt combos OR Potassium Permanganate. Fish should not be placed back into the system that contains tetrahymena until the tank has been cleared of them. I have found that repeat treatments of malachite green/ formalin combos will eradicate them 100%. Hoever, I stress that a sterile container be used for treatment as detritus (poo and uneaten food and bacterias) reduced ANY medications efficacy by using it up before it can eliminate the oganisms.

Precautions: This ciliate can easily be transmitted to other tanks via syphons and/or nets or your very own hands. Remember, as with most micro-parasites, one drop of water can contain hundreds of these guys. It only takes a single organism to start a new invasion. Thoroughly sterilze your hands and forearms with HOT soapy water if you are treating a tank or fish with tetrahymena. Especially if you have otherwise healthy tanks to consider.

Diagnosing: Microscopic examination of the slime and/or filtergoop (mulm) is the ONLY way to get a positive ID. Like Chilodonella, they are between 30 and 70 microns. However, they are completely covered with cilia and can move fast or slow. When bumping into something, they commonly throw it into reverse and perform a 3 point turn in one point. They have a pointed anterior end. This pointed end allows them to squeeeeeze into or through some VERY tight spaces. Perhaps this is why they can invade internally (in some rare cases).

Link to a great video of Tetrahymena (filmed and posted online by Doug, a member at Koivet.com) : http://home.twcny.rr.com/lawgic/paras1.mpg

In this pic you can see a number of tetrahymena cells in various states of reproduction. You'll noticed that they are stuffed with food. This food is actually soft epithelial tissues from a shed fish scale (calico colored). IF you look closely at the pic you'll be able to make out which organisms were ingesting skin from orange, black and clear/white areas of the scale. Their 'droppings' are scattered across the slide. You'll also notice the magnified box shows an interloping parasite...... chilodonella. 12900055052.jpg

Click on the images, below, to enlarge for better viewing.

Tetrahymena at 100X: 29613261291-thumb.jpg

Tetra at 400X: 29613311077-thumb.jpg

And again at 400X: 29613343514-thumb.jpg

Here's an excellent shot for size comparison:


If you can find Arcella ( shelled amoeba) in your tank (most tanks have them, expecially with plants and many fish added), you now know how large Tetra is and can ID them easier.....


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