Ich?

[MstgKillr]

I was reading on RC and found this posted

14. INTERESTING FIND: If no new MI is introduce into an infected aquarium, the MI already there continues to cycle through multiple generations until about 10 to 11 months when the MI has ‘worn itself out’ and becomes less infective. A tank can be free of an MI infestation if it is never exposed to new MI parasites for over 11 months.

What does everyone think about this?

 

[JHemdal]

By "MI" do you mean "marine ick", Cryptocaryon irritans?

I'm not sure that the Cryptocaryon gets "worn out", but fish certainly do develop a resistance to it over long periods...like those chronic cases you see in surgeonfish in reefs, where the spots come and go, but because you can't treat the reef, you can't really knock it out. In many cases, if the Cryptocaryon doesn't not become acute, the fish manage to fight it off.

At one public aquarium I worked at many years ago, a 90,000 gallon exhibit had chronic problems with Cryptocayon - the existing fish could fend it off, but any new fish added would get hit pretty hard by it.


Jay

 

[MstgKillr]

<a href=showthread.php?s=&postid=15080727#post15080727 target=_blank>Originally posted</a> by JHemdal
By "MI" do you mean "marine ick", Cryptocaryon irritans?

I'm not sure that the Cryptocaryon gets "worn out", but fish certainly do develop a resistance to it over long periods...like those chronic cases you see in surgeonfish in reefs, where the spots come and go, but because you can't treat the reef, you can't really knock it out. In many cases, if the Cryptocaryon doesn't not become acute, the fish manage to fight it off.

At one public aquarium I worked at many years ago, a 90,000 gallon exhibit had chronic problems with Cryptocayon - the existing fish could fend it off, but any new fish added would get hit pretty hard by it.


Jay

Yes, MI = Marine Ich. I didn't make the claim, I just read about it on RC.

 

[LargeAngels]

I think this is where it came from. http://atj.net.au/marineaquaria/marineich.html

"Burgess and Matthews (1994) were attempting to maintain a viable population of C. irritans which could be used in later studies. To maintain the parasite populations, they needed host fish in order for the trophonts to feed and continue the life cycle. Each host fish was only used once in a process of serial transition such that none of the hosts would die or develop an immunity. While the procedure worked very well and enabled them to maintain populations for some time, the viability of the populations decreased with time and none of the 7 isolates they used survived more than 34 cycles, around 10 to 11 months. They suggest this is due to senescence and aging in cell lines is well recognised in Ciliophora."

 

[JHemdal]

LargeAngels,

That's an intersting citation, but I could only find the abstract of the 1994 article online.

I'm not sure you can always extrapolate an in vitro population like that to aquariums....certainly the population we battled in the 90,000 gallon tank didn't become senescent - it was an ongoing issue for at least two years.
I wonder if what they saw was simply an artifact of their culture methods? Otherwise, what would the mechanism be for senescence in a clonal organism?
For sexual reproductive higher animals, we sometimes lose lines after 6 or so generations if we don't carefully monitor for inbreeding depression, but we routinely subculture microalgae and rotifers for years with no sign of senescence....

Jay

 

[LargeAngels]

Jay,

I'm not sure either about it. I'm just pretty sure that is where he got it from. I had the same issue with my first Reef tank. None of the current fish ever showed symptoms, but every new fish (QT'd or not) added got ich fast and then it went away and this was also the case for years. I also, due to traveling out of country, had a tank in which half the fish had a severe case of velvet and the other half never got it. Went on for weeks. One of the reasons I treat every fish as harboring parasites without seeing them.

 

[1geo]

+1 LargeAngels There is no substitution for a long quarantine period with treatment before introducing new fish.