Aging Cell Lines in ICK

[Megalodon]

I'm curious to know what it means by the "aging cell lines" in marine ick. I read an article that said this:

The presence of aging cell lines in C. irritans suggests that an aquarium that has been running for longer than 12 months without any additions is unlikely to have any surviving "Ich" parasites, yet another exception to "Ich" always being present.

Could someone please explain? Thanks!

http://www.petsforum.com/personal/tr...marineich.html

[ATJ]

Burgess and Matthews (1994) devised a method to maintain cultures of Cryptocaryon irritans where they would serially transfer the parasites from one set of host fish to the next. The serial transfer ensured that each host fish was naive (never been exposed to C. irritans) so immunity would not limit the capability of the hosts to provide the necessary sustenance to the parasites.

They found that while the cultures did very well for a number of cycles, the cultures crashed after a certain number. They had 7 different isolates and the longest only lasted 34 cycles (with an average cycle length of 10 days). They suggested this was caused by senescence as aging within cell lines is well recognised in the phylum of ciliated protozoa.

The reproduction of C. irritans is asexual. Each tomite/theront is produced by division of the tomonts and essentially, each daughter cell is a clone of the parent cell. It appears that most cells have a limited number of divisions in them, with the actual number determined by the species of organism and cell type. After a certain number of divisions, genetic errors creep in resulting in non-viable mutations and death of the cell line. Think of it like the serial copying of a VCR tape. With each copy, the quality gets worse and worse. This is aging within a cell line and is one of the factors in the aging of just about any organism, although it appears that the cells of some organisms don't exhibit this, or at least the cell lines a viable for a very long time.

Sexual reproduction appears to be the answer to aging cell lines, i.e. while humans die of old age, by having sexually produced offspring the species can be maintained indefinitely, and the sexual reproduction introduces genetic exchange. The puzzling aspect of this is that sexual reproduction has not yet been recorded for C. irritans so there is no simple explanation as to how the species maintains its survival in the wild.

If the parasites can't be maintained in a laboratory environment where all effort is extended to keep the parasites alive, long term survival in an aquarium where factors such as immunity will be playing a part is expected to be more constrained.

Burgess P.J. and Matthews R.A. 1994. A standardized method for the in vivo maintenance of Cryptocaryon irritans (Ciliophora) using the grey mullet Chelon labrosus as an experimental host. J Parasitol.80:288-292.

[TerryB]

ATJ,
Nice job of explaining something so complex.
Terry B

[Megalodon]

I'm curious to know how C. irritans successfully reproduces in the wild. Would anymore mind explaining this? Thanks.

And if I were to have a tank without adding any fish for 10 months, but then add one fish, would any remaining ick still be there after two months?

[ATJ]

Originally posted by Megalodon

I'm curious to know how C. irritans successfully reproduces in the wild. Would anymore mind explaining this? Thanks.

I think the people studying C. irritans are also curious. As I said, sexual reproduction has not been recorded. Asexual reproduction would be the same as in an aquarium.

And if I were to have a tank without adding any fish for 10 months, but then add one fish, would any remaining ick still be there after two months?

That depends on whether the added fish has "Ich" or not. If the new fish did not have "Ich", there would be little chance of any "Ich" surviving before you added it and adding it would not change that. If the fish you add had "Ich" then it is quite possible that "Ich" is still present two months later.

[Megalodon]

OK, thanks. My problem now is my tang has broken out in ick due to recent salt mix problems. My royal gramma got it to, but it seems to be disappearing from sight I think due to good food soaked in Zeo and fresh garlic.

I know the ick is still in there of course. I'm weighing the options of removing my fish to quarantine to administer hypo and leaving the tank fishless for six weeks, or, waiting it out and allowing the fish to acquire immunity until it's gone.

[ATJ]

How long is it since the spots left the fish? If it is less than two weeks it is very likely just part of the life cycle and the spots may be back in a day or so.

If you don't see any spots on the fish after 4 weeks you can assume that the fish now have immunity. The problem is whether they have acquired full protection or not. If the fish develop full protection from "Ich", the parasites will all die and the tank will be "Ich" free. If at least one fish only develops partial protection, you run the risk of "Ich" being present even though the fish appear not to be affected. I think this last scenario is unlikely, but possible.

The safest option would be to treat the fish because there's no easy way to tell if the fish acquired only partial protection.

[Megalodon]

Spots left the royal gramma yesterday. They were there for a few days. I've had it for almost a month and a half and this is the first I've seen on it. The tang I've had healthy for three months but appeared with ick about three weeks ago, then they disappeared, then reappeared three days ago. It's got better, but I can still see them. The cardinal has no spots that I can tell.

Perhaps it's best I keep the tank fishless for six weeks and quarantine/treat the fish? Maybe I'll wait for another four weeks giving Zoe/garlic supplementation while maintaining perfect water conditions (as always) and see if these fish win the immunity challenge. I'm not in any rush to put in anymore fish so that's not a problem. Thanks ATJ!