The Discus Thesis Progress Thread

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sinibotia

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As some of you may have heard (because I mention it constantly), I'm doing a thesis project on Discus! Specifically, as an Honors student at my university I'm required to complete some kind of thesis project related to my major in conjunction with a faculty advisor. My major is marine science/aquaculture, and one of my good friends at the university (a professor who teaches Biology of Fishes and Biology of Sharks among other classes) happens to be an avid freshwater aquarist like me, so I approached him about doing a project on discus. We chose discus because they are quite poorly studied due to their expense and relative difficulty of care, yet they are an important and growing part of tropical aquarium aquaculture. With both of our backgrounds in freshwater fishkeeping, we felt it was a challenge we could take on in order to break some interesting new ground with these fish.

The broad focus of the project is examining immunological aspects of discus mucus. There are quite a few reasons for doing this. Fish mucus in general is an important aspect of fish's immune health- the mucus itself is a barrier to pathogens, and also contains various innate and adaptive immune factors that are secreted into it by the fish. We are still discovering all kinds of new ways that fish mucus stops pathogens. In discus, the mucus is also used as a food for fry, which makes them a particularly interesting object of study, since very few other fish do this. Also, discus are both expensive and awesome, so studying their mucus (as opposed to studying, say, their blood or tissues) allows us to get samples without killing the fish. This means we can get a lot of data from a small number of fish.

There's some broad questions this research is going to be looking for answers to, or at least clues to answers. The very first of these is, how does protein expression in discus mucus vary with different physiological factors? We'll be looking at a couple of different circumstances- juvenile, adult, stressed (controlled and limited stress under safe lab conditions), and spawning (throughout the spawning process). We'll be using gel electrophoresis to sort the proteins by molecular weight and look for patterns of expression- basically, looking for proteins that might be showing up in multiple circumstances, vs ones that are only showing up under one condition. After we look at patterns of expression we can start narrowing our research based on what we find with that.

Two major hypotheses, the dumb one (mine) and the smart one (my advisor's): The first is that there will be a significant overlap in expression between stress response and spawning responses. This is because fry do not yet have fully functional immune responses- particularly an adaptive immune response- and so the mucus must be as free from pathogens as possible to protect the fry. It's also a stress on the parents as they are bitten constantly by the fry. The 2nd hypothesis is that we expect to see IgT- a form of antibody unique to fish- being passed from the adults to the fry through the mucus. This is because in other fish, it has been found that the eggs receive deposits of other antibodies as sources of nitrogen and an initial boost to adaptive immunity. We suspect that discus may do the same but through their mucus, and IgT is specifically a mucosal antibody. It might help explain why the survival rate for non-parentally reared discus is so abysmally low.

Over this summer, while I'm playing around with parasite-infected lobsters, I'll also be working on this. I've got a 125 gallon growout tank, several 55 gallon tanks set aside for spawning pairs, and access to a stupid amount of RO water. The research will likely be going on for the next year and a half, finishing right around the beginning of my final semester at university. This summer we'll at least get some results on juvenile discus, and as the discus mature and hopefully I can get them to spawn, we'll collect that data and use it to figure out where to go next. Ultimately we'd like to get this research published in a scientific journal.

I imagine that many of you might be interested in this, since many of you keep discus, and because aquarists tend to be big fans of science. I'm going to be doing this kinda like a build thread, keeping you updated as I go and showing off any cool results I get. If any of you have questions, I'd love to answer them! If you have suggestions, criticisms, whatever, I'd love to hear it! I want anyone who is interested to feel involved with what I'm doing.

Geez, that was a gigantic wall of text. Anybody still with me? I hope that you guys are interested and that you'll stick around as this project progresses! Thanks for reading and being interested!
 
Oh yeah...... im following this for sure.

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Got my interest. Just keep it dumbed down for us lay types.


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Very cool! I think I got it, you lost me a bit when you said your hypothesis but I understood your professors.
 
Basically, you were saying that the proteins will be similar because the antibodies need to be passed to the fry, right?

No, the proteins will be similar because you don't want disease having a foothold in the source of nutrition for the fry, or infecting the parents after feeding the fry.
 
No, the proteins will be similar because you don't want disease having a foothold in the source of nutrition for the fry, or infecting the parents after feeding the fry.


Alright, that makes sense. Would it also work the way I said it?
 
Ok, im not smart enough to be scientific. But this sounds similar to the effects of breast milk and the effects of whats passed from it to offspring. Both good and bad.

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And is your professor's hypothesis the same but more specific?

No, his hypothesis is that they're passing antibodies onto the fry through the mucus, either instead of or in addition to passing them through the eggs (which is what most fish do).

Mine is just that there will be overlap in general expression of immune proteins, like CRP, C-type lectins, etc., between the stress response and the spawning response.

I hope that makes sense, I feel like I'm being unclear!
 
Ok, im not smart enough to be scientific. But this sounds similar to the effects of breast milk and the effects of whats passed from it to offspring. Both good and bad.

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They've actually already done studies on discus passing the bad- if you can find it, there's a great paper on it that I used as a source for this project. I already uploaded it to one of your threads I think, but I'm hesitant to keep doing that because I'm probably not technically supposed to do that. (Thanks to the leech on human progress that is academic publishing )

Maunder, RJ, Buckley, J, Val, AL, Sloman, KA, 2013. A toxic diet: Transfer of contaminants to offspring through a parental care mechanism. Journal of Experimental Biology 216:3587-3590
 
Whew, it took me a little bit to understand what you were saying :) Looking forward to seeing how it progresses!
 
Thanks for adding this to our options of "interesting things I did today" :)

This will likely be over my head in areas but fascinating none the less. And I love Discus.

Was thinking similar thing about the breast milk if there is any similarity in transfer to the baby Discus in regards to protection.

This could be interesting if the contents of the mucous is a protection, what can it protect the fish or cells from, like protecting healthy cells from cancer cells kind of idea.

This is nice, education with out the tuition costs! Thanks for sharing!
 
I'm glad it seems for the most part people are understanding me! I try to speak English :lol:

If anything is confusing or too complicated though, please ask and I'll try to explain it out! I'm not just aspiring to be a scientist, I'd also like to be a professor- and not the crappy kind that doesn't care if people understand or not. So it's as helpful for me as it is to you if you ask me questions, so I can see where I am not being clear or where other people have trouble understanding!

Tomorrow I'll try to get pictures of my abysmal-looking setup and the few discus we already have.
 
Oh, I wanted to give a shoutout and a deep, deep thanks to the user PoppaRyno who has so generously offered me some fry from a pair of AA show grade discus if he can breed them. We lost about $300 worth of discus to an unidentified disease- I don't think anyone here was able to pinpoint anything. We suspect it may have been viral, as no treatment under the sun was effective against it. Everything else was right- water conditions, tank size, frequent water changes, etc.

In any case, while we should still be able to afford some fish from different sources, he's given us the chance to be able to do a whole heck of a lot more with this- more fish to work with and more budget in order to do more experiments (For reference, just the initial gel electrophoresis experiments are in the $1,200 range to analyze all of our initial planned samples). And apparently the university doesn't care about discus research, or my proposal wasn't good enough, because I didn't get funded by the center for undergraduate research. :( Suffice to say, this was a Godsend, thank you so much!

Pictures of the growout tank and the discus we do still have tomorrow. If anyone is interested I'll get pictures of some of the other cool stuff in the ARC- a 500+? gallon reef display, a massive lungfish, some atlantic sturgeon, two big oscars, a maine native touch tank, etc.
 
No shouts necessary my friend. Your doing work i wish i could. But my brain no work so good, lol. Im just a jayhawk that has a way with fishies. Anything i breed your always welcome to free of charge. Work hard, work smart, work together. Together we will rule the discus world. Ha ha ha.

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