What causes this defect?

[Rod Coleman]

I was recently very disappointed to find that nearly 30% of youngsters from 2 batches with different parents have a defect in the end of the spine. I had watched these fish grow every day for 3 months and hadn't once noticed the problem.

I know it's not unusual to have to cull defective fish but I would like opinions on the cause of this deformity and how frequently it occurs.

One batch was from a sibling mating of blue turqs and the other was from pb X cobalt. All the parents look fine.

I've been considering possibilites:
- calcium deficiency?
- vitamin deficiency?
- disease eg piscine TB?
- genetic inheritance?

I'm tending to think genetics.... what do you think?

Heres a fish netted - the kink comes out on this side, but not very noticably.

[Rod Coleman]

Seen from above the kink is more noticable.

[Rod Coleman]

Especially in this shot.

[Rod Coleman]

After MS222 euthanasia I defleshed the skeleton.

Viewing with a magnifying glass I could see that the problem is in the last two vertebrae in the spine. They kink out to the side and the caudal spines in the peduncle recurve back to the midline. In life, the tail lines up pretty well with the body.

This pic from above.

[Rod Coleman]

Here's the spine from another fish viewed from above and to the side.

Maybe the problem is with the blues - the turqs and the cobalt are probably all siblings.

I have a big batch of wigglers form the turqs ready to go free swim tomorrow - so I gues I'll be keeping a close watch on them. Do you think there is any way to avert the problem? If it's genetic - I guess not. :-[

Regards
Rod

[wildthing]

great pics Rod.
I have seen this before, in fry & in adults that should have been culled.
IMO it is genetic, tho with a very few it could be from rough handling when they're very young.
If it were any of the other factors you mentioned I think all or most the fry would be affected, not 30%, as they all have the same environmental situation.
When I have seen this happen it has been from fish that are a few too many 'F's down the line....ie: too far inbred.
IMO you need to break up the pair producing them & outcross . Starting with a 30% cull rate just from that , before you have to cull for all the other usual reasons, means the economics of them are as shot as their genetics

DW

Great pictures!

I would agree with David as Ive had spawns in the past that suffered from "environmental" defects...and typically its a 100% cull rate...short gill plates...No dorsal...etc.

BUT!....your getting the same defect?...roughly the same cull rate?...from TWO different pairs? A Blue turk pair..AND a PB, Cobalt pair?

I would have to say its environmental....Maybe a(borderline) vitamin deficiency(b12)...which would inhibit calcium absorption.

Just my take....

Tony

[Wolf]

Oh man sorry about that :( . That has got to be a big disappointment after puttting so much time into raising them. IMO there is no way two different set of parents have the same percentage of defects. I would have to guess enviromental also. That is a little too much to be a coincedence.

[heavyp83]

Rod,

Sorry I can't help but I just wanted to say that I really enjoyed your post. Sorry about your problems and hopefully you'll get it figured out.

Pete

[April]

great pics rod C. no solution for you..other than unless it was the same dad...then he did it. but not right?
only other solution is your water is no good.so send those fishies you won to canada before they too are doomed to make crooked spined fishies. maybe they have leprosy?
i will report back to you if the spines all work out ok in our nice clear cold canadian glacial water.
not sure i couldve sat and removed the flesh off of that fish..but great pics. and great learning tool for us more squeamish ones.

[ping]

Hi Rod,

Sorry to hear your problem. :( I dont have a solution for you. Hope that you figure out soon.

From the book that i have, it says that it will happen from sibling mating.
Only happen if your sibling mating is more than F3.
But i still dont get why you can get it with your pb x cobalt.

Thanks for sharing with us ... Nice pictures

Regards,
Ronny

[Mr. Limpet]

Rod, I believe that that is a very common defect when you get too far down in the F's. Time to outcross if the parents have good potential. JME. Paul.

[discuskrib]

i've seen a similar defect in a couple of livebearers i had a while back. best explaination i had at the time was that possibly the end of the spine was broken from a net. these fish still lived for quite a while after this.

from your pictures it looked to me like the spine may have been twisted. is this right? i could not tell clearly from the pictures.

how many fish did you deflesh to look at the skeletons? were they all kinked at the same vertebrae? kinked in the same direction?

[Rod Coleman]

Thanks for the comments and suggestions.

At first I thought some environmental factor would be likely (because of the two pairs), and this could well be the case. I'll do some more research. I did find a picture of a commercially farmed catfish with a severe spinal kink attributed to dietary deficiency.

Now I lean towards the genetic explanation. Even though different pairs were involved, the cobalt is very likely to be a sibling of the blue turqs in the other pair, so there could be something wrong with their lineage.

I don't have the fish at the moment - I had (almost) sold them all to a shop and was fairly surprised when he started pulling out bad fish. The transaction was put on hold and we are both committed to getting things right in the future. Actually I was pleased to see the LFS setting high standards! The LFS owner had previously found the same problem with fish from another source so he was obviously looking closely. It was an unpleasant surprise to me.

Last phone call he told me he had pulled out 27 from the 94 I delivered. I had a close look at some I still had, and two of those are the ones that are now skeletons. :-[

I haven't yet had a chance to see the culls at the LFS but I trust his judgement on this.

Best thing for me is probably to breed some fish from entirely different parents and see how they turn out.

(BTW Luke, you have IM)

Regards
Rod

Rod: Occasionally, I had only one or 2 in each brood had a deformity like that. Yang mentioned on his book as Genetic defect. With a great number of fish affacted by this from 2 sets of unrelated parents is unlikely caused by Genetic. I will guess a sudden change in temp during the wriggler developing stage may be the cause.
Jimmy.

[Rod Coleman]

Jimmy, that's a very interesting suggestion. Do you mean immediately after hatching? I was very careful with wc during the earliest stages but as they grew out I was doing pretty big wc. Can you suggest why sudden temp change could cause this?

Rod

Hi Rod.....

I wouldn't think that it was genetic either ::) unless the two different pairs are realated ???

I haven't seen this in Discus..... but I do have 1 angelfish with a deformed spine like that from a brood of about 600 fry :o

I keep it in my freak tank ;D .... it's actually a funny sight ::)

Ofcourse..... this is just my opinion ;)

Beth

[luke_potts]

So i take it that the general agreement is that discus with this should be culled?
Am i right about this or not?

cheers
luke

[Rod Coleman]

Hi Luke,
My advice on the "kinky" ones I unfortunately sent you is to cull them now before you put in the work on them and I will put things right. Hopefully most of them are OK.

Sorry 'bout that. We live and (hopefully) learn.

Regards
Rod

[CARY_GLdiscus]

I agree Rod,

with the others IME it was a toxin in the water! also like jimmy said heat could also playa roll.

I would cut back on W/cs for the first few weeks if possible!

Cary Gld!

[Rod Coleman]

Thanks Cary,

I will take it carefully with the current batch 2 1/2 weeks old - they look just great so far. Different pair to the others though, so not exactly a controlled experiment.

Rod

Rod: I have no scientific backing of my own obervation. I had a brood of BD disappeared from the site and no where to be found. Thinking the parents ate them and did a W/C with tap cold water to stimulate spawning activity. Turn out the parents were hiding them behind the sponge. That brood ended up with many deformaities as you described. Just an educational guess.
Jimmy.

[Smokey]

A very interesting bit of information. and USEFUL !

Thanks for the insite.

Just one thought ... if 30% were affected; could this have been a sign of a " WEAKNESS " in the fry - to begin with.
And enhanced by other factors ?

Or, as suggested; an external source may have caused the problem.

Smokey

[Rod Coleman]

I haven't had much time to research this yet but just found a very interesting article:

http://www.cabi-publishing.org/Bookshop/ReadingRoom/0851991262/1262ch1.pdf

It describes how spinal deformities in fish can result from genetic factors and also from a wide range of environmental and dietary influences.

Possible environmental causes:lighting
temperature too high or low and thermal shock (good one Jimmy!)
salinity
hormone treatments
inadequate essential amino acids in diet (eg tryptophan)
inadequate dietary Vitamin C (45% of channel catfish developed spinal curvature when raised on Vit C deficient diet)- INTERESTING!

Toxic substances:aluminium
heavy metals
organochlorine
organophosphates
carbamates
pollutants like hydrogen sulphide
pesticides
malachite green fungicide

Various infectious agents:viruses
protozoans
bacteria

Low frequency incidence can be due to genetic point mutations spontaneously occuring in ofspring.

While this development has been a blow to me, I must admit its certainly interesting. :)

Regards
Rod

[Smokey]

WoW - one very interesting article. it sure sheds light on breeding care and food requirements.

thanks for the link.

Smokey

[Rod Coleman]

Yes, what a list. Where do I start???

There was another article there too that I have to go back to check out.

I'll edit my last post later to sort out the list a bit.

Rod