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Miniature fry that don't grow


*Amanda*

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So I was wondering if any of you had any experience with "dwarf" fry that do not grow no matter what. I had 2 of these in my batch of 19 fry, which are about 3 months old. One died about a month ago. The other is hanging in there - he eats well and seems perfectly normal in all respects except size. I attached a comparison photo here. Do these guys ever catch up? I can't seem to find much info on runts, other than that they are usually culled and "never amount to anything" - but I don't know if that means they never become prize specimens (not my goal) or if they don't end up surviving. All I know is that if he doesn't start growing soon, he will fit in the other fry's mouths. So I'm very curious. I haven't culled any fry so far, but will for serious health-related defects if there is no hope of improvement.

Now, I also have a fry that appears to have an improperly formed swim bladder. Fancy Goldfish by Johnson and Hess tells me that many fish with this defect were found to have water instead of air in their swim bladders. This fry (who is the other one in the photo) is one of my favorites, and probably the best looking. Unfortunately, he swims about spastically when disturbed (head up, tail down), before sinking back to the bottom. He tries, but is unable to swim without sinking. I tried posting a video, but my phone crashes every time I try to upload it. This has been going on for at least 2 months. At first I thought his tail was too heavy (the parents both have very long tails - Mom's a VT) but now I doubt that. He's still able to eat the sinking pellets, but I worry about his quality of life ... everything I've read points to this being an incurable genetic defect. Thoughts?

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I'd keep the runt and cull the swim bladder fish. Some runts are genetically different with respect to growth hormones and some cannot assimilate nutrition well - this guy sounds like the former and you can certainly try to raise him and see what happens. But mouth, tail, and swim bladder deformities tend to get more severe with age.

Most of the time, a small defect on a small fish becomes a big defect on a big fish, unfortunately.

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I agree with Taryl. The SB issue, if from birth, won't resolve itself and culling is also what I believe to be a good option there because of that.

 

The general tiny fry is up to you, whether you would like to keep it and see if you can get it to grow or not.

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Clearly that runt has grown quite a bit since hatching.  Some really don't, and these have defects incompatible with survival and die in spite of what you do.  I have had runts that stayed tiny, some that grew to average size, and some larger than average.  Mini Me and Spot are siblings from the same spawn -- three years old.  Mini Me is ~2.5" sl and Spot is ~ 8" sl.  Golden was by far the largest fry in her sibship.  Bitsy was about 1/3 her length.  Golden matured to 6-7" sl and Bitsy to 4-5" sl.  Butterfly was the smallest fish in the small feeder tank at Petsmart and had the longest fins.  Her tankmate, Valentine, was about twice as long.  By the time they were two years old, they were the same standard length, but Butterfly had a greater tl, since her tail is longer than her body.

 

My personal hypothesis for the regular appearance of healthy runts has to do with the huge number of eggs produced by a female goldfish.  While normal cell division segregates chromosome very precisely, each daughter cell gets about half of the cytoplasm.  Measuring the amount of cytoplasm in the resulting eggs, one would expect to get a bell-shaped curve.  If you look at the size of fry a few weeks old, you do get a bell-shaped curve.  Perhaps an egg shortchanged on cytoplasm becomes a runty fry.

 

I have a lotus pond, made from a kiddie pool and fed used fish water.  I use it as a "cull pond."  Fry that are unlikely to grow up healthy go to the lotus pond, which is loaded with natural fry food.  I like to think they find it a pleasant place to spend a short life.

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Thanks everyone! And that makes sense, Sharon - I was very curious about the cause of healthy runts, since they seem to be very common. Raising these fry has been very time-consuming, but rewarding! :-)

It's interesting to me that all the fry ended up looking like fantails. The fish involved in the spawning are a pompom, 2 telescopes, a veiltail and a probable fantail/ryukin cross. I think the fantail/ryukin fathered all the babies (the male telescope is practically infertile - only 2 eggs from him ever hatched out of many spawns, which is why I introduced the other male), and they took after him rather than the mothers - I'm not seeing any telescope eyes or pompoms. I'm guessing those are recessive traits that won't show up unless both parents exhibit them?

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Yes, when people ask what they will get crossing fancy variety A with fancy variety B, I always say fantails.  Most mutations are recessive, so this prediction succeeds more often than not.  However, my "pond mutt"  fantails may carry any number of mutations.  A few express some of them weakly.  The fantail I bought at the pet store developed a small wen, and yet I suspect both parents were fantails.  One of my wakins also has a little wen, and I know both parents were wakins.  Sometimes a comet spawn will produce a fish with telescope eyes.  Well, guess what the offspring of a cross between a telescope and a comet will look like.

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How old are the fry, Amanda? Those traits can take quite awhile to show up, especially pompoms.

They're a little over 3 months old. Do you know when wens start to form? I would think pompoms fall into the same category.

What's interesting is that many of my fry have a LOT of bright yellow coloration! That's only present in a small amount on my male (who's calico), and not at all on any of the other adults. It's gorgeous! I have one big fry that's wild color (olive green); he looks like he doesn't belong, LOL.

I ended up with one single-tailed fry, which I almost culled. Now I'm glad I didn't - he has probably the best color and diamond-shaped body of all my fry, and quite the personality! I might end up keeping him. The ones I don't keep will be sold to coworkers for $3 apiece, as long as they have adequate housing for the fish. I have a few people who are interested, which is great.

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I think the fry bottoming out just have a weak swimbladder that seems to have popped (excuse the word). Actually ive had no fry as of yet that floated. It think overeating or a minor bowel inflammation can cause this, i have not found a fry recovering from this.

 

As with my ranchu spawn i also kept a 'runt' tub to see how they would develop. Like stated above, some really do catch up but do seem to be of lesser quality in the long run.

 

Great to see your effort in breeding, next attempts will be better i'm sure!

Edited by Hinfin
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