Kink at penduncle of guppy fry

[pnwch]

Hi new to having guppy fry.  I got some new females last month and the first round of fry are about a few weeks old.  I noticed about 8 fry have a bend or it kinks slightly at the peduncle (hoping I named the part properly, it's just before the tail starts).  The backs are straight and there's no problem with mobility. None of the adults (2 males, 6 females) display this.

What could cause this?  Genetic? Tank parameters?  (Ammonium Nitrite Nitrate safe, GH 11, KH 2, pH 7.8)

What should I do with kinked tail ones?  Will they outgrow this? Cull them?  Start an outdoor tub (never done it before, in the Seattle area) and whatever happens happens?  It's for a hobby, and I have plenty of other good fry (20+, thinking to take out the adult males).  The goal is to enjoy a happy living tank.

Thanks!

[Fish Folk]

Sorry to hear about this. I won’t assert that I am a very disciplined breeder in this regards, but I think that damaged fry should be culled. With Guppies, this is particularly important because of how rapidly they pass along their genetics.

If you want to wait and see, then isolate the damaged fry. But it is poor form to spread bad genetics into the hobby.

Occasionally environment may contribute issues. But anecdotally… most is genetic.

It is possible to inbreed livebearers 6-7 generations without problems showing up. But the deeper in you get without crossing out / crossing in lines, the worse things get.

Very sorry if this is discouraging. If it is any relief at all, this has happened to me a handful of times with different species.

[Guppysnail]

I agree with @Fish Folk  culling is best to keep genetic integrity.  I’m terrible about it and only do so when quality of life is affected. I do keep those separate and male/female with issues in separate tanks to prevent ever passing along those genetics. I also have stopped allowing an entire line to stop breeding because of the high rate of deformity. Those undeformed offspring were rehomed with folks I know and were given a heads up to not breed and what was occurring if they did choose to do so.  
 

That said my “special” kids are some of the dearest to my heart. 🥰

Edited July 22, 2022 by Guppysnail

[Brandon p]

On 7/22/2022 at 9:08 AM, Fish Folk said:

Sorry to hear about this. I won’t assert that I am a very disciplined breeder in this regards, but I think that damaged fry should be culled. With Guppies, this is particularly important because of how rapidly they pass along their genetics.

If you want to wait and see, then isolate the damaged fry. But it is poor form to spread bad genetics into the hobby.

Occasionally environment may contribute issues. But anecdotally… most is genetic.

It is possible to inbreed livebearers 6-7 generations without problems showing up. But the deeper in you get without crossing out / crossing in lines, the worse things get.

Very sorry if this is discouraging. If it is any relief at all, this has happened to me a handful of times with different species.

I agree with  @Fish Folkand @Guppysnail

[lefty o]

when guppies get that bend, its either from genetics, or mineral deficiency. they tend to live okay, but ideally you dont want that trait to keep being passed on.

[pnwch]

Thanks everyone, I had a feeling about it, but wanted to make sure I was doing the right thing. Appreciate the straight forward feedback.

[PineSong]

I keep my deformed guppies (mine have all been girls) in my females-only tank. When it first happened, I worried about tank temp, infection, minerals etc but I noticed only one of my strains of guppies was having this happen and there were several deformed in every batch of fry: I had zero bent spines from my other guppies or from my platies. 

I stopped breeding that strain altogether. Many of the bent fry did not survive to adulthood, but  two of the most deformed  females are still alive a year later and although they look like they would have a hard time digesting, let alone swimming, they appear to be as active and busy as the rest of the gals. 

[sumplkrum]

As others have stated, those should be culled. Any deformity of the spine will just get worse as they age.

Even if you're community-breeding, bent backs need to be culled.

Normally, you should have many batches of fry before you see even one with a spine deformity.
If you let the trait reproduce, you'll see more and more of them. It's not good for your line, or the health of the fish.