Deformities in Ameca, again

Illustrator posted: 24.02.2011

Hi all,

So let's start with the new forum!

On the yahoogroup we extensively discussed the occurence of deformities in our fish. It is not my intention to repeat this discussion here, but i like to add an observation on a specific kind of deformity and a hypothetical cause:

In the first litters of my breeding group of Ameca splendens, quite a lot of young were deformed. Untill now, most of these deformities have not occurred again, apart from a specific deformity which affects the end of the caudal peduncle and the tail fin. In some newborn fish these are bend sideways. At first I culled such fish, but out of curiousity I let some grow up. As expected these swam awkwardlyn and interestingly ...

note: the field in which I have to write is very much too small for my long messages!

... the young fish adjusted their behaviour and stayed in hiding much more than their non-deformed littermates. Then, over the cause of 1-2 weeks, the caudal peduncle and tail fin gradually straigthened untill the affected fish were indistinguishable from the non-affected ones!

As with other deformities I suspect that the cause is non-genetic, but in stead food related. My hypothesis is that these young developed their bend tail because they were in a bend position for a long time uring development, inside the mother's body. A hypothetical cause might be that ...

... young might be abnormally large because of a highly energetic diet of the mother fish (mainly granulate fish food, rather high in protein, with about once a week fresh filamentuous algae added). Then they are getting kind of "stuck" in the limited space in the mother's body. (Abnormally big young are a known occurence in captive saimiri monkeys fed on a high carbohydrate diet - this leads to birth problems in the monkeys. I did not observe birth problems in my fish.) I wonder, are there pictures of highly pregnant female goodeids from nature and do these show equally round bellies as our aquarium ones?

Grum-Schwensen posted: 25.02.2011

A pregnant from nature (Zacapu Lake, Michoacan)...

Michael Koeck posted: 26.02.2011

I had similar deformities in some births of Characodon audax, when I had different sizes and a high number of fry (well, more than 20 from a 3.5cm female). The sizes varied from well developed young with 0.9cm down to (looking not really well-developed) fry with less than 0.5cm, and deformities occured in the middle sized young. The tail bent sidewardly or upwardly directly at the beginning of the fin and the deformation disappeared again within a few days.
Best, Mike

Grum-Schwensen posted: 03.03.2011

The picture is not Ameca - but Goodea - and the fish have no deformities. But she is pregnant and huge - and just to show that is not only in captivity pregnant females of Goodeids can have very round bellies as well. That is not telling anything about the other parts of the hypothesis of "Illustrator"..:-)

Illustrator posted: 03.03.2011

Agreed, but it does solve that at least some species can in late pregnancy be similarly round in nature as in aquaria.