Variation within species and selection within our strains
Illustrator posted: 26.02.2011
Dear all,
I remember that one of you wrote about a difference in tail colour in Ameca (whitish versus yellow band). I also notice this in my fish, with the addition that not only the tail colour differs but also the colour of the whole body: my impression is that some fish are much less depositing carotenoid colours in their skin and fins than others. In juvenile fish this difference is not so clear, but the adults are dimorphic. Bothe females and males are either "greenish" or "greyish", in the latter case males have a whitish band in the tail in stead of bright yellow.
I assume that this difference has a genetic basis. In the long term, I expect that one of the varieties will take over, because of coincidence or maybe because of a preference for partners of one of the varieties.
I wonder what to do. In my small group it might be impossible to maintain both varieties, but I could, for instance, selectively remove one of them. Supposedly the group would then, after some generations, become homozygous for the remaining variety.
I would actually like to discuss this more in general: a species has several colour varieties (in the case of Ameca, there is the "dark" variety and apparently also a yellow/greyish variation - I presume that the latter are independent of "dark").
Do we have to aim to maintain all the varieties? In that case it might be sensible to set up separate strains of each variety, even if they occur in mixed populations in nature.
This, of course, would mean more administration and more aquariums needed.
The alternative is to keep them together, but this means a high risk to lose some of them because of the combined effects of inbreeding and genetic drift.
I think that we should distinguish between the "slight and apparently natural variations" which I like to discuss here and the obvious mutations like albinismm, which would in nature have lowered survival and which we can also safely cull, or maintain as "aquarium curiousity" but which are not very relevant to species conservation.
Michael Koeck posted: 26.02.2011
Hi Paul,
A difficult but important question... We have different colour varieties in tale-bands (mainly in yellow-orange or yellow-white) in tank-bred populations, but probably also in the habitat. As I have the impression, Goodeid-males often play with contrasts (yellow with black band or orange with dark body aso). Maybe these contrasts are more important in male choice than absolute colours. In my tequila group a few years ago, I had yellow and orange tailed males and both had been mating successfully. On the other hand, colour variations in small groups (or small tanks) might to lead to problems through an aberrant looking dominant male (could be aberrations hidden in females too, but that would lead too far at the beginning of this discussion, I presume). Me, for my part, I would like to have the captive-populations looking as similar to wild populations as possible, so I think in some species (Ameca splendens would belong of these species), I would advise to keep them in bigger tanks and bigger groups, starting with 250 liters to provide too much influence by one dominant "macho". In a lot of other species, there seem not to occur many variations in colour pattern, so I see this problem restricted to some species, either longterm kept in captivity or variable from nature. However, I would prefer to have "my populations" look like the wild, so I wouldn't try to keep different colour-strains to increase the genetic diversity, but that is absolutely worth to be discussed 
Best, Mike
Illustrator posted: 03.03.2011
I wonder if we should aim for maintaining overal genetic variation (if at all possible) or at maintaining fenotypic variation in each tank. I doupt that the latter is possible without occasional exchanges of fish. Even if there is not a single dominant male, i suspect that one variety might be more attractive to the females than the other, meaning that gradually the population in each aquarium could shift towards that variety.
Like in guppies there is strong female preference for bright coloured males, which is in nature balanced because the brightest coloured males are also having most risk to be eaten by predators. Therefore the outcome of female selection + predation is not the same as female selection + human selection.
Maybe the question should be if we should have some kind of registration of varieties (within population!) as well, to avoid accidentally losing some of them.
Paul Veenvliet
mandrade posted: 05.03.2011
Hi Paul,
It was me the one who have notice two different colours in Ameca splendens' tail band.
This was not a simple variation inside the same group of fish but either a distinction between two independent lineages.
In both cases all males exhibit the precise tail band tone.
The "German strain" ( because it was imported from Germany and the original population it was unclear ) had a almost whitish tail band.
The "Czech strain" ( because it was imported from Czech Republic and the original population it was unclear ) had a very canary yellow tail band.
Other very noticeable differentiations were some behavioural features and males intraspecific aggression.
If you wish any further details, please be may guest.
Best regards
Illustrator posted: 09.03.2011
I remeber your posts very well :-) In my aquarium I do notice the colour difference, but no behaviour difference (fish obtained as a single group from trade). Might be that I got a "crossbred" strain (but as far as i know all Ameca are from Teuchitlan, so it might be a cross between collection events, but hardly at all between collection localities!).
In Practice I have to choose: select in favour of either white tail bands or yellow ones, or not select. If I don't select, I suspect that one form might die out in my aquarium because the total number of adults is limited and the influence of the most dominant ones probably huge. I can also try to maintain both colour varieties, but this will be much more difficult. What should I do?
Michael Koeck posted: 23.03.2011
Hi Paul and others!
In case of doubt, we should keep both different colour types separatly; at least, until we have more information.
About Ameca-strains, I found 3. Maybe someone can help to clear the situation. Ameca has been found in two rivers, Río Teuchitlán and Río Ameca. In captivity, both locations are given. Are these really these locations, or do we have wrong locality-information? The 3rd is from the spring of the Río Teuchitlán, called Balneario Teuchitlán. I suppose, there are (at least one) additional habitat, but don't know about collections. Anyone who can clear the situation about Ameca? And if yes, do the diiferent (?) localities have different tail-colours? I only have seen yellow-tailed ones, also the original description about Río Teuchitlán-fish are about yellow-tails. What about the black (or dark variety); is this a breeding form? and where does it come from? Any collection-dates from Ameca?? Who collected when?
Best wishes, Mike
Illustrator posted: 25.03.2011
I agree with keeping types separately. However, in my case it is about a mixed group,. obtained from trade, with 2 types already present in the same group.
As far as I remember the "dark" melanistic form in Ameca showed up in the F1 or F2 offspring of relatively recently wild collected fish from Teuchitlan (i think that this all refers to the same spring!). It is genetically recessive. I suppose that Kees knows more about this. But this all points to a mutation that is in a low frequency present in the wild population.
From the apprearance of MY fish, my guess (but note that this is really guessing) is that MY while-tailed ones have difficulties storing carotenoids in their skin and fins. This points to a mutation, rather than a characteristic of a wild population (of course isolated small wild populations can be fixed for a mutation like this). I find the described behavioural difference MUCH more intreguing! Please note that it is not nessesary that Miquel's fish have the same difference as mine, we could well talk about 2 different characteristics, which we both describe in the same way!
Note also that food can have a strong influence on yellow colours in fish (after all, carotenoids are all obtained from food, not synthesysed in the body of a vertebrate). What i find intreguing is that i clearly have both colours in the same group, and all get the same food.
But the question what to do with my fish (select, replace ...) remains open.
mandrade posted: 27.03.2011
Hi there Paul and everyone,
I do agree 100% with Michael.
I regret myself for mixing both strains once in the past.
We were convinced that all Ameca splendens had come from a single collection location, like Characodon audax, for instance. So, under those circumstances, it was not considered a error of judgment merging two aquarium strains.
With the latest information and specially after been in contact with you, this will not happen again even regarding other unknown collect location lineages denominated " aquarium strain ".
My last group it was the yellow one ( originally imported from Czech Republic ).
Paul is right about guessing that white-tailed individuals or even similar lineages may possibly have difficulties storing carotenoids in their skin and fins. Anyway, I would like to remember you that, besides behaviour divergences between the two groups, all the fish had the same diet and have been kept under exactly the same environmental conditions.
So, according to my personal opinion, it could be a case of diverse original locations or even a mutation.
By the way, can any of you report any marking minor variation in females from different lineages of this species too ?
I only have seen pictures of a melanistic form of Ameca splendens.
A local hobbyist friend told me once that it was a captivity form obtained by breeders' selection in Central Europe. This information it must be accepted with reserve as we don't have any evidence or proof about that.
Kindest regards
Illustrator posted: 28.03.2011
I observed the following differences in females:
The same "white/yellow tail" difference is also see in the female Ameca, only of course not in the tail fin. There are greenish (I think "normal") and greyish females. This applies to the overall body colour.
Some females have the dark pigment on the body organised in a neat line, in others the lower edge of this line is disorganised or even much of the lower half of the body has the normal dark pigment (spots). My feeling is that this might not be caused by genetic factors, but something "social" (dominant females or females that grow up "dominant" have a nicer stripe) . This requires research!
And, not my personal observation, but clearly visible on photographs: the melanistic mutation applies equally to males and females.