Will climate change have an impact on sex ratio of wild apistogramma ?

[anewbie]

Has there been any study if the increase in heat is skewing the ratio of wild apistogramma in places where they are collected ?

 

[MacZ]

I don't know of a study on Apistogramma, but there have been studies for decades now implying ratios tilting towards more males in other species, like alligators and turtles but also in marine fish and fish in temperate climates. We also know that tweaking temperatures during embryonal development in cichlids in captivity can change the ratio as well.

But it's hard to impossible to conduct such a study in the wild in the amazon basin on an animal as small as dwarf cichlids and finding a researcher that would be interested in doing that with Apistogramma is also not easy I would assume.

So just by deduction we can expect such changes, maybe they are already happening.

 

[Frank Hättich]

Some years ago Uwe Römer presented the results of such a study (done with A. atahualpa) in a talk at SA-MAD. If I remember correctly, he studied cases of temperature rising due to deforestation and found that the sex-ratio was in fact shifted towards males.

 

[Mazan]

In Amazon habitats where Apistogramma occur, where streams and river edges are normally shaded by the forest canopy, deforestation will cause a much faster and more dramatic change in temperature than climate change, which surely will have an effect, but this will be much more subtle, long term and difficult to study. Interesting though.

 

[anewbie]

So even if the fishes can adapt to the temp change; they will likely go extinct simply because not enough of both genders are born....

 

[MacZ]

So even if the fishes can adapt to the temp change; they will likely go extinct simply because not enough of both genders are born....

One of the bitter truths of this day and age. This is happening worldwide to many, many species of invertebrates, fish, amphibians and reptiles. Birds and Mammals are barely affected, but both have other problems.

And another reason for us as hobbyists to move away from domestic varieties and towards species conservation in our tanks.

 

[Mike Wise]

I can't find the reference right now but Uwe wrote about how dominant females selectively defend water depth based on temperature. Less dominant females are restricted to shallower (= warmer) and deeper (= cooler) territories. In these cases dominant females produced ~50/50 males/females while subdominant females produced skewed ratios. Those in shallower/warmer areas produced more males; those in deeper/cooler waters produced more females. The end result was an even numbers of both sexes. This, of course, only applies to locations with water depths that allow a temperature gradient.

 

[Frank Hättich]

I can't find the reference right now

It's in sections 4.3.1 ff. of Cichlid Atlas 1.