Cichlid egg-spots shed light on evolutionary mechanism

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Keepers of African cichlids will be familiar with the egg-spots that adorn the males of many mouth-brooding cichlids. These induce the female to approach this area when picking up eggs during spawning, allowing the male to fertilise them.

A team of researchers from Basel, Switzerland have published a study in the scientific journal Nature Communications showing that the evolution of egg-spots is linked to the insertion of a mobile genetic element – a so-called “jumping gene” – in a newly identified pigmentation gene.

Evolutionary changes normally occur by progressive changes through natural selection, but the development of novel traits with new functions is not easily explained by this mechanism.

The short DNA strings that compose “jumping genes” are able to change their position and influence the regulation of other genes, in this case genes controlling pigmentation cells. The scientists were able to induce the trait by transferring the mobile element into the embryos of Zebra danios, a fish commonly used for genetic studies.

One of the study leaders, Prof Walter Salzburger, commented “These results illustrate once more the importance of changes in gene expression in evolution”.