An international team of researchers have shown how one single gene mutation is capable of making the medaka, a Japanese killifish, loose its attractive colours and display a drab grey colour which renders them significantly less attractive to medakas of the opposite sex – unless that potential mate is grey too.

In the wild, medakas come in a wide range of colours, including orange, brown and drab grey.

“We observed that the grey medaka were often rejected in favor of their brown or orange rivals“, says lead author Shoji Fukamachi. “This is the first demonstration of a single gene that can change both secondary sexual characteristics and mating preferences“.

As mentioned above, you don’t have to fear ending up without a mate just because you happen to be a grey medaka – you just have to go out looking for another grey specimen since the study showed greys to be preferentially selective for each other. This preference for choosing a member of your own colour suggests that sympatric speciation could occur in medakas as the colour determining gene is mutated, i.e. new species may form as the medakas choose to mate with specimens of their own colour.

The research is a collaborative effort by researchers from the University of Konstanz, Germany and from the University of Tokyo, Japan. The study has been published in the open access journal BMC Biology.