How male guppies can be so colourful when female ones are dull brown?

We are used to women paying more attention to their looks. At least that’s the public perception. Make-up, hairstyles and fashionable clothes – most women look nicer than most men. However, it is not like that in the animal world, where many species have more colourful males. Now scientists from the Universities of Edinburgh and Exeter conducted a genetic study to help explain this phenomenon.

Bright colours are obviously good at attracting mates. That is actually the reason why males are more colourful in many species – it helps females to choose a better, healthier and, obviously, a better looking partner. However, the method in itself is not particularly great, because the same bright colours that attract females are also easily noticeable for predators. Scientists studied genes of the guppy fish in order to see why males are so brightly coloured compared to the dull brown females. Scientists used fish bred in laboratories to see where colours are encoded and how they are passed along in reproduction.

Researchers put a lot of work into appearance of the fish. They compared genetic maps of several generations of guppies to see how genes are inherited over time. This is quite interesting, because guppies reproduce in typical sexual way. Genes from both parents should be mixed together to form either a male or a female fish. So why only males get these vivid colours? Scientists now say that male guppies have chromosomes that only exchanges genes at their very tips. This means that colours are passed to males only and are inherited almost unchanged. It also means that these colours are not passed to female offspring.

This is quite interesting because in a way genetic mixing is quite small. Male guppies inherit a lot of genes exclusively from their male parents. Scientists found that this low rate of genetic mixing enabled the evolution of the colourful appearance of the males, because it was conserved through generations. Dr Roberta Bergero, one of the authors of the study, said: “Insight into exchanges between male and female genes have helped explain how these bright colours have evolved and diversified in male guppies”.

This is providing a little bit different understanding of the evolution of guppies and other species. Males are more colourful and yet these colours are not encoded in genes that are passed onto female offspring. The mechanism is still poorly understood, but it is interesting how males can turn these genes on and females cannot.

Source: University of Edinburgh