Orange male guppies are hornier

For guppies (Poecilia reticulata) getting ready to mate, the color orange speaks volumes. The more orange coloration on a male guppy, the more virile it is, according to a study recently published in the journal Nature Ecology and Evolution. The research dives into the evolutionary mystery of why male fish have such vibrant and bold colors and patterns.

Throughout the animal kingdom, bright colors are used as a visual signal. The bright red, orange, or yellow hues of poisonous dart frogs act as a sign that says “better not eat me because I’m poisonous.” Color also communicates sex, particularly for animals that are active during daylight. Famously, male peacocks and many other bird species use brightly colored plumage in an effort to attract a female to mate with. Some fish species including darters and sticklebacks may also use color as a way to recognize and attract potential mates. Male parrotfish are also more colorful than their female counterparts–but are gender fluid and change up their sex throughout their lives. 

In this new study on guppies, zoologists Wouter van der Bijl and Judith Mank from The University of British Columbia in Canada bred three generations of increasingly orange guppies. They used deep learning–a type of machine learning that can recreate neural networks–and genetic studies to examine each generation.

They found that the more colorful males were up to two times more sexually active, performing for females for longer periods of time and at a greater rate. These guppies also attempted to sneakily copulate with the females more often. 

While it’s a known fact that female guppies prefer orange and unusual patterns on their male partners, the team found that the same cells that form their brains also control color diversity on their bodies. This suggests some kind of genetic link between how guppies appear physically and how they behave.

[ Related: Trumpetfish use other fish as camouflage. ]

“Previously, people thought perhaps males realized that if they were more orange, they were more sexy. With the genetic link, it may be that they’re healthier and fitter,” said Mank.

The guppy color genes themselves and where they were placed were tied to multiple chromosomes in this fish. Having so many locations creates a vast architecture of genetic possibilities for the fish’s color. Overall, the team identified seven orange and eight black color types. Guppies can potentially have up to 32,768 unique pattern combinations.

“Genetic variation is the raw material that evolution uses to produce resilient, adapted animals and plants, including for things like climate change or disease,” said van der Bijl. “We often look at extreme examples to understand where genetic variation comes from and how it’s maintained.”

 

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