Scientists are finally figuring out how animals get their stripes and spots

Scientists may have finally solved the mystery of how some animals get their stripes and spots.

There are many animals that have these patterns on their skin or fur – including tigers, zebras and giraffes, just to name a few. But nature’s reason for this has always remained unclear, although biologists have previously shown that in some cases they are for camouflage or to attract mates. Gene research alone does not fully explain where and how the spots or stripes develop.

A new study published in Scientific progress, found that it could be through a process known as diffusiophoresis. This occurs when a molecule moves through a liquid in response to changes in concentrations. This also causes other molecules to speed up.

Photo shows a male Ornate Boxfish. Bottom left shows a close-up photo of the fish’s natural hexagonal pattern. In the lower center, a picture shows the simulation of the fish model based on Turing’s reaction-diffusion theory. The lower right image shows the reaction-diffusion simulation enhanced with diffusiophoresis.
The Birch Aquarium/Scripps Institution of Oceanography, Benjamin Alessio/University of Colorado Boulder

Simply put, this is actually the same process that happens when we do our laundry. Without it, the laundry would not be clean.

“We were quite surprised by the findings. Diffusiophoresis is an active area of ​​research…,” said study corresponding author Ankur Gupta, an assistant professor in the Department of Chemical and Biological Engineering at the University of Colorado Boulder. Newsweek.

“It has been used for applications such as membrane-less water filters and low-cost diagnostic tools, and has also been shown to be critical in removing dirt from laundry. However, the importance of diffusiophoresis in relation to Turing models was not previously recognized. Our study suggests that diffusiophoresis is a fundamental process and has far-reaching effects spanning the formation of patterns on animal hides.”

To reach this conclusion, Gupta and Benjamin Alessio, first author of the paper and a research associate in the Department of Chemical and Biological Engineering, tested the theory using the boxfish model. They created a simulation of a purple and black hexagonal pattern – similar to the fish box pattern – using what is known as Turing’s equation, the study reports.

This equation was invented by Alan Turing in the 1950s when he discovered that as tissues evolved, so did chemical agents.

Zebra
Stock photo shows three zebras. Scientists have discovered why animals can have spots and stripes.
jamenpercy/Getty

These chemical agents then diffuse through the tissue. When these agents react, spots are sometimes formed. Sometimes when they form, it creates a space between the spots. Turing hypothesized that animal patterning is not formed by complex genetics, but rather by diffusion reactions.

In testing the simulation, the researchers added diffusiophoresis to Turing’s equations. And the result showed a bright and sharp hexagonal pattern, very similar to that seen on a box fish.

“This area of ​​research is important because if we can understand the formation of patterns on animal skin, we could, for example, create artificial skin patches that can change their patterns, going from stripes to hexagons, for example, by detecting changes in concentration, Gupta said.

“This could have applications in non-invasively measuring biomarkers in the body, which could help in early medical diagnosis. Another option is to use these patches to sense differences in chemical concentrations in the air. By changing the patterns, these patches can improve the safety of soldiers deployed in dangerous environments.”

These findings suggest that as the chemical agents diffuse through the fabric, the pigment is drawn in by diffusiophoresis—again, similar to how dirt is lifted from clothes during washing.

The end result is a clear outline of spots and streaks.

“Current research has largely focused on spherical particles. In reality, the cells responsible for skin pigmentation have anisotropic shapes,” said Gupta. “Therefore, future work should focus on studying the effects of shape. Furthermore, there is a need to improve the validity of the model by comparing the data with experiments. Finally, future research could investigate the specific biochemical pathways required for the formation of these animal models.”

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