How animals got their patterns of spots and stripes

The intricate stripes and spots found in animal patterns have long been a subject of scientific curiosity. In a new study, researchers from the University of Colorado Boulder provide new insights that might explain this natural phenomenon. 

The study points towards a process known to help clean laundry as a potential factor in the development of these patterns.

Focus of the study

“Many biological questions are fundamentally the same question: How do organisms develop complicated patterns and shapes when everything starts off from a spherical clump of cells,” said study first author Benjamin Alessio. “Our work uses a simple physical and chemical mechanism to explain a complicated biological phenomenon.”

Formation of animal patterns

This perspective aligns with the early speculations of mathematician Alan Turing who, even before the discovery of the DNA double helix, suggested that pattern formation could be the result of a reaction-diffusion model where chemical agents interact to create spots and inhibit their spread to form space between them.

Diffusiophoresis

However, Turing’s model does not account for the sharpness of the patterns observed in nature. It was during a visit to the Birch Aquarium that Alessio noted the precise patterns on a boxfish which seemed to parallel the results of his computer simulations showing sharply defined stripes through a process called diffusiophoresis. 

This phenomenon occurs when molecules move in response to concentration gradients and thereby influence the movement of other molecules. 

It’s a principle evident in everyday life, such as when dirt is removed from laundry. Soap diffuses into less concentrated water and pulls the dirt out with it, a process not occurring if the water’s soap concentration is already high.

How the research was conducted 

The team ran simulations with Turing’s equations alone, which produced blurry patterns, unlike what is observed in nature. When diffusiophoresis was incorporated, the results showed sharp and vivid patterns akin to those on the boxfish. 

The implication of their findings is that as chemical agents spread through tissue, they could be dragging pigment-producing cells into clear, sharp formations through diffusiophoresis – much like soap captures dirt.

Significance of animal patterns

This new theory has the potential to extend beyond just explaining animal patterns. It offers new insights that could spur developments in engineering, materials science, and even medical research. 

Study co-author Professor Ankur Gupta hopes that continuing this research can also improve the understanding of pattern formation, inspiring scientists to develop  innovative materials and even medicines. 

“Our findings emphasize diffusiophoresis may have been underappreciated in the field of pattern formation,” said Gupta.

“This work not only has the potential for applications in the fields of engineering and materials science but also opens up the opportunity to investigate the role of diffusiophoresis in biological processes, such as embryo formation and tumor formation.”

The study is published in the journal Science Advances.

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