2023-11-10 14:50:58
A male ornate boxfish (Aracana ornata). Bottom left: A close-up of the fish’s natural hexagonal pattern – UNIVERSITY OF COLORADO BOULDER
MADRID, 10 Nov. (EUROPA PRESS) –
The same physical process that helps remove dirt from clothing could explain how tropical fish get their colorful stripes and spots, publishes the magazine ‘Science Advances’.
“Many biological questions are fundamentally the same question: How do organisms develop complicated patterns and shapes when everything starts from a spherical group of cells?” he notes. it’s a statement Benjamin Alessio, first author of the article and researcher at the Department of Chemical and Biological Engineering–. “Our work uses a simple physical and chemical mechanism to explain a complicated biological phenomenon.”
Biologists have previously shown that many animals evolved to have fur patterns in order to camouflage themselves or attract mates. Although genes encode information about patterns such as the color of a leopard’s spots, Genetics alone does not explain where exactly spots will develop, for example.
In 1952, before biologists discovered the double-helix structure of DNA, Alan Turing, the mathematician who invented modern computing, proposed a bold theory about how animals derived their patterns.
Turing hypothesized that as tissues develop, they produce chemical agents. These agents diffuse through the tissues in a process similar to adding milk to coffee. Some of the agents react with each other, forming stains. Others inhibit the diffusion and reaction of the agents, forming spaces between the stains.
Turing’s theory suggested that, instead of complex genetic processes, this simple reaction-diffusion model could be enough to explain the foundations of biological pattern formation.
“Certainly, the Turing mechanism can produce patterns, but diffusion does not produce sharp patterns,” says corresponding author Ankur Gupta, associate professor in the Department of Chemical and Biological Engineering. For example, when milk is diffused into coffee, it flows in all directions with a diffuse outline.
When Alessio visited the Birch Aquarium in San Diego, he was impressed by the sharpness of the boxfish’s intricate pattern: It is formed by a purple dot surrounded by a well-defined hexagonal yellow outline, with a thick black space in between.
Turing theory alone could not explain the sharp contours of these hexagons, he thought. But the pattern reminded Alessio of computer simulations he had been running, in which the particles do form sharply defined stripes.
Alessio, a member of Gupta’s research group, wondered if the process known as diffusiophoresis plays a role in pattern formation in nature.
Diffusiophoresis occurs when a molecule moves through the liquid in response to changes, such as concentration differences, and accelerates the movement of other types of molecules in the same environment. Although it may seem like an obscure concept to non-scientists, it is actually how clothes are cleaned.
A recent study has shown that rinsing soapy clothing in clean water removes dirt more quickly than rinsing it in soapy water. This is because when soap diffuses out of the fabric into water with a lower concentration of soap, the movement of the soap molecules draws out the dirt. When clothes are placed in soapy water, the lack of difference in soap concentration causes the dirt to stay put.
The movement of molecules during diffusiophoresis, as observed by Gupta and Alessio in their simulations, always follows a clear trajectory and gives rise to patterns with sharp contours.
They simulated the purple and black hexagonal pattern of the boxfish’s ornate skin using only Turing’s equations. The computer produced an image of blurry purple dots with a faint black outline. The team then modified the equations to incorporate diffusiophoresis. The result was much more similar to the bright, sharp, two-color hexagonal pattern observed in the fish.
The team’s theory suggests that when chemical agents diffuse through tissues, as Turing described, they also carry pigment-producing cells with them through diffusiophoresis, just as soap carries dirt from laundry. These pigment cells form spots and stripes with a much more defined outline.
Decades after Turing proposed his seminal theory, scientists have used the mechanism to explain many other patterns in biology, such as the arrangement of hair follicles in mice and the ridges of the palate of mammals.
Gupta hopes that her study, and other ongoing research from her research group, can also improve understanding of pattern formation, inspiring scientists to develop innovative materials and even drugs.
“Our findings highlight that diffusiophoresis may have been undervalued in the field of pattern formation. This work not only has potential for applications in the fields of engineering and materials science, but also opens the opportunity to investigate the role of diffusiophoresis in biological processes, such as the formation of embryos and tumors”, says Gupta.
#theory #animals #stripes #spots