Zebra stripes confuse bloodsucking flies and could inspire anti-bug device

Sarah Knapton, science editor

20 FEBRUARY 2019 • 7:00PM

Rudyard Kipling supposed the zebra acquired its stripes so it could blend into the forest shadows, hidden away from the leopard and man.

But the markings also hold another advantage, scientists have discovered, after finding they disorientate bothersome bloodsucking horse flies.

Researchers at Bristol University used video analysis to test whether flies were more likely to attack zebra or non-striped horses at a stables in North Somerset.

They found that although flies circled and touched horses and zebras at similar rates, they actually landed on zebras 25 per cent less often.

Continued

DNA clues to how chipmunk earned its stripes

By Helen Briggs BBC News 

Its stripy back makes it one of the most recognisable of rodents - but until now it has been unclear exactly how the chipmunk earned its stripes.

Now, scientists have found the evolutionary gene change responsible for the distinctive markings of both the chipmunk and an African mouse. 

The gene normally makes the bellies of many rodents light in colour.

The stripes may have helped the animals hide from daytime predators with keen eye sight, such as birds, they say.

Prof Hopi Hoekstra, of Harvard University, US, who led the research, said: "What these two rodents have in common is that they are both diurnal [active during daylight], when one could imagine stripes could be more valuable than if they were nocturnal.

"It is notable that of the rodents that are striped, most are diurnal - again consistent with them being important for evading visual predators (for example, raptors and mammalian carnivores)."

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Computer games help explain lizard stripes

June 8, 2016 by Bob Yirka report

(Phys.org)—A pair of researchers with the Indian Institute of Science Education and Research Thiruvananthapuram has found that stripes on lizards cause predators to see them as moving slower than they actually are, causing attackers to miss their targets. In their paper published in the journal Royal Society Open Science, Gopal Murali and Ullasa Kodandaramaiah discuss their theories on why some animals have stripes, their experiments with grad students playing specially designed computer games and what they found as a result.

Many people have wondered over many years why it is that some animals have stripes—some have suggested they serve as camouflage, while others have theorized that the patterns cause confusion in the eyes of predators—stripes on zebras, for example, might perhaps cause lions to have trouble fixating on just one member of a herd. In this new effort, the research pair focused specifically on lizards, but rather than use live ones, they created virtual ones on computer screens. And rather than use real predators, they used grad students who were asked to "catch" the lizards, by simply clicking on their bodies. But, there was a catch, some of the lizards had stripes on their bodies similar to those on real lizards, while others had stripes only on their tales. In analyzing the results of play, the researchers found that the grad students were 25 percent less accurate in clicking on the bodies of the lizards when the body was striped.

In another test, the researchers asked the student volunteers to simply report which of two lizards on a computer screen was moving faster than the other. In this test, some of the lizards had stripes while others were spotted. If a volunteer reported that one was faster than the other, than the speed of that lizard was slowed down al little bit—this routine continued until the volunteer reported that the lizards were moving at the same speed. In analyzing the results of multiple tests with multiple volunteers, the researchers found that the striped lizards were actually moving 5 percent faster on average than the spotted lizards at the end of the game.

The researchers suggest their experiments show that stripes on lizards in the real world might cause predators to misjudge the speed of their prey, leaving them grabbing a tail that simply falls away as the lizard escapes.

Read more at:

Predators might not be dazzled by stripes

Date: August 11, 2015

Source: BioMed Central

Summary: Stripes might not offer protection for animals living in groups, such as zebra, as previously thought, according to research. Humans playing a computer game captured striped targets more easily than uniform grey targets when multiple targets were present. This rebukes assumptions that stripes evolved to make it difficult to capture animals moving in a group.

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Why Do Zebras Have Stripes? It's Not for Camouflage

by Laura Poppick, Live Science Contributor | January 14, 2015 06:57am ET

Zebras' thick, black stripes may have evolved to help these iconic creatures stay cool in the midday African heat, a new study suggests.

Many African animals sport somestripes on their bodies, but none of these patterns contrast as starkly as the zebra's. Researchers have long struggled to explain the purpose of the zebra's unique black-and-white coat. Some have suggested that the stripes may help zebras camouflage themselves and escape from lions and other predators; avoid nasty bites from disease-carrying flies; or control body heat by generating small-scale breezes over the zebra's body when light and dark stripes heat up at different rates.

Still, few scientists have tested these explanations, and many argue that the stripes serve a complex mix of purposes. 

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How the zebrafish gets its stripes: Uncovering how beautiful color patterns can develop in animals

Date:
August 28, 2014

Source:
Max-Planck-Gesellschaft

Summary:
The zebrafish, a small fresh water fish, owes its name to a striking pattern of blue stripes alternating with golden stripes. Three major pigment cell types, black cells, reflective silvery cells, and yellow cells emerge during growth in the skin of the tiny juvenile fish and arrange as a multi-layered mosaic to compose the characteristic color pattern. While it was known that all three cell types have to interact to form proper stripes, the embryonic origin of the pigment cells that develop the stripes of the adult fish has remained a mystery up to now. Scientists have now discovered how these cells arise and behave to form the 'zebra' pattern


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Scientists solve the riddle of zebras' stripes: Those pesky bugs

Date:

April 1, 2014

Source:

University of California - Davis

Summary:

Why zebras have black and white stripes is a question that has intrigued scientists and spectators for centuries. Scientists now examined this riddle systematically.

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Zebra stripes mystery 'explained'

Zebras' bold stripes protect the animals by masking their movements, according to a study.

The conspicuous colours do not blend in to the background and scientists have theorised they developed to dazzle predators.

Using computer models, researchers confirmed the markings create optical illusions when the animals move.

They suggest this confusion helps to protect the animals from both big cats and tiny insects.

The research, conducted by researchers from the University of Queensland, Australia, is published in the journal Zoology.

"Zebra stripes have long confused evolutionary biologists, right back to Darwin and Wallace," said lead author Dr Martin How.

Read on

How Do Tigers Get Their Stripes? Science Not So Certain Now

A decades-old explanation for how tigers get their stripes has come into question as researchers challenge what’s called the morphogen theory. The research does not nix the theory, but science may now have a hypothetical tiger by the tail as they try to figure out this aspect of how Nature works.

The morphogen theory posits that proteins controlling traits are arranged as gradients, with different amounts of proteins activating genes to create specified physical features.

This theory was first put forth in the 1950s by mathematician and World War II code breaker Alan Turing and refined in the 1960s by Lewis Wolpert. It has been used to explain why a tiger has stripes, among other phenomena.

But some biologists have raised questions about the theory, which contends that physical features are necessarily tied to absolute concentrations of proteins within the morphogen gradient.

If a certain critical mass of protein is present, then a given physical feature—for example, cells that make the skin on your forehead—will appear. If less than that critical mass is present, a different structure—say, the skin that makes your eyebrows—will appear, and a boundary will be formed between the two structures.

Alternative views have suggested physical features are not necessarily the result of a specified number of proteins, but, rather, come from more complex interactions between multiple gradients that work against one another.

Continued:  http://www.livescience.com/19967-tigers-stripes-science.html

Zebra stripes evolved to keep biting flies at bay

By Victoria GillScience reporter, BBC Nature

Why zebras evolved their characteristic black-and-white stripes has been the subject of decades of debate among scientists.

Now researchers from Hungary and Sweden claim to have solved the mystery.

The stripes, they say, came about to keep away blood-sucking flies.

They report in the Journal of Experimental Biology that this pattern of narrow stripes makes zebras "unattractive" to the flies.

They key to this effect is in how the striped patterns reflect light.

"We started off studying horses with black, brown or white coats," explained Susanne Akesson from Lund University, a member of the international research team that carried out the study.

"We found that in the black and brown horses, we get horizontally polarised light." This effect made the dark-coloured horses very attractive to flies.

It means that the light that bounces off the horse's dark coat - and travels in waves to the eyes of a hungry fly - moves along a horizontal plane, like a snake slithering along with its body flat to the floor.

Dr Akesson and her colleagues found that horseflies, or tabanids, were very attracted by these "flat" waves of light.

"From a white coat, you get unpolarised light [reflected]," she explained. Unpolarised light waves travel along any and every plane, and are much less attractive to flies. As a result, white-coated horses are much less troubled by horseflies than their dark-coloured relatives.

http://news.bbcimg.co.uk/media/images/58391000/jpg/_58391196_dscf6956_gabor-horvath.jpg

Read on: http://www.bbc.co.uk/nature/16944753

How the Zebra Gets Its Stripes: A Simple Genetic Circuit

ScienceDaily (Oct. 14, 2011) — Many living things have stripes, but the developmental processes that create these and other patterns are complex and difficult to untangle.

Now a team of scientists has designed a simple genetic circuit that creates a striped pattern that they can control by tweaking a single gene.

"The essential components can be buried in a complex physiological context," said Terence Hwa, a professor of physics at the University of California, San Diego, and one of the leaders of the study published October 14 in Science. "Natural systems make all kinds of wonderful patterns, but the problem is you never know what's really controlling it."

With genes taken from one species of bacterium and inserted into another, Hwa and colleagues from the University of Hong Kong assembled a genetic loop from two linked modules that senses how crowded a group of cells has become and responds by controlling their movements.

One of the modules secretes a chemical signal called acyl-homoserine lactone (AHL). As the bacterial colony grows, AHL floods the accumulating cells, causing them to tumble in place rather than swim. Stuck in the agar of their dish, they pile up.

Because AHL doesn't diffuse very far, a few cells escape and swim away to begin the process again.
Left to grow overnight, the cells create a target-like pattern of concentric rings of crowded and dispersed bacterial cells. By tweaking just one gene that limits how fast and far cells can swim, the researchers were able to control the number of rings the bacteria made. They can also manipulate the pattern by modifying how long AHL lasts before it degrades.

Although individual bacteria are single cells, as colonies they can act like a multicellular organism, sending and receiving signals to coordinate the growth and other functions of the colony. That means fundamental rules that govern the development of these patterns could well apply to critical steps in the development of other organisms.

To uncover these fundamental rules, Hwa and colleagues characterized the performance of their synthetic genetic circuit in two ways.

First, they precisely measured both the activity of individual genes in the circuit throughout the tumble-and-swim cycle. Then they derived a mathematical equation that describes the probability of cells flipping between swim and tumble motions.

Additional equations describe other aspects of the system, such as the dynamics of the synthesis, diffusion and deactivation of one of the cell-to-cell chemical signal AHL.

This three-pronged approach of "wet-lab" experiments, precise measurements of the results, and mathematical modeling of the system, characterize the emerging discipline of quantitative biology, Hwa said. "This is a prototype, a model of the kind of biology we want to do."

Co-authors include Jian-Dong Huang, associate professor of biochemistry at the University of Hong Kong additional researchers at Hong Kong Baptist University, the University of Marburg, and the University of Hong Kong including members of the 2008 iGEM team, which Hwa co-advised as a Distinguished Visiting Professor at UHK.

Hwa is a senior scientist with UC San Diego's Center for Theoretical Biological Physics.

http://www.sciencedaily.com/releases/2011/10/111013141820.htm