Human Echolocation: Blind Like a Bat * Lifting the Lid on Lazy Eye * Red Dwarf Stars Host Hospitable Planets * Mother Flies Dose Offspring with Alcohol * Arctic Ice Turns Green with Algae * Salmon Follow Magnetic Map
Saturday, February 23, 2013 |
Animals such as bats are well known for their ability to echolocate, but today you'll hear about sightless humans who also use reflected sound to build up a picture of their environment. We'll also find out how a stint in total darkness can lead to clearsightedness - for kittens, at least. We'll discover why Red Dwarf planets might be the best neighbourhoods for alien life, and how fruit flies "hit the bottle" to battle parasites. And we'll learn why Arctic ice is going from white to green, and why a migrating salmon.needs a magnetic personality.
Similar to bats and dolphins, many blind humans have learned to navigate by echolocation. The most common method of sending and receiving sound waves is by making clicking noises with the tongue. Previous studies have used brain scans to show that in humans without sight, areas of the brain that are activated by visual cues in sighted people, are recruited for audio, including echolocation, in blind people. But a new study by Jennifer Milne, a PhD student, and colleagues from The Brain and Mind Institute at Western University in London, took this research one step further. They found that the areas of the brain that use the echo-based cues about an object's shape are also located in the same region of the brain activated by visual cues for shape in a sighted person. The study sheds new light on brain plasticity.
In humans, amblyopia, or "lazy eye," occurs in about 4 percent of the population. It happens when the two eyes do not see equally well in young children. At this age, the connections from the eyes to the brain are still developing. To compensate, the brain shuts down the eye with poor vision, in order to salvage the eye with good vision. A new study by Dr. Kevin Duffy, an Assistant Professor in the Department of Psychology and Neuroscience at Dalhousie University in Halifax, has found that total darkness resulted in a 100 percent success rate in restoring complete vision to kittens with experimentally- induced lazy eye. In their experiment, ten days of darkness reduce neurofilaments in the brain that hold the vision system in place. This allows the brain to return to a state in which it can correct itself. It is hoped that this research can one day be applied to children with lazy eye.
Red Dwarf with orbiting planet, Credit: David A. Aguilar (CfA)
Red Dwarf stars are small, dim, and very common. They are, at most, half the size of our Sun, can't be seen by the naked eye, and about three-quarters of the stars in our galaxy are Red Dwarfs. Now, new work by Courtney Dressing, a PhD Candidate at the Harvard-Smithsonian Center for Astrophysics, suggests that Red Dwarfs might also commonly host Earth-sized planets, orbiting in the "habitable zone" where their surface temperature could sustain liquid water. By combing through data from the Kepler satellite, Ms. Dressing found several planets fitting this pattern, and her survey suggests perhaps 6% of Red Dwarfs might have potentially hospitable planets.
Fruit-flies are often victims of parasitic wasps, which lay their eggs in the fruit-fly larvae. The infant wasps then eat the fruit-fly from the inside out. However, Dr Todd Schlenke, a biologist from Emory University in Atlanta, has found that fruit-fly females have developed a strategy to aid their offspring in the fight against the wasp. When they see parasitic wasps, they choose to lay their eggs on fruit that is fermenting, and which has a high alcohol content. The alcohol thus acts as an anti-parasitic medication, as the fruit-fly larvae are resistant to the toxic effects of alcohol, but the infant wasps are not. Related Links
Algae growing in strands underneath thinning Arctic ice. Mar Fernandez-Mendez, Alfred Wegener Institute
A recent study of ice in the Central and Eastern Arctic found that it is only about one metre thick, as compared to between four and five metres thick 20 years ago. This, along with more open water in the Arctic than ever before, has known consequences. One of them is the growth of algae. But a new study by Dr. Antje Boetius, a Professor of Marine Biology from The University of Bremen in Germany, found that the growth of algae has increased to a point where the Arctic Sea floor is completely covered in many places. As the ice thins, more sunlight is able to penetrate. This promotes the growth of algae on the underside of the ice. When the ice melts, the algae drops to the bottom. These changes are a new phenomenon and may negatively effect the biodiversity of the Arctic ecosystem.
Sockeye salmon, courtesy Dr. Tom Quinn, University of Washington
Salmon migrate over thousands of kilometers of open ocean, but somehow, unfailingly find their way home to their native streams. Dr. Nathan Putman, a post-doctoral scholar in the Department of Fisheries and Wildlife at Oregon State University, has found evidence that they do so using a magnetic "sixth sense." Dr. Putman analyzed the route Fraser River salmon took on their migration home to spawn, and found that variations in that route corresponded to long-term variations in the Earth's magnetic field, suggesting the fish were using a magnetic sense and an internal magnetic map to navigate.