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Kate Horowitz
Kate Horowitz

Scientists Discover That Lichens Are Symbiotic Threesomes

Kate Horowitz
Kate Horowitz

When’s the last time you really looked at lichen? If you’re like most people, the answer is probably “never.” That’s a shame, because these unassuming little organisms are useful, amazing, and, scientists now say, a lot more complicated than we previously realized. They published their findings in the journal Science

You might not know it from the way we treat these organisms today, but humans and lichens have a long and close relationship. Cultures around the world have used lichens for thousands of years as medicine, dye, and food. Some myths say the first lichens were really scabs scraped onto a rock from the buttocks of a hero, while others say they're lizard sperm. (Do we have your attention yet?)   

So—putting aside the lizard sperm theory—what is lichen, exactly? That depends on who, and when, you ask. Naturalists in the first half of the 19th century were quite confident that they were dealing with a plant, and were scandalized by Swiss botanist Simon Schwendener’s 1868 announcement that lichens were cooperative organisms composed of one type of fungus and one type of microscopic alga. Eventually, Schwendener won over his critics. His findings entered the scientific canon, and there they stayed … until last week, when researchers in Montana and elsewhere said they’d identified a third member of the lichen household.

Microbiologist Toby Spribille of the University of Montana was part of the team shaking up the lichen establishment. “There’s been over 140 years of microscopy,” Spribille told Ed Yong at The Atlantic. “The idea that there’s something so fundamental that people have been missing is stunning.”  

Spribille and his colleagues might have missed it too, had they not taken an interest in a local pair of lichens called Bryoria tortuosa and Bryoria fremontii. The two are closely related but easy enough to tell apart—B. tortuosa is yellow, while B. fremontii is brown—and that’s really good, because B. tortuosa is toxic, while B. fremontii was historically used as food. 

B. tortuosa. Image credit: Tim Wheeler

A few years ago, researchers decided to take a look at the two species’ genes to see where they diverged. Conclusion? They didn’t. According to their genetic barcode analysis, toxic B. tortuosa and edible B. fremontii were just two different names for the same species. 

That didn’t sit right with Spribille and his colleagues, who had begun using advanced genomic techniques to understand cooperative relationships between insects and other organisms. They decided to take another crack at the puzzle using the latest sequencing technology. 

The team went out into the wilds of Montana and collected samples of both lichen types, then ground them up and sequenced their RNA. What they found contradicted not only the single-species theory, but also the one-fungus/one-photosynthesizing-microbe definition of lichen-hood. Each lichen’s genetic code contained not one, but two different types of fungus—and that second fungus was far more prevalent in deadly B. tortuosa.

To make sure they understood what they were seeing, the team then analyzed the DNA of lichen species from all over the world. Most of those species—from 52 lichen genera on six continents—also included that sneaky second fungus, a basidiomycete yeast. Of the 52 genera, all but 10 are in a single lichen family: Parmeliaceae.  

“We found it in everything,” Spribille told Gizmodo. “From Alaska to Ethiopia to Antarctica, it always was there.” 

He notes that overlooking the presence of the silent fungus partner may be the reason scientists have historically had so much trouble growing lichens in the lab. 

Whether toxic or edible, he says, every lichen is remarkable. “One thing that sets lichen apart from all other symbioses is that all the components are microbes. But when they come together, they form something self-replicating and beautiful that you can hold in your hand.”

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People Listen (and Remember) Better With Their Right Ears, Study Finds
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If you’re having trouble hearing in a noisy situation, you might want to turn your head. New research finds that people of all ages depend more on their right ear than their left, and remember information better if it comes through their right ear. The findings were presented at the annual meeting of the Acoustical Society of America in New Orleans on December 6.

Kids’ ears work differently than adults' do. Previous studies have found that children's auditory systems can’t separate and process information coming through both of their ears at the same time, and rely more on the auditory pathway coming from the right. This reliance on the right ear tends to decrease when kids reach their teens, but the findings suggest that in certain situations, right-ear dominance persists long into adulthood.

To study how we process information through both our ears, Auburn University audiologists brought 41 adult subjects (between the ages of 19 and 28) into the lab to complete dichotic listening tests, which involve listening to different auditory inputs in each ear. They were either supposed to pay attention only to the words, sentences, or numbers they heard in one ear while ignoring the other, or they were asked to repeat all the words they heard in both ears. In this case, the researchers slowly upped the number of items the test subjects were asked to remember during each hearing test.

Instructions for the audio test read 'Repeat back only the numbers you hear in the right ear.'
Sacchinelli, Weaver, Wilson and Cannon - Auburn University

They found that the harder the memory tests got, the more performance varied between the ears. While both ears performed equally when people were asked to remember only four or so words, when the number got higher, the difference between their abilities became more apparent. When asked to only focus on information coming through their right ear, people’s performance on the memory task increased by an average of 8 percent. For some people, the result was even more dramatic—one person performed 40 percent better while listening with only their right ear.

"Conventional research shows that right-ear advantage diminishes around age 13, but our results indicate this is related to the demand of the task,” one of the researchers, assistant professor Aurora Weaver, explained in a press release. In other words, when the going gets tough, the right ear steps up.

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Pigeons Are Secretly Brilliant Birds That Understand Space and Time, Study Finds
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Of all the birds in the world, the pigeon draws the most ire. Despite their reputation as brainless “rats with wings,” though, they’re actually pretty brilliant (and beautiful) animals. A new study adds more evidence that the family of birds known as pigeons are some of the smartest birds around, as Quartz alerts us.

In addition to being able to distinguish English vocabulary from nonsense words, spot cancer, and tell a Monet from a Picasso, pigeons can understand abstract concepts like space and time, according to the new study published in Current Biology. Their brains just do it in a slightly different way than humans’ do.

Researchers at the University of Iowa set up an experiment where they showed pigeons a computer screen featuring a static horizontal line. The birds were supposed to evaluate the length of the line (either 6 centimeters or 24 centimeters) or the amount of time they saw it (either 2 or 8 seconds). The birds perceived "the longer lines to have longer duration, and lines longer in duration to also be longer in length," according to a press release. This suggests that the concepts are processed in the same region of the brain—as they are in the brains of humans and other primates.

But that abstract thinking doesn’t occur in the same way in bird brains as it does in ours. In humans, perceiving space and time is linked to a region of the brain called the parietal cortex, which the pigeon brains lack entirely. So their brains have to have some other way of processing the concepts.

The study didn’t determine how, exactly, pigeons achieve this cognitive feat, but it’s clear that some other aspect of the central nervous system must be controlling it. That also opens up the possibility that other non-mammal animals can perceive space and time, too, expanding how we think of other animals’ cognitive capabilities.

[h/t Quartz]

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