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Are Honeybees Losing Their Way?

 A combo of pesticides takes a toll on their memory andcommunication skills

Honeybees learn and remember the locations of flowers, but a new study shows they may be losing

their way.

Photograph by John Kimbler, My Shot  

Christy Ullrich- National Geographic News- Published February 13, 2013 

 A single honeybee visits hundreds, sometimes thousands, of flowers a day in searchof nectar and pollen. Then it must find its way back to the hive, navigating distancesup to five miles (eight kilometers), and perform a "waggle dance" to tell the other bees where the flowers are. 

 A new study shows that long-term exposure to a combination of certain pesticides

might impair the bee's ability to carry out its pollen mission.

"Any impairment in their ability to do this could have a strong effect on their survival,"said Geraldine Wright, a neuroscientist at Newcastle University in England and co-author of a new study posted online February 7, 2013, in theJournal of Experimental Biology . 

Wright's study adds to the growing body of research that shows that the honeybee'sability to thrive is being threatened. Scientists are still researching how pesticidesmay be contributing to colony collapse disorder (CCD), a rapid die-off seen inmillions of honeybees throughout the world since 2006.

"Pesticides are very likely to be involved in CCD and also in the loss of other types of pollinators," Wright said. (See the diversity of pollinating creatures in a photo galleryfrom National Geographic magazine.)

Bees depend on what's called "scent memory" to find flowers teeming with nectar and pollen. Their ability to rapidly learn, remember, and communicate with eachother has made them highly efficient foragers, using the waggle dance to educateothers about the site of the food source.

Their pollination of plants is responsible for the existence of nearly a third of the foodwe eat and has a similar impact on wildlife food supplies.

Previous studies have shown certain types of pesticides affect a bee's learning andmemory. Wright's team wanted to investigate if the combination of differentpesticides had an even greater effect on the learning and memory of honeybees.

"Honeybees learn to associate floral colors and scents with the quality of foodrewards," Wright explained. "The pesticides affect the neurons involved in thesebehaviors. These [affected] bees are likely to have difficulty communicating withother members of the colony."

The experiment used a classic procedure with a daunting name: olfactoryconditioning of the proboscis extension reflex. In layman's terms, the bee sticks outits tongue in response to odor and food rewards.

For the experiment, bees were collected from the colony entrance, placed in glassvials, and then transferred into plastic sandwich boxes. For three days the bees werefed a sucrose solution laced with sublethal doses of pesticides. The team measuredshort-term and long-term memory at 10-minute and 24-hour intervals respectively.(Watch of a video of a similar type of bee experiment.) 

This study shows that when pesticides are combined, the impact on bees is far worse than exposure to just one pesticide. "This is particularly important because

one of the pesticides we used, coumaphos, is a 'medicine' used to treat Varroa mites[pests that have been implicated in CCD] in honeybee colonies throughout theworld," Wright said.

The pesticide, in addition to killing the mites, might also be making honeybees morevulnerable to poisoning and effects from other pesticides.

Stephen Buchmann of the Pollinator Partnership, who was not part of Wright's study,underscored how critical pollinators are for the world. "The main threat to pollinatorsis habitat destruction and alteration. We're rapidly losing pollinator habitats, naturalareas, and food-producing agricultural lands that are essential for our survival andwell being. Along with habitat destruction, insecticides weaken pollinators and other 

beneficial insects."

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 An Infinity of Virusesby Carl Zimmer  

When I talk about viruses, I have to struggle with big numbers.

If you get sick with the flu, for example, every infected cell in your airway producesabout 10,000 new viruses. The total number of flu viruses in your body can rise to

100 trillion within a few days. That’s over 10,000 times more viruses than people onEarth.

If there can be so many viruses in a single person, how many viruses are there intotal on our planet? I’ve hunted around for a number, and the one I’ve seen mostoften is 1031. As in, 10000000000000000000000000000000. As in over 10 milliontimes more viruses than there are stars in the universe. As in, if you were to stackone virus on top of another, you’d create a tower that would stretch beyond themoon, beyond the sun, beyond Alpha Centauri, out past the edge of the Milky Way,past neighboring galaxies, to reach a height of 200 million light years. 

Now it seems that I may have been lowballing that number.

Scientists don’t come up with a number like 1031 by counting every single virus onEarth. They take surveys in different environments –the soil, the water, the oceanfloor  –and then extrapolate. As they take more samples, they can adjust their estimate up or down.

It used to be that scientists could only conduct these surveys by squinting down amicroscope and actually spotting the individual viruses. That turns out to be a badway to count viruses, in part because their hosts –such as bacteria and protozoans –often don’t grow in the artificial confines of a laboratory. Without viable hosts, theviruses can’t reproduce, and so they go unnoticed. 

Things got a lot better once scientists found a new way to count. Instead of looking

for full-fledged viruses, they just looked for pieces of their DNA. The ocean, onceconsidered a desert for viruses, turned out to be a broth of viral DNA. Given thesheer volume of the oceans, most of the world’s viruses reside there. And most of the viruses that scientists discovered in the ocean turned out to be parasites of bacteria, known as bacteriophages.

But scientists have long known that there’s another kind of virus out there, one thatuses a somewhat different molecule for its genes.

DNA is a double helix, which encodes genes along both strands. When our cellsmake a protein from a gene, they make a copy on a single-stranded molecule calledRNA. DNA-encoded genes can also make RNA molecules that do other jobs, suchas sensing the concentration of various elements inside a cell.

In some viruses, RNA also takes on DNA’s job, and encodes genes. Influenza is justone example of the many RNA viruses out there (or in you). Unlike bacteriophages,RNA viruses almost never infect bacteria. Instead, they infect us, plants, fungi,protozoans –all members of the same great lineage of life known as eukaryotes.

The methods that scientists use to tally up DNA viruses often miss RNA viruses, soit’s been hard for scientists to estimate how many RNA viruses are on Earth.In thecurrent issue of the ISME Journal , scientists at the University of Hawaii describe a

new method they developed to fill that hole.

The scientists first scooped up water from off a pier on Oahu (about 115 liters alltold). They then passed the water through fine filters to exclude bacteria and larger organisms. Through a series of additional steps, they concentrated the viruses downfurther and then extracted all the DNA and RNA from their samples. The scientiststhen measured how much of each kind of molecule was present in the sea water.Based on the mass of RNA in an average virus, they could then estimate how manyRNA viruses were in the sample.

Their conclusion was remarkable: RNA viruses made up between 38 and 63% of theviruses in the sea water. In other words, about half of the viruses in the ocean areRNA viruses.

This can be surprising when you consider the number of hosts that RNA and DNAviruses can infect. In the ocean, bacteria (hosts to DNA-based bacteriophages) far outnumber eukaryotes (hosts to RNA viruses).

But it’s important to bear in mind that eukaryotes are better as virus incubators. Asingle eukaryote cell can spew out far more viruses than a single bacterium. Bacteriacan’t churn out viruses the way you can, my dear eukaryotic reader. 

This new study is just a first cut at estimating the number of RNA viruses on Earth.It’s possible that for some reason the waters off the coast of Hawaii are weirdly goodplaces to find them. The scientists themselves acknowledge that they may beoverestimating the number of RNA viruses through some flaw in their methods. Butwhen I contacted an expert on global virus surveys, Curtis Suttle of the University of British Columbia, for his opinion, he gave a thumbs-up. “I think it is an interesting andprovocative paper,” he told me. “We will have to see if it holds up.” 

If it does, I ’ll have to find some new metaphors to describe10000000000000000000000000000000 + 10000000000000000000000000000000.

 ________________________ 

*Some people say viruses are truly alive, and some say they aren’t.But if they aren’t,then we need some name that can encompass the things that are “really” alive, alongwith the things that carry genes, can evolve, and carry out all the other life -ish tasks

that viruses do.