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Archive for month: June, 2016

The Amazingly Complex World of Insect Navigation

The Amazingly Complex World of Insect Navigation

Dung beetles. Most people have seen footage of them rolling their balls of dung across a field, like little loggers at a log rolling contest. The beetles use the dung either as a material where eggs can be laid or as food. The intricate movements that they use to roll the dung are incredible, but it’s equally amazing how far they roll their spherical cargo. Moreover, they always roll the dung balls in a straight line. How do they know where they’re going?

Turns out they use a navigation technique mariners in the days of sailing ships would have recognized: Dung beetles navigate using the stars. The beetles take mental “snapshots” of celestial positions. By comparing the positions of stars or other celestial bodies during each snapshot, they can keep themselves on course.

But what about during the day? Most insects, including the beetles, use the sun. Far from their nest, ants, for example, can orient themselves using the sun as a reference point. This even works when the sun is hidden by clouds. Just as a smart explorer brings a compass in case the GPS doesn’t work, ants have a backup plan. When the sun is hidden, ants can orient themselves using polarized light, or light that only vibrates in one plane. As sunlight passes through the atmosphere, it excites electrons in all directions. Some properties of the atmosphere cause light to polarize, or only excite electrons in one plane.

These atmospheric properties cause different degrees of polarization at different angles to the sun; if ants can detect polarization, they can detect the angle of the sun and use the sun to navigate even if the sun is invisible.

Not only can ants detect polarized light, their compound eye diverts polarized light and direct sunlight into completely different navigational systems. When both polarized and direct sunlight are present, the ants will rely first on the internal compass derived from polarized light. The one drawback is that ants have to learn their local sky first; drop them in an unfamiliar area and they will not be able to orient themselves. Ants who were raised with only a restricted view of the sky could navigate, but made many mistakes based on missing data. Many different insects, including bees, navigate in this manner.

Some of these navigation systems are incredibly sophisticated. Insects don’t have a lot going on in the brain department, but there’s enough capacity to remember the positions of celestial bodies or create detailed compasses based on the type of light available. It’s enough to makes you wonder what other kinds of intelligence exist in the animal kingdom that we just haven’t noticed yet.

Source: daily.jstor.org

A Strange Butterfly-Ant Relationship Discovered in Peru

A Strange Butterfly-Ant Relationship Discovered in Peru

The immature caterpillar stages are actively tended by multiple species of ants, including the bullet ant Paraponera clavata, and were observed feeding on the extrafloral nectaries of the bamboo. Pupation of A. annulifera then occurs on the host plant near the base of the bamboo.

We also observed the butterflies stealing bamboo sap secretions from the ants, a potential form of kleptoparasitism which was previously unknown to occur with these adult butterflies.

Perhaps the butterflies are utilizing a pheromone from their larval stage, potentially allowing the caterpillars to take advantage of the ants, which would normally attack other invading insects. The three red spots on the butterfly wing also look strikingly like the red ants that they associate with, and perhaps this wing pattern serves as a form of mimicry (if a butterfly looks like red ants that bite and sting, a bird may be less inclined to eat it). This is just a hypothesis at the moment, and future work should test this putative mimicry wing pattern and chemical signals. We hope to continue investigating this fascinating species, because there certainly seems to be more to this tropical butterfly than meets the eyes.

Source: Entomology today
Writer: Aaron Pomerantz

Super-moth INVASION: Mutant insects to attack crops as numbers EXPLODE

Super-moth INVASION: Mutant insects to attack crops as numbers EXPLODE

AN INVASION of super-moths which attack crops including cabbages and cauliflowers are expected to arrive in Britain from eastern Europe.

Experts have warned of a potential explosion in numbers of the insect after exceptionally high numbers of moths arrived in the UK.

The diamondback moth (Plutella xylostella), which can be blown long distances on the wind, is considered to be a super-pest because it is resistant to most insecticides, and the centimetre-long caterpillars can cause losses to growers.

Researchers say that if the weather is warm and suitable for breeding there could be an “explosion” in numbers by the end of the season.

They say they do not know exactly where the moths have come from, but it could be eastern Europe or Russia.

Chris Shortall, a research scientist and co-ordinator of the Rothamsted light-trap network in Hertfordshire said he had seen higher than usual numbers of the moth in traps at the research centre, and online reports of a high incidence of diamondbacks.

He said: “Normally, we gather the data at the end of the year from the volunteers that run light-traps around the country, but on the basis of these reports I contacted them and asked them to provide the data that they have so far.

“They reported much higher numbers than usual. In our light-traps here at Rothamsted we have seen in two nights the number of diamondback moths that we usually record in a year, and this is reflected elsewhere in the network.

“I’m concerned for cabbage and cauliflower growers, which is why I wanted to inform the relevant organisations and growers as early as possible.

“If the summer weather is warm and favourable for the reproduction of the moths we could see an explosion in the number of them by the end of the season.”

According to long-standing annual records from the Rothamsted Insect Survey, numbers reported so far are exceptionally high, and of a similar level to that seen in 1996.

The diamondback moth is considered to be a super-pest

The diamondback moth is considered to be a super-pest

Experts hope to record numbers once the diamondback moth caterpillars have hatched

Experts hope to record numbers once the diamondback moth caterpillars have hatched

Sites in eastern England and the Channel Islands have reported around 10 times the normal yearly total over a period of a few nights, with more than 1,000 reported over three evenings from a trap in Berkshire, and 310 in one night in Guernsey.

Diamondback moths have also been found in large numbers in trap samples from cabbage fields in Kirton, Lincolnshire, and Wellesbourne, Warwickshire, the experts said.

The scientists will examine the moths to see if they are resistant to pesticides, and find a way to tackle them.

Dr Steve Foster, senior scientist at Rothamsted Research, said: “We will aim to study the moths that are immigrating currently to the UK to identify whether they are resistant to the available insecticides and look for potential management methods.

Research scientist Chris Shortall said he has seen higher numbers than usual

Research scientist Chris Shortall said he has seen higher numbers than usual

“This could take up to a few weeks.”

He urged growers to speak to their authorised advisers on spraying their crops and said the experts would provide all scientific information when it became available.

Mark Parsons, head of moth conservation at Butterfly Conservation, said the recent migration of diamondback moths, are likely due to following winds from their breeding grounds, was unusual for its large numbers but not completely unexpected in the UK.

He said: “This is an occasional minor pest in this country on brassicas and it is possible given the numbers this year it may prove to be a bit of a nuisance, but we won’t know for a few weeks until any caterpillars have hatched.”

Source: Science Daily
Writer: KATIE MANSFIELD

Ancient ants leaving a modern trail

Ancient ants leaving a modern trail

 

It is thought that ants evolved about 150 million years ago and have risen to dominance in the past 60 million years. They are now everywhere and while they are not always welcome on your kitchen counter, they are critical to ecosystems around the world for many roles, including seed dispersal and decomposition. Now new research shows that past land connections, as well as current climate, are shown to be of primary importance in determining ant diversity patterns.

It is thought that ants evolved about 150 million years ago and have risen to dominance in the past 60 million years. They are now everywhere and while they are not always welcome on your kitchen counter, they are critical to ecosystems around the world for many roles, including seed dispersal and decomposition. There are a variety of factors that can impact diversity in geographically-clustered ant communities, but it can be difficult to decipher the most important biogeographic influences on these ant populations. Patricia Wepfer, Dr. Benoit Guénard (currently at the University of Hong Kong), and Prof. Evan Economo from the Biodiversity and Biocomplexity Unit at Okinawa Institute of Science and Technology Graduate University (OIST) unravelled the web of biogeographic components to find the influences that most significantly affect ant communities. They recently published their results in the Journal of Biogeography.

“I was interested in how different these communities could be across Asia,” Patricia Wepfer, first author and OIST Ph.D. student said. “We wanted to know how a community [of ants] is composed in different places and why it is composed in that way.”

The team assembled a large dataset of ant species occurrence records for 159 areas in Asia ranging from the Ryukyu Islands to Taiwan and coastal regions of South Korea. From this data, they determined which ants existed where and what factors may be affecting the communities.

They then analysed whether the climate — temperature, rainfall — and/or space — geographical distance, water barriers — made more of a difference to the composition of ant communities. The researchers also looked more closely to see whether historical land connections significantly affect ant communities. During the Last Glacial Maximum in the Pleistocene Epoch, approximately 26,000 years ago, many areas and islands in Asia were connected. As the land moved, the ocean began to cover these areas and create separate land masses. Surprisingly, ant population configurations of today are very much influenced by these past land connections that existed in the Pleistocene.

“Interestingly, the past land connections during the Last Glacial Maximum are more important in explaining the existing ant community patterns, than the way land is configured now,” Wepfer said. “This may be due to the fact that historical land connections existed for a much longer time than the connections that we have today and ants take a long time to distribute.”

While historical land connections are the most surprising factor in determining the make-up of a geographically-clustered ant community, ecologists also have to consider current and recognized influences, such as the temperature. From the data, the team determined that the temperature played the largest role in the differentiation between ant communities. With the advent of climate change, this may have many implications on ant ecosystems, as well as the ecosystems they work to sustain.

“Temperature is the dominant factor and plays a major role in shaping ant communities,” Wepfer said. “Climate change will likely change these ant communities.”

It is well-known in ecology that temperature is of the utmost importance in shaping species distributions, but it is important to keep in mind the spatial influence upon ant communities.

“In order to understand why species are where they are, we need to think about the current climate and land connections between areas,” Economo said. “But also what the connections between areas were during the Last Glacial Maximum, which is when the sea levels were very low.”

The historical land connections can reveal how much a structural change, whether that is the shifting of continents or even on a much smaller scale, like building a dam or paving a road, can influence ecosystems.

“It is important to be aware of things that happen in the past for species composition today,” Wepfer said. “Whatever major structural changes that are made to the environment can result in different connectivity between habitats and spaces.”

Source: Okinawa Institute of Science and Technology Graduate University – OIST (Science Daily)
Date: June 9, 2016

Creating a Window into a Fly’s Brain

Creating a Window into a Fly’s Brain

Fruit flies are far from human, but not as far as you might think.

They do many of the same things people do, like seek food, fight and woo mates. And their brains, although tiny and not set up like those of humans or other mammals, do many of the same things that all brains do — make and use memories, integrate information from the senses, and allow the creature to navigate both the physical and the social world.

Consequently, scientists who study how all brains work like to use flies because it’s easier for them to do invasive research that isn’t allowed on humans.

The technology of neuroscience is sophisticated enough to genetically engineer fly brains, and to then use fluorescent chemicals to indicate which neurons are active. But there are some remaining problems, like how to watch the brain of a fly that is moving around freely.

It is one thing to record what is going on in a fly’s brain if the insect’s movement is restricted, but quite another to try to catch the light flash of brain cells from a fly that is walking around.

Takeo Katsuki, an assistant project scientist at the Kavli Institute at the University of California, San Diego, is interested in courtship. And, he said, fruit flies simply won’t engage in courtship when they are tethered.

So he and Dhruv Grover, another assistant project scientist, and Ralph J. Greenspan, in whose lab they both work, set out to develop a method for recording the brain activity of a walking fly.

One challenge was to track the fly as it moved. They solved that problem with three cameras to follow the fly and a laser to activate the fluorescent chemicals in the brain.

The other was the delicate matter of making a window into the fly’s brain. For that, Dr. Katsuki said, he removed the top of a fly’s head and glued in place a tiny glass window. It had to seal off the brain so that it wouldn’t dry out, and it had to be flat, to avoid optical distortion.

The procedure was quite a delicate matter. Now, Dr. Katsuki said, “I call myself a fly surgeon.”

And although the flies often seemed fine after the procedure and walked away, the researchers let them rest for a day, to make sure. If the surgery did not go well, a fly’s brain activity might be abnormal, and if there was a problem, a fly would probably not survive a day.

Dr. Katsuki said that he was sometimes disappointed when surgery went well but the patient escaped by flying away instead of being captured in a vial to await the next day’s experiment. But he and his colleagues operated on enough flies to prove the value of the procedure.

The researchers published the details of their work in Nature Methods in May. Now that they have shown the approach works, they can start finding out what they want to know about how a fly’s brain works.

Source: The New York Times
Writer: James Gorman

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