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Ladybird Invader Carries Deadly Parasite as Biological Weapon

When Europeans arrived in the New World, they brought devastating diseases like smallpox, which killed more native Americans than guns and other weapons. Infections go the other way too: When grey squirrels from North America arrived in the UK, they brought a squirrel pox virus that decimated the local red squirrels. Time and again, animals have invaded new regions and killed the locals by inadvertently bringing biological weapons with them.

Now, Andreas Vilcinskas from Justus-Liebig-University of Giessen has found that one the world’s most invasive insects—the harlequin ladybird—also belongs in the biological weapons club.

It hails from central Asia, but was willingly introduced to Europe, North America, and other parts of the world, by people who were seemingly undeterred by the outcomes of bringing cane toads to Australia or mongooses to Hawaii. Like those other invaders, the harlequin has brought ruin to local ladybirds, many of which have declined dramatically since its incursion.

There are probably many reasons for that. Perhaps it simply outcompete other species for food, or eats them directly. It carries a potent slew of antibacterial chemicals in its blood (or haemolymph) that makes it remarkably resistant to disease. For example, it can shrug off a deadly fungus that kills other ladybirds.

One of these antibacterials is a toxic chemical called harmonine. Many scientists suspected that this substance was poisoning other ladybirds that tried to eat the harlequin’s eggs. But Vilcinskas found that harmonine doesn’t affect native species at all. When he injected the seven-spot ladybird with high doses of the stuff, they were fine. But when he shot them up with the harlequin’s unfiltered haemolymph, they died. The invader clearly has something in its blood that’s deadly to other ladybirds, but it’s not harmonine.

Vilcinskas found the culprit by looking at harlequin haemolymph under a microscope. He found it swarming with microscporidians—a type of single-celled parasitic fungus. These parasites are found in every harlequin that the team examined, but don’t seem to do any harm. They stay in an inactive state and their genes are completely inactive. “I have worked on insect immunity for 20 years, and I had never [before] seen a haemolymph sample that was full of microsporidians that do not harm the carrier,” says Vilcinskas.

It’s possible that harmonine and other antibacterials allow the harlequin to tolerate its parasite. But the native seven-spot ladybird isn’t so well-defended. When Vilcinskas injected them with the microsporidians, they all died within two weeks.

This might be why so many native ladybirds die when the harlequin invades. Since all ladybirds eat each other’s eggs, those that chomp on the harlequin’s young could get a mouthful of lethal microsporidians.

Of course, they need to actually prove that. Helen Roy, who leads the UK Ladybird Survey, says that injecting seven-spots with microsporidians is a far cry from showing that they actually get infected in the field. For a start, she says that seven-spots very rarely eat harlequin eggs, so their chances of getting infected by microsporidians would be few and far between. Then again, seven-spots seem to be holding their own against the invaders, and are unusual among British ladybirds in showing no population declines. Perhaps other species are more wanton in their feeding habits and pay the price?

Either way, Vilcinskas’s team need to show that wild ladybirds do eat harlequin eggs, that they contract microsporidian infections, and that this contributes to their downfall. “The next steps would be to assess ecological relevance,” says Roy. “What does this mean in the real world?”

Lori Lawson Handley, who also works on the UK Ladybird Project, wonders if the microsporidians could be travelling between species through a more grisly route. Some parasitic wasps, like Dinocampus coccinellae, lay their eggs in ladybirds, and they could be spreading the parasites from the harlequin to other species. Their stings could be the equivalent of dirty needles.

A version of this piece also appears at Nature News.

Reference: Vilcinskas, Stoecker, Schmidtberg, Rohrich & Vogel.  2013. Invasive Harlequin Ladybird Carries Biological Weapons Against Native Competitors. Science http://dx.doi.org/10.1126/science.1234032

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To control cannibal toads, you just need the right bait

Australians love to destroy cane toads. Ever since these animals were first introduced in 1935, they have run amok, eating local animals and poisoning any that try to eat them. They’re captured and slaughtered in traps, bludgeoned with golf clubs, and squished with veering tyres, but still they continue to spread. Now, Michael Crossland from the University of Sydney has discovered an unlikely ally in the quest to control the cane toad: the cane toad.

Along with their unappealing appearance and milky poison, cane toads are also cannibals. Older tadpoles will hunt and eat eggs that have been recently laid in the same pond, to do away with future competitors. Crossland reasoned that the eggs must release a substance that the tadpoles can detect, so he mushed them up in his lab and separated out their chemical components.

He discovered that the eggs secrete bufadienolides – the same substances that make the milky poisons of the adult toads so deadly to Australia’s fauna. Ironically, the same chemicals that protect the eggs later in life also attract cannibalistic tadpoles. And that makes them excellent bait.


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Scientists and tourists bring thousands of alien seeds into Antarctica

Aliens are invading Antarctica. Thanks largely to scientists, they have already established a foothold on the frozen continent, and their numbers are set to increase. This might sound like the plot of John Carpenter’s classic film The Thing, but it is very real.

The aliens in question are not body-snatching monsters, but plants from other parts of the world. Steven Chown from Stellenbosch University found that in just one summer, visitors unwittingly imported around 70,000 seeds to Antarctica. And even though the continent has a reputation for being harsh and desolate, many of these immigrants have already founded populations in their new homes.

This is a new chapter in an old story. Wherever humans go, seeds hitch a lift on our clothes and belongings. If these foreigners germinate where they don’t belong, they can often out-compete native plants and uproot local ecosystems. From Japanese knotweed to kudzu vines, these invasive species cause problems throughout the world. Inhospitable though Antarctica is, it’s not immune to such invasions. It does, however, present a valuable opportunity to study them.

In most cases, we can only see the results of plant invasions when it’s too late. We know that many species are brought into new places accidentally, but it’s hard to quantify how often this happens. You can hardly stop everyone entering a country and count the number of seeds that they’re carrying. Except when you can. Travel to Antarctica is so limited that Chown managed to stop 2 per cent of all the visitors in a single summer and count the number of seeds on their persons and belongings.


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Beetle pest destroys coffee plants with a gene stolen from bacteria

For fans of a velvety latte or a jolting espresso, meet your greatest enemy: the coffee berry borer beetle. This tiny pest, just a few millimetres long, can ruin entire coffee harvests. It affects more than 20 million farming families, and causes losses to the tune of half a billion US dollars every year- losses that are set to increase as the world warms.

But the beetle isn’t acting alone. It has a secret weapon, stolen from an unwitting accomplice.

Ricardo Acuña has found that the beetle’s ancestors pilfered a gene from bacteria, most likely the ones that live in its gut. This gene, now on permanent loan, allows the insect to digest the complex carbohydrates found in coffee berries. It may well have been the key to the beetle’s global success.


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Since pythons invaded, Florida’s mammal populations have crashed

It turns out that if you unleash giant snakes into a place that didn’t previously have giant snakes, the other local animals don’t fare so well. That seems obvious, but you might be surprised at just how badly those other animals fare.

Since 2000, Burmese pythons have been staging an increasingly successful invasion of Florida. No one knows exactly how they got there. They normally live in south-east Asia and were probably carried over by exotic wildlife traders. Once in America, they could have escaped from pet stores or shipping warehouses. Alternatively, overambitious pet owners could have released when they got too large for comfort. Either way, they seem to be thriving.

With an average length of 12 feet (4 metres), the pythons are formidable predators. They suffocate their prey with powerful coils, and they target a wide variety of mammals and birds. The endangered Key Largo woodrat and wood stork are on their menu. So are American alligators (remember this oft-emailed photo?). Conservationists are trying to halt the spread of the giant snakes, out of concern that their booming numbers could spell trouble for local wildlife.

Michael Dorcas from Davidson College thinks they are right to be concerned. In the first systematic assessment of the pythons’ impact, Dorcas has found that many of Florida’s mammals have plummeted in numbers in places where the snakes now live.


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Fire ants conquered America by monopolising calorie-rich food

They came to America and found a nation overflowing with calories. Carbohydrate-rich fast food was available on every corner, and with little competition for it, the migrants ate their fill. Soon, they started spreading throughout this new land of opportunity. They are red imported fire ants (Solenopsis invicta) and their invasion is well underway.

The fire ant is an international pest. It devastates native ants, shorts out electrical equipment, damages crops, and inflicts painful stings. It hails from Argentina, but it was carried to the United States aboard cargo ships that docked at a port in Alabama. That was in the 1930s; since then, this invader has spread throughout the southern states, from California to Florida. The country spends over a billion dollars every year in attempts to stem the invasion.

Now, Shawn Wilder from Texas A&M University has found that their remarkable invasion has been driven by partnerships with local insects. The fire ants run a protection racket for aphids and other bugs, defending them from other attackers. In return, they get honeydew, a sweet nutritious liquid that the bugs excrete, after they suck the juices of plants. They are both farmers and bodyguards.


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Jellyfish shift ocean food webs by feeding bacteria with mucus and excrement

Despite its name, the Gulf of Mexico’s Dead Zone is full with life. This region stretches over 22,000 square kilometres, an area the size of Israel. Its waters are choked by a combination of fertiliser, sewage and industrial run-offs, flowing down from the businesses that line the Mississippi. These pollutants feed large blooms of algae that ultimately rob the water of oxygen, depriving it of the ability to support fish and other typical residents. Instead, the Dead Zone has become the dominion of jellyfish.

Jellyfish congregate here in their thousands. Locals like moon jellies and sea nettles are joined by foreign travellers like the Australian spotted jellyfish. These gelatinous swarms stretch for miles, covering the ocean in a web of pulsating umbrellas and stinging tentacles. At their densest, you could scoop up a hundred jellies within a single cubic metre of water. They shut down beaches, fisheries, industries and ecosystems.

The reasons for these swarms are unclear. By overfishing, we could have removed the jellies’ main competition for food. By sinking man-made debris like vehicles and rigs, we could have created habitats for their larvae. By raising the temperature of the oceans and pumping them with pollutants, we could have created warm, oxygen-poor waters that only they can thrive in.

The jellyfish blooms are a natural phenomenon but marine biologists suspect that they are becoming increasingly common. Reports are constantly flooding in of unusual thick and large swarms, not just in the Gulf of Mexico, but all over the world from the Mediterranean to the Japanese coast. The worry is that we are witnessing a transition from an ocean full of scales, shells and flippers to one that’s ruled by jelly.


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Drying out the cane toad invasion

In June 1935, the cane toad began its invasion of Australia. Sailors brought the animal over from Hawaii in an attempt to control the cane beetle that was ravaging Australia’s sugar cane crops. It was a mistake that the continent’s wildlife would pay for. The toad did nothing to stop the beetles. Instead, it launched its own invasion, spreading across the continent from its north-eastern point of entry. As it marched, it left plummeting populations of native species in its wake.

The toads are born conquerors. Females can lay 35,000 eggs many times a year, and each can develop into a new frog in less than 10 weeks. They’re unfussy eaters and they’ll munch away on bird eggs, smaller native frogs and more. And they have large glands behind their heads, which secrete a milky poison. Local predators (or domestic pets) that try to eat them tend to die.

Now, Daniel Florance from the University of Sydney has found a clever way of corralling the cane toad invasion. He realised that humans have continued to give the toad a hand, long after we first brought them to Australia. By creating dams and troughs, we provided the toad with watery staging grounds that allowed it to spread across otherwise impassably dry land.


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Invasive shrub increases risk of human disease (via ticks, deer and bacteria)

Honeysuckle_deer_tickThere are many ways of fighting disease, but Brian Allan from Washington University has suggested a most unusual one – a spot of weeding. Allan’s research shows that getting rid of a plant called the Amur honeysuckle might be one of the best ways of controlling an emerging human disease called ehrlichiosis. The plant, however, doesn’t cause the disease. The connection between the two is far more complicated than that.

The Amur honeysuckle is an Asian plant that’s naturally alien to American shores. But, like many species that are brought to new habitats, it has become an invader. It forms thick growths that deprive native plants of light, causing local diversity to plummet in the face of an expanding blanket of honeysuckle. This story has been repeated all over the world with different species cast as invasive villains, and different communities cast as suffering victims. But the true consequences of these invasions often go unnoticed.

The honeysuckle doesn’t just crowd out local plants; Allan has found that it also attracts white-tailed deer. Where the deer go, so do their parasites, and these include the lone star tick, the animal that spreads ehrlichiosis. Through their blood-sucking bites, the ticks spread five species of bacteria that infect and kill white blood cells. This weakens the immune systems of their hosts and causing the flu-like symptoms that accompany a bout of ehrlichiosis.


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The stealthy sea walnut sucks to succeed

It’s the open ocean. A baby fish, less than a centimetre long, floats through the water, completely oblivious of the danger it is in. It’s caught in a current, but one so smooth that the fish cannot detect it. Its only clue to what’s happening comes too late, as it’s suddenly sucked into a ring of tentacles and swallowed by one of the ocean’s stealthiest predators – the sea walnut.


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Beetle and yeast team up against bees


Bee hives, with their regularly arranged honeycombs and permanently busy workers may seem like the picture of order. But look closer, and hives are often abuzz with secret codes, eavesdropping spies and deadly alliances.

Bees release alarm pheromones that draw small hive beetles towards the hive.African honeybees are victimised by the parasitic small hive beetle. The beetles move through beehives eating combs, stealing honey and generally making a mess. But at worst, they are a minor pest, for the bees have a way of dealing with them.

They imprison the intruders in the bowels of the hive and carefully remove any eggs they find. In turn, the beetle sometimes fools the bees by acting like one of their own grubs, and gets a free meal instead of imprisonment. In Africa, both species have found themselves in an evolutionary stalemate.

But in 1998, American beekeepers spotted the beetle in hives of their local European-descended honeybees. These insects are gentler versions of their aggressive African relatives, and in them, the beetles found more vulnerable victims.


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Climate change responsible for decline of Costa Rican amphibians and reptiles

Miners used to take canaries into unfamiliar shafts to act as early warning systems for the presence of poisons. Today, climate scientists have their own canaries – amphibians. Amphibians – the frogs, toads and salamanders – are particularly susceptible to environmental changes because of their fondness for water, and their porous absorbent skins. They are usually the first to feel the impact of environmental changes.

The golden toad was one of the first casualties in the great amphibian decline.And feel it they have. They are one of the most threatened groups of animals and one in three species currently faces extinction. The beautiful golden toad (right) was one of the first casualties and disappeared for good in 1989. Even though they are less glamorous than tigers, pandas or polar bears, amphibians are a top priority for conservationists.

The usual factors – introduced predators and vanishing habitats – are partially to blame, but many populations have plummeted in parts of the world untouched by pesky humans. More recently, a large number of these deaths have been pinned on a fatal fungal disease called chytridiomycosis. Hapless individuals become infected when they swim in water used by diseased peers, and fungal spores attach to their skins. The disease had decimated amphibians across the Americans.

But it’s not the only killer – climate change can join their list of enemies. In Costa Rica, warmer and wetter days have led to a loss of rainforest leaf litter that has sent amphibian and reptile populations crashing. The extent of the damage may be even worse than we think. We have very little long-term data on the population sizes of many amphibian species, particularly in the tropics, where the greatest diversity exists. One of the few sites to buck the trend of ignorance is La Selva Biological Station in Costa Rica, which has been monitoring amphibian populations since the 1950s.


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Attack of the killer mice – introduced rodents eat seabird chicks alive


Blogging on Peer-Reviewed ResearchAs Charles Darwin learned several centuries ago, islands are havens for evolution. Newcomers to these isolated worlds find themselves unshackled from the predators that dogged them on the mainland. They celebrate their freedom by diversifying into a great variety of species. But predators still have ways of tracking them down, and following the footsteps of sailors is one of them. By killing adults and eating eggs, introduced predators such as rats, cats and stoats are responsible for nine in ten of the bird extinctions since 1600.

A Gough Island mice sites amid a grisly pile of chick bodies.Now, conservation agencies are getting serious about introduced predators. As an example, they have spent increasingly large budgets in recent years on the eradication of rats from troubled islands. Smaller stowaways like mice typically escape the conservationists’ wrath, and between 2001 and 2005, twenty-five times less money was spent on dealing with them. After all, mice are smaller and less opportunistic than rats and pose very little threat to seabirds.

Or at least that was what scientists used to think. In 2005, Ross Wanless, Peter Ryan and colleagues from the University of Cape Town found that on Gough Island in the south Atlantic, mice had developed sinister appetites. They were eating the chicks of local seabirds alive (see image below).

Infrared footage shows mice feeding on a chick.


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Parasites keep red tides at bay

Blogging on Peer-Reviewed ResearchOver the past decade, some coastal waters have started turning red with alarming frequency. The cause is not some Biblical plague, but dense concentrations of microscopic algae called dinoflagellates. Red tides can often contain more than a million of these cells in a mere millilitre of water. Many are harmless and essential parts of the ocean environment, but others produce toxins that can kill local wildlife and risk the health of humans who eat their poisoned flesh.

Redtide.jpgThese “harmful algal blooms” are more common in warm waters that mix poorly and are unusually rich in nutrients. Their increasing frequency has been blamed on numerous causes, from natural causes, to agricultural run-offs to increasing sea temperatures caused by climate change. But, as is becoming increasingly apparent in ecology, you’re not getting a complete picture of a habitat if you don’t know find out what the local parasites are up to.

Aurelie Chambouvet from the Station Biologique found that the algae responsible for red tides are themselves the victims of other parasitic species of dinoflagellates called Amoebophrya. The parasites act as an natural alga-stat that keeps the local algae populations under a tight leash. The red tides are what happens when that leash breaks.

Chambouvet’s team discovered the abundance of these parasites by taking water samples from an estuary of the Penze River in northern France over three consecutive years,. They used multi-coloured glowing antibodies designed to recognise and stick to molecules unique to both the host species and their parasites. The fluorescent glows revealed a life cycle that, like those of most parasites, is full of brutality and exploitation.