Bees learn new languages easily

Bees from opposite ends of the Earth can communicate more easily than people, a discovery that suggests bees can learn a new language easily.

Asian and European honeybees can live happily together in mixed colonies because they easily learn to understand one another's "dance languages" despite having evolved different dialects, an international team has shown for the first time.

	Bee happy: Apis cerana cerana queen (yellow) tended by Apis mellifera ligustica (red) and Apis cerana cerana (green) workers

The findings will shed new light on the origins of this ancient form of communication and also suggest that, like people, bees can learn a new skill.

The nine species of honeybees found worldwide separated about 30 to 50 million years ago, and subsequently developed different dance 'languages'. The content of the messages is the same, but the precise encoding of these languages differs between species.

Now researchers from Australia, China and Germany report in the journal Plos ONE that the two most geographically distant bee species - the European honeybee Apis mellifera and the Asian honeybee Apis cerana - can share information and cooperate to exploit new food sources.

'We know that the members of a honeybee colony routinely exchange information via dance about the location of newly discovered locations, like feeding places, water or new nesting sites," explains Dr Shaowu Zhang from the Research School of Biological Sciences at The Australian National University.

"The scouts perform the so-called bee dances inside the nest. The coordinates of distant locations are encoded in the waggle phase of this ballet, with the direction and distance to the food source indicated by the orientation and duration of the dance.

"This duration differs across honeybee species, even if they fly the same distance in the same environment. It's these differences which we can think of as distinct languages."

The research team is the first to successfully study the behaviour of a colony containing a mixture of two different species of bees. One of the first findings of this novel approach was that Asian and European honeybees, after some time of adjustment in the mixed colony, could share information and work together to gather food. Asian honeybees followed the dances of European forager bees, and deciphered the encoded information correctly.

"The dance language of honeybees is among the best studied communication systems in the animal kingdom. Nevertheless, surprises are still possible, as we have shown," Dr Zhang said. "This work has potentially major implications for our understanding of animal communication. Next we plan to study exactly to what extent variation is a factor between different bee dance languages."

The study was done with Drs Shenglu Chen and Songkun Su from Zhejiang University in China and Dr Jürgen Tautz from Würzburg University in Germany.

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Clues to Controlling Seizures

New approaches to modeling the brain could improve electrical-stimulation therapies.

The same type of modeling used by meteorologists to forecast the weather could help scientists design better electrical-stimulation therapies for the brain. These therapies, which involve sending small jolts of electricity to specific neural targets, are currently in use for both Parkinson's and epilepsy, two neurological diseases in which drugs have had limited success.

As neurosurgical technologies improve and medical devices become smaller and more precise, interest in stimulation therapies has blossomed: different therapies are now being tested in a range of disorders, including brain injury, obsessive-compulsive disorder, and depression. Scientists theorize that electrical stimulation blocks abnormal electrical patterns that arise with different diseases, but little is known about how these devices actually work. As use of this technology grows, it is becoming increasingly important for scientists to develop more precise ways to target aberrant brain activity while leaving normal neural communication intact.

"In some sense, we have no idea what electrical stimulation is doing to the brain," says Robert Duckrow, a neurologist at Yale University, in New Haven, CT, who tests electrical therapies. "It's almost as if we need to take a step back and say, What is the right way to stimulate the brain to achieve a specific end?"

Steven Schiff, a neurosurgeon and engineer at Pennsylvania State University, is trying to do just that. Schiff and his collaborators are borrowing an engineering technique, known as control theory, to model the networks of neurons that produce the abnormal electrical activity that is characteristic of both seizures and movement disorders such as Parkinson's. The results should allow scientists to more precisely design stimulation therapies, improving their effectiveness. "We would like to get to the point where we can minimize the energy used and minimize the effect on normal [cognitive] processes," says Schiff.

With epilepsy, 30 to 40 percent of patients fail to find relief from anticonvulsant medications, and not all patients are eligible for surgery to remove the part of the brain that generates seizures. The vagus nerve stimulator, which stimulates a nerve leading to the brain, was approved for epilepsy treatment more than a decade ago. But it has limited success: only about a third of patients who undergo the procedure report a reduction in seizure rates by 50 percent or more.

Deep brain stimulation, which involves surgically implanting electrodes directly into the brain, has become routine for treating Parkinson's disease: nearly 40,000 Parkinson's patients have undergone the procedure to date. While for many patients it's a welcome alternative to drugs, the treatment needs to be effective for many symptoms, not just the tremors which are the most obvious visible signs of the disease. "It's the inability to start a movement which is the most disabling to many patients. The harder thing to do is to be more sophisticated in how you maximize patients' ability to move, and by using models, we hope to create more effective algorithms to interact with the brain's activity in such patients," says Schiff

One drawback to the existing stimulation systems is that the pattern and amplitude of electrical signals that doctors use to stimulate the brain have been chosen largely by trial and error. "It's like the early days of cochlear implants," says Rahul Sarpeshkar, an electrical engineer at MIT who studies neural prosthetics and computational modeling of disease. "At first, people just tried things. But once they approached the problem more rationally and tried to more closely mimic the biology, people could hear better."

Building models that mimic brain activity has been a challenge because communication in networks of neurons is so complex. "Scientists are just now beginning to investigate how nerve cells interact to produce the phenomenon of seizure," says Schiff. His team uses an approach that has shown success in modeling weather and other complex nonlinear systems, and it has just recently been applied to neurons.

The idea is that if scientists can accurately model the activity leading up to and during a seizure, they can use that model to test in real time the type of stimulation parameters that are most effective at preventing abnormal activity before it evolves into a full-blown seizure.

So far, Schiff's team has been able to build models that replicate oscillating neural activity recorded from the cortex of rodents. And in a paper published earlier this year in the Journal of Neural Engineering, the researchers showed that they could control these virtual wave patterns, outlining a potential approach to controlling electrical activity via neural implants. The scientists are now trying to repeat the feat using dynamics of actual seizures recorded in the lab.

Schiff's team has also built a neural model of Parkinson's and soon hopes to test his modeling approach in patients. "We hope to sort out over the next year how to proceed with the [Parkinson's disease] control in order to make it suitable for safe human study."

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The Weird Sisters

They just keep getting weirder. The “they” I’m referring to are the bdelloid rotifers — small transparent animals that live in damp places such as puddles, or patches of moss. Among evolutionists, these animals have something of a cult following, because they have a lifestyle that is not supposed to exist. As far as anyone can tell, the bdelloid rotifers are ancient asexuals: they appear to have been living entirely without sex for more than 85 million years. And each time we learn more details of their lifestyle, the wackier it becomes.

Evolving to live without sex is easy; all sorts of organisms do it the whole time. For example: aphids, weevils, snails, water fleas, nematode worms, scorpions, even the occasional lizard, have all been known to evolve asexuality. Instead of reproducing via eggs and sperm, asexuals can reproduce in any number of ways. For instance, some bud off a piece of themselves; the piece grows into a whole new animal. The bdelloids, like many other asexuals, reproduce by means of eggs that don’t need to be fertilized.

No, evolving asexuality isn’t the hard part. The hard part is making an evolutionary success of it.

In the short-term, asexuals seem to have an advantage: they don’t have to waste time finding and seducing mates, but can just get on with reproducing. Not having to find a mate makes it easy for asexuals to live in transient habitats, such as puddles, for it doesn’t matter if they never encounter anyone else. Moreover, because asexuals only have daughters, their populations can grow rapidly. In a sexual population such as humans, females must have, on average, two children for the population to remain the same size. In an asexual population, females only need to have one. If each female has two, the population grows. Sex, in other words, is expensive.

Yet if you look at the great tree of life, asexual groups tend to be out on the twigs: there are no great branches of the tree that contain only asexuals. In other words, no one can point to a big group, such as birds or fish, or even snails, and say, “That’s a group composed only of asexuals.” What this means is that asexuality evolves often, but rarely persists for long: asexuals typically go extinct soon after they appear.

The swift extinction of asexuals, and the absence of big asexual groups, suggests that sex is essential for long-term evolutionary success: giving up sex is a Bad Idea, a kind of evolutionary suicide.

Exactly why this is so remains unclear. But it’s thought to have something to do with the fact that sex generates new gene combinations. Whereas a sexual creature like you or me inherits a unique mix of genes from our parents, asexuals are lumbered with the same set of genes their mother had. For an asexual, then, the only source of genetic novelty is mutation. (Mutations and sex are both sources of genetic variation, but they work differently. Mutations — accidental changes to DNA — are the ultimate source of genetic novelty. However, mutations tend to be harmful more often than they are helpful: they tend to disrupt genes that are already working. Sex, in contrast, takes pre-existing genetic variation and shuffles it, generating new gene combinations.)

Which brings me to the bdelloids. These animals are the great exception: a group of more than 450 species from which sex is entirely absent. How are they managing to flourish despite this epic period of abstinence? For they do flourish: bdelloids are everywhere. Go outside, collect some damp moss, and stick it under the microscope, and the odds are you’ll find some. You can even find them in Antarctica.

One possibility is that they are having sex after all, just very secretly. Certainly, other supposed ancient asexuals turned out to be having sex on the sly. For instance one group of aphids that were thought to be ancient asexuals turned out to be producing males. And genetic evidence has revealed sex in several groups, such as the Placazoa (small animals that live in the sea), that have never actually been seen doing it.

But genetic evidence suggests that the bdelloids are not having conventional sex: their genomes show no sign of it. Instead, they seem to be getting up to something else entirely.

It now looks as though the bdelloids do acquire new genes from time to time — that mutation isn’t their only source of genetic novelty. Yet their means of getting new genes is unlike anything previously known for an animal. Namely: they seem to pick up genes from the environment, and add them into their genomes.

The latest analysis of bdelloid genomes shows that the animals don’t just have rotifer genes. They also have dozens of genes from bacteria, fungi, and plants. For instance, the genome of the bdelloid rotifer Adineta vaga contains genes that bacteria use for making components of their cell walls. (What the rotifer is using them for is unclear.) Some of the other genes the animal has acquired are known only from a few groups of bacteria and fungi.

Which is seriously weird. Horizontal gene transfer — the technical term for when genes move sideways between distantly-related species — is common among bacteria, but extremely rare in animals. The likely reason for the difference is that bacteria have only one cell, and their genes are not sequestered in a cell nucleus, so adding a new piece of DNA here or there is easy. Animals, in contrast, not only keep their genes away from the rest of the cell, in a cell nucleus. They also have specialized sex cells — eggs and sperm. In order for a gene from a fungus to be permanently added to, say, the human genome, it must somehow get into the sex cells.

No one knows how the bdelloids pick up these genes. One idea is that it may be due to another oddity of their lifestyle: their ability to dry up and blow away. When the piece of moss they are living in dries up, these animals often dry up, too. It’s a state of suspended animation — add water and, all being well, they come back to life as frisky, or even friskier, than before. (This isn’t unique to bdelloids — some other small animals have evolved to endure desiccation. But most of these others can only do it at particular stages of their lives. The bdelloids can do it at any time. They can also — probably as a consequence of their desiccation abilities — survive high levels of radiation. Much higher than other animals can.) During the drying and rehydration, cell membranes may become disrupted, and their DNA fragmented. Perhaps all this makes it easier for stray bits of foreign DNA to get into the cells that will become eggs.

Some of the bacterial genes were clearly acquired a long time ago. We know this because they have evolved features that bacterial genes lack. Which suggests that getting new genes this way may be rather rare — the sort of thing that happens maybe once every five hundred thousand years or so. All the same, the occasional acquisition of foreign genes may have helped the bdelloids to their profoundly unorthodox success.

But personally, I’m glad that making a go of chastity is so difficult. For the real lesson from these weird sisters is that, for most of us, it’s far better to have sex.

**********

NOTES:

The ease of evolving asexuality, and the possible advantages of sex, have been much discussed; see, for example, Bell, G. 1982. “The Masterpiece of Nature: The Evolution and Genetics of Sexuality.” University of California Press. For a non-technical account, see chapter 13 of my book, “Dr. Tatiana’s Sex Advice to All Creation.” Metropolitan Books.

For the number of bdelloid species, see Segers, H. 2007. “Annotated checklist of the rotifers (Phylum Rotifera), with notes on nomenclature, taxonomy, and distribution.” Zootaxa 1564: 1-104. For bdelloids in Antarctica, see Izaguirre, I., Allende, L. and Marinone, M. C. 2003. “Comparative study of the planktonic communities of three lakes of contrasting trophic status at Hope Bay (Antarctic Peninsula).” Journal of Plankton Research 25: 1079-1097.

For how genetics gives clues to sexual or asexual lifestyles, and for examples of “asexuals” engaging in sex on the sly, see Normark, B. B., Judson, O. P. and Moran, N. A. 2003. “Genomic signatures of ancient asexual lineages.” Biological Journal of the Linnean Society 79: 69-84. For the detection of sex in Placozoa, see Signorovitch, A. Y., Dellaporta, S. L. and Buss, L. W. 2005. “Molecular signatures for sex in the Placozoa.” Proceedings of the National Academy of Sciences 102: 15518-15522.

For genetic evidence of the asexuality of bdelloids, see Mark Welch D. and Meselson M. 2000. “Evidence for the evolution of bdelloid rotifers without sexual reproduction or genetic exchange.” Science 288:1211-1215; Arkhipova, I. and Meselson, M. 2000. “Transposable elements in sexual and ancient asexual taxa.” Proceedings of the National Academy of Sciences 97: 14473-14477; and Barraclough, T. G., Fontaneto, D., Ricci, C. and Herniou, E. A. 2007. “Evidence for inefficient selection against deleterious mutations in cytochrome oxidase I of asexual bdelloid rotifers.” Molecular Biology and Evolution 24: 1952-1962.

For horizontal gene transfer in bdelloids (including the hypothesis that their lifestyle somehow facilitates it), see Gladyshev, E. A., Meselson, M. and Arkhipova, I. R. 2008. “Massive horizontal gene transfer in bdelloid rotifers.” Science 320: 1210-1213. For their ability to dry up and blow away, see Ricci, C. N. 1987. “Ecology of bdelloids: how to be successful.” Hydrobiologia 147:117-127. For their resistance to radiation, see Gladyshev, E. and Meselson, M. 2008. “Extreme resistance of bdelloid rotifers to ionizing radiation.” Proceedings of the National Academy of Sciences 105: 5139-5144.

Many thanks to Dan Haydon and Jonathan Swire for insights, comments and suggestions.

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