Archive for the ‘Current Biology’ Category

archer fish
Footage captured by two high-speed cameras shows the fish’s ability in detail

The jets of water that archer fish use to shoot down prey are “tuned” to arrive with maximum impact over a range of distances, according to a study.

By Jonathan Webb
Science reporter, BBC News

High-speed cameras were used to analyse fishes’ spitting performance in detail.

As they create each jet, the fish tweak the flow of water over time, causing a focussed blob of water to gather just in front of the target, wherever it is.

The ability comes from precise changes to the animal’s mouth opening, which may prove useful in designing nozzles.

Senior author Prof Stefan Schuster, from the University of Bayreuth in Germany, explained that jets of water and other fluids are used to cut or shape materials in industries ranging from mining to medicine.

He believes his new fish-based findings could improve the technology.

Patience and precision
“I’ve never seen anything in which they use a nozzle that changes its diameter,” he told the BBC. “The most standard approach is adjusting the pressure.”

But pressure, which the archer fish apply by squeezing their gill covers together, is not the secret to their ballistic precision.

Prof Schuster and his PhD student Peggy Gerullis found no evidence for pressure adjustments, nor for chemical additives or flicking movements in the water, which might account for the fishes’ ability to control the stability of the water jet, and focus the accelerating blob at its tip.

“The fish add nothing – they only shoot water, and they keep absolutely still during release of the jet,” Prof Schuster said.

“They just do it with the mouth opening diameter. It is not a simple manoeuvre… The diameter is continuously changing.”

That makes the new study, published in Current Biology, the first evidence of an animal actively manipulating the dynamics of a water jet.

Prof Schuster and Ms Gerullis trained two archer fish to hit targets at distances from 20cm to 60cm, under bright lights to help with filming.

The targets were small spheres, which allowed the team to calculate the forces involved.

Accuracy, of course, was rewarded – usually with a small fly. “You can easily train a fish to shoot at anything you want,” said Prof Schuster. “They are perfectly happy as long as something edible falls down.”

The tricky part was organising the angles.

“To be ready to monitor to the right spots with reasonable spatial resolution, you have to convince the fish somehow to fire from a defined position. That was the hardest part of the study, actually.”

With patience, the researchers collected enough measurements to reveal that the all-important blob of water at the jet’s tip, which allows archer fish to dislodge their prey, forms just before impact – no matter the target distance.

To accomplish this, the animals fine-tune not just the speed, but the stability of the water jet.

“It means that the physics the fish is using is much more complicated than previously thought,” Prof Schuster explained.

Cognitive evolution?

Dynamic jet control must now be added to an already impressive list of this fish’s abilities.

Other research has explored questions ranging from how archer fish compensate for the distortion of their vision by the water surface, to how they learn to hit moving targets by copying their companions, to exactly how they produce a water jet that catches up on itself to form their distinctive, watery missile.

Prof Schuster believes that their spitting accuracy may have evolved in a similar way to human throwing, which some theorists argue sparked an accompanying expansion of our cognitive abilities.

His team has also done fieldwork in Thailand, where they observed that the fish hunt in daylight, when their insect targets are few and far between. So having a good range, and not missing, are a big advantage for survival.

That power and precision requires brain power.

“People have calculated that to double [throwing] range requires roughly an 8-fold increase in the number of neurons involved in throwing,” Prof Schuster said.

So are these fish evolving into the cleverest animals under water?

“I don’t think they will develop into humans. [But] they have many strange abilities that you wouldn’t expect from fish.

“Maybe we can show by looking more closely at the brain, that shooting might have played a similar, prominent role in driving these abilities, as it’s thought that throwing played in human evolution.

“That’s just a crazy idea of mine.”

http://www.bbc.com/news/science-environment-29046018

Thank to Kebmodee for bringing this to the attention of the It’s Interesting community.

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Scientists investigating the silence of the crickets in Hawaii have uncovered a bizarre evolutionary story that is part horror movie, part Cyrano de Bergerac.

In the most recent edition of the journal Current Biology, researchers from Scotland’s University of St. Andrews report on the separate but nearly simultaneous quieting of chirping crickets on Kauai and Oahu.

As lead researcher Nathan Bailey explained, Hawaii crickets appear to have abandoned their chirplike mating songs to avoid parasitoid flies. The flies, which are attracted to male cricket song, would lay larvae that would then burrow into the host crickets, killing them within a week.

Adaptive crickets survived and reproduced by silencing their own songs but positioning themselves — like Christian to Cyrano — next to crickets who continued to use their chirps to woo female crickets.

The silent flatwing crickets are present on both Oahu and Kauai. At first, Bailey and his team believed that a single population of silent crickets evolved on one island and spread to the other. However, further investigation made it clear that the crickets came from separate populations but adopted the same trait around the same time.

“This is an exciting opportunity to detect genomic evolution in real time in a wild system, which has usually been quite an challenge owing to the long timescales over which evolution acts,” Bailey said in a release. “With the crickets, we can act as relatively unobtrusive observers while the drama unfolds in the wild.”

http://www.staradvertiser.com/news/breaking/20140531_Evolution_silences_some_isle_cricket_populations.html?mobile=true

Thanks to Da Brayn for bringing this to the attention of the It’s Interesting community.

In desolate caves throughout Brazil live insects that copulate for days, the female’s penetrating erectile organ sticking fast in a reluctant male’s genital chamber until he offers a gift of nutritious semen. Neotrogla seems to be unique among species with reversed sex roles — with choosy males and aggressive, promiscuous females — in also having swapped anatomy, researchers report.

Not all animal species have a male penis, but because the evolution of body parts usually works through slow modification of existing structures, there would need to be a good reason for a female to develop a penetrating organ, says entomologist Kazunori Yoshizawa of Hokkaido University in Japan, a co-author of the study.

Yoshizawa and his colleagues think that they have found that reason in Neotrogla, which was first described in 2012. The insects were originally spotted in Brazilian caves by ecologist Rodrigo Ferreira from the Federal University of Lavras in Brazil. Entomologist Charles Lienhard at the Geneva Museum of Natural History in Switzerland recognized them as a new genus — and also as possessing unusual genitalia. The team’s work describing the reproductive practices of four separate species of Neotrogla is published today in Current Biology.

When the flea-sized winged insects mate, the female mounts the male and penetrates deep into a thin genital opening in his back. Membranes in her organ swell to lock her in, and multiple spiky spines act as grappling hooks to anchor her tightly to the male. (When researchers tried to pull apart two mating insects, the female was gripping so tightly that the male was accidentally ripped in half, leaving his genitalia still attached to the female.) The tip of the female’s penis fits neatly into the male’s genitalia to allow her to receive a large, teardrop-shaped sperm capsule over their 40–70 hours of copulation.

The key to the anatomy and role reversal might be simple hunger. Neotrogla species live in extremely dry caves, says Ferreira, where there is not much in the way of food, save for bat guano and the occasional dead bat. A female needs enough nourishment to make eggs and reproduce, though, so she likely found another source of nutrition, Yoshizawa says: her mate’s semen capsule. In some other insects, males expend personal resources to create highly sought-after ‘nuptial gifts’ of sperm and nutrients that they bestow upon their mate during copulation. Although it’s not clear whether Neotrogla couples do likewise, the females accept seminal gifts and drain them even when they’re too young to reproduce, Yoshizawa says, so it’s obvious they’re using the sperm capsules for more than mere reproduction.

If Neotrogla males need to spend valuable resources producing their sperm packets, it’s likely they would be choosy about their mates, Yoshizawa says, which would help explain why the females have evolved a penis well designed to hold down reluctant mates long enough to wring out all their gifts. This might be a combination unique to Neotrogla, he says: Although other animals have swapped sex roles where the female is the promiscuous aggressor (the scorpion fly, for example), and others have swapped anatomy where the female penetrates the male (seahorses, for example), none appears to have developed both reversed sex roles and a female penis with grappling hooks.

The authors make a “convincing case” that this female penis is associated with sex-role reversal where males are choosy, as would be expected under sexual-selection theory, says William Eberhard, an evolutionary biologist at the University of Costa Rica in San Pedro.

If Neotrogla can be observed in captivity, they might be good models for studying how and why male and female roles and anatomy can get switched around during copulation, he adds.

Yoshizawa and his colleagues are now working to establish a healthy population in the lab, but the biggest challenge will be finding a suitable food to replace the cave-bat droppings, Yoshizawa says. Flour, yeast and skimmed milk are all under consideration. to replace the cave-bat droppings.

http://www.nature.com/news/female-insect-uses-spiky-penis-to-take-charge-1.15064

Thanks to Dr. Lutter for bringing this to the attention of the It’s Interesting community.

elephant

The next time you need to show an elephant where something is, just point. Chances are he’ll understand what you mean.

New research shows elephants spontaneously understand the communicative intent of human pointing and can use it as a cue to find food.

Richard Byrne and Anna Smet of the University of St. Andrews tested 11 African elephants on what’s known as the object-choice task. In this task, a food reward is hidden in one of several containers and the experimenter signals which one by pointing to it.

People understand pointing, even as young children. But the track record of other animals on the object-choice task is mixed. Domesticated animals, such as dogs, cats, and horses, tend to perform better than wild ones. Even our closest relative, the chimpanzee, typically struggles to understand pointing when it’s used by human caretakers.

What’s so remarkable about the elephants’ success on the object-choice task is that they did it spontaneously. Byrne says that in studies of other species, the animals have had the opportunity to learn the task. This is usually during the experiment itself, which consists of a prolonged series of tests over which the animals come to realize they will get rewarded with food if they follow the line of the human’s pointing.

But the elephants performed as well on the first trial as on later tests and showed no signs of learning over the course of the experiments. The elephants Byrne and Smet tested are used to take tourists on elephant-back rides in southern Africa. They were trained to follow vocal commands only, never gestures. Smet recorded the behavior of the elephants’ handlers over several months and found they never pointed their arms for the elephants. What’s more, the elephants’ ability to understand human pointing did not vary with how long they had lived with people, nor with whether they were captive-born or wild-born. “If they have learned to follow pointing from their past experiences, it’s mystery when and how,” Byrne says. “Rather, it seems they do it naturally.”

In the experiment, Byrne and Smet varied several parameters that often affect children’s and animals’ performance on the task: whether the pointing arm was nearest the correct choice or not; whether the pointer’s arm crossed the body or was always on the side of what was pointed at; and whether the arm broke the silhouette from the elephant’s viewpoint or not. None of these made any difference. Even when the experimenter stood closer to the wrong location than the correct location, the elephants performed a little worse but still mostly responded to where her arm was pointing.

The only condition that truly stymied the elephants was when the experimenter simply looked at the correct location without pointing. Byrne says that elephant eyesight is poor compared to our own, and researchers who work with elephants have commented on how bad they are at identifying things by sight. “It would perhaps have been surprising if they had spontaneously responded to the rather subtle movements of a small primate’s head!” Byrne says.

Elephants are only distantly related to humans, which means that the ability to understand pointing likely evolved separately in both species, and not in a shared ancestor. But why would elephants attend to and understand pointing? One thing elephants do share with humans is that they live in a complex and extensive social network in which cooperation and communication with others play a critical role. Byrne and Smet speculate that pointing relates to something elephants do naturally in their society. “The most likely possibility is that they regularly interpret trunk gestures as pointing to places in space,” Byrne says. Elephants do make many prominent trunk gestures, and Byrne and Smet are currently trying to determine if those motions act as “points” in elephant society.

Reference:
Smet, Anna F. and Byrne, Richard W. (2013). African Elephants Can Use Human Pointing Cues to Find Hidden Food. Current Biology http://dx.doi.org/10.1016/j.cub.2013.08.037

http://www.wired.com/wiredscience/2013/10/elephants-get-the-point/

Thanks to Kebmodee for bringing this to the attention of the It’s Interesting community.

Duck_chicken_penisRooster

Researchers have now unraveled the genetics behind why most male birds don’t have penises, just published in Current Biology.
[Ana Herrera et al, Developmental Basis of Phallus Reduction During Bird Evolution]

There are almost 10,000 species of birds and only around 3 percent of them have a penis. These include ducks, geese and swans, and large flightless birds like ostriches and emus. In fact, some ducks have helical penises that are longer than their entire bodies. But eagles, flamingos, penguins and albatrosses have completely lost their penises. So have wrens, gulls, cranes, owls, pigeons, hummingbirds and woodpeckers. Chickens still have penises, but barely—they’re tiny nubs that are no good for penetrating anything.

In all of these species, males still fertilise a female’s eggs by sending sperm into her body, but without any penetration. Instead, males and females just mush their genital openings together and he transfers sperm into her in a maneuver called the cloacal kiss.

To get to the root of this puzzle, researchers compared the embryos of chickens and ducks. Both types of birds start to develop a penis. But in chickens, the genital tubercle shrinks before the little guys hatch. And it’s because of a gene called Bmp4.

“There are lots of examples of animal groups that evolved penises, but I can think of only a bare handful that subsequently lost them,” says Diane Kelly from the University of Massachusetts in Amherst. “Ornithologists have tied themselves in knots trying to explain why an organ that gives males an obvious selective advantage in so many different animal species disappeared in most birds. But it’s hard to address a question on why something happens when you don’t know much about how it happens.”

That’s where Martin Cohn came in. He wanted to know the how. His team at the University of Florida studies how limbs and genitals develop across the animal kingdom, from the loss of legs in pythons to genital deformities in humans. “In a lab that thinks about genital development, one takes notice when a species that reproduces by internal fertilization lacks a penis,” says graduate student Ana Herrera.

By comparing the embryos of a Pekin duck and a domestic chicken, Herrera and other team members showed that their genitals start developing in the same way. A couple of small swellings fuse together into a stub called the genital tubercle, which gradually gets bigger over the first week or so. (The same process produces a mammal’s penis.)

In ducks, the genital tubercle keeps on growing into a long coiled penis, but in the chicken, it stops around day 9, while it’s still small. Why? Cohn expected to find that chickens are missing some critical molecule. Instead, his team found that all the right penis-growing genes are switched on in the chicken’s tubercle, and its cells are certainly capable of growing.

It never develops a full-blown penis because, at a certain point, its cells start committing mass suicide. This type of ‘programmed cell death’ occurs throughout the living world and helps to carve away unwanted body parts—for example, our hands have fingers because the cells between them die when we’re embryos. For the chicken, it means no penis. “It was surprising to learn that outgrowth fails not due to absence of a critical growth factor, but due to presence of a cell death factor,” says Cohn.

His team confirmed this pattern in other species, including an alligator (crocodilians are the closest living relatives of birds). In the greylag goose, emu and alligator, the tubercle continues growing into a penis, with very little cell death. In the quail, a member of the same order as chickens, the tubercle’s cells also experience a wave of death before the organ can get big.

This wave is driven by a protein called Bmp4, which is produced along the entire length of the chicken’s tubercle, but over much less of the duck’s. When Cohn’s team soaked up this protein, the tubercle’s cells stopped dying and carried on growing. So, it’s entirely possible for a chicken to grow a penis; it’s just that Bmp4 stops this from happening. Conversely, adding extra Bmp protein to a duck tubercle could stop it from growing into its full spiralling glory, forever fixing it as a chicken-esque stub.

Bmp proteins help to control the shape and size of many body parts. They’re behind the loss of wings in soldier ants and teeth of birds. Meanwhile, bats blocked these proteins to expand the membranes between their fingers and evolve wings.

They also affect the genitals of many animals. In ducks and geese, they create the urethra, a groove in the penis that sperm travels down (“If you think about it, that’s like having your urethra melt your penis,” says Kelly.) In mice, getting rid of the proteins that keep Bmp in check leads to tiny penises. Conversely, getting rid of the Bmp proteins leads to a grossly enlarged (and almost tumour-like) penis.

Penises have been lost several times in the evolution of birds. Cohn’s team have only compared two groups—the penis-less galliforms (chickens, quails and pheasants) and the penis-equipped anseriforms (swans, ducks and geese). What about the oldest group of birds—the ratites, like ostriches or emus? All of them have penises except for the kiwis, which lost theirs. And what about the largest bird group, the neoaves, which includes the vast majority of bird species? All of them are penis-less.

Maybe, all of these groups lost their penis in different ways. To find out, Herrera is now looking at how genitals develop in the neoaves. Other teams will no doubt follow suit. “The study will now allow us to more deeply explore other instances of penis loss and reduction in birds, to see whether there is more than one way to lose a penis,” says Patricia Brennan from the University of Massachussetts in Amherst.

And in at least one case, what was lost might have been regained. The cracids—an group of obscure South American galliforms—have penises unlike their chicken relatives. It might have been easy for them to re-evolve these body parts, since the galliforms still have all the genetic machinery for making a penis.

We now know how chickens lost their penises, but we don’t know why a male animal that needs to put sperm inside a female would lose the organ that makes this possible. Cohn’s study hints at one possibility—it could just be a side effect of other bodily changes. Bmp4 and other related proteins are involved in the evolution of many bird body parts, including the transition from scales to feathers, the loss of teeth, and variations in beak size. Perhaps one of these transformations changed the way Bmp4 is used in the genitals and led to shrinking penises.

There are many other possible explanations. Maybe a penis-less bird finds it easier to fly, runs a smaller risk of passing on sexually-transmitted infections, or is better at avoiding predators because he mates more quickly. Females might even be responsible. Male ducks often force themselves upon their females but birds without an obvious phallus can’t do that. They need the female’s cooperation in order to mate. So perhaps females started preferring males with smaller penises, so that they could exert more choice over whom fathered their chicks. Combinations of these explanations may be right, and different answers may apply to different groups.

Thanks to Dr. Lutter for bringing this to the It’s Interesting community.

http://www.oddly-even.com/2013/06/06/how-chickens-lost-their-penises-and-ducks-kept-theirs_/

http://news.yahoo.com/why-did-chicken-lose-penis-165408163.html

sn-math

by Emily Underwood
ScienceNOW

If you are one of the 20% of healthy adults who struggle with basic arithmetic, simple tasks like splitting the dinner bill can be excruciating. Now, a new study suggests that a gentle, painless electrical current applied to the brain can boost math performance for up to 6 months. Researchers don’t fully understand how it works, however, and there could be side effects.

The idea of using electrical current to alter brain activity is nothing new—electroshock therapy, which induces seizures for therapeutic effect, is probably the best known and most dramatic example. In recent years, however, a slew of studies has shown that much milder electrical stimulation applied to targeted regions of the brain can dramatically accelerate learning in a wide range of tasks, from marksmanship to speech rehabilitation after stroke.

In 2010, cognitive neuroscientist Roi Cohen Kadosh of the University of Oxford in the United Kingdom showed that, when combined with training, electrical brain stimulation can make people better at very basic numerical tasks, such as judging which of two quantities is larger. However, it wasn’t clear how those basic numerical skills would translate to real-world math ability.

To answer that question, Cohen Kadosh recruited 25 volunteers to practice math while receiving either real or “sham” brain stimulation. Two sponge-covered electrodes, fixed to either side of the forehead with a stretchy athletic band, targeted an area of the prefrontal cortex considered key to arithmetic processing, says Jacqueline Thompson, a Ph.D. student in Cohen Kadosh’s lab and a co-author on the study. The electrical current slowly ramped up to about 1 milliamp—a tiny fraction of the voltage of an AA battery—then randomly fluctuated between high and low values. For the sham group, the researchers simulated the initial sensation of the increase by releasing a small amount of current, then turned it off.

For roughly 20 minutes per day over 5 days, the participants memorized arbitrary mathematical “facts,” such as 4#10 = 23, then performed a more sophisticated task requiring multiple steps of arithmetic, also based on memorized symbols. A squiggle, for example, might mean “add 2,” or “subtract 1.” This is the first time that brain stimulation has been applied to improving such complex math skills, says neuroethicist Peter Reiner of the University of British Columbia, Vancouver, in Canada, who wasn’t involved in the research.

The researchers also used a brain imaging technique called near-infrared spectroscopy to measure how efficiently the participants’ brains were working as they performed the tasks.

Although the two groups performed at the same level on the first day, over the next 4 days people receiving brain stimulation along with training learned to do the tasks two to five times faster than people receiving a sham treatment, the authors reported in Current Biology. Six months later, the researchers called the participants back and found that people who had received brain stimulation were still roughly 30% faster at the same types of mathematical challenges. The targeted brain region also showed more efficient activity, Thompson says.

The fact that only participants who received electrical stimulation and practiced math showed lasting physiological changes in their brains suggests that experience is required to seal in the effects of stimulation, says Michael Weisend, a neuroscientist at the Mind Research Network in Albuquerque, New Mexico, who wasn’t involved with the study. That’s valuable information for people who hope to get benefits from stimulation alone, he says. “It’s not going to be a magic bullet.”

Although it’s not clear how the technique works, Thompson says, one hypothesis is that the current helps synchronize neuron firing, enabling the brain to work more efficiently. Scientists also don’t know if negative or unintended effects might result. Although no side effects of brain stimulation have yet been reported, “it’s impossible to say with any certainty” that there aren’t any, Thompson says.

“Math is only one of dozens of skills in which this could be used,” Reiner says, adding that it’s “not unreasonable” to imagine that this and similar stimulation techniques could replace the use of pills for cognitive enhancement.

In the future, the researchers hope to include groups that often struggle with math, such as people with neurodegenerative disorders and a condition called developmental dyscalculia. As long as further testing shows that the technique is safe and effective, children in schools could also receive brain stimulation along with their lessons, Thompson says. But there’s “a long way to go,” before the method is ready for schools, she says. In the meantime, she adds, “We strongly caution you not to try this at home, no matter how tempted you may be to slap a battery on your kid’s head.”

http://news.sciencemag.org/sciencenow/2013/05/trouble-with-math-maybe-you-shou.html?ref=hp

130318132625-large
Of course, roosters crow with the dawn. But are they simply reacting to the environment, or do they really know what time of day it is? Researchers reporting on March 18 in Current Biology, a Cell Press publication, have evidence that puts the clock in “cock-a-doodle-doo”

“‘Cock-a-doodle-doo’ symbolizes the break of dawn in many countries,” says Takashi Yoshimura of Nagoya University. “But it wasn’t clear whether crowing is under the control of a biological clock or is simply a response to external stimuli.”

That’s because other things — a car’s headlights, for instance — will set a rooster off, too, at any time of day. To find out whether the roosters’ crowing is driven by an internal biological clock, Yoshimura and his colleague Tsuyoshi Shimmura placed birds under constant light conditions and turned on recorders to listen and watch.

Under round-the-clock dim lighting, the roosters kept right on crowing each morning just before dawn, proof that the behavior is entrained to a circadian rhythm. The roosters’ reactions to external events also varied over the course of the day.

In other words, predawn crowing and the crowing that roosters do in response to other cues both depend on a circadian clock.

The findings are just the start of the team’s efforts to unravel the roosters’ innate vocalizations, which aren’t learned like songbird songs or human speech, the researchers say.

“We still do not know why a dog says ‘bow-wow’ and a cat says ‘meow,’ Yoshimura says. “We are interested in the mechanism of this genetically controlled behavior and believe that chickens provide an excellent model.”

Tsuyoshi Shimmura, Takashi Yoshimura. Circadian clock determines the timing of rooster crowing. Current Biology, 2013; 23 (6): R231 DOI: 10.1016/j.cub.2013.02.015

http://www.sciencedaily.com/releases/2013/03/130318132625.htm