Reef Fish See Colors That Humans Cannot

Reef Fish See Colors That Humans Cannot

Researchers at The University of Queensland have established that reef fish see colours that humans cannot.

A team from Professor Justin Marshall’s Sensory Neurobiology Lab at the Queensland Brain Instituteran a series of behavioral experiments with trigger fish, in a bid to decode how they see the world.

Professor Marshall said previous studies had looked into how goldfish saw colour, but this was the first study into how reef fish discriminate colours.

“Coral reefs are the most colourful environments in the world, and it’s now become clear that reef fish see colours we can’t,” Professor Marshall said.

“Some reef fish, such as the anemonefish ‘Nemo’ and other damselfish can see the UV wavelengths we protect ourselves from.

“Triggerfish, on the other hand, see more or less the same colour range we do but their colour discriminations are different.

“Thinking about it, this is no big surprise. Their colour tasks are blue-biased, as they live in a blue ocean.

“Ironically, as the colours of the reef change and disappear because of climate change, we are just beginning to understand how reef inhabitants see and experience their vibrant world,” he said.

Professor Marshall said Dr Connor Champ led a series of detailed behavioural tests, where trigger fish were rewarded for discriminating against progressively similar colours.

It emerged that trigger fish see colours in some colour regions in more detail than humans.

“Many people ask me ‘Why study fish?’ and my first answer is: “Because I love them,” Professor Marshall said.

“But this sort of comparative look at animal systems is vitally important to understand not just the beauty of nature and how to look after it, but to consider the possible applications in the human world.”

Comparative colour vision research at QBI is helping in cancer detection, satellite design and data storage on computers.

The research, published in Royal Society Open Science, was funded by the Australian Research Council.

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Fish Can Recognize Human Faces, New Study Shows

Fish Can Recognize Human Faces, New Study Shows

A species of tropical fish has been shown to be able to distinguish between human faces. It is the first time fish have demonstrated this ability.

The research, carried out by a team of scientists from the University of Oxford (UK) and the University of Queensland (Australia), found that archerfish were able to learn and recognize faces with a high degree of accuracy — an impressive feat, given this task requires sophisticated visual recognition capabilities.

The study is published in the journal Scientific Reports.

First author Dr Cait Newport, Marie Curie Research Fellow in the Department of Zoology at Oxford University, said: ‘Being able to distinguish between a large number of human faces is a surprisingly difficult task, mainly due to the fact that all human faces share the same basic features. All faces have two eyes above a nose and mouth, therefore to tell people apart we must be able to identify subtle differences in their features. If you consider the similarities in appearance between some family members, this task can be very difficult indeed.

‘It has been hypothesized that this task is so difficult that it can only be accomplished by primates, which have a large and complex brain. The fact that the human brain has a specialized region used for recognizing human faces suggests that there may be something special about faces themselves. To test this idea, we wanted to determine if another animal with a smaller and simpler brain, and with no evolutionary need to recognize human faces, was still able to do so.’

The researchers found that fish, which lack the sophisticated visual cortex of primates, are nevertheless capable of discriminating one face from up to 44 new faces. The research provides evidence that fish (vertebrates lacking a major part of the brain called the neocortex) have impressive visual discrimination abilities.

In the study, archerfish — a species of tropical fish well known for its ability to spit jets of water to knock down aerial prey — were presented with two images of human faces and trained to choose one of them using their jets. The fish were then presented with the learned face and a series of new faces and were able to correctly choose the face they had initially learned to recognize. They were able to do this task even when more obvious features, such as head shape and colour, were removed from the images.

The fish were highly accurate when selecting the correct face, reaching an average peak performance of 81% in the first experiment (picking the previously learned face from 44 new faces) and 86% in second experiment (in which facial features such as brightness and colour were standardized).

Dr Newport said: ‘Fish have a simpler brain than humans and entirely lack the section of the brain that humans use for recognizing faces. Despite this, many fish demonstrate impressive visual behaviours and therefore make the perfect subjects to test whether simple brains can complete complicated tasks.

‘Archerfish are a species of tropical freshwater fish that spit a jet of water from their mouth to knock down insects in branches above the water. We positioned a computer monitor that showed images of human faces above the aquariums and trained them to spit at a particular face. Once the fish had learned to recognize a face, we then showed them the same face, as well as a series of new ones.

‘In all cases, the fish continued to spit at the face they had been trained to recognize, proving that they were capable of telling the two apart. Even when we did this with faces that were potentially more difficult because they were in black and white and the head shape was standardized, the fish were still capable of finding the face they were trained to recognize.

‘The fact that archerfish can learn this task suggests that complicated brains are not necessarily needed to recognize human faces. Humans may have special facial recognition brain structures so that they can process a large number of faces very quickly or under a wide range of viewing conditions.’

Human facial recognition has previously been demonstrated in birds. However, unlike fish, they are now known to possess neocortex-like structures. Additionally, fish are unlikely to have evolved the ability to distinguish between human faces.

Radiant Zinc Fireworks Reveal Quality of Human Egg

Radiant Zinc Fireworks Reveal Quality of Human Egg

CHICAGO — A stunning explosion of zinc fireworks occurs when a human egg is activated by a sperm enzyme, and the size of these “sparks” is a direct measure of the quality of the egg and its ability to develop into an embryo, according to new research from Northwestern Medicine.

The discovery has potential to help doctors choose the best eggs to transfer during in vitro fertilization (IVF), the scientists said.

This is the first time the zinc sparks have been documented in a human egg.

“This means if you can look at the zinc spark at the time of fertilization, you will know immediately which eggs are the good ones to transfer in in vitro fertilization (IVF),” said Teresa Woodruff, one of the study’s two senior authors and an expert in ovarian biology at Northwestern. “It’s a way of sorting egg quality in a way we’ve never been able to assess before.”

Woodruff is the Thomas J. Watkins Memorial Professor in Obstetrics and Gynecology at Northwestern University Feinberg School of Medicine and director of Northwestern’s Center for Reproductive Science.

Scientists activated the egg by injecting a sperm enzyme into the egg that triggers calcium to increase within the egg and zinc to be released from the egg. (The eggs in the study were not fertilized with actual sperm because that is not permitted in human research under federal law.)

“It was remarkable,” Woodruff said. “We discovered the zinc spark just five years ago in the mouse, and to see the zinc radiate out in a burst from each human egg was breathtaking.

“All of biology starts at the time of fertilization, yet we know next to nothing about the events that occur in the human. This discovery required a unique partnership between biologists and chemists and non-federal dollars to support the research,” she said.

The study was published April 26 in Scientific Reports.

As the zinc is released from the egg, it binds to small molecule probes, which emit light in fluorescence microscopy experiments. Thus the rapid zinc release can be followed as a flash of light that appears as a spark.

“These fluorescence microscopy studies establish that the zinc spark occurs in human egg biology, and that can be observed outside of the cell,” said Tom O’Halloran, a co-senior author.  O’Halloran is the Charles E. and Emma H. Morrison Professor in Chemistry in the Weinberg College of Arts and Sciences and director of Northwestern’s Chemistry of Life Processes Institute.

Eggs compartmentalize and distribute zinc to control the development of a healthy embryo. Over the last six years this team has shown that zinc controls the decision to grow and change into a completely new genetic organism.

“This is an important discovery because it may give us a non-invasive and easily visible way to assess the health of an egg and eventually an embryo before implantation,” said co-author Dr. Eve Feinberg, who took care of the patients who provided eggs for the basic science study and collaborated with the research team.

Feinberg will become an assistant professor of obstetrics and gynecology at Feinberg and will be ambulatory medical director of Northwestern Medicine’s Fertility and Reproductive Medicine division beginning July 1. Feinberg currently is a physician at Fertility Centers of Illinois (FCI).

“There are no tools currently available that tell us if it’s a good quality egg,” Feinberg said. “Often we don’t know whether the egg or embryo is truly viable until we see if a pregnancy ensues. That’s the reason this is so transformative. If we have the ability up front to see what is a good egg and what’s not, it will help us know which embryo to transfer, avoid a lot of heartache and achieve pregnancy much more quickly.”

First author Francesca Duncan made the human zinc spark discovery. “We now know that the release of zinc at the time of fertilization is a conserved phenomenon, which will help us address one of the largest unanswered questions in reproductive medicine — what makes a good egg?” Duncan said.

Duncan was an assistant research professor in obstetrics and gynecology at Feinberg when she made the discovery and will become the executive director of Northwestern’s Center for Reproductive Science on August 1. She is currently an assistant professor at the University of Kansas Medical Center. Emily Que and Nan Zhang are co-first authors.

In a companion paper published in Scientific Reports on March 18, a zinc spark is shown at the precise time a sperm enters a mouse egg. This discovery was made by Zhang, a postdoctoral fellow at Northwestern. Zhang said little is known about the events that occur at the time of fertilization, because it is difficult to capture the precise time of sperm entry.

The paper is titled “The Zinc Spark is an Inorganic Signature of Human Egg Activation.”

The research was supported by the Thomas J. Watkins Endowment and a research grant from Ferring Pharmaceuticals and the W.M. Keck Foundation. All human egg activation studies were done exclusively with samples from FCI and funds from Ferring Pharmaceuticals.

Despite Their Small Brains—Ravens Are Just As Clever As Chimps

Despite Their Small Brains—Ravens Are Just As Clever As Chimps

A study led by researchers at Lund University in Sweden suggests that ravens can be as clever as chimpanzees, despite having much smaller brains, indicating that rather than the size of the brain, the neuronal density and the structure of the birds’ brains play an important role in terms of their intelligence.

“Absolute brain size is not the whole story. We found that corvid birds performed as well as great apes, despite having much smaller brains,” says Can Kabadayi, doctoral student in Cognitive Science.

Intelligence is difficult to test, but one aspect of being clever is inhibitory control, and the ability to override animal impulses and choose a more rational behaviour. Researchers at Duke University, USA, conducted a large-scale study in 2014, where they compared the inhibitory control of 36 different animal species, mainly primates and apes. The team used the established cylinder test, where food is placed in a transparent tube with openings on both sides. The challenge for the animal is to retrieve the food using the side openings, instead of trying to reach for it directly. To succeed, the animal has to show constraint and choose a more efficient strategy for obtaining the food.

The large-scale study concluded that great apes performed the best, and that absolute brain size appeared to be key when it comes to intelligence. However, they didn’t conduct the cylinder test on corvid birds.

Can Kabadayi, together with researchers from the University of Oxford, UK and the Max Planck Institute for Ornithology in Germany, therefore had ravens, jackdaws and New Caledonian crows perform the same cylinder test to better understand their inhibitory control.

The team first trained the birds to obtain a treat in an opaque tube with a hole at each end. Then they repeated the test with a transparent tube. The animal impulse would naturally be to go straight for the tube as they saw the food. However, all of the ravens chose to enter the tube from the ends in every try. The performance of the jackdaws and the crows came very close to 100%, comparable to a performance by bonobos and gorillas.

“This shows that bird brains are quite efficient, despite having a smaller absolute brain size. As indicated by the study, there might be other factors apart from absolute brain size that are important for intelligence, such as neuronal density,” says Can Kabadayi, and continues:

“There is still so much we need to understand and learn about the relationship between intelligence and brain size, as well as the structure of a bird’s brain, but this study clearly shows that bird brains are not simply birdbrains after all!”

Fossil Teeth Suggest That Seeds Saved Bird Ancestors From Extinction

Fossil Teeth Suggest That Seeds Saved Bird Ancestors From Extinction

When the dinosaurs became extinct, plenty of small bird-like dinosaurs disappeared along with giants like Tyrannosaurus and Triceratops. Why only some of them survived to become modern-day birds remains a mystery. Now, researchers reporting April 21 in Current Biology suggest that abrupt ecological changes following a meteor impact may have been more detrimental to carnivorous bird-like dinosaurs, and early modern birds with toothless beaks were able to survive on seeds when other food sources declined.

“The small bird-like dinosaurs in the Cretaceous, the maniraptoran dinosaurs, are not a well-understood group,” says first author Derek Larson, a paleontologist at the Philip J. Currie Dinosaur Museum in Alberta and PhD candidate at the University of Toronto. “They’re some of the closest relatives to modern birds, and at the end of the Cretaceous, many went extinct, including the toothed birds–but modern crown-group birds managed to survive the extinction. The question is, why did that difference occur when these groups were so similar?”

The team of researchers, which also included David Evans of the Royal Ontario Museum and the University of Toronto and Caleb Brown of the Royal Tyrrell Museum of Paleontology, began by investigating whether the extinction at the end of the Cretaceous was an abrupt event or a progressive decline simply capped off by the meteor impact. The fossil record holds evidence to support both scenarios, depending on which dinosaurs are being examined.

Delving into the bird-like dinosaurs, Larson collected data describing 3,104 fossilized teeth from four different maniraptoran families. Some were already published, but much of the information came from Larson’s own work at the microscope, cataloging the shape and size of each tooth.

Larson and his colleagues were looking for patterns of diversity in the teeth, which spanned 18 million years (up until the end of the Cretaceous). If the variation between teeth decreased over time, the team reasoned, this loss of diversity would indicate that the ecosystem was declining and may have paralleled a long-term species loss. If the teeth maintained their differences over time, however, that would indicate a rich and stable ecosystem over millions of years and suggest that these bird-like dinosaurs were abruptly killed off by an event at the end of the Cretaceous.

In the end, the tooth data favored the latter interpretation. “The maniraptoran dinosaurs maintained a very steady level of variation through the last 18 million years of the Cretaceous,” says Larson. “They abruptly became extinct just at the boundary.”

The team suspected that diet might have played a part in the survival of the lineage that produced today’s birds, and they used dietary information and previously published group relationships from modern-day birds to infer what their ancestors might have eaten. Working backwards, Larson and his colleagues hypothesized that the last common ancestor of today’s birds was a toothless seed eater with a beak.

Coupled with the tooth data indicating an abrupt Cretaceous extinction, the researchers suggest that a number of the lineages giving rise to today’s birds were those able to survive on seeds after the meteor impact. The strike would have affected sun-dependent leaf and fruit production in plants, but hardy seeds could have been a food source until other options became available again.

“There were bird-like dinosaurs with teeth up until the end of the Cretaceous, where they all died off very abruptly,” says Larson. “Some groups of beaked birds may have been able to survive the extinction event because they were able to eat seeds.”

Dinosaurs ‘Already in Decline’ Before Asteroid Apocalypse

Dinosaurs ‘Already in Decline’ Before Asteroid Apocalypse

The findings provide a revolution in the understanding of dinosaur evolution. Palaeontologists previously thought that dinosaurs were flourishing right up until they were wiped out by a massive meteorite impact 66 million years ago. By using a sophisticated statistical analysis in conjunction with information from the fossil record, researchers at the Universities of Reading and Bristol showed that dinosaur species were going extinct at a faster pace than new ones were emerging from 50 million years before the meteorite hit.

The analyses demonstrate that while the decline in species numbers over time was effectively ubiquitous among all dinosaur groups, their patterns of species loss were different. For instance, the long-necked giant sauropod dinosaurs were in the fastest decline, whereas theropods, the group of dinosaurs that include the iconic Tyrannosaurus rex, were in a more gradual decline.

Dr Manabu Sakamoto, University of Reading, the palaeontologist who led the research, said: “We were not expecting this result. While the asteroid impact is still the prime candidate for the dinosaurs’ final disappearance, it is clear that they were already past their prime in an evolutionary sense.”

“Our work is ground-breaking in that, once again, it will change our understanding of the fate of these mighty creatures. While a sudden apocalypse may have been the final nail in the coffin, something else had already been preventing dinosaurs from evolving new species as fast as old species were dying out.

“This suggests that for tens of millions of years before their ultimate demise, dinosaurs were beginning to lose their edge as the dominant species on Earth.”

Professor Mike Benton of the University of Bristol, one of the co-authors of the research, said: “All the evidence shows that the dinosaurs, which had already been around, dominating terrestrial ecosystems for 150 million years, somehow lost the ability to speciate fast enough. This was likely to have contributed to their inability to recover from the environmental crisis caused by the impact.”

It is thought that a giant asteroid’s impact with Earth 66 million years ago threw up millions of tonnes of dust, blacking out the sun, causing short-term global cooling and widespread loss of vegetation. This ecological disaster meant that large animals reliant on the abundance of plants died out, along with the predators that fed on them.

The new research suggests that other factors, such as the break-up of continental land masses, sustained volcanic activity and other ecological factors, may possibly have influenced the gradual decline of dinosaurs.

This observed decline in dinosaurs would have had implications for other groups of species. Dr Chris Venditti, an evolutionary biologist from the University of Reading and co-author of paper said: “The decline of the dinosaurs would have left plenty of room for mammals, the group of species which humans are a member of, to flourish before the impact, priming them to replace dinosaurs as the dominant animals on earth.”

Dr Sakamoto points out that the study might provide insight into future biodiversity loss. He said: “Our study strongly indicates that if a group of animals is experiencing a fast pace of extinction more so than they can replace, then they are prone to annihilation once a major catastrophe occurs. This has huge implications for our current and future biodiversity, given the unprecedented speed at which species are going extinct owing to the ongoing human-caused climate change.”

The new study is published in the journal Proceedings of the National Academy of Sciences and the work was funded by the Leverhulme Trust and The Natural Environment Research Council (NERC).

Turn Mortal Enemies into Allies? Ants Can

Turn Mortal Enemies into Allies? Ants Can

On an African plateau surrounded by flat-topped trees as far as the eye could see, wind whistled through the acacia thorns like someone blowing across a bottle. Kathleen Rudolph was more concerned with the ants raining down on her from the trees. The hat, long sleeves and garden gloves the University of Florida researcher wore for protection didn’t help.

The acacia ants she studies, Crematogaster mimosae, use their fearsome bite to defend their host trees against large animals such as elephants and giraffes that eat the trees’ leaves. Even elephants’ thick skin can’t protect them from the ants, which bite them inside their trunks.

“They really seem to have a knack for finding your soft tissue,” Rudolph said. “It’s a nasty business.”

Ants are also aggressive toward each other, fighting to the death over their tree territories. While the consequences for losing colonies are stark — loss of territory or colony death — Rudolph and UF postdoctoral research associate Jay McEntee wanted to understand the costs to the winners.

After a fight, victorious colonies have to defend their newly gained territory with a workforce heavily depleted by fighting. In a new study funded in part by a National Geographic Society/Waitt Fund Grant and published in Behavioral Ecology, Rudolph and McEntee found that victorious colonies might offset this challenge by recruiting members of the losing colonies to help.

In experiments based at Mpala Research Centre in Kenya, researchers instigated ant wars by tying unrelated colonies’ trees together, counting casualties in tarps placed below. By simulating the browsing of a large mammal, they discovered that victorious colonies are less able to defend their host trees after fights. After analyzing the DNA of nearly 800 ants, they discovered that fighting changes the genetic make-up of victorious colonies.

Long viewed as fortresses of cooperating sisters, where relatives of the queen work for her benefit, Rudolph’s work demonstrates that non-relatives can become part of the colony — and potentially defend its residents and territory.

Researchers were further surprised to find that, in some cases, fatal fights with thousands of casualties do not produce a distinct winner. Instead, colonies cease fighting and fuse together, with the queen of each colony still alive.

“Colonies are battling so aggressively that many individuals die, but then they are able to just stop fighting and form a lasting truce,” Rudolph said. “It’s pretty remarkable.”

How they know to stop fighting remains is a mystery, showing the need for research on recognition systems. One possibility, Rudolph says, is that fighting changes the odors ants use to distinguish nestmates from potential invaders.

“If so, the updated or blended cues shared by prior foes may help end aggressive responses,” Rudolph said.

Sorting out these processes could contribute to our understanding of an intriguing aspect of physical conflict — that animal combatants become more similar biologically through combat. That can be true for humans, too: A 2013 study showed that the skin bacteria communities of competing roller derby teams converge during bouts, not unlike Rudolph’s findings in ants.

“Physical combat not only yields biological winners and losers,” Rudolph said. “It can alter the identity of its combatants.”