TAU NEWS – Biology & Evolution
Analyzing some 15,000 bat vocalizations, TAU researchers identify speakers, objectives and contexts of bat conversations
Bats, like humans, are extremely social mammals. They enjoy an average lifespan of 20-30 years, settle in large colonies, and rely heavily on social interactions for their survival, using vocalizations — or calls — for communication. There is very little known about the purpose and content of these noises.
A new Tel Aviv University study published in Scientific Reports extracts critical information from bat vocalizations to offer a rare, informative look into the world of bat communication. The new research, led by Prof. Yossi Yovel of the Department of Zoology at TAU's Faculty of Life Sciences, delves into the veritable cacophony emitted by bats to identify concrete evidence of a socially sophisticated species that learns communication, rather than being born with a fixed set of communication skills.
"When you enter a bat cave, you hear a lot of 'gibberish,' a cacophony of aggressive bat noise – but is this merely 'shouting' or is there information amid the noise?" said Prof. Yovel. "Previous research presumed that most bat communication was based on screaming and shouting. We wanted to know how much information was actually conveyed — and we wanted to see if we could, in fact, extract that information."
For the purpose of the research, Mor Taub and Yosef Prat, students in Prof. Yovel's lab, recorded the sounds emitted by 22 Egyptian fruit bats in TAU's "bat cave" over the course of 75 days. The authors then assembled a dataset of approximately 15,000 vocalizations, which represented the full vocal repertoire the bats used during the experiment. By analyzing this dataset, the authors found that the vocalizations contained information about the identity of the bat emitting the call and even about the identity of the bat being addressed by the call. Moreover, while most of this species' vocalizations were emitted during aggressive encounters, by analyzing the spectral composition of the calls, the authors were also able to distinguish their specific aggressive context (such as squabbling over food, sleeping spots or other resources).
"Studying how much information is conveyed in animal communication is important if you're interested in the evolution of human language," said Prof. Yovel. "Specifically, one big unknown in the world of animal communication is their grasp on semanticity — i.e., when you hear the word 'apple' you immediately imagine a round, red fruit. We found, in our research, that bat calls contain information about the identities of the caller and the addressee, which implies that there is a recognition factor. We were also able to discern the purpose and the context of the conversation, as well as the possible outcome of the 'discussion.'"
Due to the difficulty of cataloguing animal calls, these vocalizations are often grouped into one category in acoustic studies. According to Prof. Yovel, the new findings suggest that delving into animal calls could serve a bigger purpose, shedding light on the evolution of communication altogether.
"We generated a massive amount of data — dozens of calls over three months," said Prof. Yovel. "We have found that bats fight over sleeping positions, over mating, over food or just for the sake of fighting. To our surprise, we were able to differentiate between all of these contexts in complete darkness, and we are confident bats themselves are able to identify even more information and with greater accuracy — they are, after all, an extremely social species that live with the same neighbors for dozens of years."
The researchers were even able to identify different intonations indicating the greetings of a "friend" or a "foe."
"The last finding allowed us to predict whether the two would stay together or part, whether the interaction would end well or badly," said Prof. Yovel, who is currently researching different bat accents and the assimilation of bats into different social groups.
TAU–Cornell collaboration provides insight into unique community whose history is largely unknown
A new study from Tel Aviv University, Cornell University and the Albert Einstein College of Medicine reveals genetic proof of the Jewish roots of the Bene Israel community in the western part of India. They have always considered themselves Jewish.
"Almost nothing is known about the Bene Israel community before the 18th century, when Cochin Jews and later Christian missionaries first came into contact with it," says first author Yedael Waldman of both TAU's Department of Molecular Microbiology and Cornell's Department of Biological Statistics and Computational Biology. "Beyond vague oral history and speculations, there has been no independent support for Bene Israel claims of Jewish ancestry, claims that have remained shrouded in legend."
"Human genetics now has the potential to not only improve human health but also help us understand human history," says Prof. Eran Halperin of TAU's Department of Molecular Microbiology and Biotechnology and TAU's Blavatnik School of Computer Sciences, who together with Prof. Alon Keinan of Cornell University's Department of Biological Statistics and Computational Biology advised Waldman. The research was published in PLoS One on March 24, 2016.
From folklore to science
According to their oral history, the Bene Israel people descended from 14 Jewish survivors of a shipwreck on India's Konkan shore. The exact timing of this event and the origin and identity of the Jewish visitors are unknown. Some date the event to around 2,000 years ago. Others estimate that it took place in 175 BCE. Still others believe their Jewish ancestors arrived as early as the 8th century BCE.
"In the last few decades, genetic information has become an important source for the study of human history," says Prof. Keinan, the study's senior author. "It has been applied several times to the study of Jewish populations across diasporas, providing evidence of a shared ancestry."
The research team, including members of Prof. Keinan's lab, Prof. Eitan Friedman of TAU's Sackler School of Medicine, and Prof. Gil Azmon and colleagues at Albert Einstein College of Medicine and the University of Haifa, based their study on data from the Jewish HapMap project, an international effort led by Prof. Harry Ostrer of Albert Einstein College of Medicine, to determine the genetic history of worldwide Jewish diasporas. They used sophisticated genetic tools to conduct comprehensive genome-wide analyses on the genetic markers of 18 Bene Israel individuals.
"We found that while Bene Israel individuals genetically resemble local Indian populations, they constitute a clearly separated and unique population in India," Waldman says.
How the community grew
"The results point to Bene Israel being an 'admixed' population, with both Jewish and Indian ancestry. The genetic contribution of each of these ancestral populations is substantial," adds study co-lead author Arjun Biddanda of Cornell.
The results even indicate when the Jewish and Indian ancestors of Bene Israel "admixed": some 19-33 generations (approximately 650-1,050 years) ago.
"We believe that the first encounter involved Middle-Eastern Jews and was followed by a high rate of tribal intermarriage," says Waldman. "This study provides a new example of how genetic analysis can be a valuable and powerful tool to advance our knowledge of human history."
TAU researcher discovers a unique mechanism bats use to overcome communication interference in the wild
Individual bats emit sonar calls in the dark, using the echo of their signature sounds to identify and target potential prey. But because they travel in large groups, their signals often "jam" each other, a problem resembling extreme radar interference. How do bats overcome this "cocktail party" cacophony to feed and survive in the wild?
A new Tel Aviv University study published in Proceedings of the Royal Society B: Biological Sciences identifies the mechanism that allows individual bats to stand out from the crowd. The research, by Dr. Yossi Yovel of TAU's Department of Zoology, finds that individual bats manage to avoid noise overlap by increasing the volume, duration and repetition rate of their signals.
According to Dr. Yovel, unlocking the mystery of bat echo recognition may offer a valuable insight into military and civilian radar systems, which are vulnerable to electronic interference.
Cocktail party chatter
"Imagine you are at a cocktail party where everyone is uttering the same word over and over again, and you are expected to recognize the echo of your own utterance to identify the location of the punch bowl," Dr. Yovel said. "Now imagine that this is tantamount to your survival. This is the bat experience. Bats often fly in groups and rely on sounds — very similar sounds — to find their food. They deal with two challenges: They need to detect weak echoes in a cluster of noise, and if they manage to receive the echo, they need to recognize it as their own."
Dr. Yovel and his team of TAU researchers, including Eran Amichai and Dr. Gaddi Blumrosen, tested bat responses in situations mimicking a high density of bats. They played back bat echolocation calls from multiple speakers to jam the echoes of five flying Pipistrellus kuhlii bats, simulating a naturally occurring situation of many bats flying in proximity. Under severe interference, bats emitted calls of higher intensity and longer duration, and called more often — but they did not change the pitch of their signals, as was previously believed.
The new study builds on previous research conducted by Dr. Yovel in which he developed miniature microphones, attached to bat backs, allowing for the first-ever recording of bat frequencies in real time.
"In a study we conducted last year, we found evidence that bats do not harness any such 'jamming avoidance,' as hypothesized in the past by other scientists," said Dr. Yovel. He believes that they simply recognize their own voices.
"In another paper, published in 2009, we trained bats to crawl toward one side or another, in the direction of another bat," Dr. Yovel explained. "This indicated that they indeed differentiated between the voice of one bat and another. This also proved they could identify their own calls.
"In the current study, we trained bats to fly around a small room and land on a small object – in the midst of a loud mixture of bat signals playing overhead. They found the object by increasing their emissions: crying louder and longer and shouting more frequently. They cried 'ahhhhhhh' instead of 'ah' twice as frequently — every 50 milliseconds instead of the usual 100 milliseconds."
From bats to automobiles
According to Dr. Yovel, this research may provide insight into engineering used for human beings.
"We want to understand the problem," said Dr. Yovel. "The better we understand the radar interference problem, the easier it will be to solve. In the future, we will all have radar systems in our cars, and there can be hundreds of these on a stretch of highway as well. Individuality must be built into these radar codes, very clear signature codes."
Dr. Yovel is currently seeking how individuality is intrinsic to bat codes, which continues to escape scientific research.
Collaboration with Freiburg University reveals regulator that produces moss embryos without cross-fertilization
The reproduction process is essentially the same in humans, animals and most plants. Both female and male organisms are required to contribute to the phenomenon.
A new joint Tel Aviv University–Freiburg University study offers an alternative: the discovery of a genetic trigger for the development of offspring without cross-fertilization — in moss. It identifies and explores the master genetic switch for self-reproduction in the moss Physcomitrella patens. According to the new study, the BELL1 gene triggers a pathway of genes that facilitate embryo development without fertilization to form fully functional adult moss plants.
The research was led jointly by Prof. Nir Ohad, Director of the Manna Center Program for Food Safety and Security at TAU's Faculty of Life Sciences, and Prof. Ralf Reski of the University of Freiburg. It was recently published in Nature Plants.
"The knowledge gained from our research may help to modernize agriculture, allowing us to clone certain important plants and distribute their seeds to farmers," Prof. Ohad said.
A model for self-fertilization
"Moss possesses both egg cells and motile sperm, and as such, serves as a simple model plant to understand self-fertilization processes," said Prof. Ohad. "Our results explain at the molecular level how asexual reproduction — known as parthenogenesis or apomixes — has evolved. In these processes, genetically identical plants are formed."
In reproduction, a network of genes is activated after the fusion of sperm and egg cell. This leads to the development of an embryo, which then grows into a new living being. Until now, it was unclear whether a central genetic switch for this process existed.
The team pinpoints the gene BELL1 as the master regulator for the formation of embryos and their development in moss. "This gene was conserved in evolution," said Prof. Ohad, a specialist in the epigenetic regulation of reproductive development. He helped identify the first BELL genes in seed plants 20 years ago as a member of a team led by Prof. Robert Fischer of UC Berkeley. "Our new findings may have implications for generating genetically identical offspring from high yielding crop plants."
The scientists harnessed genetic engineering to activate the BELL1 gene in moss plants and observed embryos developing spontaneously on a specific cell type. To their surprise, these embryos grew to fully functional moss sporophytes. These spore capsules later formed spores, which grew into new adult moss plants.
From plants to humans?
According to the study, the protein encoded by the BELL1 gene belongs to the class of "homeobox" transcription factors. Similar homeotic genes are also present in humans and animals, where they also control pivotal developmental processes. Whether or not a congener of BELL1 is a master regulator of embryo development in humans remains unclear.
"Our results are important beyond mosses," said Prof. Reski. "First, they can explain how algae developed into land plants and shaped our current ecosystems. Second, they may help to revive the concept of genetic master regulators in the development of plants, animals and humans."
The study was supported by the German-Israeli Foundation, the Freiburg Excellence Cluster BIOSS and the Freiburg Institute for Advanced Studies. The scientists are carrying forward their research to identify the exact genes triggered by BELL1 to facilitate the formation of embryos without fertilization.
AFTAU's "Giving Tuesday" campaign invites you to "Adopt-a-Bat" to support scientific research
Dr. Yossi Yovel, the noted biologist and physicist, has established one of the world's foremost labs for the study of bats in the heart of the Tel Aviv University Research Zoo (TAURZ). "In everything I do, and everything I study, I am trying to understand one thing: How animals make decisions in the real world — not in the lab, not in unnatural conditions, but outside, in nature," said Dr. Yovel, who maintains his own batcave of 60 bats on the TAU campus.
And according to Dr. Yovel, Israel's "Batman," insight into bats provides insight into other mammals, humans included. "We want to understand what bats say to each other, how they navigate over hundreds of kilometers, and what they think," he explained. "This is all part of our attempt to understand where our own behavior comes from, what we share with each other and with other animals, and how all this has changed over time."
Now nature enthusiasts will have a fun way to support this important research with the "Adopt-a-Bat" campaign from American Friends of Tel Aviv University, scheduled to launch on Giving Tuesday, December 1, 2015. Everyone from six to 60 will have the opportunity to "adopt" one of Dr. Yovel's little critters and even offer them for unique holiday "gifts." The Web site at http://www.aftau.org/adopt-a-bat will feature photos, fascinating bat facts, and short "biographies" of the bats, as well as a live feed from Dr. Yovel's own batcave. The campaign will continue through December 31.
How to track a bat
In the course of Dr. Yovel's doctoral research, he realized that all existing research on animal behavior had been conducted exclusively in laboratories due to the challenges of monitoring an animal outdoors over long periods of time and over large distances.
"It's not enough to follow an animal in a controlled environment," said Dr. Yovel. "You have to monitor its behavior in the wild. Is it interacting with other animals? Did it find food?" Seeking answers to these questions, he developed state-of-the-art miniature tracking devices that can be attached to a bat's back to track his/her movement and behavior over hundreds, if not thousands, of miles.
"Over the past four years, my lab has developed miniature devices, the smallest in the world, with GPS, audio, video, acceleration, EEG, and other technologies to measure physical and environmental cues that truly allow us to sense the world from a bat's point of view," said Dr. Yovel.
"Our bats are under our constant surveillance. We have been able to discover what a bat is doing even when it's flying more than 3,000 feet above the ground."
More than 1,200 species of bats account for more than 20 percent of all mammals. These miniature flying mammals are highly sociable and emit special sonar signals to sense their environment. "By recording these sounds in real time, we can tell when they're attacking prey or when they encounter another bat and how they respond to it," said Dr. Yovel. "This allows us to reveal how bats work and thrive in a group, which provides radical new insight into the social world of mammals."
City of bats
Bat colonies, or "bat cities," are inhabited by thousands of bats who live together for up to 40 years.
"The largest non-human mammalian cities on earth are bat cities — colonies of millions of bats, all of whom roost together, interact with each other, communicate vocally, fly together, and search for food together," said Dr. Yovel. "We still don't know much about their social systems. We don't know if they live in pairs or in small groups or in families — all of this is still completely unknown. We really want to understand if they transfer information the way humans do.
"We are constantly improving our technology," Dr. Yovel continued. "We are currently working on a device that will also include a camera that will allow us to see what bats see.
"We are also developing a device with electrodes that can be placed on a bat's head to record its brain activity, even while flying. We are constantly working to improve the devices we already invented, to gain even more insight into the world of bats."
Research finds a close cousin of the jellyfish evolved into a microscopic parasite that lives in fish
Children are taught that all living organisms — from animals, plants, and fungi to bacteria and single-celled organisms — belong to specifically different categories of organic life. A new discovery by Tel Aviv University researchers and international collaborators is poised to redefine the very criteria used to define and classify these animals.
Researchers have found that a close cousin of the jellyfish has evolved over time into a microscopic parasite. The finding represents the first case of extreme evolutionary degeneration of an animal body.
The research was led by Prof. Dorothée Huchon of TAU's Department of Zoology and Prof. Paulyn Cartwright of the University of Kansas, in collaboration with Prof. Arik Diamant of Israel's National Center for Mariculture and Prof. Hervé Philippe of the Centre for Biodiversity Theory and Modelling, CNRS, France. It was published this week in the Proceedings of the National Academy of Scientists.
What makes a myxozoan
The international research used genome sequencing to find that myxozoans, a diverse group of microscopic parasites that infect invertebrate and vertebrate hosts, are actually are highly degenerated cnidarians — the category or phylum that includes jellyfish, corals and sea anemones.
"These micro-jellyfish expand our basic understanding of what makes up an animal," said Prof. Huchon. "What's more, the confirmation that myxozoans are cnidarians demands the re-classification of myxozoa into the phylum cnidaria."
Despite the radical changes in its body structure and genome over millions of years, the myxozoa have retained some of the basic characteristics of the jellyfish, including the essential genes to produce the jellyfish stinger.
"The myxozoa are microscopic — only a few cells measuring 10 to 20 microns across — and therefore biologists assumed that they were single-celled organisms," said Prof. Huchon. "But when we sequenced their DNA, we discovered the genome of an extremely strange macroscopic marine animal."
The discovery of the dramatic change from macroscopic marine animal to microscopic parasite is interesting on its own, but it may also have commercial applications, as myxozoa commonly plague commercial fish stock such as trout and salmon.
"Some myxozoa cause a neurological problem in salmon called 'whirling disease,'" said Prof. Huchon. "These fish parasites cause tremendous damage to the fish industry, and unfortunately there is no general treatment against them. We hope that our data will lead to a better understanding of the biology of these organisms and the development of more effective drugs to fight against myxozoa."
The researchers are currently studying the evolution in myxozoa of genes that form the stinging organ of jellyfish. The study was funded by the National Science Foundation, the Binational Science Foundation, and the Israel Science Foundation.
TAU researcher discovers tropical organisms that expel their digestive tracts and rebuild them in 12 days
The vast range of regenerative powers within the animal kingdom has fascinated scientists since the early 18th century. From hydras to planarians and geckos, the remarkable ability of certain species to regrow parts of their bodies and subsequently regain some or all of their original form and function has presented invaluable opportunities for research on human cell signalling, development, and adaptation.
A recent Tel Aviv University study published in Scientific Reports explores the ability of the tropical ascidian Polycarpa mytiligera, a common coral reef organism, to eviscerate and regenerate its gut within 12 days and rebuild its filtration organ, the branchial sac, within 19 days. Dr. Noa Shenkar and her student Tal Gordon from the Department of Zoology at TAU's Faculty of Life Sciences and the Steinhardt Museum of Natural History and National Research Center observed a recurrent pattern of evisceration, "death," and finally rejuvenation in ascidians from the Gulf of Aqaba.
The organism is a "filter-feeder" that eats by straining suspended matter and food particles from water, usually by passing the water over a specialized filtering structure.
"Polycarpa are the most abundant ascidian species in the Gulf of Aqaba and one of the most abundant in the world," said Dr. Shenkar. "In the process of studying their distribution and depths, we noticed they would throw something at us and then immediately shrink and remain highly contracted and camouflaged. I was sure they had died, but something told me not to discard them.
"Sure enough, four days later, the organisms regained their composition — as if they had been 'reborn,'" Dr. Shenkar said. "This was very unexpected."
The researchers conducted most of their study underwater, marking individual organisms then taking movies of the process. They observed the specimens to discover how the viscera were ejected (i.e., from which end of the organism); whether they survived following evisceration; and if and how they rebuilt their organs. They found that the polycarpa ruptured its branchial sac to eject its digestive tract. Using light mechanical pressure, it contracted, camouflaging itself as "dead." See video footage of the contraction: https://www.youtube.com/watch?v=BkuYoSTRWZQ
"In the underwater observatory, we observed fish — which had not fed for a day — circling, but none of them ate the ejected digestive tract," said Dr. Shenkar. Although the eviscerated guts were unpalatable to preying triggerfish and pufferfish, the researchers' chemical analysis revealed no significant levels of toxic compounds in the expelled organs. It is possible that the digestive tract contains other compounds that are unpalatable to the fish, which are not detected in a regular chemical analysis.
A new direction for soft-tissue regeneration research
The polycarpa's evisceration response provides a unique opportunity to deepen the knowledge and revive the study of evisceration in ascidians. But perhaps more importantly, the study findings establish a solid platform from which to study regeneration of the human digestive tract in its molecular, cellular, and developmental aspects.
"All signs point to evisceration as a defense mechanism, and this alone is interesting," said Dr. Shenkar. "But this is also important and relevant to human research. Ascidians and vertebrates — and humans are vertebrates — share close affinities, so understanding ascidian regeneration pathways can point to promising new directions in human soft tissue regeneration research."
The human body and the ascidian body share many basic biochemical and cellular processes as they are both chordates. Studying Polycarpa as a model organism provides insight into the workings of other organisms, as well as an in-vivo model for research of the human immune system and regeneration.
"This information can surely be used to study different biochemical pathways involved in soft-tissue regeneration," Dr. Shenkar concluded.
TAU research changes the concept of hibernation
Many mammals — and some birds — escape the winter by hibernating for three to nine months. This period of dormancy permits species which would otherwise perish from the cold and scarce food to survive to see another spring. The Middle East, with temperate winters, was until recently considered an unlikely host for hibernating mammals.
New research published in Proceedings of the Royal Society of London by Tel Aviv University researchers is set to not only correct this fallacy but also change the very concept of hibernation. Prof. Noga Kronfeld-Schor, Chair of the Department of Zoology at TAU's Faculty of Life Sciences, and doctoral student Dr. Eran Levin found two species of the mouse-tailed bat (the Rhinopoma microphyllum and the R. Cystops) hibernating at the unusually warm and constant temperature of 68°F in caves in Israel's Great Rift Valley. From October to February, these bats were discovered semi-conscious, breathing only once every 15-30 minutes, with extremely low energy expenditures.
"Hibernation in mammals is known to occur at much lower temperatures, allowing the animal to undergo many physiological changes, including decreased heart rate and body temperature," said Prof. Kronfeld-Schor. "But we have found these bats maintain a high body temperature while lowering energy expenditure levels drastically. We hypothesize that these caves, which feature a constant high temperature during winter, enable these subtropical species to survive on the northernmost edge of their world distribution."
Taking their temperature
The researchers monitored the activity of the bats during this period and found that they neither fed nor drank, even on warm nights when other bat species were active in the same caves. The researchers used heat-sensitive transmitters to measure the bats' skin temperature in the caves. Then in the laboratory, they measured the bats' metabolic rates and evaporative water loss at different ambient temperatures.
The bats' average skin temperature in the caves was found to be about 71.6°F. Both bat species reached their lowest metabolic rates at cave temperatures (about 68°F). During hibernation, the bats also exhibited long periods of suspended exhalation.
"Until recently, it was believed that there was no mammalian hibernation in Israel, apart from hedgehogs," said Prof. Kronfeld-Schor. "But this discovery leads us to believe there may be others we don't know about. Scientists haven't been looking for incidences of hibernation at warm temperatures. This is a new direction for us.
"The second main finding is that hibernating animals don't need to lower their body temperatures in order to lower their energy expenditure. These bats exhibited dramatic metabolic depression at warm body temperatures in the hottest caves in the desert."
The researchers found that the bats, like camels, flare their nostrils to conserve water. A month before hibernating, they also changed their diets from unsaturated to saturated fats, feeding only on queen ants with wings to gain a 50 percent increase in body mass.
The researchers are further exploring the importance of heated caves for the conservation of these species.
TAU study follows the rise of individuals with the greatest influence on collective group behavior
Who takes charge during a disaster or at an accident scene? The question has intrigued sociologists since Gustave Le Bon first studied "herd behavior" in nineteenth-century France. The question of an individual's influence over the activity of a collective has perplexed researchers, in countless studies of this behavior, ever since.
Now a new Tel Aviv University study, published in Behavioral Processes, looks to the animal kingdom to track the rise of group leaders in chaotic situations and pinpoint the traits that set them apart from their followers. The research, led by Prof. David Eilam of the Department of Zoology at TAU's Faculty of Life Sciences and conducted by TAU doctoral students Michal Kleiman and Sivan Bodek, was based on experiments with voles and owls, and its conclusions may reflect on human behavior as well.
"The big controversy remains: Are group behaviors self-organized? Do they emerge spontaneously or under the guidance of a leader?" said Prof. Eilam. "The problem in studying this phenomenon among humans is the ethical consideration. One must limit the research to simulations or to after-the-fact analyses of real situations. On the other hand, collective behavior as a subject is flourishing in animal studies."
An attack from the skies
The researchers sought to establish the differential division of labor in groups by placing several small rodents called voles in a simulated life-threatening situation — an "attack" by predatory barn owls. The owls had no way of physically reaching the rodents, which were always protected by a cage barrier, but their menacing presence sparked pandemonium within the cage. Out of the chaos, the researchers discovered, vole leaders emerged.
"Our study bucks against the notion that leaders arise spontaneously," said Prof. Eilam. "There are always certain individuals who simply contribute more than others — but who they are and what traits make them leaders are the questions we've managed to answer in a limited realm."
The researchers found that, after an owl attack, larger voles calmed more quickly and smaller voles displayed greater anxiety at first, but over time the larger, older male voles assumed leadership and presented an exemplary model for the smaller male voles and female voles. As a consequence of their larger size, experience, and physical strength, the large male voles displayed more consistent behavior to their companions, hardly changing after the owl attack. The smaller male and female voles displayed an extreme range of frightened behavior before the attack, but converged to the mid-range response of the larger males afterwards. The researchers concluded that the larger male voles were less affected by the threat and set an example for the smaller group.
To protect and stabilize
"Less affected by the owl attacks, the experienced, larger male voles set the behavioral code, leading the other voles to imitate their behavior," said Prof. Eilam. "These 'leaders' have a dual role, not just to protect but also to stabilize the behavior of the group. You can also see such leaders emerge in human societies in distress — take post-9/11 New York City, for example, or even among a family in mourning. All differences are set aside and a typical behavioral code under threat emerges, with a few dominant figures at the head."
The behavioral results were further supported by a series of stress hormone tests before and after the simulated owl attacks, revealing that the smaller voles had high corticosterone levels, while the levels in the larger voles remained stable.
Prof. Eilam is currently extending the study to larger groups to obtain a better representation of the way swarms, flocks, or crowds organize behavior. "We are also trying to uncover what the 'leaders' benefit from their costly role in the group, and how information is passed on from one group to the next," he said.
TAU researcher discovers that squid recode their genetic make-up on-the-fly to adjust to their surroundings
The principle of adaptation — the gradual modification of a species' structures and features — is one of the pillars of evolution. While there exists ample evidence to support the slow, ongoing process that alters the genetic makeup of a species, scientists could only suspect that there were also organisms capable of transforming themselves ad hoc to adjust to changing conditions.
Now a new study published in eLife by Dr. Eli Eisenberg of Tel Aviv University's Department of Physics and Sagol School of Neuroscience, in collaboration with Dr. Joshua J. Rosenthal of the University of Puerto Rico, showcases the first example of an animal editing its own genetic makeup on-the-fly to modify most of its proteins, enabling adjustments to its immediate surroundings. The research, conducted in part by TAU graduate student Shahar Alon, explored RNA editing in the Doryteuthis pealieii squid.
"We have demonstrated that RNA editing is a major player in genetic information processing rather than an exception to the rule," said Dr. Eisenberg. "By showing that the squid's RNA-editing dramatically reshaped its entire proteome — the entire set of proteins expressed by a genome, cell, tissue, or organism at a certain time — we proved that an organism’s self-editing of mRNA is a critical evolutionary and adaptive force." This demonstration, he said, may have implications for human diseases as well.
Using the genetic red pencil
RNA is a copy of the genetic code that is translated into protein. But the RNA "transcript" can be edited before being translated into protein, paving the way for different versions of proteins. Abnormal RNA editing in humans has been observed in patients with neurological diseases. The changing physiological appearance of squid and octopuses over their lifetime and across different habitats has suggested extensive recoding might occur in these species. However, this could never be confirmed, as their genomes (and those of most species) have never been sequenced.
For the purpose of the new study, the researchers extracted both DNA and RNA from squid. Harnessing DNA sequencing and computational analyses at TAU, the team compared the RNA and DNA sequences to observe differences. The sequences in which the RNA and DNA did not match up were identified as "edited."
"It was astonishing to find that 60 percent of the squid RNA transcripts were edited. The fruit fly, for the sake of comparison, is thought to edit only 3% of its makeup," said Dr. Eisenberg. "Why do squid edit to such an extent? One theory is that they have an extremely complex nervous system, exhibiting behavioral sophistication unusual for invertebrates. They may also utilize this mechanism to respond to changing temperatures and other environmental parameters."
"Misfolding" the proteins
The researchers hope to use this approach to identify recoding sites in other organisms whose genomes have not been sequenced.
"We would like to understand better how prevalent this phenomenon is in the animal world. How is it regulated? How is it exploited to confer adaptability?" said Dr. Eisenberg. "There may be implications for us as well. Human diseases are often the result of 'misfolded' proteins, which often become toxic. Therefore the question of treating the misfolded proteins, likely to be generated by such an extensive recoding as exhibited in the squid cells, is very important for future therapeutic approaches. Does the squid have some mechanism we can learn from?"
The researchers recently received an Israel-U.S. Binational Science Foundation grant to explore the subject of genetic editing in octopuses.
TAU researcher launches world's first feasibility study on meat cultured in a lab
Concrete buildings, clean drinking water, and antibiotics are just a few of the "unnatural" benefits of modernity. Now cultured meat engineered in a laboratory, also known as in-vitro meat, may be poised to join this estimable list.
Tel Aviv University, together with the Modern Agricultural Foundation, has just launched a trailblazing feasibility study on cultured chicken breast production. The study will determine, among other things, how cultured meat, grown in a lab from animal stem cells, could be manufactured commercially, and examine the costs, technology, and potential problems involved. Prof. Amit Gefen of TAU's Department of Biomedical Engineering, one of the world's leading experts in tissue engineering, is leading the study on cultured meat production.
Cultured meat is produced by placing stem cells in a growth culture (fetal bovine serum, for example, is extracted from cow uteruses and rich with energy substrates, amino acids, and inorganic salts that support cell metabolism and growth). The cells divide and grow, creating solid pieces of meat.
There are many reasons to prefer cultured meat, researchers advise. First, the real thing isn't exactly "real" anymore. Animals raised for eventual slaughter are shot full of growth hormones and antibiotics, which are later ingested by people. Animal cruelty, which offends the values of many cultures, is another important reason, not to mention that health and safety regulations are often overlooked in factories.
But even if meat could be produced humanely, naturally, and safely, the world is fast approaching its production limit. By 2050, the world's population is projected to reach 9.2 billion, and meat production will need to be at least double what it is today, say experts.
For more, read the story in the Times of Israel: "'Test-tube steak' could be coming to your plate soon"
TAU researcher discovers bat homing call informs other bats of enticing prey several hundred feet away
The sound of a bag of potato chips being torn open cuts through a darkened movie theater. The noise, in an otherwise silent space, pinpoints for all moviegoers exactly where the chips are being devoured. According to a new Tel Aviv University study, bats operate in a similar fashion.
Bats, hunting at night in groups, improve their chances of finding the best patches of insects by engaging in reciprocal eavesdropping, says the study's lead investigator Dr. Yossi Yovel of TAU's Department of Zoology. "Bats emit sonar signals to sense their environment. By recording them in real time, we can tell when they're attacking prey or when they encounter another bat and how they respond to it. This reveals new knowledge on the world of these miniature flying mammals, which account for more than 20% of mammalian species. It is an example of how an animal gains from working in a group, and it could even provide insight into operating swarms of drones in a collective search mission, for example."
The research, published recently in the journal Current Biology, was conducted in part by TAU graduate students Noam Cvikel, Katya Egert-Berg, and post-doc Eran Levin.
Eavesdropping on the eavesdroppers
The subject of the study, the Rhinopoma microphyllum, also known as the greater mouse-tailed bat, preys on flying queen ants, an insect that congregates in highly-dispersed patches that can be difficult to find. While bats are able to use biosonar to detect their prey within 33 feet, their remarkable "eavesdropping" honing radar is able to identify other bats eating that prey from some 328 feet away. The study, conducted over two summers (2012-13) in Israel's northern Galilee region, found that bats' unique ability to snoop on others' hunting improved their collective chance of feeding well.
For the purpose of the study, Dr. Yovel and his team rigged 30 greater mouse-tailed bats, a highly social species of bats that migrate to Israel for the summer, with very small, GPS-enabled ultrasonic recorders. The chips were attached with surgical glue which wore off after a week, causing them to fall off the bats. The team collected these chips to analyze the data they contained. They were only able to retrieve 40 per cent of the recorders, but they contained valuable recordings of 1,100 bat interactions, allowing the researchers to identify when the bats were hunting down prey and when they were simply chatting with other bats.
"The high bat density might result in a few possible sources of interference," said Dr. Yovel. "A bat might compete for the same prey, bat signals might theoretically jam others' sonar calls, and bats might suffer because they constantly need to track other bats while at the same time tracking food. We found this last source to be of most importance to the bats. Imagine that you are tracking a fly and a baseball is thrown towards you — you will have to stop tracking the fly. This is a kind of trade-off. Foraging in a group is beneficial, but not when the group is too dense."
Using high-tech to study low-tech animals
"We seek to understand nature," Dr. Yovel said. "We seek to understand how animals make decisions in the wild, but we are very limited in our ability to track animals in their natural environment, to accurately track their behavior, their foraging tactics and interactions with counterparts. In this study we were lucky to be able to harness a novel technology to gain insight into the secret world of bats."
The researchers are continuing to study bat behavior, comparing bats that use different foraging strategies. Dr. Yovel is also developing new sensors to monitor a host of other bat biological markers.
TAU study offers first global picture of the evolutionary origins of proteins
Each cell contains thousands of proteins, each one of which bears a unique signature. All proteins, distinct in shape and function, are built from the same amino acid strings. Many proteins are vital, as evidenced by the plethora of diseases linked to their absence or malfunction. But how exactly did proteins first come to be? Do they all share a single common ancestor? Or did proteins evolve from many different origins?
Forming a global picture of the protein universe is crucial to addressing these and other important questions, but it's nearly impossible to do. Such a bird's-eye view demands comparisons of nearly innumerable pairs of known and unknown proteins. Now, new research published in the journal PNAS by Prof. Nir Ben-Tal of the Department of Biochemistry and Molecular Biology at Tel Aviv University's Faculty of Life Sciences, Prof. Rachel Kolodny of University of Haifa's Department of Computer Science, and Dr. Sergey Nepomnyachiy of New York University's Polytechnic Institute, is providing a first step toward piecing together a global picture of the protein universe.
"This is the first study that combines sequence and shape similarity between proteins within the context of networks to provide a bird's eye view of the protein universe," said Prof. Ben-Tal. "The network offers a natural way to organize and search among all proteins. It could be used to theorize about protein evolution, suggest evolutionary pathways, and even suggest strategies for the design of new proteins."
A master of their domain
Conveniently, proteins are comprised of various combinations of domains — conserved and commonly occurring parts that can function on their own; it is therefore sufficient to analyze relationships among these. The researchers studied the evolutionary relationships among a representative set of 9,710 domains. They compared them, searching for common motifs. The motif includes parts of each of the two compared domains, and can therefore indicate an evolutionary relationship among them. The researchers presented their results as a series of networks, in which edges connect domains with a shared motif.
According to their analysis of protein pairs, the researchers revealed a truly complex picture of protein space — a large, connected component with many isolated "islands."
"The protein network can be interpreted as a collection of evolutionary paths in protein space," said Prof. Ben-Tal. "Paths in the major connected component of the network include many domains, and demonstrate the sequence and shape resemblance between them. The large number of paths within the major connected component suggest it is particularly easy to add and delete motifs in the continuous region of protein space without impeding stability. Apparently, evolution took advantage of this property to design new proteins with novel functions."
The researchers are currently working on ways of supplementing the study with data on protein function (such as DNA/RNA binding), its role in disease pathology, and drug binding to individual proteins.
New TAU study finds a slow pace of life is the secret to longevity of lizards and snakes
Doctors tell us that the frenzied pace of the modern 24-hour lifestyle — in which we struggle to juggle work commitments with the demands of family and daily life — is damaging to our health. But while life in the slow lane may be better, will it be any longer? It will if you’re a reptile.
A new study by Tel Aviv University researchers finds that reduced reproductive rates and a plant-rich diet increases the lifespan of reptiles. The research, published in the journal Global Ecology and Biogeography, was led by Prof. Shai Meiri, Dr. Inon Scharf, and doctoral student Anat Feldman of the Department of Zoology at TAU's Faculty of Life Sciences, in collaboration with Dr. Daniel Pincheira-Donoso of the University of Lincoln, UK, and other scientists from the US, the UK, Ecuador, and Malaysia.
The international team collected literature on 1,014 species of reptiles (including 672 lizards and 336 snakes), a representative sample of the approximately 10,000 known reptiles on the planet, and examined their life history parameters: body size, earliest age at first reproduction, body temperature, reproductive modes, litter or clutch size and frequency, geographic distribution, and diet. The researchers found that, among other factors, early sexual maturation and a higher frequency of laying eggs or giving birth were associated with shortened longevity.
Putting the brakes on physical stress
"There were aspects of this study that we were able to anticipate," said Prof. Meiri. "Reproduction, for example, comes at the price of great stress to the mother. She experience physiological stress, is unable to forage efficiently, and is more vulnerable to her surroundings. This reflects evolutionary logic. To relate this to humans, imagine the physical stress the body of an Olympic gymnast experiences — and the first thing that disappears is her period. In reptiles, it also increases the probability of being preyed upon.
"We found that reptiles that were sexually mature early on were less likely to make it to old age," Prof. Meiri continued. "Live fast and die young, they say — but live slow, live long."
Eat your greens
The team also discovered that herbivores — lizards with a plant-rich diet — lived longer than similar-sized carnivores that ate mostly insects. Ingestion of a protein-rich diet seemed to lead to faster growth, earlier and more intense reproduction, and a shortened lifespan. Herbivorous reptiles were thought to consume nutritionally poorer food, so they reached maturity later — and therefore lived longer.
Hunting may also be riskier than gathering fruits and leaves — at least for animals, the researchers concluded. "If you're an animal, hunting your food can be dangerous," said Prof. Meiri. "You risk injury or even death. This is why you cannot simply transfer this logic to humans. Going to buy a head of lettuce at the supermarket is just as risky as going to the meat department. As a reptile, if you eat plants, you may need to be frugal, take life more slowly, and save your calories for digestion. You are forced to have a slower life, a more phlegmatic existence."
The researchers also found correlates that suggested reptiles in geographically colder regions lived longer — probably due to two factors: hibernation, which offers respite from predators, and slower movement due to a seasonal drop in metabolic rate. "Our main predictors of longevity were herbivorous diets, colder climates, larger body sizes, and infrequent and later reproduction," said Prof. Meiri. "I stress that you cannot simply transfer the results of a study on lizards to humans — but this is the first study of its kind on reptiles, which does open up an avenue for further research on other factors that lead to longevity of these and other species."
The good news: Swarms present an opportunity for regional collaboration, says TAU researcher
Celebrated as the eighth plague visited on the people of Egypt in the story of Passover, locusts have been pestering farmers for millennia. Common in Sudan and Egypt, now swarms have arrived in Israel, too—just in time for the holiday in which they play a role in the Israelites' escape from slavery.
Though the timing is uncanny, researchers note that the current plague is a normal ecological phenomenon rather than a form of divine punishment. In the Middle East, locusts typically swarm every 10 to 15 years, and the pattern can be unpredictable. In this case, a rainy winter caused excessive vegetation growth—and a boom in the locust population.
Because the swarms impact several countries in the region, Prof. Amir Ayali of Tel Aviv University's Department of Zoology believes this could be an opportunity for collaboration, in much the way birders and ornithologists from Israel, Jordan, and Palestine cooperate in monitoring bird migration. "Maybe scientists should work to bridge the gaps in the region," he says in a recent article in Smithsonian. "We could take the opportunity of this little locust plague to make sure together that we're better prepared for the next."
From a solitary pest to a dangerous plague
A locust begins life as a form of grasshopper. When it switches from a sedentary, solo lifestyle to a swarming lifestyle, it undergoes a series of physical, behavioral, and neurological changes, representing one of the most extreme cases of behavioral plasticity found in nature. Before swarming, locusts change from their normal tan or green coloring to a bright black, yellow, or red exoskeleton. Females begin laying eggs in unison, which hatch in synch and fuel the swarm. In this way, millions of insects can become billions in a matter of months. The swarm will consume any vegetation in its path, and will move to new feeding grounds after devouring everything at hand.
The damage caused by locust swarms is expensive, taking into account the cost of pesticides, crop damage, replacement food provisions and more. And while it's important to develop new methods for dealing with the swarms, the best strategy would be to prevent the swarms from taking flight in the first place through monitoring of locust-prone areas. "We really want to find them before they swarm, as wingless nymphs on the ground," explains Prof. Ayali. "Once you miss that window, your chances of combating them are poor and you're obliged to spray around like crazy and hope you catch them on the ground."
For the full story on this modern-day locust plague, see the smithsonian.com story:
Israeli and American researchers discover the genetic mechanism that passes on physical responses to hardship
During the winter of 1944, the Nazis blocked food supplies to the western Netherlands, creating a period of widespread famine and devastation. The impact of starvation on expectant mothers produced one of the first known epigenetic "experiments" — changes resulting from external rather than genetic influences — which suggested that the body's physiological responses to hardship could be inherited. The underlying mechanism, however, remained a mystery.
In a paper published recently in the journal Cell, Dr. Oded Rechavi, Dr. Leah Houri-Ze'ev, and Dr. Sarit Anava of Tel Aviv University's Faculty of Life Sciences and Sagol School of Neuroscience, Prof. Oliver Hobert and Dr. Sze Yen Kerk of Columbia University Medical Center and the Howard Hughes Medical Institute, and Dr. Wee Siong Sho Goh and Dr. Gregory J. Hannon of the Cold Spring Harbor Laboratory and the Howard Hughes Medical Institute, explore a genetic mechanism that passes on the body's response to starvation to subsequent generations of worms, with potential implications for humans also exposed to starvation and other physiological challenges, such as anorexia nervosa.
"There are possibly several different genetic mechanisms that enable inheritance of traits in response to changes in the environment. This is a new field, so these mechanisms are only now being discovered," said Dr. Rechavi. "We identified a mechanism called 'small RNA inheritance' that enables worms to pass on the memory of starvation to multiple generations."
Does RNA have a memory?
RNA molecules are produced from DNA templates in response to the needs of specific cells. "Messenger" RNA molecules (mRNAs) contain instructions for the production of proteins, which service cells and allow them to function. But other RNA molecules have different regulatory functions. Small RNAs are one species of these regulatory RNAs — short molecules that regulate gene expression, mostly by shutting genes off, but sometimes by turning them on.
Dr. Rechavi first became interested in studying starvation-induced epigenetic responses following a discovery made as a post doctorate in Prof. Hobert's lab at Columbia University Medical Center in New York. "Back then, we found that small RNAs were inherited, and that this inheritance affected antiviral immunity in worms. It was obvious that this was only the tip of the iceberg," he said.
In the course of the new study, worms (C.elegans nematodes) were starved early in their development. They responded by producing small RNAs, which function by regulating genes through a process that is known as RNA interference (RNAi). The researchers discovered that the starvation-responsive small RNAs target genes that are involved in nutrition. More important, the starvation-induced small RNAs were inherited by at least three subsequent generations of worm specimens.
"We were also surprised to find that the great-grandchildren of the starved worms had an extended life span," said Dr. Rechavi. "To the best of our knowledge, our paper provides the first concrete evidence that it's enough to simply experience a particular environment — in this case, an environment without food — for small RNA inheritance and RNA interference to ensue. In this case, the environmental challenge is starvation, a very physiologically relevant challenge, and it is likely that other environments induce transgenerational inheritance of small RNAs as well.
"We identified genes that are essential for production and for the inheritance of starvation-responsive small RNAs. RNA inheritance could prove to be an important genetic mechanism in other organisms, including humans, acting parallel to DNA. This could possibly allow parents to prepare their progeny for hardships similar to the ones that they experience," Dr. Rechavi said.
The researchers are currently researching a wide variety of traits affected by inherited small RNAs.
TAU researcher suggests converting the expansive species into a useful resource
A United Nations report released in May called on scientists worldwide to join a war on jellyfish. Jellyfish have disrupted the marine ecosystem and are seen by scientists as "terrorists" in the food chain. For example, a recent report describes how a bloom of jellyfish, spanning four square miles, devoured 100,000 salmon at a fish farm in Northern Ireland, causing damages of $1.5 million. And even though 450,000 tons of jellyfish are fished every year for the East Asian food industry, jellyfish consumption is far from effective in reducing or controlling the rapidly reproducing creatures’ population growth.
According to a recent article in Haaretz, Tel Aviv University has been successful in turning jellyfish to more useful purposes. Prof. Shahar Richter of TAU's Department of Materials Science and Engineering and Center for Nano Science and Nanotechnology, Prof. Michael Gozin of TAU's School of Chemistry, and TAU students Liron Reshef, Gad Kedem, Roman Nudelman, and Dr. Tamila Giolahamdov have devised a way of turning jellyfish into a resource that could be used in various industries, providing an incentive to fish the creatures en masse and reduce their number.
Richter's method, now being registered as a patent, could turn jellyfish into an attractive resource for paramedical, hygiene, and perishable-product industries. They could be used for environmentally safe medical treatments, advanced bandages, and other plastic products.
The jellyfish's triple threat
"Jellyfish cause damage in three major areas," Richter told Haaretz. "First, they clog up and paralyze atomic or electric power stations and desalination plants. In fact, they spell disaster for any facility that uses sea water. This happens in many places, including Korea, Japan, Sweden and India."
Second, jellyfish have had a dramatic impact on the world fishing industry, snagging and blocking fishing nets with their massive size. The third industry to come under jellyfish attack is tourism. While jellyfish on Israeli shores cause painful burning at worst, the species off Australia's shores are deadly, requiring the closure of beaches for extended periods.
A jellyfish consists of an umbrella-shaped bell and trailing tentacles; 90 percent of it is water. In studies, the researchers first cut off the tentacles and then ground the jellyfish to eliminate the water. The remaining substance consisted of two proteins useful in the biotechnological industries — collagen (found in human skin) and mucin (found in mucous tissues). The team developed methods to turn this jellyfish "essence" into composite materials, adding nanoparticles with useful properties, like electrical conductivity, anti-bacterial materials, medicines, and glowing substances.
"The result is a composite biological material. Our innovation is proving that the material is perishable, so that if we bury it in the ground it will decompose, not pollute or cause environmental damage," Prof. Richter told Haaretz. The team is currently examining industrial and commercial applications for this material.
Read more in Haaretz:
"Israeli scientist turning jellyfish plague into plenty"
TAU researchers discover eyeless Mexican cavefish use suction to navigate
Blind fish found in the pools of Mexican caves use high-frequency waves generated with their mouths to navigate, Tel Aviv University researchers have discovered.
In a study published last month in the Journal of Experimental Biology, Dr. Roi Holzman and Dr. Shimrit Perkol-Finkel of TAU's School of Zoology and Prof. Gregory Zilman of TAU's School of Mechanical Engineering observed a previously unknown mechanism by which Mexican blind cavefish (Astyanax fasciatus) produce suction waves to create vibrations in the water around them, then measure their distance to nearby objects by detecting changes to water pressure on their skin.
The researchers described the practice as being somewhat similar to echolocation, the method used by bats and dolphins to gauge their distance from objects by emitting sound waves and measuring how long they take to bounce back. But unlike echolocation, the fish's method does not measure time but the ways in which water pressure changes as a result of the suction movement.
The team conducted experiments in which they observed the mouth movements of specimens, noting that the fish made much more frequent movements when around new objects than when swimming in familiar territory. They also noted that the suction action increased dramatically the closer the fish came to solid objects.
For more, read the Times of Israel story:
TAU researchers develop a computer algorithm that identifies genes whose activation is lethal to bacteria
Like little factories, cells metabolize raw materials and convert them into chemical compounds. Biotechnologists take advantage of this ability, using microorganisms to produce pharmaceuticals and biofuels. To boost output to an industrial scale and create new types of chemicals, biotechnologists manipulate the microorganisms' natural metabolism, often by "overexpressing" certain genes in the cell. But such metabolic engineering is hampered by the fact that many genes become toxic to the cell when overexpressed.
Now, Allon Wagner, Uri Gophna, and Eytan Ruppin of Tel Aviv University's Blavatnik School of Computer Science and Department of Molecular Microbiology and Biotechnology, along with researchers at the Weizmann Institute of Science, have developed a computer algorithm that predicts which metabolic genes are lethal to cells when overexpressed. The findings, published in Proceedings of the National Academy of Sciences, could help guide metabolic engineering to produce new chemicals in more cost-effective ways.
"In the lab, biotechnologists often determine which genes can be overexpressed using trial and error," said Wagner. "We can save them a lot of time and money by ruling out certain possibilities and highlighting other, more promising ones."
Gaining an EDGE
When metabolic genes are expressed, the genetic information they contain is converted into proteins, which catalyze the chemical reactions necessary for life. Overexpression means that greater-than-normal amounts of proteins are produced. Biotechnologists typically overexpress native genes of an industrial microorganism to boost a certain metabolic pathway in the cell, thus increasing the production of desired compounds. Sometimes they overexpress foreign genes — genes transferred from other organisms — in an industrial microbe to build new metabolic pathways and allow it to synthesize new compounds. But they often find that their efforts are hindered by the toxicity of the genes that they wish to overexpress.
Prof. Ruppin's laboratory builds large-scale software models of cellular metabolism, one of the most fundamental aspects of life. These models convert physical, chemical, and biological information into a set of mathematical equations, allowing scientists to learn how cells work and explore what happens if they are tweaked in certain ways. The newly developed algorithm, Expression Dependent Gene Effects, or EDGE, predicts what happens if scientists manipulate cells to overexpress certain genes. EDGE allows biotechnologists to foresee cases in which the overexpressed genes become toxic and then direct their efforts toward other genes.
To validate their method, TAU researchers used genetic manipulation tools to overexpress 26 different genes in E. coli bacterial cells. Comparing the results of their computer simulations with the actual growth of the overexpressed strains that was measured in the lab, they saw that EDGE was able to predict which of the overexpressed genes turned out to be lethal to E. coli. EDGE was also successful in identifying cases of foreign genes that were toxic to E. coli, as the researchers learned from comparing the simulations' results with data collected by their collaborators at the Weizmann Institute of Science.
EDGE's applications appear to extend beyond bacteria. The researchers conducted tests showing that the genes EDGE predicted to be toxic when overexpressed are expressed at low levels not only in microorganisms like bacteria, but also in multicellular organisms, including humans. The researchers say these results reflect the vital evolutionary need to keep the expression of potentially deleterious genes in check.
"Although EDGE's current focus is biotechnology, gene overexpression also plays a central part in many human diseases, particularly in cancer. We hope that future work will apply EDGE to those directions," Wagner said.
TAU researchers unlock the secrets of echolocation's relationship to vision
Blessed with the power of echolocation — reflected sound — bats rule the night skies. There are more than 1,000 species of these echolocating night creatures, compared with just 80 species of non-echolocating nocturnal birds. And while it seems that echolocation works together with normal vision to give bats an evolutionary edge, nobody knows exactly how.
Now Dr. Arjan Boonman and Dr. Yossi Yovel of Tel Aviv University's Department of Zoology suggest that bats use vision to keep track of where they're going and echolocation to hunt tiny insects that most nocturnal predators can't see. The findings, published in Frontiers in Physiology, add to our scientific understanding of sensory evolution.
"Imagine driving down the highway: Everything is clear in the distance, but objects are a blur when you pass them," said Dr. Boonman. "Well, echolocation gives bats the unique ability to home in on small objects — mostly insects — while flying at high speeds."
Battle of the senses
Bats do most of their feeding at dusk, when insects are most active and there is still plenty of light. Under these conditions, vision seems a better option than echolocation — it conveys more information, and more quickly, at a higher resolution. The researchers wondered: If bats evolved vision before echolocation, as scientists believe, why did echolocation ever come along?
The team set out to answer this question by comparing the distances at which the two senses can detect small objects. To estimate the range of ultrasonic bat echolocation, the researchers played taped calls of two species of bats in a soundproof room and recorded the way the sound bounced off four dead insects — a moth, an ant, a lacewing, and a mosquito. Vision is hard to simulate, so, extrapolating from the findings of two previous studies, the researchers calculated the distance at which bats would be able to see the same insects in medium to low light.
Even erring on the side of vision in their estimates, the researchers found that echolocation was twice as effective as vision in detecting the insects in medium to low light — from 40 feet away versus the 20 feet that was the effective range with vision. They also note that echolocation is unaffected by objects in the background, while visual range is three-to-five fold worse when it has to contend with obstacles like vegetation. Previous studies have shown that echolocation provides more accurate estimates of the distance and velocity of objects, and sometimes even of the distance of the background behind them.
These results suggest that echolocation gives bats a huge evolutionary advantage, allowing them to track insects from further away and with greater accuracy at peak feeding time. Echolocation also, of course, allows bats to continue hunting into the night, when their competitors are blinded by darkness.
A one-two evolutionary punch
On the negative side, bat echolocation was poor at detecting large objects in the distance: Vision can detect large objects at distances several orders of magnitude greater than echolocation does. The researchers think that bats therefore use both senses in combination — vision mostly for orientation, navigation, and avoiding large objects in the distance, and echolocation to search for small prey. Different species of bats probably combine the senses somewhat differently.
"We believe that bats are constantly integrating two streams of information — one from vision and one from echolocation — to create a single image of the world," said Dr. Yovel, also of TAU's Sagol School of Neuroscience. "This image has a higher definition than the one created by vision alone."
The combination of vision and echolocation opened up a large nocturnal advantage for bats in which they have multiplied and diversified — bats account for 20 percent of all classified mammal species on earth today. The researchers speculate that nocturnal birds may not have evolved their own ultrasonic echolocation for anatomical reasons. The next steps are to research how bats integrate echolocation and vision and what the evolutionary costs of echolocation are.