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Tag: Life Sciences

Eyes Wide Shut: Bats Can Navigate Long Distances Using Sound Alone

Written by Hilary on . Posted in Newsroom.

Researchers found that bats can create a mental “sound map” of their environment.

A new study by Tel Aviv University and the Steinhardt Museum of Natural History has proven, for the first time, that bats can navigate in nature over many kilometers using only echolocation, without relying on other senses. The researchers explain: “It’s well-known that bats are equipped with a natural sonar, allowing them to emit sound waves that bounce back from nearby objects, helping them navigate. However, it’s also known that bats use their sense of sight during flight. Laboratory studies have shown that bats can navigate within enclosed spaces using only echolocation — but sonar ‘sees’ only about 10 meters ahead, so what happens under natural conditions, in open areas stretching over many kilometers? Can bats rely solely on echolocation for long-distance navigation?” In this study, that question was explored in depth for the first time.

They Follow the Echo

The research was led by Prof. Yossi Yovel of Tel Aviv University’s School of Zoology, Sagol School of Neuroscience, and Steinhardt Museum of Natural History, along with Dr. Aya Goldshtein, formerly a doctoral student of Prof. Yovel and currently a researcher at the Max Planck Institute in Germany. Additional partners from Tel Aviv University included Prof. Sivan Toledo of the Blavatnik School of Computer Science; Xing Chen, Dr. Eran Amichai, and Dr. Arjan Boonman of the School of Zoology; and Lee Harten of the Sagol School of Neuroscience. Prof. Ran Nathan and Dr. Yotam Orchan of the Hebrew University and Prof. Iain Couzin of the Max Planck Institute in Germany also participated in the study, which was published in the journal Science.

The innovative research carried out over six years, utilized a unique tracking system installed in Israel’s Hula Valley. Using this GPS-like technology, the researchers could track the flight of tiny bats from the species known as Kuhl’s pipistrelle, each weighing only six grams —— the smallest mammal ever to be monitored in this way.

For the study, the researchers collected around 60 bats from their roost in the Hula Valley area and moved them about three kilometers away from the roost — still within their familiar habitat. A tag was attached to each bat, and the eyes of some were covered with a cloth strip, temporarily preventing them from seeing during flight, though they could remove the covering with their feet upon landing. In addition, the researchers employed techniques to temporarily disrupt the bats’ sense of smell and magnetic sense, thereby creating conditions in which they would be able to find their way home using only echolocation. Remarkably, the bats managed to return to their roost without difficulty.

In the second phase, the researchers built a computerized acoustic model of the bats’ natural environment in the Hula Valley. Prof. Yovel explains: “This model is based on a 3D map of the area where the bats navigate, reflecting the echoes that the bat hears as it uses echolocation to journey through its surroundings. In examining the bats’ flight paths, we discovered that they choose routes where the echoes contain a lot of information, which helps them navigate. For example, an area rich in ​​vegetation, such as bushes and trees, returns echoes with more information than an open field, making bats less likely to fly over open terrain. We also found that some areas are characterized by distinct echoes, which are picked up by the bats. These findings strengthened our hypothesis that in any given area, bats know where they are based on the echoes. The bats effectively create an acoustic map in their head of their familiar environment, which includes a variety of active ‘sound landmarks’ (echoes) — just as every sighted person has a visual map of their everyday surroundings”.

פרופ' יוסי יובל

The Reason Behind the Dancing Sunflowers

Written by Hilary on . Posted in Newsroom.

As they grow, sunflowers “dance” to avoid blocking each other’s sunlight

Flowers have long fascinated scientists and nature enthusiasts alike, not just for their beauty, but also for their subtle, almost imperceptible movements. Over a century ago, Charles Darwin was the first to observe that plants, including flowers, exhibit a kind of cyclical movement as they grow. This movement, seen in both stems and roots, puzzled researchers: Was it just a byproduct of growth, or did it serve a crucial purpose?

A new study by Tel Aviv University, in collaboration with the University of Colorado, Boulder, discovered that plants that grow in dense environments, where each plant casts a shadow on its neighbor, find a collective solution with the help of random movements that help them find optimal growth directions. In this way, the study sheds light on the scientific enigma that has occupied researchers since Darwin, namely the functional role of these inherent movements called circumnutations.

The research was conducted under the leadership of Prof. Yasmine Meroz from the School of Plant Sciences and Food Security at the Wise Faculty of Life Sciences at Tel Aviv University, in collaboration with Prof. Orit Peleg from the University of Colorado Boulder in the USA. The research team included Dr. Chantal Nguyen (Boulder), Roni Kempinski and Imri Dromi (TAU). The research was published in the prestigious journal Physical Review X.

Do flowers have a sense of direction?

Prof. Meroz explains: “Previous studies have shown that if sunflowers are densely planted in a field where they shade each other they grow in a zigzag pattern – one forward and one back – so as not to be in each other’s shadow. This way they grow side by side to maximize illumination from the sun, therefore photosynthesis, on a collective level. Plants know how to distinguish between the shadow of a building and the green shadow of a leaf. If they sense the shadow of a building – they usually don’t change their growth direction, because they ‘know’ that will have no effect. But if they sense the shadow of a plant, they will grow in a direction away from the shadow”.

According to the researchers, Darwin was the first to recognize that all plants grow while exhibiting a kind of cyclical movement known as “circumnutation”, which is observed in both stems and roots. However, until today—except for a few cases, such as climbing plants that grow in large circular movements to find something to grab onto—it was unclear whether this was an artifact or a critical feature of growth. Why would a plant invest energy to grow in random directions?

In the current study, the researchers examined how sunflowers “know” to grow optimally—maximizing sunlight capture for the collective—and analyzed the growth dynamics of sunflowers in the laboratory, where they exhibit a zigzag pattern. Prof. Meroz and her team grew sunflowers in a high-density environment and photographed them during growth, taking pictures every few minutes. The photographs were then combined to create a time-lapse movie. By tracking the movement of each sunflower, the researchers observed that the flowers were “dancing” a lot.

Shake your Tail Petal

Prof. Meroz stated, “As part of our research, we conducted a physical analysis that captured the behavior of each sunflower within the collective, revealing that the sunflowers ‘dance’ to find the optimal angle, ensuring that each flower does not block the sunlight of its neighbor. We quantified this movement statistically and demonstrated through computer simulations that these random movements are used collectively to minimize shadowing. It was also surprising to find that the distribution of the sunflowers’ ‘steps’ was very wide, ranging over three orders of magnitude, from nearly zero displacements to movements of up to two centimeters every few minutes in various directions”.

In conclusion, Prof. Meroz adds: “The sunflower plant takes advantage of its ability to use both small, slow steps and large, fast ones to find the optimal arrangement for the collective. If the range of steps were smaller or larger, the arrangement would result in more mutual shading and less photosynthesis. It’s somewhat like a crowded dance party, where individuals move around to create more space: if they move too much, they’ll interfere with the other dancers, but if they move too little, the crowding problem won’t be solved, leaving one corner of the square overcrowded and the other empty. Sunflowers exhibit a similar communication dynamic—a combination of responding to the shade of neighboring plants and making random movements regardless of external stimuli”.

Animals Experience War Stress Too

Written by Hilary on . Posted in Newsroom.

TSU study examines the impact of the Israel-Hamas war on wildlife

A new study conducted at Tel Aviv University’s School of Zoology, Wise Faculty of Life Sciences and Steinhardt Museum of Natural History reveals that the Israel-Hamas war has had a severe impact on animals. The study, which focused on geckos, found that the sound of explosions from fired rockets induces stress and anxiety in these creatures, leading to a sharp increase in their metabolic rates — an energy cost that, if chronic, may be life-threatening. The researchers hypothesize that these stress responses characterize many other animals, especially those who live in the conflict zones in northern and southern Israel.

The study was led by a team of researchers from TAU’s School of Zoology and Steinhardt Museum of Natural History — Shahar Dubiner, Prof. Shai Meiri, and Prof. Eran Levin — in collaboration with Dr. Reut Vardi of the University of Oxford. The study was published in the journal Ecology.

Energy Changes in Wildlife

Prof. Shai Meiri explains: “The most tragic aspect of war is the loss of human life, among both soldiers and civilians. However, animals are also severely affected, both directly and indirectly, in ways that may threaten their survival. A few weeks before October 7, we began working on a long-term study to measure the rate of energy consumption of small ground geckos of the species Stenodactylus sthenodactylus. We obviously did not foresee the outbreak of the war, but unintentionally, we recorded the energy consumption of five geckos during the rocket barrages launched into Tel Aviv in the first month of the war”.

The study’s findings showed that at the sound of the bombings, the geckos’ metabolic rate jumped to double what it was when they were at rest. Their breathing became faster, and they clearly exhibited signs of stress. The experiment lasted up to four hours after the barrages, yet even within this timeframe the geckos did not calm down and return to their resting levels. Moreover, even after a month of continuous fighting, the geckos did not acclimate to the sound of the explosions — their stress response remained unchanged.

Left to right: Prof. Shai Meiri and Prof. Eran Levin.

Prof. Levin: “A state of stress is detrimental to both humans and animals. To compensate for the increase in oxygen consumption and depletion of energy reserves, animals need to eat more. Even if they manage to find food, in the process they expose themselves to predators and lose opportunities to reproduce. In a situation of ongoing conflict, such as the current reality in Gaza, the Gaza Envelope, and along the Israeli-Lebanese border, the metabolic cost can be significant and have a real impact on the energy reserves and activity periods of reptiles and other animals. This can exacerbate their conservation status, especially for species that are already endangered”.

The researchers note that the findings of this study are consistent with another experiment conducted during Operation Guardian of the Walls, in which they also observed a stress response in a small snake of the species Xerotyphlops syriacus.

Shahar Dubiner concludes: “Our research was conducted in a laboratory at Tel Aviv University and pertained to the reverberations of explosions from interceptions in the Tel Aviv area. However, given the unequivocal results showing symptoms of stress, we can infer that animals that are in the immediate conflict zones in the south and north of the country, where the intensity and frequency of fire are much higher, suffer from significantly more severe stress and anxiety symptoms that may endanger their lives”.

How a Brain Parasite Becomes a Brain Cure

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TAU research paves the way to brain healing with parasites

Have you ever imagined that parasites could be beneficial for brain diseases? TAU Researchers have reengineered Toxoplasma gondii, the ‘cat parasite,’ transforming it from a feared threat into a groundbreaking tool for delivering drugs directly to the brain. This surprising innovation not only overturns our expectations but also opens new possibilities for treating neurological disorders.

In a breakthrough study by an international team of scientists led by researchers from Tel Aviv and Glasgow Universities, the ‘cat parasite’ Toxoplasma gondii was engineered to deliver drugs to the human brain. The study was led by Prof. Oded Rechavi from the Department of Neurobiology and the Sagol School of Neuroscience at Tel Aviv University, together with his PhD student Dr. Shahar Bracha, and with Prof. Lilach Sheiner, an Israeli scientist and toxoplasma expert from the University of Glasgow in Scotland. The results were published in the leading scientific journal Nature Microbiology.

“One of the biggest challenges in treating neurological diseases is getting through the blood-brain barrier (BBB),” explains Prof. Rechavi. “It is tough to deliver drugs to the brain via the bloodstream, and this is especially true for large molecules such as proteins, the critical ‘machines’ that carry out many important functions inside the cell”.

Toxoplasma gondii – the ‘cat parasite’

The creative solution proposed by the TAU team utilizes the unicellular parasite Toxoplasma gondii, which can infect a vast variety of organisms, but reproduces only in the guts of cats. The parasite is very effective in infecting humans, with an estimated third of the global population infected at some point in their lives. Prof. Rechavi explains: “Most people don’t even feel the infection or only experience mild flu-like symptoms.

Dormant Parasite Sparks New Treatment

The parasite is, however, dangerous for people with immune failure due to conditions like AIDS, and for fetuses whose immune system has not yet developed. This is why pregnant women are advised not to eat raw meat which might contain the parasite, and to stay away from cats, which might deliver it through their feces. While ridding the body of the parasite, a healthy immune system has only limited access to the brain, and the parasite remains in the brain throughout the carrier’s lifetime”.

The parasite’s ability to penetrate the human brain and survive there in a dormant state, without reproducing, made it a perfect candidate for the researchers’ novel approach: genetically engineering Toxoplasma gondii to secrete therapeutic proteins.

Can Parasites Deliver Medications to the Brain?

“The parasite has three distinct secretion systems and we ‘hitched a ride’ on two of them”, says Prof. Rechavi. “We did not intervene with the first system, which secretes proteins outside the neurons. The second system ‘shoots’ a ‘harpoon’ into the neuron, to enable penetration. Once inside, the parasite forms a kind of cyst that continues to secrete proteins permanently. We engineered the parasite’s DNA to make it produce and secrete the proteins we want, which have therapeutic potential”.

“The parasite’s ability to pass through the BBB and communicate with the neurons, combined with our ability to engineer the parasite, generate a golden opportunity for solving the great therapeutic challenge of delivering medications to the brain”, says Prof. Sheiner.

Illustration of the activity of neurons

In this study, the team used transgenic model animals that were injected with parasites genetically engineered to produce and secrete proteins that travel into cell nuclei. Several lines of evidence proved that the proteins had been delivered to the target area and remained active in the neurons’ nuclei. One of these was especially eye-catching: a protein that, delivered by the parasite, entered the nuclei and cut out specific DNA segments, causing the transgenic animals’ brains to glow in the dark.

New Method for Rett Syndrome

This breakthrough can have far-reaching implications for a series of severe diseases. In the present study, the researchers specifically demonstrated the delivery of a protein called MeCP2, whose deficiency is associated with Rett syndrome. “This is a deadly syndrome caused by a deficiency in a single gene called MePC2 in brain cells, and our engineered Toxoplasma gondii was able to deliver it to the target cells”, says Prof. Rechavi. “But this is just one example. There are many other diseases caused by deficiency or abnormal expression of a certain protein”. To ensure the method’s safe and effective therapeutic implementation, for both drug delivery and genetic editing, a company named Epeius was established in collaboration with Ramot – the technology transfer company of Tel Aviv University, and with the University of Glasgow’s research and innovation services.

Can Bats Think Ahead of Time?

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TAU researchers discover that bats have episodic memory and plan ahead

Researchers at Tel Aviv University tracked free-ranging Egyptian fruit bats from a colony based in the TAU’s I. Meier Segals Garden for Zoological Research to answer a long-standing scientific question: Do animals have high and complex cognitive abilities, previously attributed only to humans? In particular, the study focused on the traits of episodic memory, mental time travel, planning ahead, and delayed gratification, arriving at highly thought-provoking conclusions.

The study was led by Prof. Yossi Yovel and Dr. Lee Harten from the School of Zoology and Sagol School of Neuroscience at Tel Aviv University. Other researchers included: Xing Chen, Adi Rachum, Michal Handel, and Aya Goldstein from the School of Zoology, Lior de Marcas from the Sagol School of Neuroscience, and Maya Fenigstein Levi and Shira Rosencwaig from the National Public Health Laboratory of Israel’s Ministry of Health. The paper was published in Current Biology.

Prof. Yossi Yovel.

Prof. Yovel: “For many years the cognitive abilities to recall personal experiences (episodic memory) and plan ahead were considered exclusive to humans. But more and more studies have suggested that various animals also possess such capabilities. Still, nearly all of these studies were conducted under laboratory conditions, since field studies on these issues are difficult to perform. Attempting to test these abilities in wild animals, we designed a unique experiment relying on the colony of free-ranging fruit bats based in TAU’s I. Meier Segals Garden for Zoological Research”.

How Bats Keep Track of Food Resources

The researchers assumed that bats depending on fruit trees for their survival would need to develop an ability to track the availability of food both spatially (where are the fruit trees?) and over time (when does each tree give fruit?).  Navigating through landscapes with numerous fruit and nectar trees, they would need to mentally track the resources in order to revisit them at the appropriate time. To test this hypothesis, a tiny high-resolution GPS tracker was attached to each bat, enabling the documentation of flight routes and trees visited for many months. The vast data collected in this way were thoroughly analyzed, producing some amazing results.  

The first research question was: Do bats form a time map in their minds? To explore this issue, the researchers prevented the bats from leaving the colony for varying periods of time, from one day to a week. Dr. Harten: “We wanted to see whether the bats could tell that time had elapsed and behave accordingly. We found that after one day of captivity, the bats would return to trees visited on the previous night. However, when a whole week had gone by, the older bats, based on past experience, avoided trees that had stopped bearing fruit in the interval. In other words: they were able to estimate how much time had passed since their last visit to each tree and knew which trees bore fruit for a short time and were no longer worth visiting. Young, inexperienced  bats were unable to do this, indicating that this is an acquired skill that must be learned”.

While the first research question looked at past experiences, the second dealt with the future: Do the bats exhibit future-oriented behaviors? Are they capable of planning ahead?  To address this issue the researchers observed each bat’s route to the first tree of the evening, possibly indicative of plans made before leaving the colony. Chen Xing: “We found that usually the bats fly directly to a specific tree they know, sometimes 20 or 30 minutes away. Being hungry, they fly faster when that tree is further away, suggesting they plan where they are heading.

Moreover, focused on their chosen target, they will pass by other trees, even good sources visited just yesterday – indicating a capacity for delayed gratification. We also found that the first bats to leave the colony choose trees bearing fruits rich in sugar, while the bats that leave later seek proteins.” All these findings suggest that the bats plan their foraging before they leave the colony, and know exactly where they are flying and what kind of nourishment they are looking for.

Rethinking Intelligence in Animals

Prof. Yovel: “The cognitive gap between humans and animals is one of the most fascinating issues in science. Our study demonstrates that fruit bats are capable of quite a complex decision-making process involving the three questions indicative of cognitive abilities: Where? (each tree’s location); When? (when the tree bears fruit); and What? (the nourishment it provides – sugar vs. proteins). Once again we find that the gap is not cleat-cut, and that humans are not as unique as some might think. Apparently, humans and animals are all located on a spectrum, with almost any human ability found in animals as well”.

 

Tel Aviv University Shatters Limits with Self-Repairing Glass

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TAU researchers create transparent, self-repairing adhesive glass that forms in contact with water.

Researchers from TAU have created a new type of glass with unique and even contradictory properties, such as being a strong adhesive (sticky) and incredibly transparent at the same time. The glass, which forms spontaneously when in contact with water at room temperature, could revolutionize in an array of diverse industries such as optics and electro-optics, satellite communication, remote sensing and biomedicine. The glass has been discovered by a team of researchers from Israel and the world, led by PhD student Gal Finkelstein-Zuta and Prof. Ehud Gazit from the Shmunis School of Biomedicine and Cancer Research at the Faculty of Life Sciences and the Department of Materials Science and Engineering at the Faculty of Engineering at TAU. The research results were published last week in the prestigious scientific journal Nature.

“In our laboratory, we study bio-convergence and specifically use the wonderful properties of biology to produce innovative materials”, explains Prof. Gazit. “Among other things, we study sequences of amino acids, which are the building blocks of proteins. Amino acids and peptides have a natural tendency to connect and form ordered structures with a defined periodic arrangement, but during the research, we discovered a unique peptide that behaves differently from anything we know: it didn’t form any ordered pattern but an amorphous, disordered one, that describes glass”.

(Left to right) Gal Finkelstein-Zuta and Prof. Ehud Gazit.

Just Add Water

At the molecular level, glass is a liquid-like substance that lacks order in its molecular structure. Still, its mechanical properties are solid-like. Glass is usually manufactured by rapidly cooling molten materials and “freezing” them in this state before they are allowed to crystallize, resulting in an amorphous state that allows unique optical, chemical and mechanical properties – alongside durability, versatility, and sustainability. The researchers from TAU discovered that the aromatic peptide, which consists of a three-tyrosine sequence (YYY), forms a molecular glass spontaneously, upon evaporation of an aqueous solution, under room-temperature conditions.

“The commercial glass we all know is created by the rapid cooling of molten materials, a process called vitrification”, says Gal Finkelstein-Zuta. “The amorphous liquid-like organization should be fixed before it arranges in a more energy-efficient way as in crystals, and for that energy is required – it should be heated to high temperatures and cooled down immediately. On the other hand, the glass we discovered made of biological building blocks, forms spontaneously at room temperature, without the need for energy such as high heat or pressure. Just dissolve a powder in water – just like making Kool-Aid, and the glass will form. For example, we made lenses from our new glass. Instead of undergoing a lengthy process of grinding and polishing, we simply dripped a drop onto a surface, where we control its curvature – and hence its focus – by adjusting the solution volume alone”.

Solid peptide glass after preparation.

The properties of the innovative glass from TAU are unique in the world – and even contradict each other: it is very hard, but it can repair itself at room temperature; It is a strong adhesive, and at the same time, it is transparent in a wide spectral range, ranging from the visible light to the mid-infrared range.

An Unbreakable Marvel

“This is the first time anyone has succeeded in creating molecular glass under simple conditions”, says Prof. Gazit, “but not less important than that are the properties of the glass we created. It is a very special glass. On the one hand, it is very strong and on the other hand, very transparent – much more transparent than ordinary glass. The normal silicate glass we all know is transparent in the visible light range, the molecular glass we created is transparent deep into the infrared range. This has many uses in fields such as satellites, remote sensing, communications and optics. It is also a strong adhesive, it can glue different glasses together, and at the same time, can repair cracks that are formed in it. It is a set of properties that do not exist in any glass in the world, which has great potential in science and engineering, and we got all this from a single peptide – one little piece of protein”.

 

Global Coral Crisis: Deadly Sea Urchin Disease Discovered

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TAU Researchers Found the Cause of Sea Urchin Deaths in the Red Sea, Potentially Threatening Coral Reefs Worldwide.

A continuing study from TAU found that the deadly epidemic discovered last year, which has essentially wiped out Eilat’s most abundant and ecologically significant sea urchins, has spread across the Red Sea and into the Indian Ocean. According to the researchers, what appeared to be a severe but local epidemic has quickly spread through the region and now threatens to become a global pandemic.

Sea urchin mortalities on Reunion Island. Photo credit: Jean-Pascal Quod.

The researchers estimate that since it broke out in December 2022, the epidemic has annihilated most of the sea urchin populations (of the species affected by the disease) in the Red Sea, as well as an unknown number of sea urchins, estimated at hundreds of thousands, worldwide. Sea urchins are considered the ‘gardeners’ of coral reefs, feeding on the algae that compete with the corals for sunshine – and their disappearance can severely impact the delicate balance on coral reefs globally. The researchers note that since the discovery of the epidemic in Eilat’s coral reefs, the two species of sea urchins previously most dominant in the Gulf of Eilat have vanished completely.

The Research Team. Photo credit: Tel Aviv University.

The study was led by Dr. Omri Bronstein from the School of Zoology and the Steinhardt Museum of Natural History (SMNH), together with research students Lachan Roth, Gal Eviatar, Lisa Schmidt, and May Bonomo, as well as Dr. Tamar Feldstein-Farkash from the SMNH. Research partners throughout the region and Europe also took part in the study, which encompassed thousands of kilometers of coral reefs. The alarming results were published in the leading scientific journal Current Biology.

Deadly Urchin Pathogen Found

By using molecular-genetic tools, the research group at TAU was able to identify the pathogen responsible for the mass mortality of sea urchins of the species Diadema setosum in the Red Sea: a scuticociliate parasite most similar to Philaster apodigitiformis. The researchers explain that this unicellular organism was also responsible for the reoccurring mass mortality of Diadema antillarum in the Caribbeans about two years ago, following the notorious 1983 sea urchin population collapse there which led to a catastrophic phase shift of the coral reef.

Infected sea urchin on Reunion Island. Photo credit: Jean-Pascal Quod.

As noted, in December 2022, Dr. Bronstein was the first researcher to identify mass mortality of sea urchins of the species Diadema setosum – the long-spined black sea urchins that were very common in the northern Gulf of Eilat, Jordan, and Sinai. Dr. Bronstein and his team also found that the epidemic was lethal for other, closely related sea urchins from the genus Echinothrix. These results suggest that the once most abundant and significant seabed herbivores in the region are now practically gone. Thousands of sea urchins died a quick and violent death – within two days a healthy sea urchin turned into a bear skeleton with no tissues or spines, and most were devoured by predators as they were dying, unable to defend themselves. According to estimates, today only a few individuals of the affected sea urchin species remain throughout the coral reefs of the Gulf of Aqaba.

The sea urchin Diadema setosum before (left) and after (right) mortality. The white skeleton is exposed following tissue disintegration and loss of spines. Photo credit: Tel Aviv University.

Dr. Bronstein explains that sea urchins in general, and specifically diadematoids (the sea urchin family affected by the disease), are considered key species essential for the healthy functioning of coral reefs. Acting as the reef’s ‘gardeners’, the sea urchins feed on the algae that compete with the corals for sunshine, and prevent them from taking over and suffocating the corals.

According to Dr. Bronstein, the most significant and widely studied mass mortality of sea urchins to date occurred in 1983, when a mysterious disease spread through the Caribbeans, killing most sea urchins of the species Diadema antillarum – relatives of Eilat’s sea urchins. Consequently, the algae spread uncontrollably, blocking the sunlight from the corals, and the entire reef was transformed from a coral reef into an algae field. Moreover, even though the mass mortality event in the Caribbeans occurred 40 years ago, both the corals and the sea urchin populations never fully recovered, with repeated mortality events observed through the years.

The latest Caribbean outbreak in 2022 killed surviving populations and individuals from the former mortality events. This time, however, researchers had the scientific and technological tools to decipher the forensic evidence. A research group from Cornell University was able to identify the responsible pathogen, a scuticociliate parasite.

‘A Growing Ecological Crisis’

Dr. Bronstein emphasizes: “This is a growing ecological crisis, threatening the stability of coral reefs on an unprecedented scale. Apparently, the mass mortality we identified in Eilat back in 2023 has spread along the Red Sea and beyond – to Oman, and even as far as Reunion Island in the Indian Ocean.

The deadly pathogen is carried by water and can affect vast areas in a very short time. Even sea urchins raised in seawater systems at the Interuniversity Institute for Marine Sciences in Eilat, or at the Underwater Observatory, were infected and died, after the pathogen got in through the recirculating seawater system. As noted, death is quick and violent. For the first time, our research team was able to document all stages of the disease – from infection to the inevitable death – with a unique video system installed at the Interuniversity Institute for Marine Sciences in Eilat. 

Moreover, until recently, only one species of sea urchins was known to be impacted by this pathogen – the Caribbean species. Today we know that additional species are susceptible to the disease – all belonging to the same family of the most significant sea urchin herbivores on coral reefs”.

 Four healthy sea urchin species on Reunion Island. Photo credit: Jean-Pascal Quod.

Dr. Bronstein adds: “In our study we also demonstrated that the epidemic is spreading along routes of human transportation in the Red Sea. The best example is the wharf in Nueiba in Sinai, where the ferry from the Jordanian city of Aqaba docks. When we published our report last year, we already knew of sea urchin mortalities in Aqaba but had not yet identified signs of it in Sinai. The first spot in which we ultimately did identify mortality in Sinai was next to this wharf in Nueiba. Two weeks later the epidemic had already reached Dahab, about 70km further south. The scene underwater is almost surreal: seeing a species that was so dominant in a certain environment simply erased in a matter of days. Thousands of skeletons rolling on the sea bottom, crumbling and vanishing in a very short time so that even evidence for what has occurred is hard to find”.

Can We Stop the Sea Urchin Plague?

According to Dr. Bronstein, there is currently no way to help infected sea urchins or vaccinate them against the disease. We must, however, quickly establish broodstock populations of endangered species in cultivation systems disconnected from the sea – so that in the future we will be able to reintroduce them into the natural environment. 

“Unfortunately, we cannot repair nature, but we can certainly change our own behavior. First of all, we must understand what caused this outbreak at this time. Is the pathogen transported unknowingly by seacraft? Or has it always been here, erupting now due to a change in environmental conditions? These are precisely the questions we are working on now”.

 

Wake-Up Call: Global Warming and Deforestation Threaten Wildlife

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A New TAU Study Shows that Global Warming and Deforestation Could Cause Mass Animal Extinctions.

A joint study by TAU and the University of Colorado (CU) states that the combination of global warming and extreme heat events, alongside the continued expansion of deforestation in the world, may be devastating for many species of animals, especially those that know how to climb trees. As part of the study, the researchers focused on lizards and showed that following the effects of climate change, they will seek refuge from the hot ground by spending a lot of time on trees. However, due to human-related activities, such as deforestation, urbanization and the expansion of agricultural lands at the expense of natural lands, the availability of trees in the areas where the lizards live will decrease, and this may lead to the collapse of many populations.

The research was conducted under the leadership of doctoral student Omer Zlotnick from the laboratory of Dr. Ofir Levy at the School of Zoology, the Wise Faculty of Life Sciences and the Steinhardt Museum of Natural History at TAU and in collaboration with Dr. Keith Musselman from CU. The study was published in the journal Nature Climate Change. 

Climate Crisis: Animals Seeking Comfort in Trees

The researchers explain that the climate crisis and global warming force animals to search for more comfortable places to stay to escape the extreme heat, just as we look for a shady area on a hot day. For climbing animals, trees can serve as a comfortable and pleasant refuge. One of the reasons for this is that the farther you get from the ground, the lower the air temperature gets, and the stronger the wind becomes. Therefore, on hot days, for example, animals can climb up trees to escape from the hot ground.

The importance of trees, then, is expected to increase as the climate warms. The problem is that in many places in the world, the density of trees is decreasing, mainly due to phenomena such as deforestation and the expansion of the use of trees for various purposes such as construction, etc. This phenomenon creates a situation where, on the one hand, due to climate change, animals will depend more on trees for their survival, while on the other hand, the destruction of habitats will lead to a decrease in the availability of trees.

Lizards’ Habitat Loss

Doctoral student Omer Zlotnik: “As part of the research, we wanted to examine how the combined effect of these two processes would be on animals. Specifically, we focused on lizards because they are very dependent on their environment to maintain a normal body temperature, and a lack of comfortable places to stay can affect them dramatically. In the study, we used a computer simulation to simulate where the lizard should be, in the sun, in the shade, or on the tree, every minute for 20 years, under the climate conditions that existed in the past and under those expected in the future. Using the simulation, we examined how populations of lizards would be affected by climate change when trees are available and how their situation would change following the felling of trees in their habitat”.

Left to right – Dr. Ofir Levy & Omer Zlotnick

The results showed that, in general terms, climate change is going to benefit many lizard populations. In most places, the expected warming will allow lizards to be active longer throughout the day and the year, as there will be fewer times when it is too cold to come out of their burrows. However, when climate change occurs at the same time as the felling of trees, the trend is likely to reverse, so that many lizard populations may collapse. In areas with a warm climate, climate change, even if no trees are cut down, is expected to harm lizard populations, and cutting down trees will make the situation even worse.

“What’s really interesting about lizards is that they just need to be able to move a short distance around the tree trunk to get to a very different climate and habitat environment”, said Keith Musselman, an assistant professor in the Department of Geography and CU Boulder’s Institute of Arctic and Alpine Research. 

Musselman: “These microhabitats are particularly important when we think about how we modify our natural environment and make conservation decisions”.

Dr. Ofir Levy concludes: “Our research focused on lizards, but it actually demonstrates a broader problem that is relevant to many species of animals. Our results demonstrate that trees are crucially important to the ability of animals to cope with climate change, and in many cases, their availability can be, for the animals, the difference between crawling and collapsing. Our research proves how important it is to preserve forested areas and trees in general, especially in light of the changing climate. As part of the research, we also provide more practical tools for decision-makers, such as the height or density of trees required in different areas. We hope that this research will be used to build more effective programs for the conservation and restoration of natural areas so that we can provide the animals with what they need to survive”.

Go Fish: Decline in Poleward-Moving Fish

Written by AUFTAU on . Posted in Newsroom.

How Does Global Warming Impact Fish Abundance?

An extensive international study led by researchers from Tel Aviv University found a decline in the abundance of marine fish species that rapidly move toward the poles to escape rising sea temperatures. The researchers explain that many animal species are currently moving toward cooler regions as a result of global warming, but the velocity of such range shifts varies immensely for different species. Examining thousands of populations from almost 150 fish species, the researchers show that contrary to the prevailing view, rapid range shifts coincide with widescale population declines. According to the study, on average, a poleward shift of 17km per year may result in a decline of 50% in the abundance of populations. The international study was led by Ph.D. student Shahar Chaikin and Prof. Jonathan Belmaker from the School of Zoology in the Wise Faculty of Life Sciences and the Steinhardt Museum of Natural History at Tel Aviv University. The paper was published in the leading scientific journal Nature Ecology & Evolution. For the first time, the new study correlated two global databases: (1) a database that tracks fish population size over time, and (2) a database that compiles range shift velocities among marine fishes. Altogether, 2,572 fish populations belonging to 146 species were studied, mostly from the Atlantic and Pacific Oceans in the Northern Hemisphere.   Left to right - Prof. Jonathan Belmaker Shahar Chaikin Left to right – Prof. Jonathan Belmaker and Shahar Chaikin

Off the Hook

Prof. Belmaker explains: “We know that climate change causes animal species to move – northward, southward, upwards, or downwards – according to their location relative to cooler regions. In the mountains they climb upwards, in the oceans they dive deeper, in the Southern Hemisphere they move south toward Antarctica, and in the Northern Hemisphere, they move north toward the North Pole. In the present study we wanted to see what happens to species that move from one place to another: do they benefit by increased survivability, or are they in fact harmed by the shift – which was initially caused by greater vulnerability to climate change? We found that the faster fish shift toward the poles, the faster their abundance declines. Apparently, it is difficult for these populations to adapt to their new surroundings”.
PhD student Chaikin: “We found that species shifting their geographical range more rapidly towards the poles, are in fact more likely to lose their abundance (e.g. European seabass). Additional findings show differences between populations that are closer to or further from the poles – within the geographical range of a particular species. While it might have been assumed that populations closer to the cooler polar margins of the species range would be less affected by climate change, we found that the opposite is true: fast poleward range shifts of populations from higher latitudes resulted in a more rapid decline in abundance compared to equatorial populations of the same species”.
The researchers highlight that the new findings can and should guide environmental decisionmakers, by enabling a reevaluation of the conservation status of various species and populations. The study’s results suggest that populations exhibiting rapid poleward range shifts require close monitoring and careful management. Thus, for example, pressures that threaten their survival can be mitigated through measures like fishing limits. Prof. Belmaker: “The common belief is that rapid range shifts safeguard a species against local population decline. But in this study, we found that the opposite is true. Apparently, species rapidly shifting their range in search of cooler temperatures do so because they are more vulnerable to climate change, and consequently require special attention. Last year we published another study that focused on local fish species along Israel’s coastline, which resulted in similar findings: species that move towards deeper and cooler habitats in the face of rising water temperatures exhibit declining populations. In the next stage of our research, we intend to investigate this causal relationship in additional marine species, other than fish”.  

Do Viruses Have Consciousness?

Written by AUFTAU on . Posted in Newsroom.

Bacteria-Targeting Viruses Adapt, Improving their Decision-Making.

Researchers from the Shmunis School of Biomedicine and Cancer Research at Tel Aviv University have deciphered a novel complex decision-making process that helps viruses choose to turn nasty or stay friendly to their bacterial host. In a new paper, they describe how viruses co-opt a bacterial immune system, intended to combat viruses like themselves, in this decision-making process. The study was led by Polina Guler, a PhD student in Prof. Avigdor Eldar’s lab, in addition to other lab members, at the Shmunis School of Biomedicine and Cancer Research, George S. Wise Faculty of Life Sciences. The paper was published in Nature Microbiology.  

All-You-Can-Eat Bacteriophage

  Bacteriophages, also known as phages, are types of viruses that infect bacteria and use the infected bacteria to replicate and spread. Even though the word ‘bacteriophage,’ meaning ‘bacteria devouring’ in ancient Greek, suggests destruction, many phages can adopt a “sleeping” mode, in which the virus incorporates itself into the bacterial genome. In fact, in this mode of action, the virus can even have a symbiotic relationship with the bacteria, and its genes can help its host prosper.     In general, Eldar explains that phages usually prefer to stay in the “sleeping”, dormant mode, in which the bacteria “cares” for their needs and helps them safely replicate. Previous research published by the Eldar lab has shown that the phages’ decision-making uses two kinds of information to decide whether to stay dormant or turn violent: the “health status” of their host and signals from outside indicating the presence of other phages around.    
“A phage can’t infect a cell already occupied by another phage. If the phage identifies that its host is compromised but also receives signals indicating the presence of other phages in the area, it opts to remain with its current host, hoping for recovery. If there is no outside signal, the phage ‘understands’ that there might be room for it in another host nearby and it’ll turn violent, replicate quickly, kill the host, and move on to the next target”, Eldar explains.
 

Death by Phage

  The new study deciphers the mechanism that enables the virus to make these decisions. “We discovered that in this process the phage actually uses a system that the bacteria developed to kill phages”, says Guler. If it does not sense a signal from other phages—indicating that it has a good chance of finding new hosts—the phage activates a mechanism that disables the defense system. “The phage switches to its violent mode, and with the defense system neutralized, it is able to replicate and kill its host”, describes Guler. “If the phage senses high concentrations of the signal, instead of disabling the defense system, it utilizes its defense activity in order to turn on its dormant mode”.     “The research revealed a new level of sophistication in this arms race between bacteria and viruses,” adds Eldar. Most bacterial defense systems against phages were studied in the context of viruses that are always violent. Far less is known about the mechanisms of attacks and interaction with viruses that have a dormant mode. “The bacteria also have an interest in keeping the virus in the dormant mode, first and foremost to prevent their own death, and also because the genes of the dormant phage might even contribute to bacterial functions,” says Eldar.     “This finding is important for several reasons. One reason is that some bacteria, such as those causing the cholera disease in humans, become more violent if they carry dormant phages inside them – the main toxins that harm us are actually encoded by the phage genome,” explains Eldar. “Another reason is that phages can potentially serve as replacements to antibiotics against pathogenic bacteria. Finally, phage research may lead to better understanding of viruses in general and many human-infecting viruses can also alternate between dormant and violent modes”.

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