Tag: Life Sciences

The phenomenon of marine animals invading distant regions endangers local marine environments and their resident species. A new study from Tel Aviv University included a pioneering experiment simulating the changing environmental conditions encountered en route by marine animals ‘hitching a ride’ by clinging to the bottom of container ships, traveling with the ship to distant regions around the globe. In this study, researchers demonstrate that suitable regulation can decrease this phenomenon and prevent potential invaders from reaching new habitats.

The study was led by research student Doron Bereza under the supervision of Prof. Noa Shenkar of the School of Zoology at the George S. Wise Faculty of Life Sciences and the Steinhardt Museum of Natural History at Tel Aviv University. The paper was published in the prestigious journal Science of the Total Environment. 

“At any given moment, thousands of marine creatures travel from one location to another by marine vessels.”

Harmful to Local Species

The experiment demonstrated that the animals’ ability to survive the arduous journey depends on factors like the type of vessel and the route it navigates, as well as the changing temperature and salinity of seawater.

According to the researchers, the routes of vessels of different sizes are determined mainly by technical limitations of infrastructures at different ports, as well as economic trends in the shipping industry. This results in unique geographic routes that create completely different sets of environmental and other challenges for creatures attaching themselves to these vessels. 

“At any given moment, thousands of marine creatures travel from one location to another by marine vessels,” says Prof. Shenkar. “They do this in two different ways: in the ballast water – seawater taken on by the vessel for stabilizing, or by clinging to the ship’s hull. The problem of invasive species transferred by ballast is addressed by legislation, but the ‘hitchhikers’ clinging to the ships are not – and thus numerous species are transferred from place to place along international trade routes.”

Prof. Noa Shenkar

An experiment conducted by research student Doron Bereza, together with Prof. Shenkar, examined the survivability of two species of ‘ascidians’ [marine invertebrates, or cold-blooded animals with no backbone], known to be harmful, on a journey that follows a typical trade route – from Southeast Asia to Northern Europe. Ascidians attach to hard surfaces such as rocks, breakwaters, and ship hulls. There are hundreds of species of ascidians, and the rise in global trade enables some opportunistic species to disperse over great distances, sometimes establishing themselves as invasive species and harming both marine infrastructures and local species in their new habitats.

Doron Bereza: “We focused on two species of ascidians that are common in the Mediterranean, including Israel, and are known to be transferred by ships. I created a comprehensive database, comprising info from about 200 container ships, and used it to build a route representing the trade routes of two different types of container ships – giant vessels, over 395m in length, vs. ‘regular’ container ships that can be served by the infrastructures of more harbors. In addition, I collected data about changes in seawater temperatures and salinity, as well as chlorophyl concentrations, as a measure for the availability of food on the voyage and at the different ports along the way.”

“We were surprised to discover that one tropical ascidian species survived the entire journey to Rotterdam. This does not mean that the creatures enjoyed their trip, but the fact is that they did survive, and just a few individuals are sufficient for launching an invasive population in the new territory.” 

Making their Trip Unbearable

In the second stage of the study, the researchers exposed both species of ascidians to similar conditions in the lab. Bereza: “We discovered that survivability was significantly impacted by several factors: environmental conditions, the type of vessel, and traits of the animal itself. Under extreme conditions, found in some eastern ports, such as a combination of high temperatures and low salinity, one species died out completely, while no mortality was observed in the other species.”

“In real life, even when routes are generally similar, these ports are not visited by ships over a certain size, for lack of suitable infrastructures. Thus, we concluded that docking at ports with different extremes in conditions can significantly diminish the survival chances of specific species clinging to the ships. Additional experiments of this kind, specifically addressing groups of marine animals that pose a threat, can lead to effective regulatory measures for preventing the conveyance of species.”

Prof. Shenkar adds: “We were surprised to discover that one tropical ascidian species survived the entire journey to Rotterdam. This does not mean that the creatures enjoyed their trip, but the fact is that they did survive, and just a few individuals are sufficient for launching an invasive population in the new territory. Moreover, global warming is expected to enable tropical species to thrive in water that is still too cold at present. The fact that the environmental conditions in some ports on the way proved deadly to almost all members of a certain species, suggests that such locations may be utilized as environmental barriers to prevent the spreading of invasive species.”

Today, when coral reefs around the world are being severely damaged by climate change and other human impacts, many are pinning their hopes on deeper reefs to provide a ’lifeline’ of support for shallow-water coral reefs, which may be more exposed to some hazards. A new Tel Aviv University study, in collaboration with the Interuniversity Institute for Marine Sciences in Eilat, suggests that this hope might have been overestimated.

The findings of the study show that coral spawning events in the Gulf of Aqaba and Eilat, Red Sea, at the deep end of the focal species’ depth range (~30–45 m) occur at much lower intensities than those at shallow water (0–30 m). While in shallow water about half of the corals engaged in each reproductive event, this proportion dropped to only 10–20 percent in the deeper part of the reef.

According to the researchers, the significance of this finding is that there is an insufficient basis for the prevalent hope that deep reefs can serve as a ‘lifeline’ for degraded shallow reefs. In fact, they suggest that for some coral species, the opposite is true—to survive through time, deeper coral populations may more often rely on shallow-reef coral more than vice versa.

The study also demonstrates that sharp increases in water temperature within a day or two affected the onset of the breeding events in the examined species.

The study was led by PhD candidate Ronen Liberman from Tel Aviv University’s School of Zoology and Dr. Tom Shlesinger from Florida Institute of Technology; and supervised by Prof. Yehuda Benayahu of Tel Aviv University’s School of Zoology and Steinhardt Museum of Natural History. Prof. Yossi Loya, also of TAU’s Zoology School and Steinhardt Museum, participated in the study as well. The research was recently published in the prominent journal Ecology, the study partially funded by the European Commission as part of its Horizon 2020 program.

Capturing the Moment

The uniqueness of the study lies within the long-term and intensive examination of coral reproduction throughout a wide depth gradient spanning 0–50 m. The study was conducted over the course of five years to include five breeding seasons. It examined the reproduction of soft corals, also called “Octocorallia,” some of which live throughout a wide depth range in the Gulf of Aqaba and Eilat. Specifically, the researchers focused on a species of a soft coral, called Rhytisma fulvum, which reproduces by “surface-brooding”—a reproductive mode by which the coral brood, or hatch, their strikingly yellow larvae glued externally to the coral surface for several days. This unique reproductive mode helps scientists overcome many of the difficulties in examining and monitoring coral reproductive events, especially in the more challenging-to-work depths.

Ronen Liberman explains: “Most coral species are hermaphrodites, meaning that each individual functions as both male and female, and they reproduce by brief and synchronous spawning events, which usually occur once a year in the summer months. During this synchronized event, many corals simultaneously release a huge amount of sperm and eggs which meet externally in the water, where they undergo fertilization and form embryos. In other species, male corals release sperm into the water, and these cells migrate into female corals and fertilize the eggs internally, so that fertilization and embryonic development occurs within the coral. In both cases, the event lasts only a few minutes, mostly at night, so it is very difficult for researchers to ‘capture the moment,’ especially at great depths where divers cannot remain for a long time. Therefore, very little is known about coral reproduction at depths greater than approximately 15 m.”

A Colorful Event

In the present study, the researchers focused on the soft coral Rhytisma fulvum which lives in the Gulf of Eilat and Aqaba along a large depth range: from reef flats close to the sea surface and down to 50m. A particular reason for the choice of this species is its unique reproductive strategy, called “surface-brooding”. This reproductive process begins when male colonies release sperm cells in a synchronized manner, which later reach female colonies where internal fertilization occurs.

Unlike in other coral species, however, in this species, embryos do not proceed to develop internally within the coral. Instead, the fertilized eggs are released and cling to the colony via mucus for six days, where they develop into larvae. “The developing embryos have such a vibrant yellow color that makes it a very colorful event, lasting for several days. Thanks to that fact, we were able to monitor rather easily a large number of colonies along a large depth range throughout five annual reproductive seasons,” says Ronen.

Trying to create their own sunshine? (Photo: Tom Shlesinger)

Corals Like it Hot

The researchers dove to various depths, positioned temperature sensors, and examined several characteristics of the breeding events–timing, duration, and intensity of the events.

They sought to understand which environmental factors influence the onset of reproductive events:

The study showed that the timing and synchronization of reproduction events, at any given depth are associated with a clear and fast increase in water temperature of 1–1.5 degrees Celsius within 24-48 hours – a kind of a “heat wave” that is typical in the waters of the Gulf of Aqaba and Eilat in early summer. In shallow water (approx. 5-15 m), the reproductive events always occurred days to weeks before they were observed at the greater depths. The researchers attributed this phenomenon to the short-term “heat waves” in the deeper water usually occurred only several days to weeks after they occurred in the shallow water.

The reproductive intensity was measured by the number of colonies that reproduced and released embryos at each event. “We found that the number of colonies releasing embryos was significantly smaller at a depth greater than 30 meters,” Ronen adds. “Whereas at a shallow depth, about half of the colonies participated in each spawning event, in the deeper water the participation rate dropped to only 10–20 percent.”

Considering these findings, the researchers believe that the deep-water coral populations are less likely to thrive on their own and are reliant to some extent on populations from the shallower reef. Because of their lower breeding intensity, it appears that the deep-water coral population requires the contribution of the larvae from the corals found in the shallower water. The researchers suggest that this ‘weakness’ among the deep corals may be linked to the much lower intensity of sunlight that reaches their habitat. Sunlight is necessary for photosynthesis, in which symbiotic algae found within the coral tissue convert light energy to provide the coral host with the chemical energy it needs.

Protecting those at High Risk

The researchers conclude: “Today, when coral reefs around the world are being severely damaged by climate change and other human impacts, many are pinning their hopes on deeper reefs to provide a ’lifeline’ of support for shallow-water coral reefs, which may be more exposed to some hazards. While we do not wish to diminish the optimism, our research suggests that this hope might have been overestimated. Rather, it looks like it is the deeper coral populations that need the shallow ones to persist more than vice versa. Therefore, these hidden deep reefs require attention and protection on their own right, perhaps even more than the shallow reefs.”

Wheat supplies about one fifth of all calories and proteins consumed by humanity. However, through the millennia, the process of cultivation has reduced the diversity of wheat varieties, and consequently modern wheat varieties are more vulnerable than their predecessors to diseases, pests, and climate hazards. The escalating climate crisis creates an urgent need to produce wheat varieties capable of thriving in extreme environmental and climatic conditions and withstanding pests and diseases.

An international research team that includes researchers from Tel Aviv University has isolated three disease-resistance genes from wild grasses, enabling resistance to rust diseases that cause severe damage to wheat yields worldwide.

It’s in The Genes

The project was facilitated by several technological innovations that drastically cut down the time needed to identify and isolate genes from wild plant species and transfer them into cultivated plants.

“Since wheat first originated in our part of the world, wild cereals growing in our region are the progenitors of cultivated wheat, still carrying a rich variety of genetic traits that can be used to develop improved wheat varieties.”

The three genes were isolated from plants preserved in the Liberman Okinow Gene Bank of Wild Cereals at the Institute for Cereal Crops Research (ICCR) at the George S. Wise Faculty of Life Sciences at Tel Aviv University. Two of the genes, providing immunity against stem rust disease, were isolated by an international team led by researchers from the UK. The third gene, isolated by researchers at TAU, provides resistance against two different diseases – leaf rust and stripe rust, currently exacerbated due to rising temperatures around the world.

Prof. Amir Sharon, Head of ICCR, says that isolating the genes was enabled by several technological breakthroughs, and that these novel technologies can also be used to isolate genes for other beneficial properties. Transferred into the genome of cultivated wheat, such genes will serve to generate better wheat varieties – featuring higher yields, and resistant to diseases, pests, and harsh environmental conditions. “Just as each of us carries only a small part of his/her grandparents’ genes, cultivated wheat contains only a remnant of its ancient ancestors’ genetic heritage. Since wheat first originated in our part of the world, wild cereals growing in our region are the progenitors of cultivated wheat, still carrying a rich variety of genetic traits that can be used to develop improved wheat varieties,” explains Prof. Sharon.

“Certain traits of wild plants have already been incorporated into cultivated wheat over the years, however this great genetic potential remained mostly untapped, since, until recently, it took more than a decade to isolate a single gene. Today, thanks to several technological breakthroughs, especially genome sequencing and bioinformatics, we can isolate new genes in less than a year. Thus, in the past year alone, three genes providing resistance to various rust diseases were isolated from seeds of wild plants preserved in our gene bank. These genes, implanted in cultivated wheat, can significantly reduce damage from the relevant diseases with no need for pesticides – preventing yield losses while also protecting the environment.”

In addition to disease resistance, Prof. Sharon’s team is collaborating with researchers worldwide to isolate genes for other beneficial traits. Thus, for example, they work with researchers from Ben-Gurion University who recently isolated pest-resistance genes from wild wheat, and in our own Institute they’ve identified a new gene in wheat progenitors, that may provide endurance in an arid climate.

Prof. Amir Sharon & Dr. Arava Shatil Cohen in the lab

‘Safe Box’ to Tackle Climate Change

In addition to new methods for isolating genes, great advances have been made in biotechnology, specifically in technologies for gene transfer and genome editing. These technologies enable the transfer of new genes to crop plants, as well as introduction of changes into existing wheat genes.

“Essentially, the collection serves as a safe box for genes needed to create new, improved varieties of wheat that will give humanity larger crops and meet the challenges of climate change.”

ICCR implements these new technologies, offering services of wheat gene transformation and genome editing to researchers in other institutes, as well as commercial companies. “With the support of the Chief Scientist of Israel’s Ministry of Agriculture, and the Israeli Center for Genome Editing in Agriculture, we have established a center for wheat transformation and genome editing at ICCR,” shares Prof. Sharon. “This is an important milestone, enabling us, for the first time, to perform effective wheat transformation here in Israel,” says Prof. Sharon.

Dr. Arava Shatil Cohen, Head of the wheat transformation unit, adds: “With these technologies we can implant new genes and use genome editing methods to give wheat new properties. We utilize our systems to promote research at ICCR and help companies and researchers from other institutions who wish to use this technology”.

Today, ICCR’s gene bank includes over 17,000 seeds of 20 different species of wild cereals, collected in Israel over the past 50 years. The collection is unique, both because of its large number of species related to cultivated wheat, and because a large portion of the plants preserved in the gene bank were collected in natural habitats that no longer exist due to rapid urban development in Israel. “Essentially, the collection serves as a safe box for genes needed to create new, improved varieties of wheat that will give humanity larger crops and meet the challenges of climate change,” says Prof. Sharon. “The new technologies are the key to the safe box: they enable us to identify and extract the needed genes quickly and incorporate them into cultivated wheat.”

Researchers from Tel Aviv University and the Israel Oceanographic and Limnological Research Institute in Haifa have developed an innovative technology that enables the growth of “enriched seaweed” infused with nutrients, proteins, dietary fiber, and minerals for human and animal needs.

According to the researchers, the state-of-the-art technology significantly increases the growth rate, protein levels, healthy carbohydrates, and minerals in the seaweed’s tissues – making the “enriched seaweed” a natural superfood with extremely high nutritional value, which can be used in the future for the health food industry and to secure an unlimited food source.

The research was led by Ph.D. student Doron Ashkenazi, under the guidance of Prof. Avigdor Abelson from the School of Zoology, George S. Wise Faculty of Life Sciences at Tel Aviv University and Prof. Alvaro Israel of the Israel Oceanographic and Limnological Research Institute (IOLR) in Tel Shikmona, Haifa. The article was published in the scientific journal Innovative Food Science & Emerging Technologies.

“Seaweed can be regarded as a natural superfood, more abundant in the necessary components of the human diet than other food sources.”

A Natural Superfood

Doron Ashkenazi explains that in the study, local species of the algae Ulva, Gracilaria and Hypnea were grown near fish farming systems under different environmental conditions. The special conditions allowed the seaweed to flourish and enabled a significant improvement in their nutritional value ​​to the point of their becoming “enriched seaweed,” a superfood.

“Seaweed can be regarded as a natural superfood, more abundant in the necessary components of the human diet than other food sources,” Ashkenazi adds. “Through the technological approach we developed, a farm owner or entrepreneur will be able to plan in advance a production line of seaweed rich in the substances in which they are interested, which can be used as health foods or nutritional supplements; for example, seaweed with a particularly high level of protein, seaweed rich in minerals such as iron, iodine, calcium, magnesium, and zinc, or in special pigments or anti-oxidants. The enriched seaweed can be used to help populations suffering from malnutrition and nutritional deficiencies, for example disadvantaged populations around the world, as well as supplements to a vegetarian or vegan diet.”

In fact, the use of seaweed as a rich food source that meets all human nutritional needs is reminiscent of the biblical manna that fed the Israelites in the desert.

Layout of the land-based, outdoor, aquaculture system as was stationed at the IOLR institute, Haifa, Israel

“Technologies of this type are undoubtedly a model for a better future for humanity, a future where humans live in idyll and in health in their environment.”

Aquaculture, Tomorrow’s Agriculture

Unlike terrestrial agriculture, aquaculture, and in particular the proposed seaweed farming approach, does not require extensive land, fresh water, or large amounts of fertilizer. Environmentally friendly, it preserves nature and the ecological balance by reducing environmental risks. The new methodology, in fact, offers an ideal situation, of sustainable and clean agriculture.

Today, integrated aquaculture is beginning to receive support from governments around the world due to its environmental benefits, which include the reduction of nutrient loads to coastal waters and of the emission of gases and carbon footprints. In this way, it contributes to combatting the climate crisis and global warming.

“Technologies of this type are undoubtedly a model for a better future for humanity, a future where humans live in idyll and in health in their environment,” concludes Ashkenazi.

The research was conducted in collaboration with other leading researchers from around the country, including Guy Paz and Dr. Yael Segal of the Israel Oceanographic and Limnological Research Institute (IOLR) in Haifa, Dr. Shoshana Ben-Valid, an expert in organic chemistry, Dr. Merav Nadav Tsubery of the Department of Chemistry in the Faculty of Exact Sciences at Bar-Ilan University, and Dr. Eitan Salomon from the National Center for Mariculture in Eilat.

Shortly after outbreak of the Corona epidemic, accusations were voiced among the public, as well as within the scientific community, claiming that the bats are considered a health threat, as reservoirs of viruses’, including the Covid-19 virus. A new Tel Aviv University study rejects this correlation between the Covid-19 outbreak and bats, which the researchers say was not based on sufficient compelling scientific proof. Bats have a highly effective immune system that enables them to deal relatively easily with viruses that are considered lethal for other mammals.

Bats with a Bad Rap

The study was led by Dr. Maya Weinberg from the laboratory of Prof. Yossi Yovel, Head of the Sagol School of Neuroscience and faculty member of the School of Zoology and the Steinhardt Museum of Natural History at Tel Aviv University. The research team reviewed dozens of leading articles and studies in this field, and their conclusions were published in writing in the prestigious iScience Journal.

The researchers explain that the infamous reputation of the bats is well known among both the scientific community and the public at large, namely that they are often accused of being reservoirs of viruses including Covid-19, thus posing a threat to public health. While there is indeed evidence that the origin of the “ancient potential” Covid-19 was in bats, the researchers note that two years after the pandemic first broke out, we still do not know for sure what the exact origin of the COVID-19 variant is.

“Bats have a highly effective immune system that enables them to deal relatively easily with viruses considered lethal for other mammals.”

Dr. Weinberg: “In general, bats are mistakenly conceived of as reservoirs of many contagious disease, only due to their being positive serologically positive; in other words, in possession of antibodies, which means that bats have survived the disease and developed an immune response. After that, they overcame the virus altogether and disengaged from it; hence, they are no longer its carriers. Nevertheless, in many cases, a virus similar to a human pathogen is liable to be found in bats; however, it is not pathogenic to humans, and is not sufficient to use bats as a reservoir.”

Dr. Weinberg with a friend

Capable of Coping with Different Viruses

To examine the overall situation, the researchers conducted a meta-analysis of literature on over 100 viruses for which bats are considered potential reservoirs, including Ebola, SARS, and COVID. “We found that in a considerable number of cases (48%) this claim was based on the incidence of antibodies or PCR tests, rather than actual isolation of identical viruses. Moreover, many of the reported findings are not convincing,” says Dr. Weinberg.

“The mere isolation of a virus is not enough to see an animal as a reservoir, since a minimum number of index cases is required in which the virus is isolated in order to be considered a reservoir animal, as well as the existence of an established path of transmission. Furthermore, the very detection of a particular virus in bats does not necessarily ensure further infection. Additional biological, ecological, and anthropogenic conditions must exist for such an event to occur.”

According to the researchers, simultaneously, in recent years evidence is accumulating of the fact that bats are capable of coping with different viruses, including lethal ones, better than humans and most other mammals. After over 100 years of focus on viruses carried by bats, it appears that bats’ immune system is characterized by a restrained response during inflammatory processes. As we see it, bats have developed an excellent balance between resistance and tolerance: an increased defense response of the host, and immune tolerance through a number of different mechanisms. Moderate inflammatory pathways contribute to immune tolerance with bats, and a well-balanced response that prevents the virus from developing.

“The comprehensive study we’ve conducted raises serious doubts regarding the possibility of bats being the origin of the Covid19 outbreak. The findings give rise to the opposite perspective, according to which we must study in-depth the immunological anti-viral capabilities of bats, and thus obtain new and effective means of coping in humanity’s struggle against contagious disease, aging, and cancer,” concludes Dr. Weinberg.