Tag: Zoology

An Underwater Journey Following the Vanishing of Sponge Species from the Shallow Water of the Israeli Coast

The researchers believe that the sharp rise in water temperatures may lead to the death and disappearance.

Researchers from Tel Aviv University embarked on an underwater journey to solve a mystery: Why did sponges of the Agelas oroides species, which used to be common in the shallow waters along the Mediterranean coast of Israel, disappear? Today, this species can be found in Israel mainly in deep sponge grounds – rich habitats that exist at a depth of 100 meters. The researchers assess that the main reason for the disappearance of the sponges was the rise in seawater temperatures during the summer months, which in the past 60 years have risen by about three degrees.

The study was led by Prof. Micha Ilan and PhD student Tal Idan, in collaboration with Dr. Liron Goren and Dr. Sigal Shefer, all from the School of Zoology at the George S. Wise Faculty of Life Sciences and the Steinhardt Museum of Natural History. The article was published in the journal Frontiers in Marine Biology.

Tal Idan explains: “Sponges are marine animals of great importance to the ecosystem, and also to humans. They feed by filtering particles or obtain substances dissolved in the seawater and making them available to other animals, and are used as a habitat for many other organisms. Also, the sponges contain a wide variety of natural materials – chemicals that are used as a basis for the development of medicines. In our study, we focused on the Agelas oroides species – a common Mediterranean sponge that grew throughout the Mediterranean Sea, from a depth of less than a meter to 150 meters deep, but which has not been observed in Israel’s shallow waters for over 50 years.”

During the study, the researchers used a research vessel and an underwater robot belonging to the NGO “EcoOcean,” and with their help located particularly rich rocky habitats on the seabed at a depth of about 100 meters, approximately 16 kilometers west of Israeli shores. The most dominant animals in these habitats are sponges, which is why the habitats are called “sponge gardens.” The researchers collected 20 specimens of the Agelas oroides sponge, 14 of which were transferred to shallow waters at a depth of 10 meters, at a site where the sponge was commonly found in the 1960s. The remaining six specimens were returned to the sponge gardens from which they were taken, and used as a control group.

underwater robot. Photo: Tal Idan

The findings of the study showed that when the water temperature ranged from 18 to 26 degrees (in the months of March to May), the sponges grew and flourished: they pumped and filtered water, the action by which they feed, and their volume increased. However, as the water temperature continued to rise, the sponges’ condition deteriorated. At a temperature of 28 degrees, most of them stopped pumping water, and during the month of July, when the water temperature exceeded 29 degrees, within a short period of time all of the sponges that had been transferred to the shallow water died. At the same time, the sponges in the control group continued to enjoy a relatively stable and low temperature (between 17 and 20 degrees) which allowed them to continue to grow and thrive.

Thus, the researchers hypothesize that the decisive factor that led to the disappearance of the sponges from the shallow area was prolonged exposure to high seawater temperature. According to them, “In the past, the temperature would also reach 28.5 degrees in the summer, but only for a short period of about two weeks – so the sponges, even if damaged, managed to recover. Today, seawater temperatures rise above 29 degrees for three months, which likely causes multi-system damage in sponges, which leaves them no chance of recovering and surviving.”

Prof. Ilan: “From 1960 until today, the water temperature on the Israeli Mediterranean coast has risen by three degrees, which may greatly affect marine organisms, including sponges. Our great concern is that the changes taking place on our shores are a harbinger of what may take place in the future throughout the Mediterranean. Our findings suggest that continued climate change and the warming of seawater could fatally harm sponges and marine life in general.”

The researchers add that in recent years, in collaboration with the Ministry of Energy and the Israel Nature and Parks Authority, they have been conducting extensive surveys in a number of sponge gardens along the coast, with the clear aim of protecting these unique habitats and changing their status so that they are recognized as particularly vulnerable. Three of the research sites have now been made part of the Nature and Parks Authority’s Marine Nature Reserves Program, in the hopes that they will eventually receive official recognition as marine nature reserves.

Featured image: Tal Idan

Why Do Bats Fly Into Walls?

A sensory misperception – like people bumping into a glass wall

Why do bats fly into walls, even though they can hear them? Researchers at Tel Aviv University conducted an experiment in which they released dozens of bats in a corridor blocked by objects of different sizes, made of different materials. To their surprise, the researchers discovered that the bats collided with large sponge walls (that produce a weak echo) as if they did not exist. The bats’ behavior suggested that they did this even though they had detected the wall with their sonar system, indicating that the collision did not result from a sensory limitation, but rather from an acoustic misperception. The researchers hypothesize that the unnatural combination of a large object (wall) and a weak echo disrupts the bats’ sensory perception and causes them to ignore the obstacle (much like people who bump into transparent walls).

The study was led by Dr. Sasha Danilovich then a PhD student in the lab of Prof. Yossi Yovel, Head of the Sagol School for Neuroscience and faculty member at the School of Zoology at the George S. Wise Faculty of Life Sciences. Other participants included Dr. Arian Bonman and students Gal Shalev and Aya Goldstein of the Sensory Perception and Cognition Laboratory at the School of Zoology and the Sagol School of Neuroscience. The paper was published in PNAS.

At the next stage of the experiment, the researchers methodically changed the features of the echoing objects along the corridor in terms of size, texture and echo intensity. They concluded that the bats’ acoustic perception depends on a coherent, typical correlation of the dimensions with objects in nature. For example: large object- strong echo; small object – weak echo.

“Bats excel in acoustic perception. They are able to detect objects as tiny as mosquitoes, using sound waves,” explains Prof. Yovel. “Using echolocation they can calculate the 3-dimensional location of both small and large objects, perceiving their shape, size and texture. To this end a bat’s brain processes various acoustic dimensions from the echoes returning from the object (such as frequency, spectrum and intensity). This perception is based on several senses that combine many different dimensions, such as color and shape.”

In addition, the researchers at TAU discovered that bats are not born with this ability. Repeating the experiment with young bats they found that they do not fly into walls.  The study also found that adult bats can quickly learn the new correlations among the dimensions.

“By presenting the bats with objects whose acoustic dimensions are not coherent, we were able to mislead them, creating a misconception that caused them to repeatedly try to fly through a wall, even though they had identified it with their sonar. The experiment gives us a peek into how the world is perceived by these creatures, whose senses are so unique and different from ours,” says Sasha Danilovich.

Pharmaceutical residuals pose a serious threat to Marine life

A study by Tel Aviv University reveals worrying evidence of environmental contamination

A study led by Prof. Noa Shenkar and graduate student Gal Navon, from the Tel Aviv University (TAU) School of Zoology and the Steinhardt Museum of Natural History, has found significant concentrations of residual pharmaceuticals at 11 sampled sites along the Israeli coastline. These substances have been found in ascidians – marine, filter-feeding, sessile invertebrates. This study was conducted with the participation of the Hydrochemistry Lab of the Water Research Center of the Porter School of the Environment and Earth Sciences, Raymond & Beverly Sackler Faculty of Exact Sciences, Tel Aviv University, headed by Prof. Dror Avisar. The study was published in the journal “Marine Pollution Bulletin”, in August 2020. The study involved sampling of ascidians from 9 different sites along the Mediterranean coastline (Achziv, Acre, Haifa Marina, Sdot Yam, Hadera power station, Acadia beach in Herzliya, HaSela beach in Bat-Yam, Ashdod Marina and Ashkelon Marina) and 2 different Red Sea sites (Eilat Marina and Dolphin Reef). Ascidians are marine invertebrates, few centimetres in size that attach to hard surfaces – such as rocks, peers or breakwaters. Since ascidians feed on small particles found in the water, large quantities of particles from the marine environment accumulate in their bodies over time – including different pollutants. The researchers have performed chemical analysis of the collected ascidians, searching for active compounds of three frequently used pharmaceuticals: Bezafibrate, which reduces blood lipids content; Carbamazepine, an antiepileptic, and mood stabilizer; and Diclofenac, an anti-inflammatory agent present in the well-known medicine Voltaren. These three substances are extremely durable, are hardly degraded by sewage treatment facilities, and last long in the marine environment. The findings are extremely worrisome: in 10 out of 11 sampled sites significant concentrations of the tested pharmaceuticals have been found.
  • All three substances have been detected at 4 of the tested sites (Ashdod, Ashkelon, Sdot Yam and Haifa).
  • Residuals of two of the pharmaceuticals have been detected at 5 of the tested sites (Achziv, Acre, Herzliya, Bat-Yam and the Eilat Marina).
  • One site – Eilat Dolphin Reef, has shown signs of one pharmaceutical only – Diclofenac, though at a concerning concentration
  • Ascidians collected from deep water at the Hadera power station were the only ones to show no traces of pharmaceuticals.
  • Especially high concentrations of Diclofenac and Bezafibrate were found in Acre, Ashdod and Ashkelon.
  Did they take their medicine today? Ascidians Prof. Shenkar and the researcher Gal Navon explain that various pharmaceuticals consumed by humans are not fully metabolized in the body, and high percentage of their active compounds are later excreted in their original form. In addition, lack of public awareness often results in the disposal of unused drugs in toilets or home garbage bins. Currently existing sewage treatment facilities are not suitable for the treatment of medication residuals, and, unlike other pollutants, their final concentrations at the endpoint of sewage treatment are not monitored. Eventually, a substantial amount of pharmaceuticals is discharged into the sea by sewage water. According to the research team, a variety of pharmaceutical residuals can be found in marine ecosystems worldwide – antibiotics, anti-inflammatory drugs, analgesics, anti-depressants and many more. “Many of these compounds are very stable”, the researchers say, “These take a long time to degrade in the marine environment, and the damage they cause to marine life could be extremely excessive, since these pharmaceuticals are designed to affect biological systems (the human body). For example, various studies performed in different sites around the world have shown that Estrogen, present in birth control pills, leads to the development of female features in male fish in certain species, thus damaging their fertility; Prozac triggers increased aggressiveness and risk-taking in crustaceans; anti-depressants impair memory and learning in cuttlefish, and more”. Prof. Avisar: “We have been studying the chemo-physical fate of drug residuals in groundwater and surface water for the past 15 years, and their detection in marine ecosystems has been surprising. The results indicate a chronic large-scale pharmaceutical residuals contamination, as well as the absorption of micro- and nano-pollutants, measured at very low concentrations in marine organisms”. “Our study shows that Israel is no stranger to the global serious issue of seawater pharmaceutical contamination.”, Prof. Shenkar concludes. “The medications we use end up in the sea, mainly through sewage discharge, and cause great damage to the marine environment, indirectly affecting humans, who feed on sea foods that are exposed to such contamination. There are different ways to tackle this problem: on the individual level, we recommend that the population as a whole takes personal responsibility, disposing of unused pharmaceuticals into designated containers – which can be found at pharmacies and health maintenance organizations’ facilities. In addition, we are working to expand research on monitoring pharmaceutical contamination along the Israeli coastline, using advanced analysis of a greater variety of widely used medication, while examining the changes exerted upon the various organisms exposed to the environmental concentrations of those pharmaceuticals”.

Bats navigate just like humans – using their excellent eyesight and a cognitive map

A new study investigates the navigation capabilities of bats from birth to maturity

For the first time in history, researchers at Tel Aviv University tracked fruit bats from birth to maturity, in an attempt to understand how they navigate when flying long distances. The surprising results: Fruit bats, just like humans, build a visual cognitive map of the space around them, making use of conspicuous landmarks. In this case, bat pups from Tel Aviv University came to know the city by looking for large unique structures such as the Azrieli Towers, the Dizengoff Center etc. The groundbreaking study was conducted by Prof. Yossi Yovel, together with students Amitai Katz, Lee Harten, Aya Goldstein and Michal Handel from the Sensory Perception and Cognition Laboratory at the Department of Zoology. The paper was published in July 2020 as the cover story of the prestigious Science Magazine. “How animals are able to navigate over long distances is an ancient riddle,” explains Prof. Yovel. “Bats are considered world champions of navigation: they fly dozens of kilometers in just a few hours, and then come back to the starting point. For this study we used tiny GPS devices – the smallest in the world, developed by our team, in an experiment never attempted before: tracking bat pups from the moment they spread their wings until they reach maturity, in order to understand how their navigation capabilities develop. No such study has ever been conducted on any living creature, and the findings are very interesting.” The researchers monitored 22 fruit bat pups born in a colony raised at TAU – from infancy to maturity, tracking them as they scoured the city for food. The results show that Tel Aviv bats navigate the space around them in much the same way as the city’s human inhabitants. “Bats use their sonar to navigate over short distances – near a tree, for example,” says Prof. Yovel. “The sonar doesn’t work for greater distances. For this, fruit-bats use their vision. Altogether we mapped about 2000 bat flight-nights in Tel Aviv. We found that bats construct a mental map: They learn to identify and use salient visual landmarks such as the Azrieli Towers, the Reading Power Station and other distinct features that serve as visual indicators. The most distinct proof of this map lies in their ability to perform shortcuts. Like humans, bats at some stage get from one point to another via direct new routes not previously taken. Since we knew the flight history of each bat since infancy, we could always tell when a specific bat took a certain shortcut for the first time. We discovered that when taking new, unknown routes the bats flew above the buildings. Sending up drones to the altitude and location where a bat had been observed, we found that the city’s towers were clearly visible from this high angle. Here is another amazing example of how animals make use of manmade features.”

Coral danger: breakdown in spawning could mean extinction

Synchronized coral spawning has become erratic, endangering the long-term survival of coral species, Tel Aviv University researchers say

Coral reefs are among the most diverse and productive ecosystems on our planet. But due to climate change and other human stressors, reef-building corals that reproduce by means of broadcast-spawning — the simultaneous release of eggs and sperm into open water — may now be under threat of extinction.

A new Tel Aviv University study finds that the highly synchronized, iconic spawning events of certain reef-building corals in the Gulf of Eilat/Aqaba, Red Sea, have completely changed over time and lost their vital synchrony, dramatically reducing chances of successful fertilization.

According to the research, led by Prof. Yossi Loya and PhD candidate Tom Shlesinger of TAU’s School of Zoology and published in Science, the breakdown in coral spawning synchrony has led to a dearth of new recruits and stagnant aging populations, creating circumstances for extinction.

It’s all in the timing

“Coral spawning, often described as ‘the greatest orgy in the world,’ is one of the greatest examples of synchronized phenomena in nature,” explains Prof. Loya. “Once a year, thousands of corals along hundreds of kilometers of a coral reef release their eggs and sperm simultaneously into the open water, where fertilization will later take place. Since both the eggs and the sperm of corals can persist only a few hours in the water, the timing of this event is critical.”

Successful fertilization, which can take place only within this narrow time window, has led to the evolution of a precise spawning synchrony. Such synchronicity relies on environmental cues: sea temperature, solar irradiance, wind, the phase of the moon and the time of sunset.

In 2015, the researchers initiated a long-term monitoring of coral spawning in the Gulf of Eilat/Aqaba. Over four years, they performed 225 night field surveys lasting three to six hours each during the annual coral reproductive season from June to September and recorded the number of spawning individuals of each coral species.

“We found that, in some of the most abundant coral species, the spawning synchrony had become erratic, contrasting both the widely accepted paradigm of highly synchronous coral spawning and studies performed on the exact same reefs decades ago,” says Shlesinger.

Extinction through reproductive failure

The researchers then investigated whether this breakdown in spawning synchrony translated into reproductive failure. They mapped thousands of corals within permanent reef plots, then revisited these plots every year to examine and track changes in the coral community — i.e., how many corals of a given species had died compared with new juveniles recruited to the reef.

“Although it appeared that the overall state of the coral reefs at Eilat was quite good and every year we found many new corals recruiting to the reefs, for those species that are suffering from the breakdown in spawning synchrony, there was a clear lack of recruitment of new juvenile generations, meaning that some species that currently appear to be abundant may actually be nearing extinction through reproductive failure,” says Shlesinger.

The future of corals?

“Several possible mechanisms may be driving the breakdown in spawning synchrony that we found,” Prof. Loya concludes. “For example, temperature has a strong influence on coral reproductive cycles. In our study region, temperatures are rising fast, at a rate of 0.31 degrees Celsius per decade, and we suggest that the breakdown in spawning synchrony reported here may reflect a potential sublethal effect of ocean warming. Another plausible mechanism may be related to endocrine (hormonal) disrupting pollutants, which are accumulating in marine environments as a result of ongoing human activities that involve pollution.”

“Regardless of the exact cause leading to these declines in spawning synchrony, our findings serve as a timely wake-up call to start considering these subtler challenges to coral survival, which are very likely also impacting additional species in other regions,” says Shlesinger. “On a positive note, identifying early-warning signs of such reproductive mismatches will contribute to directing our future research and conservation efforts toward the very species that are at potential risk of decline, long before they even display any visible signs of stress or mortality.”

Inside a bat’s brain

Prof. Yaniv Assaf and Prof. Yossi Yovel are working together on a unique collection of brain scans of different mammals

It’s a chicken versus egg scenario: Does behavior build a neural network or does the design of a brain network dictate behavior? It turns out that they both influence each other.

“Evolutionary science holds that particular behaviors drives the brain to develop and evolve in a particular way. Later, brain networks may drive behavior,” explains Prof. Yossi Yovel of the Department of Zoology, George S. Wise Faculty of Life Sciences. Yovel specializes in bat echolocation – the location of objects by reflected sound – at his Bat Lab of Neuro-Ecology. 

A number of years ago he approached his former MSc advisor, Prof. Yaniv Assaf, Head of the Department of Neurobiology, with a surprising request. Yovel sought to draw on Assaf’s expertise in MRI imaging techniques to scan the brains of wild bats. Could the images show how bats’ use of sound rather than vision to navigate the world influences the development of their neural networks? “I focus on human brain imaging,” says Assaf. “Now, five years later, we have scanned over 100 species – all expired of natural causes – including many species of bats, of course,” Assaf continues with a nod to Yovel. “We use the MRI machine after hours so as not to interfere with ongoing research, and we have found that, yes, bat brain networks have highly developed aural – rather than visual – networks.”

From bats to all mamals

What began as a scientific hobby has become a scientific first. The scans, which are specially calibrated to show the design and function of brain microstructure, pathways, and networks, reveal the principles governing the mammalian brain.

“Like the internet and other computer networks, or road and transportation systems, the brain is a network. The brain’s two hemispheres are connected with fibers. Our scans show that mammals with a greater number of inter-hemisphere connecting fibers will have, inversely, poorer connectivity within the hemisphere itself and vice-versa,” says Assaf. “This information can influence how networks are constructed.”

The true story of the autistic man who inspired the film Rain Man illustrates this phenomenon: The hemispheres of his brain were completely unconnected. The local network in each hemisphere was so strong that he could perform complex computations within seconds. But the lack of connection between hemispheres affected his function and behavior. We need a mix of both for a functional, strong network.

Access for researchers worldwide

”While evolutionary scientists are certainly interested in our scans, it is mathematicians and computer scientists working on smart, efficient computer networks and artificial intelligence who are the most excited,” says Assaf.

Yovel continues, “When people hear about our project at conferences or by word of mouth, they immediately want to see our findings. But we are not yet ready. We aim to scan 10% of all mammals, which means about 500 species including those transported from abroad, which will be very costly. We need graduate students to help build the collection more quickly. We aim to create the only collection of its kind worldwide – a digital collection of scans at the Steinhardt Museum of Natural History that can be accessed by scientists around the world.”

Featured image: Prof. Yossi Yovel and Prof. Yaniv Assaf 


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