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.

For centuries, nature lovers and scientists have been fascinated by the fact that creatures in the sea are able to glow. The phenomenon is very common in reef-building corals, but its biological role has been the subject of constant debate. Numerous hypotheses have been tested over the years. Some suggested that this phenomenon protect against radiation. Or perhaps it contributed to the optimization of the photosynthesis? Maybe the glowing property helped protect the coral against herbivores or to attract symbiotic algae to the corals?

A new Tel Aviv University study, in collaboration with the Steinhardt Museum of Natural History, and the Interuniversity Institute for Marine Sciences in Eilat, has proven for the first time that the magical phenomenon – whereby corals in deep reefs display glowing colors (fluorescence) – is intended to serve as a mechanism for attracting prey.

The study was led by Dr. Or Ben-Zvi, in collaboration with Yoav Lindemann and Dr. Gal Eyal, under the supervision of Prof. Yossi Loya from the School of Zoology and the Steinhardt Museum of Natural History at Tel Aviv University.

Chasing the Glow

The researchers first sought to determine whether plankton (small organisms that drift in the sea along with the current) are attracted to fluorescence, both in the laboratory and at sea. Then, in the lab, the researchers quantified the predatory capabilities of mesophotic corals (corals that live between the shallow coral reef area and the deep, completely dark zone of ​​the ocean), which exhibit different fluorescent appearances.

To test the planktons’ potential attraction to fluorescence, the researchers used, among other things, the crustacean Artemia salina, which is used in many experiments as well as for food for corals. The researchers noted that when the crustaceans were given a choice between a green or orange, fluorescent target versus a clear ‘control’ target, they showed a significant preference for the fluorescent target.

Moreover, when the crustaceans were given a choice between two clear targets, its choices were observed to be randomly distributed in the experimental setup. In all of the laboratory experiments, the crustaceans vastly exhibited a preferred attraction toward a fluorescent signal. Similar results were presented when using a native crustacean from the Red Sea. However, unlike the crustaceans, fish that are not considered coral prey did not exhibit these trends, and rather avoided the fluorescent targets.

Fluorescent Traps

The second phase of the study was carried out about 40 meters deep in the sea, where the fluorescent traps (both green and orange) attracted twice as many plankton as the clear trap.

“We conducted an experiment in the depths of the sea to examine the possible attraction of diverse and natural collections of plankton to fluorescence, under the natural currents and light conditions that exist in deep water,” says Dr. Or Ben-Zvi. “Since fluorescence is ‘activated’ principally by blue light (the light of the depths of the sea), at these depths the fluorescence is naturally illuminated, and the data that emerged from the experiment were unequivocal, similar to the laboratory experiment.”

“This phenomenon may play a greater role in marine ecosystems than previously thought.”

 

The “Light Trap Hypothesis”

In the last part of the study, the researchers examined the predation rates of mesophotic corals that were collected at 45 m depth in the Gulf of Eilat. They found that corals that displayed green fluorescence enjoyed predation rates that were 25 percent higher than corals exhibiting yellow fluorescence.

Prof. Loya: “Many corals display a fluorescent color pattern that highlights their mouths or tentacle tips, a fact that supports the idea that fluorescence, like bioluminescence (the production of light by a chemical reaction), acts as a mechanism to attract prey. The study proves that the glowing and colorful appearance of corals can act as a lure to attract swimming plankton to ground-dwelling predators, such as corals, and especially in habitats where corals require other energy sources in addition or as a substitute for photosynthesis (sugar production by symbiotic algae inside the coral tissue using light energy).”

Dr. Ben-Zvi concludes: “Despite the gaps in the existing knowledge regarding the visual perception of fluorescence signals by plankton, the current study presents experimental evidence for the prey-luring role of fluorescence in corals. We suggest that this hypothesis, which we term the ‘light trap hypothesis’, may also apply to other fluorescent organisms in the sea, and that this phenomenon may play a greater role in marine ecosystems than previously thought.”