Alex Jordan: "Fish are not stupid, they're different!"

Alex Jordan is a behavioral ecologist at the Max Planck Institute of Animal Behavior in Konstanz, Germany. His main interest: he wants to know why animals do what they do. He is especially devoted to fish, having been a hobbyist since a young age, and seeing the value of being able to study animals equally well in the wild as in captivity.

Alex, a few years ago you conducted a study that resonated strongly in the scientific community on the reaction of cleaner wrasses to their mirror image. What did you find out in the process?

We placed marks on the cleaner wrasses' bodies that they could only see in a mirror. The fish then tried to remove these marks. We performed various tests to make sure that the fish only reacted to marks that they saw on their own bodies in the mirror an nothing else.

A mirror test passed in this way is considered by researchers to be evidence of self-awareness. Only a few species score positively in this test, for example apes, corvids, dolphins - and now cleaner wrasses.

What do you conclude from this? Are the fish aware of themselves?

No, I don't think so. I suspect the wrasses have simply learned that a mirror creates an image of something - in this case, themselves. Since dark spots on fish bodies are an important signal for wrasses by nature - they usually represent parasites, which the wrasses feed on - they are naturally particularly interested in this. However, they probably do not possess self-awareness or even self-consciousness.

In any case, the test demonstrates that the fish are extremely adaptive and can exploit new opportunities for themselves. 

What can the mirror test then tell us in the first place?

In my opinion, the mirror test is not well suited for studying self-awareness in animals. We also did the test with African cichlids from Lake Tanganyika. They didn't care about the marks on their bodies at all. Also the cleaner wrasses passed the test only if the marks were brown. They didn’t care about marks of other colors. It is important to remember that other highly evolved animals, such as dogs or cats, do not pass the test either.

There are different reasons why an animal does not react to the marks, so in my opinion the test is not suitable to answer the question about self-awareness. It was developed by humans for humans. For most animals, it just doesn't fit.

How can you find out what other organisms think, feel, perceive?

That is very difficult in principle. Even you and I differ in how we perceive things. But you can at least describe your cognitive status to me. Since we can hardly or not at all communicate with animals, we can only infer what they feel, want, think. Some degree of uncertainty will always remain, because we can't help but take ourselves as the measure of all things. To leave our human world of experience and to put ourselves into the world of a fish is all but easy.

How could we nevertheless get an idea of what is going on inside a fish?

We want to try this with a completely new approach. We will measure the activity of nerve cells in the brain when zebrafish react to conspecifics or when they face their mirror image. If there are different activation patterns in the brain in the two cases, this would indicate that the fish are not seeing a conspecific, but themselves. That would be a strong hint for the fish being self-aware.

Fish are commonly regarded as primitive and not very intelligent. Is this justified?

Not at all. We need to stop seeing ourselves as the pinnacle of evolution and ranking other animals in descending order below. All organisms on earth are the result of millions of years of evolution. They and their predecessors have always managed to defy all odds and adapt. Seen in this light, even a bacterium is highly evolved.

Consequently, fish are not dumber or worse than us, they are just different!

How smart are fish?

We don't know exactly yet, but there are definitely differences between species. Fish that migrate in large anonymous schools through the ocean probably need less higher mental abilities than those that defend territories, for example. So I would expect more from a Tanganyika cichlid than from a mackerel.

It is known from other groups of animals that species with a narrow food spectrum are less capable cognitively than those that eat a variety of foods. Thus, the omnivores among fishes might generally be "smarter" than specialists.

Marine fish often exhibit more complex behaviors than freshwater species - simply because inland waters have not existed as long as the oceans, and therefore they have less time to develop such behaviors.

What can fish do?

Some fish are very sophisticated. They can play and use tools, they predict the actions of others, and they even cheat and reconciliate. Some species thus possess higher cognitive abilities than other vertebrates. They may not be that far from apes and humans.

Fish can also recognize people. They know who to expect food from and who not to expect it from, as many aquarium owners can attest. In our research area in Lake Tanganyika, for example, predatory fish from the genus Lepidiolamprologus have learned that they can prey  when my colleague and I are out diving. In doing so, they don't follow me, but her, because she flushes out most of the fish.

And not only that: some species can also distinguish conspecifics individually. Damselfish, for example, have individual color markings on their faces that are only visible in ultraviolet light, which they use to recognize each other.

Another fascinating example, which we plan to investigate ourselves, is how mullet and wrasses work together in the Mediterranean. When a mullet is foraging and scavenging on the sand, it is often accompanied by a wrasse, which preys on small critters scared up by the mullet. This alone would be nothing special, but the wrasse keeps touching the mullet - it literally caresses it. Probably the mullet knows in this way that there is no danger from above while it burrows underground. The "masseur" thus ensures that the mullet stays in its territory.

What do these findings mean for how we treat fish today?

Even if there is still a lot we don't know, one thing is clear: fish can do more than we have given them credit for up to now. They are sentient animals capable of cognitive engagement with the world around them, including social interactions, fear, suffering, and enjoyment.

Thank you for this interview!

Interview by Harald Rösch

Source / Credit: MAX-PLANCK-GESELLSCHAFT

‘Vegetarian’ giant tortoise filmed attacking and eating seabird

 The hunting tortoise was seen in July 2020 on Frégate Island, a privately owned island in the Seychelles group managed for ecotourism, where around 3,000 tortoises live. Other tortoises in the same area have been seen making similar attacks.

“This is completely unexpected behavior and has never been seen before in wild tortoises,” said Dr Justin Gerlach, Director of Studies at Peterhouse, Cambridge and Affiliated Researcher at the University of Cambridge’s Museum of Zoology, who led the study.

He added: “The giant tortoise pursued the tern chick along a log, finally killing the chick and eating it. It was a very slow encounter, with the tortoise moving at its normal, slow walking pace – the whole interaction took seven minutes and was quite horrifying.” 

The interaction was filmed by Anna Zora, conservation manager on Frégate Island and co-author of the study. 

“When I saw the tortoise moving in a strange way I sat and watched, and when I realized what it was doing I started filming,” said Zora.

The finding is published today in the journal Current Biology.

All tortoises were previously thought to be vegetarian - although they have been spotted feeding opportunistically on carrion, and they eat bones and snail shells for calcium. But no tortoise species has been seen actively pursuing prey in the wild before.

The researchers think that this entirely new hunting behavior was driven by the unusual combination of a tree-nesting tern colony and a resident giant tortoise population on the Seychelles’ Frégate island.

Extensive habitat restoration on the island has enabled sea-birds to recolonize, and there is a colony of 265,000 noddy terns, Anous tenuirostris. The ground under the colony is littered with dropped fish and chicks that have fallen from their nests.

In most places, potential prey are too fast or agile to be caught by giant tortoises. The researchers say that the way the tortoise approached the chick on the log suggests this type of interaction happens frequently.

On the Galapagos and Seychelles islands, giant tortoises are the largest herbivores and eat up to 11% of the vegetation. They also play an important role in dispersing seeds, breaking vegetation and eroding rocks.

“These days Frégate island’s combination of tree-nesting terns and giant tortoise populations is unusual, but our observation highlights that when ecosystems are restored totally unexpected interactions between species may appear; things that probably happened commonly in the past but we’ve never seen before,” said Gerlach.

This research was supported by Fregate Island Foundation.

Reference

Zora, A. & Gerlach, J.: ‘First documented observations of giant tortoises hunting and consuming birds.’ Current Biology, August 2021, DOI: 10.1016/j.cub.2021.06.088

Source / Credit: University of Cambridge 

Attribution 4.0 International (CC BY 4.0)

Wildfire Smoke and Early Births

Wildfire smoke exposure during pregnancy increases preterm birth risk, Stanford study finds

Smoke from wildfires may have contributed to thousands of additional premature births in California between 2007 and 2012. The findings underscore the value of reducing the risk of big, extreme wildfires and suggest pregnant people should avoid very smoky air.

Exposure to wildfire smoke during pregnancy increases the risk that a baby will be born too early, a new Stanford University study suggests.

The study, published Aug. 14 in Environmental Research, finds there may have been as many as 7,000 extra preterm births in California attributable to wildfire smoke exposure between 2007 and 2012. These births occurred before 37 weeks of pregnancy when incomplete development heightens risk of various neurodevelopmental, gastrointestinal and respiratory complications, and even death.

Wildfire smoke contains high levels of the smallest and deadliest type of particle pollution, known as PM 2.5. These specks of toxic soot, or particulate matter, are so fine they can embed deep in the lungs and pass into the bloodstream, just like the oxygen molecules we need to survive.

The research comes as massive wildfires are again blazing through parched landscapes in the western U.S. – just a year after a historic wildfire season torched more than 4 million acres of California and produced some of the worst daily air pollution ever recorded in the state. During the 2020 fire season, more than half of the state’s population experienced a month of wildfire smoke levels in the range of unhealthy to hazardous.

This year could be worse, said Stanford environmental economist Marshall Burke, a co-author of the new study. And yet much remains unknown about the health impacts of these noxious plumes, which contribute a growing portion of fine particle pollution nationwide and have a different chemical makeup from other ambient sources of PM 2.5, such as agriculture, tailpipe emissions and industry.

One possible explanation for the link between wildfire smoke exposure and preterm birth, the authors say, is that the pollution may trigger an inflammatory response, which then sets delivery in motion. The increase in risk is relatively small in the context of all the factors that contribute to the birth of a healthy, full-term baby. “However, against a backdrop where we know so little about why some women deliver too soon, prematurely, and why others do not, finding clues like the one here helps us start piecing the bigger puzzle together,” said co-author Gary Shaw, DrPH, a professor of pediatrics and co-primary investigator of Stanford’s March of Dimes Prematurity Research Center.

Extreme wildfires

The new results show wildfire smoke may have contributed to more than 6 percent of preterm births in California in the worst smoke year of the study period, 2008, when a severe lightning storm, powerful winds, high temperatures and a parched landscape combined for a deadly and destructive fire season – one that has now been dwarfed by the record-setting infernos of 2020 and ongoing blazes like the Dixie fire in Northern California.

“In the future, we expect to see more frequent and intense exposure to wildfire smoke throughout the West due to a confluence of factors, including climate change, a century of fire suppression and construction of more homes along the fire-prone fringes of forests, scrublands and grasslands. As a result, the health burden from smoke exposure – including preterm births – is likely to increase,” said lead author Sam Heft-Neal, a research scholar at Stanford’s Center on Food Security and the Environment.

The research provides new evidence for the value of investing in prescribed burns, mechanical thinning, or other efforts to reduce the risk of extreme wildfires. Given that premature births cost the U.S. healthcare system an estimated $25 billion per year, even modest reductions in preterm birth risk could yield “enormous societal benefits,” said Burke, an associate professor of Earth system science at Stanford’s School of Earth, Energy & Environmental Sciences (Stanford Earth). “Our research highlights that reducing wildfire risk and the air pollution that accompanies it is one way of achieving these societal benefits.”

‘No safe level of exposure’

The researchers analyzed satellite data of smoke plumes from the National Oceanic and Atmospheric Administration (NOAA) to identify smoke days for each of 2,610 zip codes. They paired these data with estimates of ground-level PM 2.5 pollution, which were developed using a machine learning algorithm that incorporates data from air quality sensors, satellite observations and computer models of how chemicals move through Earth’s atmosphere. They pulled additional data from California birth records, excluding twins, triplets and higher multiples, which commonly arrive early.

After accounting for other factors known to influence preterm birth risk, such as temperature, baseline pollution exposure and the mother’s age, income, race or ethnic background, they looked at how patterns of preterm birth within each zip code changed when the number and intensity of smoke days rose above normal for that location.

They found every additional day of smoke exposure during pregnancy raised the risk of preterm birth, regardless of race, ethnicity or income. And a full week of exposure translated to a 3.4 percent greater risk relative to a mother exposed to no wildfire smoke. Exposure to intense smoke during the second trimester – between 14 and 26 weeks of pregnancy – had the strongest impact, especially when smoke contributed more than 5 additional micrograms per cubic meter to daily PM 2.5 concentrations. “If one can avoid smoke exposure by staying indoors or wearing an appropriate mask while outdoors, that would be good health practice for all,” Shaw said.

The findings build on an established link between particle pollution and adverse birth outcomes, including preterm birth, low birth weight and infant deaths. But the study is among the first to isolate the effect of wildfire smoke on early births and to tease out the importance of exposure timing.

“Our work, together with a number of other recent papers, clearly shows that there’s no safe level of exposure to particulate matter. Any exposure above zero can worsen health impacts,” said Burke, who is also deputy director of the Center on Food Security and the Environment and a senior fellow at Stanford’s Freeman Spogli Institute for International Studies. “While as a society it will be extremely difficult to fully eliminate all pollutants from the air, our research suggests that further reductions in key pollutants below current ‘acceptable’ levels could be massively beneficial for public health.”

This work was supported by the Robert Wood Johnson Foundation and the March of Dimes Prematurity Research Center at Stanford University School of Medicine.

Source / Credit: Stanford University

Blue-green algae key to unlocking secrets of ancient past

Oxygen-producing bacteria emerged a thousand millions years before the great oxygenation event approximately 2400 million years ago, scientists have found.

The blue green algae, which is responsible for seeping oxygen into the Earth’s atmosphere, changing the planet forever, diversified from its relatives to cope with the rise of the gas.

To understand how oxygen shaped early life, scientists at the University of Bristol have been investigating when cyanobacteria evolved and when they began using antioxidants called superoxide dismutase enzymes (SODs) to manage reactive oxygen.

They devised a ‘molecular clock’ using geochemical records, cyanobacteria fossils and genetic information to create a timeline of events.

Around 2500 million years ago, young Earth was unrecognizable. No ozone layer existed and there was no oxygen to breathe in the atmosphere. Instead, the planet was dominated by microbes. Cyanobacteria are the only bacteria capable of oxygenic photosynthesis, a process also used by plants to convert carbon dioxide into oxygen using sunlight. Today, cyanobacteria are widespread throughout the ocean, but then they were mostly restricted to freshwater and land.

Oxygen is highly reactive and toxic. Cyanobacteria uses SODs to protect against e these effects which all have different evolutionary origins - and use different trace metals. 

Group leader author of the paper Dr Patricia Sanchez-Baracaldo of Bristol’s School of Geographical Sciences said: “We studied the evolutionary history of four of these antioxidant enzymes: NiSOD, CuZnSOD and Fe- and Mn-utilising SODs. Such SODs are found in everything from animals to plants and bacteria, where they manage ROS by converting superoxide free radicals into hydrogen peroxide.

PhD student, Joanne Boden said: “We discovered that cyanobacteria had acquired their SOD genes from other bacteria on several occasions throughout history. As a result, different strains used different antioxidant enzymes depending on their circumstances. For example, cyanobacteria which live planktonic lifestyles, floating in the ocean, often use NiSOD. Whereas most cyanobacteria, regardless of their habitat, use Mn- or Fe-SODs.

“The evolutionary trajectory of a different SOD, using copper and zinc cofactors instead of nickel matched those of older, more ancestral cyanobacteria which diversified at least 2,700 million years ago. This suggests that oxygen-producing bacteria were equipped with mechanisms of managing ROS before the global atmosphere was flooded with oxygen.”

This genomic record, which has been published in Nature Communications, contains vital information about ancient habitats and proves the existence of life on land and in the ocean at that time.

Dr Sanchez-Baracaldo said: “Cyanobacteria worked out early in their evolution how to protect themselves against the side effects of oxygen.  

"Our analyses of metalloenzymes dealing with reactive oxygen species (ROS) show that marine geochemical records alone may not predict patterns of metal usage by living organisms found in other environments such as freshwater and terrestrial habitats.”

The team now plan to investigate when other antioxidants evolved.

Paper:

‘Cyanobacteria and biogeochemical cycles through Earth history’ in Nature Communications by J Boden, KO Konhauser, LJ Robbins, and P Sánchez-Baracaldo.

Source / Credit: University of Bristol