At the end of the 1970s, to accompany his future wife, Vera Maria Fonseca de Almeida, the biologist and São Paulo native Adalberto Luiz Val moved from São Carlos, in inland São Paulo State, to Manaus, the capital of the state of Amazonas. He quickly became fascinated by the diversity and the biological adaptation mechanisms of the fish in the Amazon. Around 3,000 species live there, from the tiny Priocharax manus, which measures 15 millimeters, to the pirarucu (Arapaima gigas), which can grow up to 3 meters in length.
Little by little, with the group he created at the National Institute of Amazonian Research (INPA), Val identified the unexpected physiological and biochemical mechanisms of various species, particularly the tambaqui (Colossoma macropomum), which captures air with its lips at the surface of the water column, and the pirarucu, which has a modified swim bladder that enables it to absorb oxygen from the air when it surfaces.
In recent years, in light of changes in the region, such as population expansion, pollution, and deforestation—worsened by global warming—he has begun looking at whether the fish could survive another environmental shift, like those they have experienced over millions of years. He discovered that while some species are more resistant than others, aquatic organisms are generally extremely sensitive to temperature variations. This finding explains the mortality of fish and dolphins in the drought that hit the Amazon in 2023, when water temperatures reached 40.9 degrees Celsius (ºC).
Vale and Vera have two sons, Fernando and Pedro, who are also researchers. He is the coordinator of the National Institute of Science and Technology for Adaptations of Aquatic Biota of the Amazon (INCT-ADAPTA), a member of the Brazilian Academy of Sciences (ABC), and a winner of the Bunge Foundation Award in the Life and Work category in 2023. He spoke with Pesquisa FAPESP in June.
Field of expertise
Amazonian fish
Institution
National Institute of Amazonian Research (INPA)
Education
Undergraduate degree in Biological sciences from the Barão de Mauá Brazilian Center (1980), master’s degree (1983), and PhD (1986) from INPA
Why did you decide to study the fish in the Amazon?
To answer, I have to go back to my childhood. I was born and raised on a farm in Campinas, in the countryside of the state of São Paulo. One of my weekend pastimes was fishing in a lake that had few species of fish, basically tilapia and lambari. From going there so often, I became curious about how the fish lived underwater. One day, I caught some fish in a net, put them in a wide-mouthed bottle, closed it, and took it home. At first, they swam, but the next day they were all dead. I must have been around 12 years old. I was really upset and decided that I wanted to learn more about fish; I needed to know how they are able to live underwater.
And what did you do?
I pestered my father, until he ended up giving me some magazines about fish. When I went to high school, I decided to take a technical course in biochemistry. At the end of the year, I moved to São Carlos, went through a recruitment process to become a technician and was hired by the Federal University of São Carlos (UFSCar) to work with a researcher studying fish blood. It was a good start, but I still needed to take a higher education course. I chose biology. During this period, I was dating Vera, who was also from Campinas and was finishing her master’s degree and had been invited to work at INPA, in Manaus. I was at the end of my undergraduate studies. Vera went to visit INPA and I went with her. I remember that I was fascinated upon seeing an enormous collection of fish. In a market in Manaus, I found lots of species, much bigger than those I saw in São Paulo. It was then I made the decision: I want to live here. We both moved to Manaus. I did a master’s at INPA and after was hired by the institute. This was at the start of the 1980s.
What else caught your attention when you arrived in Manaus?
Right away, I realized that the Amazon is an extremely dynamic environment. The rivers and lakes experience intense variations in water level, temperature, and dissolved oxygen. There are also the rivers with acidic waters, like the Negro. The first question I asked myself was how the fish cope with these fluctuations. I was also intrigued by the diversity of fish in the Amazon, close to 3,000 species, while the farm in Campinas only had two or three. In my master’s program, I studied two species of jaraqui [Semaprochilodus insignis and S. taeniurus], fish with peculiar characteristics. During the breeding season, they migrate approximately 1,600 kilometers, from the upper Rio Negro to the confluence with the Solimões. When they are born, the baby fish are dragged downstream and spread across the floodplains. Still small, they begin swimming back, enter the Rio Negro, and migrate upstream. That really intrigued me. How could a fish know that it was migrating to the white waters of the Solimões and then to the black waters of the Negro? My sadness came from finishing my master’s dissertation and not being able to answer my main questions—those that I formulated at 12 years of age and those I came up with when I arrived in the Amazon. I added others and, therefore, dedicated my life to studying the fish in the Amazon. I’ve been here for 45 years.
Over time, the fish from the region have developed morphological responses to adapt to the environmental changes
What species did you study in your PhD?
The tambaqui [Colossoma macropomum], which is still our study model today. I studied the hemoglobin of the tambaqui. My advisor was professor Arno Rudi Schwantes [1939–2014], of UFSCar, the same advisor I had for my master’s, who was also accredited as a collaborating professor at INPA. During this period, I began to interact with two foreign researchers who played important roles in my career. The first was Grant Bartless, from the Laboratory of Comparative Biochemistry, of the University of California, San Diego, USA. He studied small molecules within red blood cells, organic phosphates, that regulate the function of hemoglobin. Through him, I met David Randall [1938–2024], of the University of British Columbia, in Vancouver, Canada, an expert on the physiology of fish. In 1976, Randall had coordinated one of the main scientific expeditions of foreign researchers to the Amazon, which became known as Alpha Helix. One of its focuses—and which attracted me the most—was the physiology of the fish. At that time, the participation of a Brazilian representative was mandatory on scientific expeditions. The person chosen was Schwantes. With that, it created the conditions which enabled me to approach Randall and seek an opportunity to do a postdoctoral fellowship with him—my objective was to specialize in physiology. This collaboration was fantastic and resulted in the publication of the book Fishes of the Amazon and their Environment [Springer Verlag, 1995], which was heavily cited for a long time.
What were your main findings about Amazonian fish?
In general, they don’t tolerate extreme temperature variations. It is the opposite of what was thought. The water in the region’s rivers is always above 28 or 30 oC. We imagined that, if it got hotter, the fish would cope. But no. They are more sensitive than those from the temperate zone. This has many implications for their physiology and for breeding in captivity. Not long ago we published an article in Nature about the effects of the drought that struck the Amazon in 2023, when the water temperature reached 40.9 oC. It was probably this temperature that caused the mass mortality of fish and dolphins. When the temperature reaches that level, the amount of oxygen in the water falls and the metabolic rates of the animals rise dramatically. Fish cannot regulate their body temperature, so the environmental temperature directly effects all their biochemical and physiological processes. As a result, they are unable to meet their metabolic demands. In the case of dolphins, being mammals, it’s different. They are able to regulate their body temperature like humans, which requires an additional energy expenditure with a high cardiac demand. This can lead to rising blood pressure and, in some cases, the animal can suffer vascular accidents.
What other effects do the environmental variations have on the fish?
They have developed a set of morphological responses to the environmental changes. The tambaqui serves as an interesting example. It expands its lower lips to channel the more oxygenated surface layer of the water column toward its gills. Other modifications occur inside the bodies of fish. For example, they are able to control the binding of hemoglobin with oxygen. In the case of tambaqui, jaraqui, and other species, the regulation of organic phosphate levels occurs within the cells, based on the variations of oxygen in the water. This adaptation allows them to maintain stable oxygen transfer from the aquatic environment to their tissues. This discovery was phenomenal, because it answered that question I had when I was 12 years old: how are fish able to live below water? During the day, light enables photosynthesis, which produces oxygen. At night, however, in the still waters of ponds, lakes, and flooded areas, there is less oxygen. But fish have mechanisms that regulate the binding of hemoglobin with oxygen and increase the capacity of the blood to extract oxygen from the water. Even the species that rely on other strategies need this mechanism. This finding was fundamental, as it showed that a single response is not always enough to minimize the effect of environmental oxygen variation on the body.
Are there other examples?
Yes. The tamoatá [Hoplosternum littorale], the cascudo [Liposarcus multiradiatus], and some catfish have parts of their stomachs and intestines that are vascularized and adapted for gas exchange. They swim to the surface and swallow water mixed with air. Gaseous exchange takes place at the transition from the stomach to the intestine, without compromising the regulation of hemoglobin’s affinity for oxygen. We discovered that some fish, instead of having conventional organic phosphates—ATP [adenosine triphosphate] and GTP [guanosine triphosphate]—have other ones. Tamoatá has 2.3-DPG [diphosphoglycerate], a compound that humans also possess. The production of 2.3-DPG does not respond to oxygen availability but rather to temperature variation. As the temperature rises and the quantity of oxygen in the water reduces, the fish increase 2.3-DPG production. Such adaptations involve genes that control essential proteins involved in this process.
And the pirarucu, what have you discovered about it?
It is a truly exceptional fish. An obligate air breather, it is born with the capacity to synthesize ATP and GTP. But, during its first year of life, it replaces these two phosphates with a third called inositol pentaphosphate, which, surprisingly, also exists in the red blood cells of birds. The pirarucu is the only fish with this phosphate. It breathes air through a modified swim bladder, and not through lungs. The South American lungfish [Lepidosiren paradoxa] is the only lungfish in the Amazon.
Pirarucu (left), one of the largest fish in the Amazon; tambaqui, Val’s study model; and jaraqui (right), a migratory speciesCitron / Wikimedia commons | Wikimedia commons | Fiver, der Hellseher / Wikimedia commons
Will the adaptive capacity of Amazonian fish allow them to overcome the challenges posed by climate change?
That is the main question of our INCT-ADAPTA project. For millions of years, since the uplift of the Andes, the Amazon has experienced tectonic and climatic changes. Much of what we see today developed during the formation of the Amazon basin. These movements provided the conditions for species diversification in the region. At the same time, they allowed the organisms to develop adaptations throughout the evolutionary process. Those better adapted to the environmental challenges survived better. Now we want to know whether Amazonian fish have retained the information in their genome that enabled them to cope with climate change in the past and if they are able to express these characteristics again. We don’t have a definitive answer. We know that some species are able to make adjustments and survive up to a certain limit. Others cannot. Sometimes, different species from the same genus respond differently. This suggests that some groups have lost the information that would enable them to survive, in part, the environmental challenges. I say in part for the following reason: the processes of acquiring these adaptations occurred over millions of years. And the current climatic variations occur extremely quickly, without giving the organisms time to adapt.
Can you give an example?
The tambaqui. If we isolate the temperature, we are able to make it survive until around 40 oC. But when we add carbon dioxide into the equation, which is one of the causes of the greenhouse effect, 40% of the fry begin to show skeletal deformities and pericardial effusion. They will be preyed upon and disappear. Those that survive, without these deformities, may be able to produce offspring. Some will exhibit these deformities, while others will survive, creating a new evolutionary process. We don’t know how it will turn out.
What other impacts on the aquatic fauna resulting from anthropogenic environmental changes are already known?
We have studied the synergistic effects of climate change alongside other factors, such as pollution from metals, plastics, oil, and pharmaceuticals. When water temperature rises and oxygen levels fall, fish beat their operculum [protective structures of the gills] more rapidly, to move more water over their gills, in order to keep their blood oxygenated. However, when they move more contaminated water over their gills, they absorb more contaminants. And then there is an additional complication. Some fish have learned during evolution that, when there is no oxygen in the water, they can rise to the surface to breathe or swallow water mixed with air. If the river is contaminated with oil, they will take in more oil and internalize it in their bodies. When humans interfere with the environment, some adaptations which arose during the evolutionary process can work against the animals.
Does deforestation also threaten the fish?
Yes. The forest cover protects the animals, since it helps to reduce the temperature of the aquatic environment. The more deforestation there is, the greater the temperature increase of the system. As the fish are vulnerable to increased temperature, they are threatened. The worst thing is, humans are also at risk, because 90% of the protein consumed by the population of the Amazon comes from fish. Reducing the production of fish will cause a serious food security problem. The pollution of the rivers from sewage is also worrying. The large cities in the region have a primitive sewage treatment system. Everything is dumped into the river. When you have a city with 10,000 inhabitants, a river the size of the Amazon can handle the situation. But when the city has 2.1 million people, like Manaus, it’s a different story.
What is the objective of INCT-ADAPTA?
ADAPTA has around 30 research groups and 100 researchers, several of them abroad, including in Amazonian countries. Our Ecophysiology and Molecular Evolution Laboratory, LEEM, at INPA, is the headquarters of INCT. We have climate rooms to reproduce the environmental conditions predicted for 2100. The objective is to study how fish, insects, and plants will face these new conditions. One room reproduces the temperature, carbon dioxide levels, light, and humidity of the forest in real time based on data transmitted by a tower located in the forest. The other three rooms reproduce future scenarios—mild, intermediate, and extreme—in accordance with the IPCC [Intergovernmental Panel on Climate Change] model for 2100. We have discovered that fungi grow much more in extreme scenarios. If they are edible fungi, fantastic, we would have more food. But if they are infectious fungi, there will be more problems. In the case of the malaria mosquito, the findings are worrying. The more extreme the environmental conditions are, the greater the number of mosquito generations in a specific time interval. As a result, the number of mosquitoes able to transmit malaria, for example, is greater per unit of time.
The pirarucu is an exceptional fish. It breathes air from above the surface of the water through a modified swim bladder
One of your recent projects compared the effects of climate change on the fish in the Amazon and the Atlantic Forest. What are the main conclusions?
We analyzed freshwater fish from the region of Santos and São Vicente, on the São Paulo State coastline, and from the Ducke biological reserve, in the Amazon. In the reserve, due to the preserved forest, there is thermal stability, with a temperature of around 25 oC. In the Atlantic Forest, it varies naturally throughout the year. We see that fish from the Atlantic Forest are able to support a larger temperature range than those from the Amazon. The second point is related to dissolved organic carbon, which gives the black coloring to the waters of the Rio Negro and the water bodies of the Atlantic Forest. The properties of this carbon vary depending on the time of year and the region. It also protects the respiratory rates of aquatic organisms in relation to metals, especially those in acidic environments, such as fish in the Rio Negro. We wanted to know whether the dissolved organic carbon in the Atlantic Forest, which is different from that found in the Amazon, also has these properties. Its effects in the two locations differs. We are monitoring and describing these differences. The issue of dissolved organic carbon is of global interest. The increase in carbon dioxide in the environment is causing a darkening of water bodies in several regions around the world, which is concerning. Through this study comparing the Atlantic Forest and the Amazon, we are trying to gain a better understanding of this issue.
How do you view the possibility of oil exploration in the mouth of the Amazon?
It is something very worrying. In the event of a leak, part of the oil, which has a lower density than water, rises to the surface. A recent study by our group has shown that for air-breathing species, whether facultative or obligate, oil is internalized in their bodies. Additionally, when oil is subjected to solar radiation, it causes the formation of compounds that are highly toxic to fish, leading to high mortality rates. In the event of an accident, depending on the climatic conditions, winds, and other variables, the oil on the surface of the water column could enter the interior of the Amazon basin and profoundly affect the animals. Marine currents could carry the leaked oil to the north, reaching the coasts of neighboring countries and causing diplomatic issues. We also must not forget that there are corals sensitive to environmental changes at the mouth of the Amazon.
Is it true that microplastics have already been found in Amazonian fish?
Yes. Unfortunately, there is intense pollution from plastics in the Amazon due to the inadequate disposal of solid waste. Plastic has already been found in the musculature, bones, liver, and even in the otolith, a small bone in the inner ear of fish. The otolith usually forms rings through which you can measure the age of the fish. When researchers scraped these rings for analysis, they found plastic at some points. If there is plastic in the fish, people who consume these fish are also consuming plastic. The problem is exacerbated by plastic’s high capacity to absorb pollutants and pharmaceuticals. It acts as a transporter of these substances into organisms.
Deforestation raises the temperature of the water in rivers and lakes. As fish are vulnerable to this variation, they are threatened
How have your studies contributed towards food security in the Amazon?
We seek to optimize production processes, so that fish grow more in a shorter time. We also have the perspective of producing fish meat in the laboratory. Another target is to reduce the impact of temperature and metals, especially copper, on breeding processes. Heavily used in agriculture, copper is leached into breeding tanks. We have studied new feed compositions, integrated breeding systems, and the administration of certain products as substitutes for antibiotics. This is a serious problem in breeding stations. The water with antibiotics from the stations falls into the natural environments and causes a disaster, especially for small-scale animals that are vital for the food chain. Based on physiological, biochemical, and genetic information about fish, we can manipulate the breeding conditions.
What transformations has the Amazon suffered in the 45 years since your arrival to the region?
First, I would say there has been a population revolution. When I arrived, Manaus had around 500,000 inhabitants; today there are more than 2 million. A city of this size requires infrastructure and a range of products and processes that put pressure on the environment. There has also been an expansion of mining, including on Indigenous lands, which has led to contamination of the aquatic environment from mercury and other metals. There has been increased contamination of the rivers from pharmaceuticals as a result of the population expansion. However, there have also been positive changes.
What are they?
In the field of science, for example. When I arrived here, you could count the number of doctors in Manaus on your fingers. There wasn’t a single research support foundation in any Amazonian state; today they all have one. The only postgraduate course at INPA was in botany, inherited from the Emílio Goeldi Museum, in Pará. Quickly, another three—ecology, entomology, and freshwater biology and inland fisheries—were established. In Pará, there was the postgraduate program in geosciences at UFPA, a fantastic course that generated relevant information for the mineral production processes in the region. After a while, the whole world began showing strong interest in the Amazon. With this, there was increased demand for scientific cooperation in the region, which unfortunately was not met equally. Awareness of the need for environmental conservation in the region has grown significantly, but it has been difficult to convert it into action. However, there are projects that deserve highlighting, such as Semear Leitores, by the Bunge Foundation, which shares regenerative practices in family agriculture.
What else should be done?
The Brazilian government needs to understand that it needs to make a strategic investment in science and technology in the region, which means strengthening research and personal training in universities and research institutions, and creating spaces for international cooperation. Investment in science and technology in the Amazon doesn’t exceed 3% or 4% of the total allocated to the sector in the country. This results in a weak production of information for the development and conservation of the Amazon. We need strategic investment in the region, not the continuation of historical spending rates.
What do you like doing in your free time?
The problem is finding this free time. But there are two things that I really enjoy. First, walking. I walk a lot, especially first thing in the morning. The second is reading. At the moment, I am rereading Arrabalde: Em busca da Amazônia (Outskirts: In search of the Amazon), by João Moreira Salles. It’s a book that discusses the issue of deforestation and the challenges of environmental conservation in the region.
