What Can an Animal That Lives Between Land and Water Teach Us?

Before she joined Columbia University in 2019, Maria Antonietta Tosches primarily researched turtles and lizards. But when she moved from the Max Planck Institute for Brain Research in Frankfurt, where she was a postdoctoral fellow, to New York, she decided to turn her attention to Iberian ribbed newts, a species of salamanders that splits their time between land and water. She believed these animals could offer fresh, specific insight into the evolution of the vertebrate brain. This spring, Tosches, an associate professor of biological sciences, received the MIND Prize from the Pershing Square Foundation for research that improves “our ability to predict, prevent, and treat neurodegenerative diseases.” Columbia News spoke to Tosches about her research, and what she hopes newts can show us.

What does your lab look at in general?

We’re interested in the evolution of the brain. We look at brains across vertebrate species to understand the diversity of neurons, the brain’s building blocks. We’re doing this work by classifying and then comparing neuronal cell types across multiple species.

The main species we’re studying in my lab is an amphibian, the newt Pleurodeles waltl. We chose amphibians because they occupy an interesting position between fish on one end, and mammals and birds on the other—all of which are more commonly studied in neuroscience. These newts have an ability to live in different environmental conditions, on both land and in freshwater ponds. They also regenerate: If they lose a limb or even a substantial number of brain cells, they can grow them back.

The idea is that by studying these animals we can discover new biology and, from there, further understand how the vertebrate nervous system is organized, and how plasticity in the nervous system works.

Newts’ ability to regenerate brain cells and limbs is obviously interesting, but what can it tell us biologically? 

One aspiration is that it can tell us more about neurodegenerative diseases—like Alzheimer's, Parkinson's, and Amyotrophic Lateral Sclerosis (ALS)—and how to combat them.

Humans and other mammals cannot regenerate neurons: The neurons we have at birth are the ones we have for the rest of our life, and that’s it.

Mammals generally react to brain injury or neuron loss by forming scar tissue, which then limits the spread of the damage. 

But newts respond to neuron loss in a completely different way. Instead of creating scar tissue, they activate different cellular processes to then make new neurons.

Our idea is to really look at the extreme opposite of neurodegeneration and try to understand how these brains react to neuronal loss and manage to repair themselves.

What makes the fact that newts live between water and land so illuminating?

Water and air pose completely different challenges to animals on a number of levels.

One level is the senses. Light and sound propagate in completely different ways in water and air, for example, because water makes light and sound scatter more. So, in animals that inhabit both worlds, the eyes and ears have to be set up to detect these sensory stimuli in both environments. Smell, too, is completely different in air and water—volatile molecules are good odorants on land, whereas water-soluble molecules are good odorants in water. So, presumably the brain has to be able to adjust sensory processing in order to extract meaningful information from these two sensory worlds.

Other things that are different on land and water are locomotion, how you move, and respiration, how you breathe. It is very clear that many changes took place during evolution as animals transitioned from water to land. However, we don’t know enough about what’s different in the brains of aquatic and terrestrial vertebrates. By looking at a species that can cope with both environments, we can identify the minimal set of changes that the brain has to implement to make sense of the world in water and on land.

Are newts the only animals that split their time between two environments like this? 

The ability to remodel the anatomy of the brain to adapt to different environments—which is known as plasticity—is relatively rare in vertebrates. There are vertebrates that have modest seasonal plasticity, like birds that change their singing behavior in the spring when they mate. But in general, the degree of plasticity we see in newts is pretty extreme.

There are a few other animals that live in both wet and dry environments, some of which we have in our lab, like the Polypterus senegalus fish, which live in lakes in Africa that dry out seasonally, and they then spend significant time on land. They’re not as well-adapted as newts to terrestrial lifestyles, but when people raise baby fish in an entirely terrestrial environment, the morphology of their pectoral fins changes to support walking on land. We don’t know if their brains have the same regenerative capabilities as newt brains.

What techniques does your lab use to investigate these questions?

We use single cell RNA sequencing to sequence all the genes expressed in each individual single brain cell. It’s a way to identify cells that have similar gene expression, and to classify cells and identify neuron types and cell types. We’re building a model of the newt brain this way, and we also use our data to compare cells across multiple species. We are also using machine-learning tools to look at animal behavior, and imaging to study neuronal activity in the brain.

What do you like to do outside of your work?

I’m from Italy and I love to cook. When I can, I make bread. I also make pasta, panettone, and ice cream. I approach long and challenging recipes like experiments in the lab.

Do you have a favorite New York activity?

Life with two young kids gets pretty busy! I like to explore the city by taking them to new playgrounds—there are more than 20 in Central Park alone!