Photo: Gabriella Kovac Gvidi

A vital sense of smell

How does a female butterfly recognize the plant on which she will lay her eggs? How does she find a male to mate with and how is she attracted to energy-rich nectar sources? Behavior depends largely on olfactory cues, although other types of sensory input contribute. 

Behavior needs to be relevant to the situation at hand; if you are looking for a mate, you should not be distracted by irrelevant scent signals from plants. So there should be some overriding control of the scent response. 

These are questions that have fascinated Mikael Carlsson at Zootis for many years. He tries to understand how butterflies "think", what guides their decision-making and where in the brain this takes place.

But how do you study it?

Equally fascinating are the methods he uses for his studies. He literally looks inside the butterfly's head to map which neurons and neural pathways are activated when a butterfly is stimulated with different types of scents. 

The method is called functional imaging and is based on the fact that added fluorescent substances bind specifically to certain other substances in physiologically active cells or tissues. When the brain is studied under a microscope and imaged on a computer screen, it shows up as colorful spots where in the brain the substances have bound.

When Mikael first became interested in butterflies' sense of smell, he studied moths. But now he focuses on butterflies of the day, primarily the currant and nettle butterflies. They are interesting to compare, because although they are fairly closely related, the currant louse is a generalist while the nettle butterfly is a specialist, strongly linked to stinging nettles. 

During the season, wild butterflies are captured in the wild, but they are also bred at the institution. It is primarily adult butterflies that are studied, although the larval stages are also interesting.

From Skåne to Stockholm via Södertälje

Even as a child, Mikael was fascinated by butterflies and other insects - but he didn't intend to become a biologist just for that. After his school days in Malmö, he was quite lost and tried all sorts of things: studied languages and marketing and traveled a lot. 

It was not until he was in his thirties that his interest in biology returned, and he went on to study biology in Lund, specializing in zoophysiology. In 2003 he defended his thesis on the olfactory system of moths.

A few years after his dissertation, the family moved to Stockholm. Mikael got a job at AstraZeneca in Södertälje and continued to work with sensory biology, but now it was the visual sense of rats. His time at AstraZeneca provided good training in working in a goal-oriented way and finishing projects on time, but Mikael didn't feel at home there, he missed the creative university environment. 

So when AstraZeneca ran into financial problems and Mikael had to leave, he wasn't too sad about it, especially as he got a postdoc at Zootis in 2008 and has been there ever since. 

Teaching zoology

Mikael mainly teaches zoomorphology and zoophysiology. "Actually, the boundary between morphology and physiology is artificial; structure must be linked to function for it to be meaningful to the students," says Mikael. 

As it happens to be "Biodiversity Day" when the interview is conducted, we also touch on the huge number of animals in the world. How do you tackle it? - "We focus on big important phyla," says Mikael; arthropods, for example, get three full days on the Organismal Diversity and Evolution course, while more obscure worm groups are skipped. 

Mikael, together with Emily Baird, has also developed a course in sensory biology that was first given in 2020. It is now called Sensory Biology and Animal Communication 7.5 credits and is given at advanced level.

Mikael enjoys lecturing - "because I didn't become a rock star". But isn't the lecture an outdated form of teaching, I ask somewhat provocatively. "I'm happy to try new methods like the 'flipped classroom'," says Mikael, but lectures still have a right to exist, especially on undergraduate courses where students need to be guided into the subject by someone who knows it. 

Many other interests

Many biologists also have the profession as a hobby. But Mikael has other hobbies besides biology. Besides family life with two daughters, cooking and wine tasting, he enjoys photography, mainly "street photography" and portraits. He also loves to travel, especially to big cities; his favorite destination is dynamic Berlin.