Evolution of heart size in birds - Altimiras Group

We seek understanding of the function of the heart in animals. Currently, our main project is the study of the evolution of the heart in birds, particularly how the heart grows and how it reacts to environmental challenges. 

As an example: when a bird is placed in a harsher (read cooler) climate the heart gets enlarged. Chickens raised in cold conditions have a heart size twice as large as that of a chicken raised indoors.  This is interesting from an evolutionary perspective, but it also has relevant biomedical implications because pathological enlargement of the heart (so called cardiac hypertrophy) leads to heart failure.

Need for basic cardiology research

Cardiac pathological hypertrophy differs from the normal growth of the heart associated with exercise in humans, or with cold exposure in birds. Although we know a great deal about the problems and consequences of hypertrophic enlargement of the heart, less is known about the actual mechanisms responsible for such growth. My belief is that the basic research we carry out will be able to explain the evolutionary roots of hypertrophic growth and its genetic architecture.

Studies on the evolution of the heart have typically focused on the heart in crocodiles because it is the most ancient type of four-chambered heart (two atria and two ventricles). In my opinion, however, this approach neglects the importance of heart size in overall performance. Thus I suggest that important clues can also be found by studying the most ancient group of extant birds, the South American tinamous. Unlike its closest relatives, the ostriches, tinamous can fly and they do that with a heart that is half the size of the hearts of most other, comparable bird species.

Transformation in heart size 

Reptiles have a small heart while birds have a larger heart. What mechanisms guided that transformation? Through the study of tinamous we want to understand the evolution of reptiles into birds with larger hearts. In comparison with modern birds, tinamous are quite limited because they do not fly well and they can only do so for short periods of time. They do, however, keep a high body temperature.

Studying tinamous is an attempt to study the past in the present. Comparing physiological performance and gene expression in tinamous, crocodiles, and modern birds, we expect to find out how changes in gene expression lead to an enlargement of the heart and, consequently, an increase in its performance.

Opportunities for Student Projects

Biology students at Linköpings universitet carry out a mandatory bachelor project (so called "kandidatarbete") in their last semester of bachelor level studies, and a one-year research project as part of their master’s degree. In my research group, students have the opportunity to travel to South America with scholarships from the Linnaeus-Palme exchange program or the Minor Field Studies program. The field research projects are done in collaboration with Alvaro Garitano from the Universidad Mayor de San Andrés in La Paz, Bolivia and Roberto Nespolo from Universidad Austral de Chile in Valdivia, Chile, and the results are integrated in our group's research.

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