The constructive evolution of gustation: Molecular, organismal and environmental attributes of taste tuning

Living organisms display enormous diversity in their appearance and behavior. Although a great deal of effort has been committed to understanding the breadth of this diversity, it remains unclear exactly how and why differences evolve over time. In this project, the researchers examine how the sensory system of taste changes.

The researchers focus on different populations of fish that are very closely related. In spite of being closely related, these fish live in waters that taste very different from one another. By examining the fish, the organs they use for taste, and the differing environments in which they live, the researchers will understand how and why sensory systems change.

This project is important in that it will explain how organisms adapt and survive in very different environments. This, in turn, will assist in understanding the amazing diversity of living organisms. The researchers will share the information that is learned from this work with students, colleagues, and the general public.

Because cavefish are so unusual and visually intriguing, they make excellent educational resources for both local public schools and international audiences.

The researchers will study fish living in rivers and streams and other fish living in deep, dark caves. The researchers will first analyze the sequences of genes that encode taste receptors. These taste receptors detect very specific types of taste such as sweet, bitter or savory flavor.

By examining the sequence of these genes, the researchers will discover how the receptors physically change in ways that affect their function. These changes will be studied in the context of each nutritional environment to identify patterns associated with certain receptor changes. Taste receptors will then be visualized in the taste buds on fish from each population.

Interestingly, fish living in surface rivers and streams have taste buds mainly in their mouths and in their oral cavities. Cavefish, however, have taste buds spread all over their heads. Our hypothesis is that cavefish have “tuned” the taste buds on their head to detect the available taste molecules in their environment.

Expression experiments will enable the researchers to compare how the positions of taste receptors on the heads of cavefish may differ depending on the types of nutrients they encounter in the wild. Finally, using chemical analyses of the environment itself, the researchers will determine the relative abundance of different taste molecules within different caves.

This will allow the researchers to connect the available taste molecules in each cave to the types of receptors present in the fish inhabiting each cave. Collectively, these techniques will provide a comprehensive picture of how the environment determines what is sensed by organisms, and how the sensory ability of taste changes in closely related animals.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.