IOS-0818390 Collaborative Research: Mechanisms of Signal Diversity in Electric Fish Communication
In this collaborative project, researchers from Cornell University in Ithaca and Washington University in St. Louis will explore the mechanisms responsible for the large-scale diversification of animal communication signals. The mormyrids are a diverse group of fishes from Africa that communicate using species-specific electric organ discharges (EODs) that are essential for species recognition. However, some species are polymorphic, with different individuals having distinct EOD forms and correspondingly different electric organ morphology. This project will focus on the polymorphic species Paramormyrops kingsleyae as a microcosm of electric signal evolution throughout the mormyrids. The researchers will use a combination of field work, molecular genetic techniques, electrophysiology, and behavioral playback experiments to determine the genetic basis for electric signal diversity in P. kingsleyae, and the importance of this diversity in driving reproductive isolation between populations and adapting different populations to their particular environments. The results of these studies will lead to specific hypotheses about the root causes of electric signal diversification throughout the mormyrids, which the researchers will test using similar techniques across a wide range of species. This research will prove broadly applicable by providing a mechanistic understanding of how animal communication signals diversify, as well as insight into the ultimate causes for this diversification and the resulting consequences for speciation and the evolution of communication behavior. Broader impacts: The project includes an educational outreach program for public school students, which uses electric fish to provide hands-on demonstrations for linking basic concepts in the physical sciences and biology. In addition, the researchers will create an online searchable database of electric signals that researchers, students, and the general public will be able to access. This database will be used to archive and catalogue thousands of EODs collected during more than 20 years of field work in Africa.
Animals communicate with each other using a wide variety of signals, including visual, auditory, chemical, and electrical signals. The goal of this project was to understand the causes of signal diversity. Researchers from Washington University in St. Louis, in collaboration with researchers from Cornell University, performed field and laboratory studies of African electric fishes to address this question using an integrated approach that included molecular biology, anatomy, electrophysiology, and behavior. These fishes, called mormyrids or elephant fishes, use an electric organ to generate weak pulses of electricity. They also have electroreceptors for detecting these pulses, and they are therefore able to communicate with each other using electricity. These electric pulses provide information about the identity of the fish, including its species, sex, relative dominance status, and possibly even its individual identity. There are over 200 species of mormyrids, and their electric signals are characterized by remarkable diversity. In addition, it is relatively easy to relate characteristics of these signals to their underlying neural basis, and to study how the brain processes these signals. Mormyrids are therefore an excellent model system for relating signal diversification to evolutionary changes in the nervous system. Using comparative anatomy, the researchers discovered dramatic evolutionary change in the electrosensory system. By monitoring behavioral responses to signal playback, the researchers discovered that this evolutionary change established the novel perceptual ability to analyze the waveform (shape) of electric signal pulses. Statistical analysis of signal variation across species, combined with evolutionary modeling, revealed that this new perceptual ability was associated with remarkable increases in the rates of signal evolution and species diversification. These findings raise the intriguing possibility that the evolution of new perceptual abilities can affect the processes that shape the origins and maintenance of biodiversity. In addition, the researchers gained new insights into how electric signals are detected by electroreceptors and how this information is processed by central electrosensory pathways within the brain. These results shed light on how communication signals in any sensory modality are analyzed by the nervous system to establish the behavioral ability to perceive different aspects of these signals. Finally, the researchers uncovered how evolutionary change in the anatomy of cells in the electric organ can lead to signal diversification. Besides their research activities, the researchers also regularly engaged in public outreach involving weakly electric fish to teach basic concepts in electricity, neuroscience, and animal communication. This included: hands-on demonstrations and lectures targeted to K-12 students held at the St. Louis Science Center in conjunction with Brain Awareness Week; a Neuroscience Day targeted towards middle school students held at the St. Louis Science Center; and participation in the St. Louis Area Brain Bee, a regional competition associated with the Society for Neuroscience’s National Brain Bee. These activities included a hypothesis-testing component to expose students and the public to question-oriented, hypothesis-driven science, which helps to demystify the scientific process and make science more accessible as a career choice and as a way of knowing.
