The Origin of Electric Organs

Zoology Professor Jason Gallant, of the Department of Zoology at Michigan State University, is broadly interested in the genomics basis of phenotypic evolution and diversification, particularly in animal phenotypes that are related to communication behavior. Currently, Dr. Gallant's laboratory focuses on two main projects.

1. The Origin of Electric Organs

Many studies have elucidated the genetic and developmental processes underlying major vertebrate traits (fins, limbs, etc.) in extant lineages. Most of these traits have evolved only once, limiting insights into the degree of constraint and repeatability of the evolutionary processes. In contrast with most other vertebrate traits, there have been six independent origins of electrogenesis, the ability to generate electric discharges from an electric organ, within fishes. Despite their clear benefit as a model for understanding general principles of parallel evolution of complex vertebrate tissues, we know little about the molecular and developmental processes underlying this tissue. In every group that has evolved electrogenesis, electric organs originate during development from skeletal muscle. The long-term goal of the Electric Fish Laboratory at Michigan State University is to characterize the evolutionary steps that have occurred to modify the developmental program in skeletal muscle to give rise to the electric organ. A recent study (Gallant et al. 2014, Science) identified suites of genes in four species, representing three independent origins of electrogenesis, which appear to be critical in evolution of electric organs. Using cutting edge techniques in evolution and development (including transgenics, genomics and molecular biology), they plan to test the hypotheses concerning the roles of these genes in the evolution of electric organs.

2. The Evolution of Communication Diversity

The relative contribution of divergent natural selection and sexual selection on communication signals in the evolution of reproductive isolation is a central question in biology. Progress is limited by poor knowledge of how divergent communication signals originate at the genetic, cellular, and morphological levels, as well as difficulty connecting population level processes prior to speciation with the macroevolutionary patterns of diversity observed after speciation is completed. The more than 200 nominal species of mormyrids are ideally suited for circumventing such problems, producing easily measured and quantified electric discharge signals (EODs), which have a discrete anatomical and physiological basis. EOD signals are typically species-specific and have been demonstrated to be a necessary component of courtship behavior, particularly for a rapidly evolved "species flock" of mormyrids in the genus Paramormyrops. Recently they have focused on linking these macroevolutionary patterns of electric signal diversity to population-level processes. They have identified a key species to use newly developed techniques in evolutionary genomics to identify genes responsible for macroevolutionary patterns of electric signal diversity, critical in the speciation process.