Meeting Abstract
The vertebrate lateral line system is a useful model for investigating the embryonic and evolutionary diversification of sensory organs and cell types within the nervous system. In non-teleost vertebrates, including lampreys, this sensory system comprises neuromasts containing hair cells that detect local water movement, electrosensory organs containing electroreceptor cells that respond to low-frequency cathodal electric fields (used primarily for hunting), and the afferent neurons for both organ types, projecting to adjacent medullary nuclei. The electrosensory division was independently lost in the bony fish lineages leading to teleosts and to frogs (amniotes lost the entire lateral line system during the transition to life on land). Within the teleosts, ampullary organs that respond to low-frequency anodal stimuli evolved independently at least twice in different groups, likely via the diversification of neuromast hair cells; their afferent lateral line neurons project to novel medullary nuclei. Some lineages also independently evolved both electric organs and tuberous organs that detect high-frequency electric organ discharges. We are using a comparative RNA-seq approach to investigate electroreceptor development and evolution. In a non-teleost fish, the paddlefish Polyodon spathula, we have identified expression in developing electrosensory organs of transcription factor genes critical for hair cell development, and genes essential for glutamate release at hair cell ribbon synapses, suggesting close developmental, physiological and evolutionary links between non-teleost bony fish electroreceptors and hair cells. We have also identified candidates for the voltage-sensing L-type Cav channel and rectifying Kv channel predicted from skate (cartilaginous fish) electrosensory organ electrophysiology. Overall, our results illuminate electroreceptor development, physiology and evolution.
