Repetition is the branding iron of knowledge: Lessons from the mulitple origins of enhanced hearing

Enhanced hearing, the ability to detect minute fluctuations in ambient pressure, has evolved independently or nearly so within every major group of vertebrates. Within Teleost fishes, enhanced hearing has evolved perhaps as many as 20 times. Within one subset of cichlid fishes, the Malagasy and south Asian Etroplinae + Ptychochrominae, several lineages appear to have independently evolved morphological specializations that might enhance hearing. There are approximately 25 species of cichlids on Madagascar and all are narrowly endemic with well-defined habitats ranging from shallow floodplain lakes to rheophilic habitats. The gas bladders of individual species range from unspecialized (Katria katria) to highly modified (Paretroplus sp). All species of Paretroplus possess paired intracranial auditory bulla, but individual species vary in the degree of gas bladder modification (e.g., tunic stiffness, diverticula structure). This diversity presents a unique opportunity to explore the relationships among habitat noise and hydrodynamics, morphological specializations, and hearing ability within a specific phylogenetic hypothesis. This talk will present the history of hearing evolution within Malagasy cichlids, covering ecological, morphological, and functional aspects. The multiple independent origins of hearing will be emphasized as replicates of evolutionary experiments. Such replication highlights the commonalities behind the evolution of hearing in all vertebrates.