Electroreception is found throughout the animal kingdom from invertebrates to mammals and is thought to play an important role in prey detection, facilitating social behaviours, the detection of predators and orientation to the earth's magnetic field for navigation. Electroreceptors in elasmobranchs, the ampullae of Lorenzini, detect minute electric fields and independently process these stimuli, thereby providing spatial information to the central nervous system on the location of a source, often potential prey. The ampullae of Lorenzini are individually connected to a single somatic pore on the surface of the skin, with the spatial separation of each pore directly influencing how electrical stimuli are detected and processed. Pore abundance varies across taxonomic groups resulting in unique species-specific differences. However, the intricate distribution patterns created by the specific positioning of somatic pores on the surface of the head and the clustering of the ampullae electroreceptors beneath the skin are consistent within families, resulting in patterns that are identifiable at higher taxonomic levels. Variation in the type of electrosensory stimuli that a species is likely to encounter and the physical parameters of their habitat (i.e. water conductivity) may significantly influence the morphology of the electrosensory system. Therefore, by investigating the specific clustering of ampullae electroreceptors between species that adopt unique feeding behaviours, and between species that live in different environments, it is possible to determine the phylogenetic and ecological factors that influence their function. Nevertheless, despite the important role electroreception plays in the behaviour of elasmobranchs, to date, there have been few studies to assess the central nervous processing of electrosensory stimuli and no studies have assessed the specific number of electrosensory axons that project from the peripheral ampullae to the central nervous system. Quantifying the abundance of electrosensory nerve axons from individual ampullae and between discrete clusters of ampullae may reveal further insights in to their functional significance. Improving our understanding of how various elasmobranch species sense and interact with their environment using electroreception has distinct commercial applications through the development of electric shark repellents used to protect ocean users from aggressive encounters with sharks. In addition, the identification of specific electrosensory cues that may repel elasmobranchs may also lead to effective solutions for reducing bycatch and improving the efficiency of fisheries.
|Doctor of Philosophy
|Unpublished - 2014