ABSTRACT
Elasmobranchs are renowned for their extremely sensitive electrosensory system, which is used to detect predators, prey, and mates, and is possibly used for navigation. The proper functioning of the electrosensory system is thus critical to fitness. The objective of this study was to test whether exposure to crude oil impairs the electroreceptive capabilities of elasmobranch fishes. Electrosensory function was quantified from six stingrays before and after exposure to a concentration of oil that mimicked empirically measured concentrations along the coast of Louisiana following the Deepwater Horizon spill. Orientation distance (cm), and angle with respect to the dipole axis of a prey-simulating electric field were used to derive the electric field intensity that elicited a response. Oil exposed stingrays continued to exhibit feeding behavior, but they initiated orientations to prey-simulating electric fields from a significantly closer orientation distance. The mean orientation distance after oil exposure was 5.29 ± 0.41 SE cm compared to a pre-exposure orientation distance of 7.16 ± 0.66 SE cm. Stingrays required a mean electric field intensity of 0.596 ± 0.21 SE µV cm-1 to initiate a response after oil exposure, compared to a mean of only 0.127 ± 0.03 SE µV cm-1 in uncontaminated seawater. Oil exposed stingrays thus exhibited a response to a stimulus approximately 4.7 times greater than controls. Stingrays impacted by an oil spill appear to experience reduced electrosensory capabilities, which could detrimentally impact fitness. This study is the first to quantify the effects of crude oil on behavioral electrosensory function.
