Meeting Abstract
Sharks and rays are hypothesized to use geomagnetic cues to orient and navigate across the ocean, but magnetoreception is not well documented in elasmobranchs. Yellow stingrays (N=10) were held in a flow through seawater tank under a 12:12 hr light dark cycle and were fed daily. Rays were trained to associate a magnetic stimulus with food by giving each ray a morsel of food when it swam over a magnet buried in the sand. Neodymium magnets and non-magnetic controls were coated in epoxy to prevent galvanic currents between the metal and seawater that would stimulate the electroreceptors. The learning criterion was the minimum latency for each ray to correctly orient and stop over a buried magnet (≥75%) in four tests per day for three consecutive days. Once criterion was met the training stopped and memory retention tests began without additional reinforcement. Each test was a simple choice between a magnet and a demagnetized control buried under the sand at a random location within the arena. Memory retention was tested at 30, 60, and 90 days after training ceased. All rays were demonstrated a magnetoreception because they reached criterion within two weeks and retained the memory for over 60 days. Future experiments will determine the nature and range of magnetic stimuli that elasmobranchs can detect, and whether these stimuli are potential cues for orientation and navigation.
