Meeting Abstract
77.2 Tuesday, Jan. 6 Internarial timing differences steer sharks GARDINER, J.M.*; ATEMA, J.; HUETER, R.E.; MOTTA, P.J.; University of South Florida; Boston University Marine Program; Mote Marine Laboratory; University of South Florida jmgardin@mail.usf.edu
Sharks are hypothesized to orient to odors by performing bilateral comparisons between the nares and turning towards the highest concentration. However, odor dispersal fields result from fluid mixing and show chaotic intermittency with great temporal and spatial variance. The time-averaged concentration converges too slowly to be useful to determine a gradient, but an animal may get directional information from the pattern of the timing of the slopes of the concentration peaks. We fitted smooth dogfish, Mustelus canis with headsets to deliver odor to the two inflow nares, connected to programmable syringe pumps to precisely control the timing of odor delivery. The nares were presented with 0.5ml of squid rinse of identical concentration with the timing varied such that one naris received the pulse ahead of the other with 0.1, 0.2, 0.5 and 1s delays. To determine the contribution of concentration to odor patch orientation, both nares were simultaneously stimulated, one with full strength squid rinse, the other with a 100 fold dilution. Finally, the nares were stimulated with these concentration differences but with a 0.5s delay such that the weaker odor was received before the stronger odor. Animals displayed turns, defined as a 30 degree change in heading pre vs post-stimulation, towards the side receiving the first odor pulse, regardless of concentration differences. Simultaneous pulses of different concentrations resulted in turns towards either side with equal frequency. These results suggest that the temporal pattern of odor patches presents the most salient information for orientation and that the decision to turn is made within 0.5 seconds so subsequent, stronger pulses do not affect these behaviors. Using timing differences for steering is an essential component of the eddy chemotaxis hypothesis.
