Abstract
Active sensing organisms, such as bats, dolphins, and weakly electric fish, generate a 3-D space for active sensation by emitting self-generated energy into the environment. For a weakly electric fish, we demonstrate that the electrosensory space for prey detection has an unusual, omnidirectional shape. We compare this sensory volume with the animal's motor volume—the volume swept out by the body over selected time intervals and over the time it takes to come to a stop from typical hunting velocities. We find that the motor volume has a similar omnidirectional shape, which can be attributed to the fish's backward-swimming capabilities and body dynamics. We assessed the electrosensory space for prey detection by analyzing simulated changes in spiking activity of primary electrosensory afferents during empirically measured and synthetic prey capture trials. The animal's motor volume was reconstructed from video recordings of body motion during prey capture behavior. Our results suggest that in weakly electric fish, there is a close connection between the shape of the sensory and motor volumes. We consider three general spatial relationships between 3-D sensory and motor volumes in active and passive-sensing animals, and we examine hypotheses about these relationships in the context of the volumes we quantify for weakly electric fish. We propose that the ratio of the sensory volume to the motor volume provides insight into behavioral control strategies across all animals.
Highlights
Bats, dolphins, and electric fish are well-known examples of animals that emit energy into the environment for the purpose of sensing their surroundings
An Omnidirectional Sensory Volume Using synthetic prey capture trajectories, the sensory volume for active electrosensory prey detection in A. albifrons was estimated by computing a detection isosurface surrounding the fish, such that every point on the surface generates a threshold level of activation after summing and filtering the electrosensory afferent signals
To interpret the sensory and motor volumes presented in this study, an analogy may prove useful
Summary
Dolphins, and electric fish are well-known examples of animals that emit energy into the environment for the purpose of sensing their surroundings. We refer to these as ‘‘active’’ sensing systems [1], to distinguish them from ‘‘passive’’ systems that rely on extrinsic sources of energy, such as sunlight. One constraint is related to the metabolic cost of energy emission, which scales steeply with sensing range Both the outbound probe energy and the return signal are subject to the inverse-square dependence of spherical spreading loss, which means that the strength of the return signal falls as 1/r4, where r is the distance to the target. For the general case, doubling the active sensing range would require a 16-fold (24) increase in emitted energy [1,3]
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