Making sense: Weakly electric fish modulate sensory feedback via social behavior and movement

Animals rely on sensory information for the control of their behavior. Understanding this process requires a detailed description of the sensory feedback that they receive, which is often determined by an animal's proximity to conspecifics and its own movement within the environment. This dissertation examines the role of social behavior and movement for the modulation of electrosensory feedback in weakly electric fish.;We made observations of weakly electric fish in their natural habitats and found that some species of fish, which typically have more complex social behaviors, are most often found in groups. As a result of social grouping these fish receive continuous electrosensory oscillations (amplitude and phase modulations) caused by the interactions of the electric fields of each individual. Interestingly, both social grouping and movement can produce higher order modulations (termed 'envelopes'), which can have lower frequency content than the first order modulations. Curiously, we did not observe low frequency envelopes in the majority of our samples. To determine why that might be the case we tested the behavioral responses of weakly electric fish to envelope stimuli in controlled laboratory experiments.;We found that Eigenmannia will increase or decrease their electric organ discharge (EOD) frequency in response to social envelope stimuli, termed the Social Envelope Response (SER). The strength of the SER was dependent on the initial envelope frequency and the stimulus amplitude, whereby lower frequency envelopes and higher stimulus amplitudes resulted in the strongest EOD changes. As a consequence of the EOD change the envelope frequency during the course of a trial was increased, suggesting that the SER may be a mechanism for avoiding low frequency social envelopes. These results may explain our field results that showed weakly electric fish do not typically produce low-frequency envelopes in natural social groups.;These fish are not only processing electrosensory information from their social behavior but are also simultaneously processing electrosensory information from their own movement and the relative movement of nearby objects in their environment. To investigate the relationship between movement and the modulation of sensory feedback we tested the ability of Eigenmannia to track a moving refuge under varied sensory conditions by changing the illumination and conductivity across trials. When the fish relied solely on electrosensory information during tracking they performed additional movements that consisted of whole-body oscillations and tail bends, which may be used to shape electrosensory feedback.;Our results indicate that weakly electric fish continuously process two streams of information, one derived from social interactions and the other from movement, which are used for the independent control of the fish's electric organ and the fish's locomotor system. In addition, both social behavior and movement can be used to modulate electrosensory feedback. Future studies should examine sensory processing in the context of the animal's social behavior and their movement within the environment, as it can categorically change the signals that the animal is receiving.