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The Behavioral Dynamics and Temporal Evolution of Wall- Following Behaviour in Blind and Sighted Morphs of the Species Astyanax fasciatus

by Sharma, Saurabh

Abstract (Summary)
Mexican blind cavefish exhibit an unconditioned wall-following behavior in response to novel environments. Similar behaviors have been observed in a wide variety of animals, but the biological significance of this behavior and its evolutionary history are largely unknown. In this study, the behaviors of sighted river morphs and congenitally blind, cave-dwelling morphs of the same species, Astyanax fasciatus were videotaped during and after their initial introduction into a novel arena under dark (infrared) and visible light conditions. The swimming movements of fish in the experimental arena were tracked with an automatic image-tracking system to provide a post-hoc analysis of how the fish's swimming speed and position (distance and orientation) with respect to the arena walls varied over time. In response to the novel environment in the dark, both sighted and blind morphs exhibited wall-following behaviors with subtle but significant differences. Blind morphs swam more nearly parallel to the wall, exhibited greater wall-following continuity and persistence and reached maximum and stable swimming speeds (~1.5 BL/s) much more quickly than sighted morphs. In contrast, sighted morphs placed in the same novel, but well-lit environment exhibited dramatically different behaviors that consisted of either holding stationary positions near the wall for long periods of time or moving in and around the central region of the environment without moving along the walls. These results are consistent with the idea that both blind and sighted morphs have inherited primitive wall-following behaviors from their common sighted ancestor that serve an exploratory function under visually-deprived conditions. Under well-lit conditions, the proclivity of some sighted morphs to remain motionless near the wall of a novel environment suggests that near-wall preferences may also serve a protective function under some circumstances. It appears that wall-following behaviors of blind morphs rely more heavily on active sensing by the lateral line and have become more finely honed for exploratory purposes than those of sighted morphs.
Bibliographical Information:

Advisor:

School:Bowling Green State University

School Location:USA - Ohio

Source Type:Master's Thesis

Keywords:mexican blind cavefish wall following behavior lateral line

ISBN:

Date of Publication:01/01/2008

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