Subterranean Fishes of the World

4748

2010

Many behaviors exhibited by aquatic animals rely on the ability to sense water flow. In fish, flow sensation is mediated by hair cells within the lateral line system. This system is composed of two classes of receptors: superficial and canal neuromasts. Ethological investigations have sought to separate the roles of these two receptor classes using an aminoglycoside antibiotic, gentamicin. Gentamicin is believed to disrupt the function of canal, but not superficial, neuromasts. We tested this theory in vivo. In this study we used florescent vital dyes (DASPEI and FM1-43) following exposure to a solution of gentamicin. Contrary to the prevailing assumptions, we found that gentamicin disrupts the hair cells in both receptor classes. A significant effect was found for both the superficial and canal neuromasts of two different fish species (Astyanax mexicanus and Danio rerio). Furthermore, by labeling hair cells prior to gentamicin exposure, we observed that, in both classes, disrupted hair cell function is at least partially due to cell death. We conclude that gentamicin is not a reliably selective blocker of canal neuromasts. In light of this result, we have revisited the effect of gentamicin exposure on rheotaxis, an unconditioned orienting response to water flow. Prior studies have concluded that gentamicin exposure does not affect the rheotactic response, and that canal neuromasts are not important for rheotaxis. However, after carefully validating drug exposure with vital dye staining, we found that gentamicin exposure disrupted rheotaxis in the blind Mexican cave fish, Astyanax mexicanus. These results demand re-evaluation of many prior behavioral studies of the lateral line system.

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9th International Congress of Neuroethology

2010

2010

2010