Design, prototyping, and testing of an apparatus for establishing a linear temperature gradient in experimental fish tanks

Abstract

Immunology researchers require a new type of fish tank that provides a linear thermal gradient for experimental zebrafish in order to improve the accuracy and validity of their research. Zebrafish require the ability to select their surrounding water temperature in order to react to a simulated viral infection with an optimized immune response. Although countless immunology studies have been performed with zebrafish to date, their validity came into question in early 2013 when it was demonstrated by MacKenzie et. at that the immune response in fish is critically coupled with a form of environmental temperature selection known as behavioral fever. Current research tanks feature a uniform temperature throughout, preventing the fish from being able to "choose" their surrounding water temperature in response to a simulated viral infection. "Fish that are not offered a choice of temperatures and that therefore cannot express behavioral fever show decreased survival under viral challenge." (MacKenzie, et al., 2013) In this study, a conceptual thermal-fluid system was designed, built, and tested for its ability to establish a stable, linear thermal gradient in a standardsize 10L laboratory tank. The thermal profile of the volume of water contained within the experimental tank was determined from temperature measurements taken at incremental depths. The apparatus was found to produce a suitably linear temperature gradient over a base-to-surface temperature difference of 19.6°0C; far greater than the temperature difference of 8°C necessary for unrestricted behavioral fever to be expressed in experimental zebrafish. As such, it was determined that the approach taken is suitable for future use in the development of aquaria for immunology research and water tanks for other applications.