Fish get the “rotten egg gas” chills.

At long last, resulting from herculean efforts of a number of former students, our paper is published. Out today in Royal Society Open Science, our paper entitled: “Hydrogen sulfide exposure reduces thermal set point in zebrafish” represents the efforts of two honours students (JC Shaw and CD Dobell) and the writing and analytical skills of a great PDF and colleague (DA Skandalis).

Here is a link to the study and full citation:

Skandalis DA, Dobell CD, Shaw JC, Tattersall GJ. 2020 Hydrogen sulfide exposure reduces thermal set point in zebrafish. R. Soc. Open Sci. 7: 200416.

https://royalsocietypublishing.org/doi/10.1098/rsos.200416

We tested whether dissolved H2S in the water will alter thermal preference. Previously, work in mice has suggested that mice could be induced to adopt a “hibernation-like” state, although there was some doubt (in the literature) as to whether H2S signalled a change in thermoregulatory state or simply acted as a metabolic inhibitor. By testing this in zebrafish, we could test formally whether they prefer cooler temperatures with H2S exposure, and they did. Not only did they choose to cool down, but they continued to make thermoregulatory decisions, swimming back and forth between cool and warmer water, suggesting they are still making thermoregulatory decisions and not simply caught in the cold water. So…yeah, complicated. H2S might induce a behavioural anapyrexia (a lowered thermal set-point). We discuss the potential environmental and neurophysiological context in the paper for those interested. The rotten egg reference is to the smell of H2S gas.

To conduct this study, we used a system built by Brock University’s Technical Services and employed in our research lab that allows us to track fish in a two chamber thermal shuttle box:

Schematic of the Shuttle Box System (see Figure S1 in the paper).

This setup allows us to heat and cool a tank and track the fish’s choices over time. Here is a thermal image depicting an earlier version of the shuttle box (correcting the spill over of warm-water in the centre can be corrected using baffles and a circular chamber system, but I haven’t taken a new picture with the thermal camera during the pandemic lockdown):

There was some considerable interest in developing H2S as a therapeutic to put mammals and/or tissues/organs into a suspended state. It is intriguing that animals like zebrafish that can behaviourally regulate body temperature continue to do so under this exposure. Anaprexic stategies are commonly seen in ectotherms and perhaps by hijacking an innate signalling system, H2S evokes this response.

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