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'Rotten' gas may help fish survive low oxygen environments

Research investigating how fish sense oxygen, carried out by the University of Exeter’s Dr. Cosima Porteus and her Canadian colleagues, has been published today in the prestigious Journal of Physiology.

Dr Porteus believes that understanding how this occurs provides insight into how fish can acclimatise to or avoid low oxygen in a changing environment. It also demonstrates a link between oxygen-sensing in mammals, where oxygen-sensing cells are known to use the gas hydrogen sulphide and in fish, where oxygen-sensing mechanisms remain largely unknown.

Dr Porteus, of Biosciences, points out that: “Over the past 50 years, the frequency and severity of low oxygen events has been on the rise in aquatic environments, largely due to human interference,” it is therefore vital that research contributes to our understanding of how fish may cope with these changes.

Mammals may detect oxygen levels in blood, however fish gills possess oxygen-sensing cells capable of monitoring the level of oxygen in both the blood and in external water. Hydrogen sulphide is a gas that most will recognise as the smell of “rotten eggs”; it acts as a biological signalling molecule in cells - one of only three gases known to do this - and has been proposed to play an important role during oxygen-sensing in mammalian sensor cells.

This research aimed to determine whether hydrogen sulphide is involved in oxygen-sensing in fish as it is in mammals, supporting evidence that suggests that oxygen-sensing cells in fish gills are related to their mammalian counterparts.

Dr. Porteus, along with Canadian colleagues, carried out this research at the University of British Columbia in Canada. She chose to study zebrafish because it is a model fish species whose genetics are well known and cell culture techniques are well established. This knowledge was crucial for this research.

The researchers discovered that increasing the amount of hydrogen sulphide available to the fish (in both adult and larval life stages) resulted in increased ventilation - a common response to low oxygen environments. When the team prevented the action of genes specifically involved in hydrogen sulphide production, the fish did not hyperventilate upon introduction to a low oxygen environment. These genes were also specifically found in the oxygen-sensing cells, showing that hydrogen sulphide can be produced in these cells in zebrafish, where it appears to play an important role in controlling ventilation responses necessary to cope with low oxygen environments.

Dr. Porteus is now investigating how CO2 induced ocean acidification may affect sea bass sense of smell at the University of Exeter.

The article can be found here.

Date: 24 April 2014

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