Abstract
The present study aimed to document the interaction between mercury (Hg), as a model chemical stressor to an aquatic organism, and Fatty acid (FA) profile in the longitudinal muscle of the sea cucumber Holothuria forskali. To assess the sensitivity of this species to the toxic effects of Hg, young H. forskali were exposed to gradual doses of Hg (40, 80 and160 µg·L-1) for 96 h. The results showed that following Hg exposure, the FA profile of H. forskali corresponded to an increase in the level of saturated fatty acids, and the decrease in the level of monounsaturated and polyunsaturated fatty acids. The most prominent changes in the FA composition were recorded at the lowest dose with noticeable decreases in linoleic, arachidonic and eicosapentaenoic acid levels and an increase of docosahexaenoic acid. The occurrence of a state of oxidative stress induced by Hg contamination was evidenced by the enhanced levels of malondialdehyde, hydrogen peroxide and lipid hydroperoxide. Overall, the low concentration of mercury exerted the most obvious effects on lipid metabolism, suggesting that changes in fatty acid composition may be act as an early biomarker to assess mercury toxicity in this ecologically and economically important species.
Highlights
Over the last centuries, the environmental impacts of heavy metal pollution have increased in the coastal areas, causing a major threat to the ecosystems and the biota they support (Ruiz et al, 2014)
Polyunsaturated fatty acids (PUFAs) like eicosapentaenoic acid (20:5n-3, EPA) and docosahexaenoic acid (22:6n-3, DHA) are targets that are damaged by reactive oxygen species (ROS), and play a key role in enhancing an organism’s adaptation to environmental stress (Munro et al, 2016)
Significant increases (p < 0.05) in H2O2 and LOOH levels were recorded in the treated H. forskali, respectively, compared to the controls (Figure 1)
Summary
The environmental impacts of heavy metal pollution have increased in the coastal areas, causing a major threat to the ecosystems and the biota they support (Ruiz et al, 2014) Among these xenobiotics, mercury (Hg) is listed as one of the most toxic elements due to its tendency to bioaccumulate and biomagnify through the food chain (Balshaw et al, 2007). It appears that lipids and their constitutional components could be closely involved in cellular responses to pollutants such as Hg in aquatic organisms (Ferrain et al, 2018) In this context, it has been proven that the susceptibility of individual FA to peroxidation increases exponentially with an increasing number of double bonds on the carbon chain (Holman, 1954). FAs were recently argued to be promising bioindicators to assess stress exposure and ecosystem health in a marine environment (Silva et al, 2017)
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