Browsing by Author "Wang, Wenjing"
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- Independent effects of seawater pH and high P-CO2 on olfactory sensitivity in fish: possible role of carbonic anhydrasePublication . Velez, Zélia; Costa, Rita; Wang, Wenjing; Hubbard, PeterOcean acidificationmay alter olfactory-driven behaviour in fish by direct effects on the peripheral olfactory system; olfactory sensitivity is reduced in CO2-acidified seawater. The current study tested whether this is due to elevated P-CO2 or the consequent reduction in seawater pH and, if the former, the possible involvement of carbonic anhydrase, the enzyme responsible for the hydration of CO2 and production of carbonic acid. Olfactory sensitivity to amino acids was assessed by extracellularmulti-unit recording from the olfactory nerve of the gilthead seabream (Sparus aurata L.) in normal seawater (pH similar to 8.2), and after acute exposure to acidified seawater (pH similar to 7.7) but normal P-CO2 (similar to 340 mu atm) or to high P-CO2 seawater (similar to 1400 mu atm) at normal pH (similar to 8.2). Reduced pH in the absence of elevated P-CO2 caused a reduction in olfactory sensitivity to L-serine, L-leucine, L-arginine and L-glutamine, but not L-glutamic acid. Increased P-CO2 in the absence of changes in pH caused reduced olfactory sensitivity to L-serine, L-leucine and L-arginine, including increases in their threshold of detection, but had no effect on sensitivity to L-glutamine and L-glutamic acid. Inclusion of 1 mmol l(-1) acetazolamide (a membrane-permeant inhibitor of carbonic anhydrase) in the seawater reversed the inhibition of olfactory sensitivity to L-serine caused by high P-CO2. Ocean acidification may reduce olfactory sensitivity by reductions in seawater pH and intracellular pH (of olfactory receptor neurones); the former by reducing odorant-receptor affinity, and the latter by reducing the efficiency of olfactory transduction. The physiological role of carbonic anhydrase in the olfactory receptor neurones remains to be explored.
- Neuronal effects of ocean acidification in gilthead seabream (Sparus aurata)Publication . Wang, Wenjing; Velez, Zélia; Costa, Rita Alves; Hubbard, Peter ColinAs atmospheric CO2 increases, so does the amount of CO2 dissolved in the ocean; this causes ocean acidification. The impact of ocean acidification on marine biodiversity and ecosystems has received considerable attention; however, study of its effects on fish physiology and behaviour is just beginning. Although there is evidence that the atmospheric CO2 concentrations predicted to occur by the end of this century have mal-adaptive effects on olfactory-mediated behaviour of reef fish, the cellular mechanism(s) involved is unclear. In the current study, we recorded the olfactory responses of gilthead seabream (Sparus aurata) to explore the effects of high pCO2 and low pH – separately - on olfactory sensitivity. Exposure to elevated pCO2 (but at normal pH) significantly decreased olfactory sensitivity to some odorants, such as L-serine, L-leucine and L-arginine. Moreover, low pH (but at normal pCO2) also decreased olfactory sensitivity to L-serine, L-leucine and L-arginine and L-glutamine. At the histological level, medium-term exposure to ocean acidificaiton increased the ratio between non-sensory epithelium/total length of the lamella significantly at one week, three weeks and four weeks. Furthermore, the number of mucous cells increased significantly after four weeks of exposure to high pCO2 water. These structural changes suggest that the olfactory epithelium can respond to the changes in low pH and/or high CO2 levels, but cannot fully counteract the effects of acidification on olfactory sensitivity. Together, these results show that both high pCO2 and low pH can independently reduce olfactory sensitivity in marine fish, and that although acidification can evoke structural changes in the olfactory epithelium, these changes cannot fully restore olfactory sensitivity.