Effects Of Ocean Acidification On Olfaction And Gustation Mediated Foraging Behavior In The Black Sea Bream.acanthopagrus Schlegelii

Since the industrial revolution,anthropogenic activities such as the utilization of coal,fuels,and gas have emitted large amounts of carbon dioxide(CO2)into the atmosphere.An enormous part(approximately 1/4 to 1/3)of anthropogenic CO2 has been absorbed by the ocean,which leads to lower pH and alteration in seawater chemistry characteristics,a phenomenon termed as ocean acidification(OA).In recent years,ocean acidification has drawn worldwide concern over its potential threat to marine organisms and ecosystems.However,the behavioral impacts of ocean acidification and especially the underlying physiological and molecular mechanisms causing these impacts are still poorly understood in marine species.Therefore,in the present study,the effect of ocean acidification(pH7.8 and pH7.4)on the olfaction and gustation mediated foraging behavior were investigated in the larval black sea bream.The results showed that larval sea breams reared in pCO2 acidified seawater(pH at 7.8 and 7.4)for 15 days tend to swim with a significant slower velocity in a more zigzag manner towards food source and take more time to reach the food source.Furthermore,the consumption of pellets with feed and the percentage of feed-containing pellets swallowed to the corresponding number of pellets snapped were significantly reduced.These findings indicate that feeding behavior mediated by olfaction and gustation was significantly impaired by ocean acidification in black sea bream.In addition,compared to the control,significant reductions in the in vivo contents of y-aminobutyric acid(GABA),Acetylcholine(ACh),and 5-hydroxytryptamine(5-HT)were detected in OA-treated sea breams.Moreover,OA exposure led to a significant down-regulation of the expression of genes encoding positive regulators including olfaction-specific G protein(Golf)and the G-protein signaling 2(RGS2),whereas an evident up-regulation of that of negative regulators,the G protein-coupled receptor kinase(GRK)and Arrestin in the olfactory transduction pathway.Similarly,the expression of genes encoding key components from the gustatory transduction pathway,the taste 1 receptor member 3(T1R3),the inositol 1,4,5-trisphosphate receptor type 3(IP3R),the transient receptor potential cation channel subfamily M member 5(TRPM5),and the pyrimidinergic receptor P2Y4(P2Y4)were all significantly suppressed in the larval sea breams reared in pCO2 acidified seawater.In general,data obtained indicate that OA may hamper the foraging behavior through disrupting the olfactory and gustatory neural signal transduction.The results obtained in this study should contribute positively to improve present understanding of the impacts of ocean acidification.