Centro de Ciências do Mar, Universidade do Algarve, Campus de Gambelas, 8005-139 Faro, Portugal.
Centro de Ciências do Mar, Universidade do Algarve, Campus de Gambelas, 8005-139 Faro, Portugal
J Exp Biol. 2021 Mar 26;224(Pt 6):jeb238485. doi: 10.1242/jeb.238485.
Ocean acidification may alter olfactory-driven behaviour in fish by direct effects on the peripheral olfactory system; olfactory sensitivity is reduced in CO-acidified seawater. The current study tested whether this is due to elevated or the consequent reduction in seawater pH and, if the former, the possible involvement of carbonic anhydrase, the enzyme responsible for the hydration of CO and production of carbonic acid. Olfactory sensitivity to amino acids was assessed by extracellular multi-unit recording from the olfactory nerve of the gilthead seabream ( L.) in normal seawater (pH ∼8.2), and after acute exposure to acidified seawater (pH ∼7.7) but normal (∼340 µatm) or to high seawater (∼1400 µatm) at normal pH (∼8.2). Reduced pH in the absence of elevated caused a reduction in olfactory sensitivity to l-serine, l-leucine, l-arginine and l-glutamine, but not l-glutamic acid. Increased 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 acetazolamide (a membrane-permeant inhibitor of carbonic anhydrase) in the seawater reversed the inhibition of olfactory sensitivity to l-serine caused by high 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.
海洋酸化可能通过对周围嗅觉系统的直接影响改变鱼类的嗅觉驱动行为；在 CO 酸化的海水中，嗅觉敏感性降低。本研究测试了这是否是由于海水 pH 值升高或随之降低所致，如果是前者，是否可能涉及碳酸酐酶，该酶负责 CO 的水合作用和碳酸的产生。通过在正常海水中（pH 值约为 8.2）和急性暴露于酸化海水（pH 值约为 7.7）但正常（约 340µatm）或高（约 1400µatm）时，从金头鲷（L.）的嗅神经进行细胞外多单位记录来评估对氨基酸的嗅觉敏感性正常 pH（约 8.2）。在没有升高的情况下降低 pH 值会导致对 l-丝氨酸、l-亮氨酸、l-精氨酸和 l-谷氨酰胺的嗅觉敏感性降低，但对 l-谷氨酸没有影响。在没有 pH 值变化的情况下增加会导致对 l-丝氨酸、l-亮氨酸和 l-精氨酸的嗅觉敏感性降低，包括其检测阈值增加，但对 l-谷氨酰胺和 l-谷氨酸的敏感性没有影响。在海水中加入 1mmol·l-1 乙酰唑胺（碳酸酐酶的膜通透抑制剂）可逆转高 海洋酸化对 l-丝氨酸嗅觉敏感性的抑制作用可能是通过降低海水 pH 值和细胞内 pH 值（嗅觉受体神经元）来实现的；前者通过降低气味受体亲和力，后者通过降低嗅觉转导效率。碳酸酐酶在嗅觉受体神经元中的生理作用仍有待探索。
