CO-Induced Ocean Acidification Alters the Burrowing Behavior of Manila Clam by Reversing GABA Receptor Function.

Biological burrowing behavior is an important driver shaping ecosystems that is being threatened by CO-induced ocean acidification; however, the effects of ocean acidification on burrowing behavior and its neurological mechanism remain unclear. This study showed that elevated CO significantly affected the burrowing behaviors of the Manila clam , such as increased foot contraction, burrowing time, and intrabottom movement and decreased burrowing depth. Delving deeper into the mechanism, exposure to elevated CO significantly decreased extracellular pH and increased [HCO]. Moreover, an indicator GABA receptor, a neuroinhibitor for movement, was found to be closely associated with behavioral changes. hybridization confirmed that the GABA receptor was widely distributed in ganglia and foot muscles, and elevated CO significantly increased the mRNA level and GABA concentration. However, the increase in GABA receptor and its ligand did not suppress the foot movement, but rather sent "excitatory" signals for foot contraction. The destabilization of acid-base homeostasis was demonstrated to induce an increase in the reversal potential for GABA receptor and an alteration in GABA receptor function under elevated CO. This study revealed that elevated CO affects the burrowing behavior of Manila clams by altering GABA receptor function from inhibitory to excitatory.