Two central pattern generators from the crab, Cancer borealis, respond robustly and differentially to extreme extracellular pH

Animals and their neuronal circuits must maintain function despite significant environmental fluctuations. The crab, Cancer borealis , experiences daily changes in ocean temperature and pH. Here, we describe the effects of extreme changes in extracellular pH – from pH 5.5 to 10.4 – on two central pattern generating networks, the stomatogastric and cardiac ganglia of C. borealis . Given that the physiological properties of ion channels are known to be sensitive to pH within the range tested, it is surprising that these rhythms generally remained robust from pH 6.1 to pH 8.8. Unexpectedly, the stomatogastric ganglion was more sensitive to acid while the cardiac ganglion was more sensitive to base. Considerable animal-to-animal variability was likely a consequence of similar network performance arising from variable sets of underlying conductances. Together, these results illustrate the potential difficulty in generalizing the effects of environmental perturbation across circuits, even within the same animal. Abbreviations STG stomatogastric ganglion CG cardiac ganglion CPG central pattern generator AB Anterior Burster PD Pyloric Dilator LP Lateral Pyloric PY Pyloric SC Small Cell LC Large Cell lvn lateral ventricular nerve ANOVA analysis of variance PTX picrotoxin IPSP inhibitory post-synaptic potential LG Lateral Gastric MG Medial Gastric LPG Lateral Posterior Gastric GM Gastric Mill DG Dorsal Gastric AM Anterior Median Int1 Interneuron 1 mvn medial ventricular nerve dgn dorsal gastric nerve lgn lateral gastric nerve ion inferior oesophageal nerve IC Inferior Cardiac VD Ventricular Dilator MCN1 Modulatory Commissural Neuron 1 VCN Ventral Cardiac Neuron CPN2 Commissural Projection Neuron 2 CoG commissural ganglion KDE kernel density estimate IQR interquartile range CI confidence interval