Temperature and pH-dependent Potassium Currents of Muscles of the Stomatogastric Nervous System of the Crab, Cancer borealis

Marine crustaceans, such as the crab Cancer borealis, experience large fluctuations in temperature and pH, yet their stomatogastric neuromuscular system must remain functional to support feeding. We examined 16 of the ~40 pairs of stomach muscles and found that warming consistently hyperpolarized muscle fibers (~10 mV per 10 °C) and reduced excitatory junctional potentials and currents. Voltage-clamp analysis in the gastric muscle 5b (gm5b) revealed a temperature-activated conductance with a reversal potential near the potassium reversal potential, consistent with a potassium current, and insensitive to tetraethylammonium. Quantitative RT-PCR identified expression of two putative two-pore domain potassium (K2P) channels in these muscles. Muscle responses were also strongly influenced by extracellular pH. We observed an optimal operating window between pH 6.7-8.8; outside this range, responses diminished and abnormal activity, including spontaneous firing, appeared. Voltage-clamp recordings confirmed pH modulation of the same potassium conductance. Together, these results demonstrate that muscle excitability in Cancer borealis is shaped by temperature- and pH-sensitive currents, presumably carried by K2P channels. Functionally, these channels provide a plausible mechanism for stabilizing neuromuscular output despite environmental perturbations. As temperature increases, the pyloric and gastric rhythms accelerate, increasing synaptic drive to muscles. Activation of K2P channels counterbalances this input by reducing excitability, thereby preventing over-contraction and extending its dynamic range. This work highlights a muscle-intrinsic contribution to the well-known robustness of the stomatogastric system and identifies K2P channels as key players in adapting motor performance to changing environments.