Abstract
Motor systems depend on temperature-sensitive processes at every level, from ion channel
kinetics to cross-bridge cycling. In poikilotherms, these processes must be well-coordinated such
that motor output remains functional across the animal’s thermal range. The stomatogastric
nervous system (STNS) of the crab, Cancer borealis, is a well-established model for studying
temperature robustness in neural circuits, yet comparatively little is known about how
temperature affects the muscles these circuits innervate. Here, I characterize the temperature
sensitivity of stomatogastric muscles by applying high K contractures across five temperatures
(11–26°C) to muscles with distinct functional roles: the gastric mill chewing muscle gm6 and the
pyloric filtering muscles cpv4, cpv6, and p1. I find that gm6 exhibits a pronounced bell-shaped
force–temperature relationship, with peak contracture force near 16°C and marked decline at
thermal extremes, while the pyloric muscles show comparatively stable contracture amplitudes
across the same range. I construct a biophysical model which suggests that the lack of
temperature sensitivity in the pyloric muscles may be related to their stronger activation during
high K contractures and confirm this experimentally. Finally, I compare the dynamics of both
muscles and find that the pyloric muscles contract more slowly during high K contractures, but
more quickly during physiological nerve-evoked stimulation. These results suggest that the two
muscles possess distinctive biological adaptations suited to their respective purposes, with
pyloric muscles better suited to long periods of activity without depression.