Nervous systems must maintain coordinated activity patterns despite perturbations from unstable environmental factors (e.g., temperature, pH, and salinity). Marine organisms experience daily and seasonal changes in temperature, and precipitation and ocean currents alter sea water salinity. We examined how the stomatogastric nervous systems (STNS) from two species of decapod crustaceans ( Cancer borealis and Homarus americanus) were affected by altered temperature and salinity. We used the patterned activity of the pyloric rhythm to assay the tolerance of the STNS to these two perturbations, independently and combined. The pyloric rhythm is generated by a well-characterized circuit containing a small number of identified neurons. These species exhibited distinct increases in frequency as temperature was increased with the pyloric rhythm crashing between 25°C and 38°C. When salinity was increased to 1.25x that of the physiological (1x) saline, the pyloric rhythm crash temperature was ~3-5°C lower in both species. While the C. borealis pyloric rhythm crash temperature was similar between 1x and 0.75x salinities, in H. americanus, it crashed ~3°C higher in 0.75x salinity. Although C. borealis and H. americanus share a common habitat, they exhibited differences in their responses to these perturbations. Despite each species having a similarly configured pyloric circuit, the order in which neurons crashed were species specific. In summary, the C. borealis was unaffected by salinity alone, but increased temperature and the combination of the two perturbations altered the pyloric frequency. In H. americanus, the pyloric frequency was affected by both perturbations individually as well as the combination of the two.
Carrier et al. (Tue,) studied this question.