In vivoEffects of Temperature on the Heart and Pyloric Rhythms in the Crab,Cancer borealis

Abstract

Summary StatementTemperature elevation increases the frequency of the heart and pyloric rhythms of the crab,Cancer borealis, but the heart rhythm has a higher critical temperature than the pyloric rhythm.AbstractThe heart and pyloric rhythms of crustaceans have been studied separately and extensively over many years. Local and hormonal neuromodulation and sensory inputs onto these central pattern generating circuits play a significant role in the animals’ responses to perturbations, but are usually lost or removed duringin vitrostudies. To examine simultaneously thein vivomotor output of the heart and pyloric rhythms, we used photoplethysmography (PPG). In the population measured (n = 49), the heart rhythm frequencies ranged from 0.3–2.3 Hz. The pyloric rhythms varied from 0.2–1.6 Hz. During multiple hour-long recordings, many animals held at control temperature showed strong inhibitory bouts in which the heart decreased in frequency or become quiescent and the pyloric rhythm also decreased in frequency. Many animals show significant coherence in frequency between the rhythms at the frequency of the heart rhythm. We measured the simultaneous responses of the rhythms to temperature ramps by heating or cooling the saline bath while recording both the heart and pyloric muscle movements. Q10s, critical temperatures (temperatures at which function is compromised), and changes in frequency were calculated for each of the rhythms tested. The heart rhythm was more robust to high temperature than the pyloric rhythm.