Studies on the cardiac physiology of Onychophora and Chilopoda

Cardiac physiology in Onychophora and Chilopoda has not yet been studied by electrophysiological methods. Here we present ECGs and the first intracellular recordings from dorsal vessel muscle cells in Scolopendra cingulata, Lithobius forficatus and Peripatopsis sp. In Onychophora, a myogenic automatism generates the heart function. In the Chilopoda examined, heartbeat is triggered by a neurogenic automatism that is superimposed over a basic myogenic rhythm, which occurs under experimental conditions. The neuropeptide proctolin and the head peptide have no significant effects in the species investigated. The results are discussed from the viewpoints of comparative physiology and phylogenetics.