Abstract
Central Pattern Generators (CPGs) produce rhythmic behaviour across all animal phyla. Cnidarians, which have a radially symmetric nervous system and pacemaker centres in multiples of four, provide an interesting comparison to bilaterian animals for studying the coordination between CPGs. The box jellyfish Tripedalia cystophora is remarkable among cnidarians due to its most elaborate visual system. Together with their ability to actively swim and steer, they use their visual system for multiple types of behaviour. The four swim CPGs are directly regulated by visual input. In this study, we addressed the question of how the four pacemaker centres of this radial symmetric cnidarian interact. We based our investigation on high speed camera observations of the timing of swim pulses of tethered animals (Tripedalia cystophora) with one or four rhopalia, under different simple light regimes. Additionally, we developed a numerical model of pacemaker interactions based on the inter pulse interval distribution of animals with one rhopalium. We showed that the model with fully resetting coupling and hyperpolarization of the pacemaker potential below baseline fitted the experimental data best. Moreover, the model of four swim pacemakers alone underscored the proportion of long inter pulse intervals (IPIs) considerably. Both in terms of the long IPIs as well as the overall swim pulse distribution, the simulation of two CPGs provided a better fit than that of four. We therefore suggest additional sources of pacemaker control than just visual input. We provide guidelines for future research on the physiological linkage of the cubozoan CPGs and show the insight from bilaterian CPG research, which show that pacemakers have to be studied in their bodily and nervous environment to capture all their functional features, are also manifest in cnidarians.
Highlights
Central Pattern Generators (CPGs) produce rhythmic behaviors across all animal phyla [1,2,3,4]
We show that a simple resetting interaction of four swim pacemakers could not account for the proportion of long inter pulse intervals (IPIs) of the animals, and suggest additional mechanisms controlling the pulse rate in box jellyfish
Swim pulse analysis of animals with one and four rhopalia under different light conditions The IPI distributions of T. cystophora medusae obtained by highspeed camera observation of tethered swimming animals were in agreement with observations from several previous studies of box jellyfish: They had characteristic long tails towards longer IPIs, which has been described for electrophysiological recordings from single isolated pacemakers [16,17] and intact animals [26]
Summary
Central Pattern Generators (CPGs) produce rhythmic behaviors across all animal phyla [1,2,3,4]. Recent work has shown that CPGs are best studied in their bodily and nervous environment to understand their characteristics and function properly [5,6]. Due to their fundamentally different body plan and nervous system organization, cnidarian CPGs provide an interesting comparison to those of bilaterians. Information is transmitted across their body by diffuse bipolar nerve nets and the ring nerve, a central nerve like structure containing several specialized conduction pathways [7,8,9,10,11]
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have