From single neurons to behavior in the jellyfish Aurelia aurita.

Fabian Pallasdies,Wilhelm Braun,Sven Goedeke,Raoul-Martin Memmesheimer

doi:10.7554/elife.50084

Abstract

Jellyfish nerve nets provide insight into the origins of nervous systems, as both their taxonomic position and their evolutionary age imply that jellyfish resemble some of the earliest neuron-bearing, actively-swimming animals. Here, we develop the first neuronal network model for the nerve nets of jellyfish. Specifically, we focus on the moon jelly Aurelia aurita and the control of its energy-efficient swimming motion. The proposed single neuron model disentangles the contributions of different currents to a spike. The network model identifies factors ensuring non-pathological activity and suggests an optimization for the transmission of signals. After modeling the jellyfish's muscle system and its bell in a hydrodynamic environment, we explore the swimming elicited by neural activity. We find that different delays between nerve net activations lead to well-controlled, differently directed movements. Our model bridges the scales from single neurons to behavior, allowing for a comprehensive understanding of jellyfish neural control of locomotion.

Highlights

The remaining unknown features of the model are the membrane capacitance and the synapse model. We choose them such that (i) the excitatory postsynaptic potentials resemble in their shape the experimentally found ones (Anderson, 1985), (ii) the inflection point of an action potential (AP) is close to 0 mV (Anderson and Schwab, 1983) and (iii) it takes approximately 2.5 ms for an AP to reach peak amplitude after stimulation via an excitatory postsynaptic current (EPSC) (Anderson, 1989)
The model yields an explanation for experimental findings, such as the long refractory period of Motor nerve net (MNN) neurons (Anderson and Schwab, 1983), in terms of ion channel and synapse dynamics
The slow outward current does not contribute to the neuron dynamics in the considered physiological regime

Summary

Introduction

Some behavioral (Horridge, 1956; Gemmell et al, 2015) and anatomical (Nakanishi et al, 2009) evidence suggests that a rhopalium might activate the DNN together with the MNN in response to a strong sensory stimulus These points indicate that each rhopalium is responsible for steering the animal by stimulating either one or both of the nerve nets. This, together with the observation that DNN activation creates no visible contraction of the circular muscles in Aurelia (Horridge, 1956), suggests that MNN and DNN each control one set of muscles and that this enables steering of the jellyfish.

Results

Discussion

Materials and methods

Funding Funder