ABSTRACT
Jellyfish are radially symmetric organisms without a brain that arose more than 500 million years ago. They achieve complex organismal behaviors through coordinated interactions between autonomously functional body parts. While jellyfish neurons have been studied electrophysiologically, it has not been possible to investigate their neural function at the systems level. Here I introduce Clytia hemisphaerica as a transparent and genetically tractable jellyfish model for neuroscience. I report efficient generation of stable transgenic and knock-out lines for whole-organism GCaMP imaging and conditional cell ablation. Using these tools and computational analyses we find that an apparently unstructured subnetwork of RFamide-expressing neurons gives rise to spatiotemporally structured ensemble activity that controls localized umbrella infolding during feeding. Looking forward, Clytia affords a tractable platform for high resolution studies at the interface of nervous system development, regeneration, evolution, and function.