Molecular and cellular basis of life cycle transition provides new insights into ecological adaptation in jellyfish

Jellyfish are renowned for their complex life cycles and important ecological and evolutionary position. The unique transition from the sessile polyp to motile medusa stages is a key process determining a switch in jellyfish behaviour and regulating the formation of jellyfish blooms. Here, we presented a comprehensive cell atlas spanning four successive life cycle stages during the polyp-to-medusa transition in the scyphozoan jellyfish Aurelia coerulea. Moreover, we characterised the variation in cell composition and gene expression patterns during the phase transition, especially in the neuromuscular system. We found several previously unreported cell types that potentially underpin the complex swimming behaviour of jellyfish. Furthermore, we discovered the pivotal role of HOX1 in modulating the genesis of striated muscles in A. coerulea. Collectively, this study provides valuable insights into the cellular and molecular mechanisms underlying the complex life cycle transition and helps to advance our understanding of ecological adaptation in jellyfish.