A cell-type atlas from a scyphozoan jellyfishAurelia coerulea(formerly sp.1) provides insights into changes of cell-type diversity in the transition from polyps to medusae

Abstract

We provide here a detailed single cell transcriptomic atlas covering the life cycle of the cosmopolitan scyphozoan Aurelia coerulea. We show that there is an increase in cell type diversity in the medusa stage, which is reflected by an increase in the number of unique transcripts expressed. We highlight parallels in both cell complement and specification pathways between Aurelia and the sea anemone Nematostella, two lineages separated by more than 500 MY. We find that several cell types of the neuroglandular lineages are specified by the same transcription factors that arose by gene duplications in the common ancestor of medusozoans and anthozoans. This confirms gene duplications as a source for the increase of cellular complexity during the evolution of cnidarian neuroglandular lineages dates to the common ancestor of all cnidarians. We validated spatial expression domains corresponding to molecular profiles of smooth and striated muscles and followed the development of the striated muscle in the medusa. Our data suggests that striated muscles in the subumbrella of the medusa derive directly from smooth muscles in the jellyfish, and that these two muscle cell types are characterized by distinct molecular profiles. Further, reconstruction of putative cell trajectories indicates multipotent cell states derive from tissues at the boundary between epithelial layers and highlight molecular characteristics not typical of other cnidarians.

The evolution of cnidarian stinging cells supports a Precambrian radiation of animal predators

“…However, the transfer of pgsAA from bacteria to animals is not cnidarian-specific, and is therefore not evidence that cnidocytes themselves arose through horizontal transfer. More recent analyses that look wholistically at gene expression show that the cnidocyte's transcriptional regulation is similar to the neuron (Chari et al, 2021;Link et al, 2023;Siebert et al, 2019;Steger et al, 2022) and that a small number of genes can change the cell fate from neuron to cnidocyte (Babonis et al, 2022). This is consistent with an alternative hypothesis that cnidocytes and neurons share a common ancestor (Galliot & Quiquand, 2011).…”