Ctenophore mesoglea: building a mucus-like body

Ctenophores are one of our most distant animal relatives and highly abundant and widespread marine predators, yet much of their biology remains undiscovered. Their bodies are dominated by a gelatinous, largely extracellular mesoglea of unknown composition. Ctenophores lack homologs for fibrous collagens that form the typical metazoan extracellular matrix (ECM), so the composition of their extracellular material is unknown. Using spectroscopic analyses of Mnemiopsis leidyi and Pleurobrachia pileus mesoglea, we found abundant mucus-related proteins and sulfated polysaccharides. The mucins and glycans appear unlinked, unlike the typical heavily glycosylated mucins. Our results suggest that ctenophores have a mucus-like mesoglea, a marked contrast from standard collagenous ECMs and mucus. This study indicates that ctenophores are even more different from other animals than previously appreciated, and expands our understanding of soft body composition and biophysics in animals.