Dr Barr wondered if they were actively working with their hosts to keep down the level of pathogenic bugs that might otherwise set up shop in the hosts' mucus membranes.
But if the cells that make up a tissue need to, say, brew up hormones or mucus, they'll need the internal machinery it takes to make that stuff, and that takes up a lot of space.
Dr Rotter's research is still in the early stages, but it's hoped that jellyfish mucus could hold the key to a future free of microplastic polluted oceans.
Normally you hold about half a liter of fluid in your lungs, so when you sneeze, you're able to spray as much as a water bottle's worth of mucus into the air around you.