How does this jellyfish sting without touching you?

The video explains why upside-down jellyfish can sting even when not in direct contact. Scientists discovered that these jellyfish release toxin-filled mucus containing cassiosomes, which are balls of stinging cells. These cassiosomes can harm swimmers and kill prey like brine shrimp. The research team has also found cassiosomes in other jellyfish species closely related to the upside-down jellyfish.

How do cassiosomes affect swimmers and prey?

What other jellyfish species have been found to contain cassiosomes?