Young cancer crabs are often found clinging to this jelly, even inside the gut. The crab helps the jelly by eating the parasitic amphipods that feed on and damage the jelly.

Human activities can hit nearshore habitats hard. Dredging, dumping and silt build-up can wipe out underwater communities in bays, estuaries and reefs. Several jelly species live in nearshore habitats. And many that don't live near the shore do develop in nearshore "nurseries" when they're young. Harming these habitats could reduce the overall jelly population.

• The purple-striped jelly's lifecycle was first discovered in its entirety at the Monterey Bay Aquarium. 
• How does a jelly move? The bell pulses to move short distances — to go farther a jelly rides the current. 
• Since divers have seen ocean sunfish eating these jellies, we know some fishes must be immune to the sting.