Head to head
Upside-Down Jellyfish vs Moon Jellyfish
An upside-down jellyfish and a moon jellyfish both belong to the broader jellyfish group, but the two have landed on almost entirely different lifestyles, one settled and stationary, the other constantly adrift.
| Upside-Down Jellyfish | Moon Jellyfish | |
|---|---|---|
| Scientific name | Cassiopea spp. | Aurelia aurita |
| Typical orientation | Bell-down on the seafloor | Bell-up, free-swimming |
| Primary nutrition source | Symbiotic photosynthetic algae | Captured plankton |
| Swimming behaviour | Minimal, mostly stationary | Active, continuous swimming |
| Habitat | Shallow, sunlit coastal water | Open coastal and ocean water |
| Sting severity | Mild | Mild |
| Diet | Omnivore, algae plus plankton | Carnivore, plankton |
| Conservation status | Least Concern | Not Evaluated |
Upside-Down Jellyfish vs Moon Jellyfish: common questions
Why does the upside-down jellyfish rest on the seafloor instead of swimming?
The upside-down jellyfish hosts photosynthetic algae within its tissue and needs to expose them to sunlight, so resting bell-down against the shallow seafloor with its arms angled upward toward the light supports this nutritional relationship far better than the constant swimming lifestyle of a species like the moon jellyfish.
Which jellyfish is more dangerous to swimmers?
Neither jellyfish poses a serious sting risk to most people; both the upside-down jellyfish and the moon jellyfish deliver only a mild sting, though the upside-down jellyfish can additionally release stinging cells suspended in mucus into the surrounding water, causing mild irritation even without direct contact.
Do both jellyfish eat the same things?
Not entirely; the moon jellyfish is a straightforward carnivore capturing plankton with its trailing tentacles, while the upside-down jellyfish is better described as an omnivore, obtaining much of its nutrition from symbiotic algae and supplementing that with captured plankton rather than relying on hunting alone.