The worst offender is the Portuguese man-of-war, which is actually not a
true jellyfish but a jellyfish-like animal, classed as a siphonophore.
All four penguin species consumed
true jellyfish, with 187 different Cnidaria species spotted in the videos.
Here in Florida we have many varieties of jellyfish, some of which can cause significant pain including the Portuguese man-of-war (although not a
true jellyfish).
Man-O-War is not a true jellyfish, but a siphonophore - a single animal made up of a colony of organisms, which normally lives far out in the ocean - and can sting even when they are dead and washed up.
MAN-O-WAR is not a true jellyfish but a single animal made up of a colony of organisms and usually lives in the middle of the ocean
The
true jellyfish, however, are part of the cnidarians, a phylum that also includes corals and sea anemones.
Distant cousins to the true jellyfish, comb jellies don't have stinging cells.
For example, the animals known as comb jellies look in many ways like true jellyfish, but are actually distant cousins.
(1,2) Cnidaria include "hydrozoans (fire coral and Portuguese man-of-war), scyphozoans (
true jellyfish), and anthozoans (sea anemones).
Lacking stinging tentacles, Mnemiopsis is not a
true jellyfish. Instead, it belongs to the Ctenophora, a family of planktonic animals that depend on tiny cilia to paddle feebly about.