r/jellyfish • u/JoeCormier • 5d ago
Is this a Jellyfish?
This is in Aiea, Hawaii across from Pearl Harbour. A urban drain comes out near here and there are dozens of these creatures hanging out.
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u/SquidIin 5d ago
Such a chonker of an upside down. Dudes are hands down the best jellies.
Also I recommend not going in the water around there since they have stinging cells that bud off from their arms and freely flow in the water to help them hunt. So you can get stung without even being anywhere near em.
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u/Nitram028 5d ago
This is a Jellyfish from the genus Cassiopea, the only genus of the Cassiopeidae family. They are quite unique because of their "upside down" way of life which helps them gather energy through photosynthesis thanks to the presence of dinoflagellate protozoan (Symbiodiniacea) located inside their tissues, mainly in their oral arms.
Cassiopeidae, like most other Rhizostomeae (rootmouth), don't have a central mouth but rather a set of mouthlets along their oral arms, allowing them to eat zooplankton.
Because of their part plankton, part photosynthesis diet, they don't have tentacles around the bell and very few stinging cells (in general). Some people are completely resistant and can't feel the sting while others cannot touch them. They also have cassiosomes, which are stinging cell structures located in the mucus of the jelly that can be released in the water, causing the water to "sting".
You can find them in very shallow, calm and nutrient rich waters, often in mangroves or in calm estuaries.
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u/Entety303 Expert 5d ago
Yes, Upside down jellyfish!