ObservanceWednesday, November 3, 2027
World Jellyfish Day
- Date
- Recurs
- Every year on November 3
- Category
- Nature
World Jellyfish Day falls on November 3 and is marked by aquariums, marine labs, and at least one federal science program: NOAA's ocean exploration office publishes a run of deep-sea jellyfish footage for it. Who started the day, and why they chose November 3, is not recorded anywhere reputable — a shame, because the animal at its center has one of the longest records on earth.
History
The origin of this observance is not well documented. Nothing reputable records who established World Jellyfish Day, when, or why November 3 was chosen; the date circulates on holiday calendars without a traceable citation behind it. What can be sourced is that the day is observed inside the US government: NOAA's Office of Ocean Exploration and Research marks November 3 by collecting what it calls its jellyfish greatest hits from deep-ocean expeditions in the Pacific.
The animals are far older than the observance, and older than almost anything they share the water with. Smithsonian Ocean dates jellyfish and comb jellies — two separate phyla, Cnidaria and Ctenophora, and not close relatives despite the shared look — to at least 500 million years in the ocean, and possibly as far back as 700 million, roughly three times as old as the first dinosaurs.
They manage it with very little equipment. Both groups are about 95 percent water, their bulk a thick, elastic middle layer called mesoglea between an outer epidermis and an inner gastrodermis. NOAA notes they have no bones and no brain — only a nerve net, with no central nervous system — and that despite the name they are not fish but invertebrates, in the same phylum as sea anemones and corals. They sting with their tentacles to catch plankton, a mechanism Smithsonian Ocean describes as venom-bearing harpoons inside specialized cells that fire in about 700 nanoseconds.
Blooms are the part that reaches the news — a mass of jellyfish can also be called a swarm or a smack — closing beaches, clogging power plant intakes, and fouling fishing gear. Smithsonian Ocean says it "seems likely that their spread is human-caused," while noting that some scientists argue blooms are part of a natural cycle, and lists overfishing, fertilizer runoff, warming water, and the hard surfaces of docks and platforms where polyps can settle among the likely causes.
Timeline
- At least 500 million years ago — the oldest ancestors of modern jellies are already in the ocean; Smithsonian Ocean puts the upper estimate as far back as 700 million years.
- 505 million years ago — the age of the jellyfish fossils found in Utah and reported in 2007.
- 1980s — the sea walnut, Mnemiopsis leidyi, reaches the Black Sea in ship ballast water, one of the most-studied cases of a jelly moved by human traffic.
- April 24, 2016 — NOAA's Deepwater Exploration of the Marianas films a jelly at about 3,700 meters at a site informally called Enigma Seamount.
- May 6, 2017 — on the Mountains in the Deep expedition, NOAA records jellies on midwater transects from 1,400 to 300 meters in the Pacific Remote Islands Marine National Monument.
- August 2018 — NOAA publishes its myth-busting article on jellyfish, finding urine ineffective on stings and recommending vinegar instead.
How to observe
Learn the sting protocol before you need it. NOAA's guidance is to look for any tentacle still stuck to the skin, flush the area with cold ocean water, and not rub it, since rubbing can push the venom further in; if pain continues, apply vinegar or an evidence-based commercial product. Urine, NOAA says flatly, has been tested and proven unhelpful.
Then watch the footage NOAA publishes for the day. Two dives are worth finding: the jelly filmed on April 24, 2016 at about 3,700 meters at a site informally called Enigma Seamount, and the midwater transects of May 6, 2017, which ran from 1,400 meters up to 300 meters in the Jarvis Unit of the Pacific Remote Islands Marine National Monument — one of the few parts of that monument where the water column is protected and not just the seafloor.
And if you are near a coast, ask the local aquarium or marine lab what turns up in your water and when; jellyfish seasons are regional.
Frequently asked questions
Are jellyfish fish?
No. NOAA notes that despite the word "fish" in the name they are invertebrates, with no bones and no brain, in the phylum Cnidaria alongside sea anemones, sea whips, and corals.
Does urine help a jellyfish sting?
No. NOAA says the use of urine on stings has been tested and proven unhelpful, and recommends flushing with cold ocean water, not rubbing the area, and applying vinegar or an evidence-based commercial product if pain continues.
How long have jellyfish existed?
At least 500 million years, and possibly as long as 700 million, according to Smithsonian Ocean — roughly three times as long as the first dinosaurs. Jellyfish fossils found in Utah and reported in 2007 are 505 million years old.
How many kinds of jellyfish are there?
It depends where you draw the line, which is why published counts differ. Smithsonian Ocean gives about 200 species in Scyphozoa, the true jellyfish, within fewer than 4,000 Medusozoa and more than 10,000 Cnidaria overall; a 2018 NOAA article states the same narrow figure as more than 200 documented species.
Who started World Jellyfish Day?
No one traceable. The origin of this observance is not well documented, though NOAA's Office of Ocean Exploration and Research marks the date with a collection of deep-sea jellyfish footage.
When is World Jellyfish Day?
| Year | Date | Day |
|---|---|---|
| 2027 | November 3 | Wednesday |
| 2028 | November 3 | Friday |
| 2029 | November 3 | Saturday |
| 2030 | November 3 | Sunday |
| 2031 | November 3 | Monday |
Sources
- NOAA Office of Ocean Exploration and Research, November 3: World Jellyfish Day — https://oceanexplorer.noaa.gov/facts/worldjellyfishday.html → that NOAA marks the day on November 3 with jellyfish footage from Pacific deep-ocean expeditions; bloom, swarm and smack as collective nouns; that jellyfish are not fish but invertebrates, lacking bones and a brain and having a nerve net rather than a central nervous system; that they sting prey with their tentacles and eat plankton; predators including tunas, sharks, turtles and humans; the jelly filmed at about 3,700 meters at Enigma Seamount on April 24, 2016; the May 6, 2017 midwater transects from 1,400 to 300 meters in the Jarvis Unit of the Pacific Remote Islands Marine National Monument and the note that its water column is protected.
- Smithsonian Ocean, Jellyfish and Comb Jellies — https://ocean.si.edu/ocean-life/invertebrates/jellyfish-and-comb-jellies → jellyfish and comb jellies as separate phyla, Cnidaria and Ctenophora; at least 500 million and possibly 700 million years in the ocean, three times as old as the first dinosaurs; the 505-million-year-old Utah fossils reported in 2007; 95 percent water and the mesoglea; species counts of more than 10,000 Cnidaria, fewer than 4,000 Medusozoa and about 200 Scyphozoa; nematocysts as venom-bearing harpoons firing in about 700 nanoseconds; blooms, the assessment that their spread seems likely to be human-caused and the natural-cycle counterargument; overfishing, nutrient runoff, warming water and submarine structures as likely causes; Mnemiopsis leidyi reaching the Black Sea in ballast water in the 1980s.
- NOAA Ocean Service, What are jellyfish made of? — https://oceanservice.noaa.gov/facts/jellyfish.html → about 95 percent water; the epidermis, mesoglea and gastrodermis layers; the nerve net; membership of the phylum Cnidaria with sea anemones, sea whips and corals; that most stings in humans cause only minor discomfort.
- NOAA, Fact vs. fiction: 3 things you thought you knew about jellyfish, August 30, 2018 — https://www.noaa.gov/stories/fact-vs-fiction-3-things-you-thought-you-knew-about-jellyfish → "more than 200 documented species of true jellyfish (and many more of their stinging relatives)"; that contact with jellyfish is incidental rather than deliberate; that urine has been tested and proven unhelpful and that vinegar or an evidence-based commercial product is better; the flush-with-cold-ocean-water and do-not-rub steps; NOAA's jellyfish forecasting work using the Chesapeake Bay as a test area.
- Not sourced, and therefore not claimed on this page: any founder, sponsoring body or first observance of World Jellyfish Day, and any reason for its placement on November 3.
- Rejected as sources: nationaltoday, nationaldaycalendar, checkiday, timeanddate and other daily-holiday aggregators.
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