Weird But True: Jellyfish Facts

Ever wondered how Jellyfish reproduce? Or how many anuses a sea wasp has? Well, probably not, but you can find out here anyway.


  • The Box jellyfish has 64 anuses.
  • The Box jellyfish also has 24 eyes, but despite this, it can only see in a blurry fashion.
  • Jellyfish do not have a brain, respiratory system, circulatory system, or indeed an excretory system. Because of this, the jellyfish’s ‘mouth’ is also used for waste expulsion.


  • Jellyfish NEVER stop growing.
  • Jellyfish are 95% water, and some types, nearly 98%.
  • Jellyfish are not actually classified as ‘fish’, some people prefer to refer to them as ‘sea jellies’. They do not have gills (or lungs)
  • To “swim”, jellyfish shoot jets of water that propel them forwards. However, most jellyfishes movements are limited to up and down, they are carried along by the tide.
  • Jellyfish are actually older than dinosaurs (well, as a species, not individually)
  • To breathe, Jellyfish absorb oxygen through their membrane-like skin.
  • Jellyfish are EVIL (not strictly true, but they look it)


  • Though jellyfish are most commonly as large as a big plate, one type of jellyfish in the Arctic sea can be up to 7 ft in diameter, and the tentacles can also be up to 120 feet long!
  • The biggest jellyfish can be up to 2 and a half meters wide, and it’s tentacles can be half as long as a standard football pitch.
  • One of the biggest jellyfish is called the lion’s mane.


Yup, it’s what you sick people out there have been wanting… probably…

  • During different parts of its life, the jelly fish is able to reproduce sexually AND asexually:
  • Jellyfish can be either Male, or Female, and each sex develops their sperm or eggs in a special pouch on the inside of the jellyfish.
  • They then (technically) throw up the sperm/eggs, as it passes through the stomach, and then the mouth.
  • Some of the eggs stick to the mouth of the female jellyfish, and these are the ones that are fertilized.
  • The embryo develops into, not a baby jellyfish, but a planula, and from there it begins a long journey, being carried by ocean currents. It eventually evolves into a polyp, which can then create more polyp via a process called budding. Eventually, grooves appear on the polyp, and it breaks open, revealing lots of disc-like saucers, which are in fact, baby jellyfish. So one egg fertilized makes a lot more than one baby jellyfish!


  • There is a type of jellyfish that lies upside-down on the seabed near coastlines (probably just waiting for a wader or some toddler to come and step on them…) that is plant-like in the way that it collects energy from the sun’s light.
  • The Box Jellyfish, also named the ‘SEA WASP’ is the most poisonous jellyfish, and it’s sting can kill in 3 minutes… and it can move at almost 2 meters per second. If stung, the odds of getting back to the shore, or even SURVIVING are almost 0.
  • Jellyfish kill more people than sharks (and for that matter, being hit on the head with a falling coconut)
  • The jellyfish population can be decreased by particularly rainy season, because they prefer salt water.
  • The amount of venom in a Box Jellyfish could kill 60 people.
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69 Responses to “Weird But True: Jellyfish Facts”
  1. Charlie Says...

    On September 1, 2007 at 4:57 pm

    A bit sad, bt interesting all the same. ok, i guess

  2. ecrivan Says...

    On September 1, 2007 at 10:21 pm

    Some good information but are you not repeating yourself when referring to the largest jellyfish? The life cycle you referred to: the polyp anchoring itself and then multiple grooved discs developing at the head of the polyp which eventually detach, turn right side up and form the cap or Medusa form is intriguing.How about the Portuguese Man of War, how does that rate?

  3. Emily Says...

    On January 19, 2008 at 11:54 am


  4. krissy Says...

    On October 1, 2008 at 6:07 pm

    very interesting
    it really helped me with my project and research

  5. Sami Says...

    On October 19, 2008 at 3:17 pm

    Thanks I really needed that for facts about jellyfish for school!

  6. Mopi Says...

    On October 20, 2008 at 1:51 pm

    That really helped me a lot!

  7. georgy Says...

    On November 4, 2008 at 8:41 pm

    Thank you i needed those facts for school and those facts are cool

  8. nate Says...

    On November 11, 2008 at 9:24 pm


  9. 1234 Says...

    On December 28, 2008 at 3:09 pm


  10. hello Says...

    On December 30, 2008 at 11:36 pm


  11. lol Says...

    On January 8, 2009 at 7:32 am

    i never go in to the sea because of jellyfish lol

  12. tina Says...

    On January 12, 2009 at 4:25 pm

    that suck you don’t have brain oyu idiot

  13. courtney Says...

    On January 23, 2009 at 6:52 am

    That waz awesome! U should type more!

  14. Amanda Says...

    On January 28, 2009 at 11:18 pm

    thx!…I didnt really NEED them for school, but im doing it for extra marks….So that i dont fail…no duh. well nice job n thx!

  15. salim Says...

    On February 4, 2009 at 6:45 pm

    danm i never thought to here that

  16. Lisney Says...

    On February 26, 2009 at 7:09 pm

    Thanks for the info!!
    It really help 4 my school work

  17. loza Says...

    On February 27, 2009 at 10:00 am

    i copyd this for homework

  18. brooke Says...

    On March 9, 2009 at 11:03 am

    i have done my research on this website its GREAT !!!!!!!!!!

  19. me Says...

    On March 11, 2009 at 4:51 pm

    yo iloved this thanks for the help with my science project thanks:>

  20. clara fitzpatrick Says...

    On March 13, 2009 at 6:16 pm

    very interesting i would like if ye named what they eat though

  21. elizabeth Says...

    On March 16, 2009 at 11:44 am

    nice i used this for my research

  22. Rinne Says...

    On March 17, 2009 at 3:06 pm

    Thanks for the cool info it really helped me with my research. It also told me some interesting things that i never knew about. So again thank you very much!

  23. :) Says...

    On March 24, 2009 at 4:16 am

    great info and i liked how you kept this interesting the entire way though. thanks!

  24. Brittney Says...

    On April 2, 2009 at 3:34 pm

    thanks i needed those facts for a school project!

  25. Mya Alexzandria Says...

    On April 2, 2009 at 4:44 pm

    thz who eva made this!!! it helped me with this science project im doing *

  26. cagedstowgee Says...

    On April 7, 2009 at 10:47 am

    thanx for the info;)

  27. yarely Says...

    On April 9, 2009 at 8:04 pm

    I believe the jellyfish is the most incredible creature in the planet!! Just amazing.

  28. Lilly Says...

    On April 21, 2009 at 6:44 pm

    thnx i need those facts for school too my and my reader’s workshop partner addy kao are doing a project together!

  29. me Says...

    On April 28, 2009 at 12:26 pm

    finally some help

  30. heather Says...

    On April 30, 2009 at 11:03 am

    this really helped me on my biology project :)

  31. Leena Says...

    On May 2, 2009 at 6:35 pm

    cool facts that acuattly helped me…gr8 job!!!! =)

  32. puta Says...

    On May 9, 2009 at 1:27 pm

    fabien is gay

  33. joyce Says...

    On May 22, 2009 at 8:25 pm

    my jellyfish are cool!!!

  34. jade Says...

    On May 25, 2009 at 1:15 pm

    I like it and some is decusstun

  35. Rachel Says...

    On June 1, 2009 at 11:43 am

    Very gd it helped me with my homework a lot thx.

  36. the cookie monster... Says...

    On June 2, 2009 at 5:15 pm

    thx! i finally have help with my science project. so much better than that complicated stuff that scientists say which i can barely understand. thx!

  37. bob the builder Says...

    On June 4, 2009 at 7:56 pm

    how did u find the time to do that? I’m concerned for your mental state and whether you even have a life…

  38. Juliet Pickering Says...

    On July 7, 2009 at 5:47 am

    Great info! It took me a while to find such great facts – Thankyou!
    Hopefully some more facts from you soon.

  39. Orangina Redlit Says...

    On July 7, 2009 at 5:50 am

    So glad I found such a great Website for my research – thank you!

  40. Shianne Says...

    On September 12, 2009 at 4:06 am

    its awsome on this website u should write more its a very good website and i copied it downn for my homework. hahah i cheated hahah lol. what is your name? do u have any kids? thank u very much i have got loads of information about jellyfish in my book thanks. THANK YOU THANK YOU THANK YOU.

  41. roseanne Says...

    On September 17, 2009 at 5:16 am

    wow thats really cool it helped me on my research

  42. ROCK , ROLL HOTTY Says...

    On September 24, 2009 at 5:58 pm


  43. Hannah Montana Says...

    On September 24, 2009 at 6:04 pm

    Hey ya’ll . This is Hannah Montana speaking. My favorite type of sea animal is a jellyfish . well gotta go , daddy wants me to help write a song.

  44. YASMINA Says...

    On November 9, 2009 at 7:34 pm

    these facts are helpful because im doing a grade6 science project on jellyfish but u should add more facts on what they eat!but either than that THIS WEB SITE ROCKS!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!


  45. jose Says...

    On December 14, 2009 at 12:11 pm

    thanks helped my 6 grade report

  46. tori Says...

    On January 25, 2010 at 12:31 pm

    liar jelly fish rok

  47. Hailey Says...

    On March 2, 2010 at 10:32 am

    Thanks my teacher was proud!

  48. doglover Says...

    On March 4, 2010 at 1:53 pm

    thats really cool

  49. i likecoffee,i liketea,i liketheboys andtheboyslikeme Says...

    On March 4, 2010 at 4:44 pm

    do you use vodka or pee on jellyfish stings??

  50. minnie mouse Says...

    On March 13, 2010 at 4:04 pm

    gots lots of info thx!

  51. cookie cookie cookie starts with K just kidding Says...

    On April 6, 2010 at 9:03 pm


  52. cookie cookie cookie starts with K just kidding Says...

    On April 6, 2010 at 9:07 pm

    i need more info now!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! what do they eat my teachers name is mrs P.E . MRS P.E if you see this hi!!!!!!!!!!!!!!!!!!!!


  53. cookie cookie cookie starts with K Says...

    On April 6, 2010 at 9:08 pm

    i need more info now!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! what do they eat my teachers name is mrs P.E . MRS P.E if you see this hi!!!!!!!!!!!!!!!!!!!!


  54. derek ray Says...

    On April 14, 2010 at 11:18 am

    this has not helped me one bit so u dont need to write nothing else on this site

  55. Liberty Michelle:D Says...

    On April 14, 2010 at 9:55 pm

    omg i didnt know this stuff verey helpfull for my report thank you:D

  56. Timothy, Gavin, and jaime Says...

    On May 5, 2010 at 4:47 am

    I didnt need these facts for anythng other than to show the kids, but we all enjoyed it. lol after I read this to them they wanted to see a video on Jellyfish. well thx a lot. keep it goin.

  57. bob Says...

    On May 5, 2010 at 10:08 am

    these facts didnt help at all

  58. Amber Says...

    On May 11, 2010 at 7:37 pm

    Thanks this really helped on my school report. :-)

  59. JELLYFISH FAN Says...

    On June 29, 2010 at 2:58 pm

    thanksx i LOVE JELLYFISH! Cos they rock

  60. EZ Says...

    On October 3, 2010 at 4:49 pm


  61. Garushi Ganegoda Says...

    On October 12, 2010 at 9:43 am

    Thank u so much for assisting me to get amazing facts about
    jelly fish to do my shcool project about marvalous animals in earth…. i love jelly fish!!!!!!!!!!!!!!!!!! so amazing and interesting,
    cool….. do more and more like these , so it will help our school projects…………

  62. leah devries Says...

    On October 19, 2010 at 8:52 pm

    thank you so much for that awesome information! it is helping me so much with my project in gr.6 by the way if you want to here something funny about jellyfish go to youtube and watch julian smith jellyfish song. i’m showing it for my project i know everyone will lol and i know you will 2. i guarentee it

    your wicked :)

    -little lovely LOUD leah LA! LA! LA!

  63. lary Says...

    On February 14, 2011 at 8:13 pm

    hope these are all true, im using them for my speech

  64. hotgirl Says...

    On June 3, 2011 at 4:35 pm

    thx i need lot of fact about jellyfish:);):):)

  65. BOB Says...

    On September 25, 2011 at 6:36 pm

    needs to have bibliography

  66. Billy Bob Joe Says...

    On January 19, 2012 at 10:46 pm

    nice i love jellyfish! i saw a video of a jellyfish getting eaten it was funny!!!

  67. page Says...

    On March 7, 2012 at 11:16 pm

    Awesome thx

  68. jellyfish 808 Says...

    On March 22, 2012 at 12:41 am

    i love jellyfish i went with my class to the ocean and i saw those weird upside down jellies and they were in a tide pool and the whole tide pool was covered with them and i actually got stung by by one of those it was pain full and sucked so much but i love jellyfish and iv been studying them for years there like aliens of the sea

  69. Alex Says...

    On April 7, 2012 at 3:57 pm

    For the last time, Portuguese Man of Wars are NOT jellyfish! They are not even just one animal!

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