Such fantastic sunshine has meant we’ve all been in enjoying the beach and the waves.
Of course, the sight of a jellyfish in the water sends them all screaming and running.
“Don’t be so silly, not all jelly fish sting, it’ll be fine!” I hear myself say.
Later, its only when I find myself swimming headlong into a rather curious looking blue, dinner plate size one only inches from my nose that it did occur to me maybe now was the time to check my facts!
So, here it is kids. Facts discussed with sources at Sherkin Island Marine Station and researchers at University College Cork for Jellyfish.ie. Other sources include Smithsonian.com, Howstuffworks.com, and Wikipedia. I’ve also put together a board game to learn the anatomy of a jellyfish. Read on.
This is what I’ve found out.
- Jellyfish are scientifically referred to as ‘Cnidaria’ a group of animal species exclusive to marine environments that all posses cnidocytes which are the specialized cells for capturing prey on the tentacles.
YES, all jellyfish do sting!
- It transpires that yes all jellyfish do sting (boy, did I eat my words!). Its just that some stings are mild and not felt whereas others are quite serious. Also, every person can react differently to them so, its not an easy call to make. General guide: be wary but still no need to scream and shriek.
- They really are fascinating creatures if we can call them that as they don’t have bones ,brains or a heart. Although they do have eyes, which strikes me as funny as they don’t have brains, they sense light which triggers a reaction in their nervous system.
- Box jellyfish (so called because of its cube shaped medusa) have 24 eyes, four of which look up to see mangrove swamp above which is ideal feeding ground for them.
- Jellyfish are carnivores, larger jellyfish eat small aquatic animals or other jellyfish. Smaller ones eat plankton, crustaceans and similar.
- Jelly fish don’t have a very advanced digestive system and so lack certain organs meaning any waste from the body comes out through the same passage it went in. Yes, you heard that right, just wait until you tell your kids that, the poop comes out the mouth! ugh!
- They do not seek out humans to sting, their sting is both a predatory method and a defense mechanism. Each tentacle has thousands of cells on them which house the stinging threads, when a receptor is activated by contact with prey, the stinging charge is released which shoots out of the cell into the prey so paralyzing it.
See the board game as part of this post for more details of the anatomy.
Life cycle of the jellyfish
The adult medusa is the stage that we most recognize as a jellyfish and what we see in the water but this is only part of the life cycle that takes place. These adult medusa reproduce sexually forming larvae which grow into polyp phase. This in turn grows into a colony of polyps which reproduce asexually producing the medusa bud, which grows into an ephra and then an adult medusa completing the cycle.
A swarm is a group of jelly fish in one area as result of winds or currents where as a bloom is a group of jellyfish as a result of a mass of reproduction.
Some jellyfish are seen as culinary delicacies in parts of Asia, other predators of jellyfish include sea turtles or sun fish. Jellyfish are nearly all water, apparently evidence has been found that they were around long before the dinosaurs.
Unlike other sources, the researchers at the coastal and marine development centre UCC for jellyfish.ie recommend the best practice in the event of a sting is to rinse with salt water, this will wash off any remaining stinging cells that haven’t activated. Its important to remember that different jellyfish need different treatment. A Lion’s mane jellyfish or Portuguese man’o’war jellyfish sting will be made worse by vinegar. Although on Box jellyfish stings vinegar is effective and could save your life. Having said that, Box jellyfish are not usually found in european waters, but there have been sightings of Portuguese man‘o’war in waters around UK and Ireland.
As it turns out, what I swam into was a Blue jellyfish (Cyanea Lamarckii) as I identified it from the Jellyfish.ie ID card which is well worth a look. Its on their downloads page.
Turns out I didn’t find out how bad the sting was, but I’ll let you know if I do.
So, just for a bit of fun and to learn the anatomy of a cnidaria, here’s a jellyfish game, ‘ The Jellyfish Jiggle’ you’ll need a dice and to print of the two A4 game sheets, one is the jellyfish body game board and the other the instructions and player markers.
Let me know how you get on.
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