Thursday, March 15, 2018

What's A Jellyfish Without Water?

Without water a jellyfish becomes a BLOB!  The reason?  Jellyfish are 95% water.

What are jellyfish made of?

Jellyfish are very simple creatures.  They have no bones, brain, heart, or blood.  Yet, each jellyfish has a three-layered body.  

  • The outer layer, called epidermis, makes up the 'skin' of the jellyfish and serves as protection.  It contains the cnidocysts or stinging cells.
  • The middle layer, called the mesoglea, is thick, elastic, and jelly-like.  This jelly layer helps with floatation.
  • The inner layer is called the gastrodermis.

In addition to the layers, the jellyfish has a simple nervous system that allows the animal to smell, see light, and feel touch.  With these senses the jellyfish can detect both predator and prey swimming near its tentacles. 

Sea Nettles

Are They Fish?

Contrary to their name, jellyfish are not fish.  Fish have backbones. Jellyfish are invertebrates. They belong to the phylum Cnidaria, which makes them related to coral and sea anemones. For this reason, scientists call them jellies or sea jellies.

How Do They Sting?

Surrounding the bell are the tentacles.  Each tentacle contains many cnidocysts: harpon-like stinging cells used to insert a numbing toxin into prey before consumption.  

Jellyfish sting humans, too, if they get too close.  Even dead jellyfish washed up on shore can sting.  Some jellyfish stings have little effect on humans, others can be very uncomfortable.   

Moon Jellies

How Do They Move?

Most of the time jellyfish drift along in the water.  However, they can propel themselves short distances by using a muscle that expands and contracts their bell.

How Long Do They Live?

Jellyfish have been on earth since before the dinosaurs.  Some live only a few months.  Others live longer than 30 years.

Interesting Facts About Jellyfish     

  • A group of jellyfish can be called a 'swarm', a 'bloom', or a 'smack'.
  • Some jellyfish squirt water from their mouth to propel them through the water.
  • Moon jellies flew on the space shuttle Columbia in 1991 as part of a study on weightlessness.
  • Some jellyfish give off light, which is called 'bioluminescence'.
  • The largest jellyfish can weigh up to 500 pounds.

Jellyfish are amazing!

Research Sources:

1.  "What are Jellyfish Made Of?"  Web.  11 Mar. 2018.  National Oceanic Atmospheric Administration.  <>.

2.  "Are Jellyfish Made Of Jelly?"  Web.  12 Mar. 2018. Wonderopolis: National Center For Families Learning. < >.

3.  "Jellyfish."  Web.  14 Mar. 2018.  NOAA Ocean Explorer.  <>.

Photo Credits:

2.  Jellyfish by Pexels is licensed under CO Creative Commons.

3.  Moon Jellies by PublicDomainPictures is licensed under CO Creative Commons. 

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