These pictures I took are of the Spotted Jellyfish from the Monterey Bay Aquarium. Aren't they amazing!? At the aquarium there is an entire room full of various Jelly Fish. Tomorrow I'll show you the Egg Yolk Jelly. Can you guess what it looks like? Jellyfish are zooplankton.
Jellyfish do not have brains. They are cnidarians, pronounced nih dhar' ee uhnz. Their name comes from the Greek word, "knide", which means nettle. The spotted jelly in my pictures are Phyllorihiza punctata and are commonly found around Australia in the summertime. Most people know that Jellyfish sting anything that comes in contact with their tentacles. Their stings can be deadly. The process for stinging is similar to a bee sting. The bee inserts the stinger which then leaves the bee's body, while the Jellyfish inserts a hollow thread that is attached to a cell within their body called a nematocyst. The thread is attached to a little arrow like sharp point which breaks the skin, then the thread delivers the poison to the victim. The threads are attached to the tentacles which then bring the now paralyzed victim to the mouth of the jelly for consuming. Humans are too big for a jellyfish to digest, so if stung by a jelly, you will not be eaten by one! However, the jelly's sting is full of poison and will cause swelling and irritation. Some people are allergic to this poison and may suffer more than others; still others have died from jellyfish stings. So, stay away from jellyfish!
While it is true that jellys do not have brains, they are far from simple. In reading just a few pages from my kids' science books, I am truly amazed! Once they use up their nematocysts, more grow in their place. Once a bee stings you, it dies. If a jellyfish stings you, it just regenerates the nematocysts. Their lifecycle is complicated. The way they reproduce is astounding. They are not able to process visual information, but they DO have eyes which can detect light from dark! This is very important for their survival because it allows them to tell up from down. Survival is toward the light, or the surface. They rise to the surface at night to avoid predators like the leatherback turtle. In the day they sink toward the bottom of the ocean. Some jellyfish can grow to be 400 pounds! Jellyfish eat fish. A group of jellyfish is called a smack.
I'll post the Egg Yolk Jelly tomorrow along with an orange jelly. My information on jellyfish comes from "Exploring Creation with Zoology 2" from Apologia Science.