Jellyfish are gelatinous, marine animals belonging to the phylum Cnidaria. They are known for their distinctive bell-shaped bodies and long, trailing tentacles. There are thousands of species of jellyfish, and they can be found in oceans around the world, from surface waters to the deep sea.

Here are some key characteristics and features of jellyfish:

1. Body Structure:
   • Bell (Medusa): The main body of a jellyfish is called the bell or medusa. It is typically gelatinous and has a dome-like shape, often resembling an umbrella.
   • Tentacles: Hanging from the bell are long, stinging tentacles. These tentacles contain specialized cells called cnidocytes that release venom to capture prey and deter predators.
2. Life Cycle:
   • Jellyfish have a complex life cycle that includes both a medusa stage (the familiar jellyfish form) and a polyp stage. The polyp is usually attached to a substrate, such as a rock or the ocean floor.
3. Movement:
   • Jellyfish move by contracting and relaxing their bell, which propels them through the water. Their movement is often slow and rhythmic.
4. Diet:
   • Jellyfish are carnivorous and primarily feed on plankton, small fish, and other microscopic organisms. Their tentacles are equipped with stinging cells to capture prey.
5. Habitats:
   • Jellyfish are found in various marine environments, from coastal waters to deep-sea trenches. Different species have adapted to different temperature ranges and salinity levels.
6. Bioluminescence:
   • Some species of jellyfish are bioluminescent, meaning they can produce light. This ability is often used for communication, attracting prey, or deterring predators.
7. Stinging Cells:
   • The stinging cells (cnidocytes) on their tentacles are used for defense and prey capture. When a jellyfish’s tentacle comes into contact with a potential threat or prey, the stinging cells release venom.
8. Human Interaction:
   • Certain jellyfish species can deliver painful stings to humans. Contact with their tentacles can result in skin irritation, and in some cases, more severe allergic reactions. However, not all jellyfish are harmful to humans.

Jellyfish play a significant role in marine ecosystems, contributing to the food web and influencing the populations of other marine organisms. While they can be fascinating to observe, it’s important to be cautious around them due to the potential for stinging.