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Environmental Outlook: Jellyfish And The Health Of The Ocean

Jellyfish are over 560 million years old. They have no brains and no spines, yet these gelatinous animals are among the worlds’ most successful organisms. While other creatures evolved to develop tails and feet, jellyfish continued to thrive staying just the same. But lately scientists are concerned the animals are thriving too well -- overrunning beaches, forcing nuclear power plants to shut down and disrupting the ecosystem. And experts say it is human-caused changes to the environment that’s behind the rise in jellyfish. For our June Environmental Outlook, Diane and her guests discuss jellyfish and the health of the ocean.

Jellyfish At The National Aquarium

All images copyright National Aquarium ©.

Little-Known Facts About Jellyfish

Courtesy of the National Aquarium

Leidy’s Comb Jellyfish

  • The comb jelly looks different from other jellies because it’s not made up of a bell and tentacles. Instead, it is a translucent walnut-shaped body with wart-like bumps. For this reason, it’s sometimes called a sea walnut.

  • Comb jellies are translucent but refract light, appearing to have rainbow colors running down their bodies on the track of internal moving cilia. They can also make their own light (bioluminescence), flashing when disturbed.

Spotted Lagoon Jellyfish

  • These spotted jellies have rounded bells and strange clumps of oral arms with club-like appendages that hang down below.

  • Instead of a single mouth, they have many small mouth openings on their oral arms.

Purple-Striped Jellyfish

  • This jelly has a white bowl-shaped bell with 16 purple stripes, and very long tentacles.

  • Young crabs are often found hitching a ride in this jelly's bell. This is a symbiotic relationship—by eating parasitic amphipods that damage the jelly, the crabs get a free meal, and the jelly gets a free cleaning.

Pacific Sea Nettle Jellyfish

  • The Pacific sea nettle’s bell is yellow to reddish-brown, and the long, ruffled tentacles can be yellow to dark maroon.

Northern Sea Nettle Jellyfish

  • This jelly's bell can be white to dark purple/red, with dark lines radiating from the top of the bell. The species derives its name from the Greek words melas and aster, which translates to "black star" in reference to the pattern on its bell.

Moon Jellyfish

  • Translucent white, saucer-shaped bell, with a blue-gray transparent disk at its center through which the horseshoe-shaped gonads are visible. Short, delicate, fringe-like tentacles hang from the bell margins.

  • When deprived of food, they can shrink to 1/10th of their original size to save energy. They redevelop to normal size when food is available.

Blue Blubber Jellyfish

  • This venomous jelly can be safely eaten once it's been correctly dried and processed. Dried jellies are popular in many Asian countries, especially Japan, where they're considered a culinary delicacy. The texture is reportedly crispy, yet elastic—hence the name "rubber band salad" for a dish sold in China. The Chinese believe eating jellies will reduce high blood pressure.

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