Many people would name jellyfish as the most soothing creatures in an aquarium. Tokyo Sea Life Park 's "Tokyo Sea" area displays the well-known Moon Jellyfish year-round, but they have also started exhibiting the spotted jellyfish near the center of the same area.

The spotted jellyfish is found in calm, sheltered bays from summer to early autumn. It has eight oral arms (which carry food to the stomach) extending from its hemispherical bell, each with a rod-like appendage at its end. These appendages resemble the legs (arms) of an octopus, and its brownish body color is also characteristic of the "octopus jellyfish."

The reason why the spotted jellyfish is brown is because algae called "zooxanthellae" live inside its body. The spotted jellyfish obtains nutrients from these zooxanthellae through photosynthesis. In addition to nutrients from zooxanthellae, it also eats zooplankton, like other jellyfish. With the energy it obtains in this way, the spotted jellyfish can swim quite actively in the water.

On the other hand, the jellyfish's body provides a safe habitat for the zooxanthellae. Furthermore, they can efficiently obtain the carbon dioxide necessary for photosynthesis. The coexistence of jellyfish and zooxanthellae is mutually beneficial.

Compared to Moon Jellyfish, which drifts gracefully with the current, the spotted jellyfish, which swims actively, may seem a little frantic, but both are popular attractions at aquariums.

[Namiko Tomura, Animal Care and Exhibition Staff, Tokyo Sea Life Park]

(October 1, 2010)