The lion's mane jellyfish can be up to 8 feet wide. In spite of its large size, it has no structures for bulk flow to deliver oxygen to its cells. How can it be so large and yet lack a mechanism for bulk flow?

The lion's mane jellyfish's skin is so thin that the body receives oxygen through difussion.

Explanation:

The lion's mane jellyfish - giant jellyfish - is the largest species of jellyfish.

This species does not possess a 'usual' respiratory system that would enable to deliver oxygen to its cells. Instead, the lion's mane jellyfish's skin is so thin that the body receives oxygen through difussion.

Thanks to diffusion (oxygen molecules moving from an area of high concentration to an area of low concentration), oxygen that is already dissolved in the ocean then is converted into an equal amount of oxygen inside the jellyfish.

that is wrong, its not thymus.

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