View Jellyfish A Natural History US. Curtis cuba, a lifeguard in hawaii, holds up two box jelly fish on waikiki beach. As they move the jellyfish has a natural defense mechanism.
Their tentacles are composed of stinging cells called cnidoblasts to stun and paralyze prey.
Hanging from that bell, you can see the long, thin tentacles of the jelly fish. Most jellyfish undergo two distinct life history stages ( body forms ) during their lifecycle. No heart, no brain, no circulatory system and no bones. Jellyfish have a rounded bell with a mouth on the underside, short tentacles and longer stinging arms.