Trivia: The Aquarium’s Crowd Favorite! A Quiz About Jellyfish

Don't breathe

Jellyfish do not have specific respiratory organs such as lungs or gills; in fact, it’s accurate to say they do not “breathe.” Their cells take in oxygen directly from the water through the body surface and release carbon dioxide, thereby sustaining vital functions.

Over approximately 500 million years ago

Jellyfish are thought to have appeared in the Cambrian period, over 500 million years ago. This was long before the age of the dinosaurs and represents a very early stage in the history of life on Earth. Fossil records have been found indicating that jellyfish have existed since ancient times, and it is believed that their simple structure has enabled them to survive for such a long period.

Jellyfish (kaigetsu/kurage or shuimu)

Jellyfish are written in kanji as “海月 (kurage)” or “水母 (suibo).” This comes from the jellyfish’s moon-like appearance and the image of a mother drifting in the water. Both are used as standard spellings.

gelatinous

A jellyfish’s body is about 95% water, and most of the remaining 5% of solids is made of gelatinous material. This gives jellyfish their soft, jelly-like bodies. Jellyfish swim by expelling water with their gelatinous bodies and moving forward.

95%

A jellyfish’s body has a very simple structure, and most of it is water. In fact, about 95% of a jellyfish’s body is composed of water. Because of this, jellyfish depend so heavily on moisture that when they dry out, they become almost invisible.

Turritopsis dohrnii (immortal jellyfish)

The crimson jellyfish (formally Turritopsis dohrnii, often called the immortal jellyfish) is said to be capable of repeating its lifespan indefinitely. After becoming an adult, it can revert to its juvenile polyp stage when conditions become unfavorable, and then grow into an adult again. This phenomenon is called transdifferentiation, in which cells change from a differentiated state into another type of cell.

It’s moving by a nerve reflex.

Jellyfish can move even without a brain or a heart. This is made possible by their simple nervous system. This system functions as a nerve net spread throughout the body, enabling reflex movements in response to stimuli. When they react to something—such as the flow of water—this nerve net transmits signals, causing the body to contract and producing a swimming-like motion.