Jellyfish

Transparent Inhabitants of the Oceans with Millions of Years of History

Jellyfish (phylum Cnidaria) are among the oldest animals on the planet, having inhabited the oceans for over 500 million years. They have no brain, heart, or bones, yet they have perfectly adapted to life in the sea. Their bodies are composed of 90–95% water, and they move with rhythmic pulsations of their bell, while their tentacles, equipped with stinging cells, serve both for defense and hunting.

Jellyfish live from surface waters to the deep ocean, and their size ranges from tiny millimeter-sized species to the giant lion’s mane jellyfish, whose tentacles can reach over 30 meters. Although they appear fragile, they are an important part of the ecosystem – serving as food for fish, turtles, and birds, and helping regulate plankton populations.

BASIC INFORMATION

Size:
from a few millimeters up to more than 2 meters in diameter
Tentacles:
up to 30–40 meters
Body:
90–95% water, without bones or a brain
Life cycle:
alternation between polyp and medusa stages
Habitat:
oceans worldwide, from the surface to the deep sea

INTERESTING FACTS

Powerless Travelers:
they are carried by ocean currents.
Stinging Cells:
can paralyze fish and sting humans.
Bioluminescence:
some species are bioluminescent.
The “Immortal” Jellyfish:
Turritopsis dohrnii can revert to a younger life stage.
Ecological Impact:
overpopulation of jellyfish can affect fishing and tourism.