Méduses

Méduses, commonly known as jellyfish, are free-swimming marine animals that belong to the phylum Cnidaria. They are characterized by their bell-shaped bodies, which are composed of a gelatinous substance called mesoglea. Trailing from the bell are tentacles, armed with stinging cells called cnidocytes. These cells contain nematocysts, which are used to capture prey and for defense.

Jellyfish are found in all oceans, from the surface to the deep sea. They vary greatly in size, from less than an inch to several feet across. Their diet typically consists of plankton, small fish, and crustaceans, which they immobilize with their stinging tentacles. Reproduction in jellyfish can be sexual or asexual, often involving a complex life cycle with both polyp and medusa stages.

While most jellyfish stings are harmless to humans, causing only minor irritation, some species possess venom that can be dangerous, even fatal. These include the box jellyfish and the Portuguese man o' war. Jellyfish play an important role in marine ecosystems, serving as both predators and prey for other marine animals. Their populations can fluctuate significantly, sometimes leading to massive blooms that can impact coastal communities and fisheries.