How many species of jellyfish are there? Jellyfish are sometimes called sea jellies. They belong to a group called Medusozoa which is divided into four classes: Hydrozoa, Scyphozoa, Cubozoa and ...

Jellyfish populations fluctuate naturally, and people tend to notice only the boom part of the cycle. Hydrozoans are in a class apart from true jellies. Some species never grow up; they remain ...

The integral jellyfish is a new hydrozoan species found in the northwest Pacific off the coast of Japan. Photo by Sugimoto, Izumi, Collins (2025) Nearly seven years later, Sugimoto, Collins ...

According to the Smithsonian National Museum of Natural History, scientists divide the more than 4,000 species known as jellyfish into four groups: Scyphozoa or "true" jellyfish, Cubozoa or box ...

The teen enlisted the help of one of the world’s top experts when the specimens he collected grew into something he didn’t ...