Fresh water jellyfish of Komae

The freshwater jellyfish found in the Tama River of Komae are microscopic creatures with translucent bodies and delicate tentacles. These organisms drift through the water and form visible colonies that can be observed during certain times of year.

These jellyfish originated in China and spread across the globe through connected waterways over many decades. Scientists identified them in the Tama River and recognized their significance to Japan's freshwater environment.

These tiny creatures have become part of how locals understand their river ecosystem, representing the hidden life beneath the water's surface. The designation reflects how communities value even the smallest organisms in their natural surroundings.

The best time to observe these creatures is late summer when water conditions are warmest and they are most active. Since their appearance is unpredictable and depends on water temperature and other environmental factors, flexibility in timing improves your chances of seeing them.

These creatures reproduce in two strikingly different ways simultaneously: they can breed sexually like typical animals and also clone themselves without any partner involvement. When winter arrives, they transform into dormant capsules that hide in river sediments waiting for warmer water to awaken.