Nomura's jellyfish

Nomura's jellyfish (Nemopilema nomurai) is one of the largest jellyfish in the ocean, found in the waters of East Asia. It belongs to a group called rhizostome jellyfish and is similar in size to the lion's mane jellyfish, which is the largest known cnidarian in the world. Nomura's jellyfish is the only species in its genus, making it quite unique—it is described as monotypic.

While people sometimes eat Nomura's jellyfish, it is not considered a high-quality food. However, its large size and numbers can cause problems for fishing communities because the jellyfish can damage nets and outcompete fish for resources.

Scientists are studying Nomura's jellyfish to find new ways to use it. One interesting area of research is looking at the jellyfish's venom, which might have useful applications in medicine. This work helps scientists understand the jellyfish better while also finding ways to manage its impact on fisheries.

Description

Nemopilema nomurai can grow up to 2 m (6 ft 7 in) in diameter and weigh up to 200 kg (440 lb), which is about the height of an average human. This jellyfish was named after Mr. Kan'ichi Nomura, Director General of the Fukui Prefectural Fisheries Experimental Station, who sent a specimen to Professor Kishinouye in 1921 for study.

These jellyfish have a translucent whitish body with pinkish or reddish parts and transparent immature gonads. Researchers discovered that certain genes in the jellyfish’s bell help it move, showing that its muscles play an important role in swimming.

Distribution

Nomura's jellyfish are mainly found in the waters between China and Japan, especially in the Yellow Sea and East China Sea. Their numbers seemed to grow more often between 1989 and 2009. Some think this increase might be due to climate change, overfishing, or changes along the coast that help them grow.

Life cycle

The life cycle of Nomura's jellyfish is similar to that of other jellyfish. These jellyfish are usually found in the Yellow Sea, where populations stay year round. In June and July, changes in water salinity cause young jellyfish to move through the Tsushima strait. By late October in some years, like 2005, there have been large groups of these jellyfish. In just six months, Nomura's jellyfish can grow from the size of a grain of rice to more than 6 feet (1.8 meters) wide.

Ecology

Nomura's jellyfish eat zooplankton at all stages of their life, and as they grow larger, they also eat bigger fish. Their predators include swordfish, tuna, sunfish, leatherback turtles, and humans.

Jellyfish blooms, large groups of jellyfish appearing suddenly, have been seen in the Sea of Japan for a long time. But blooms of Nomura's jellyfish became more common in the 20th century. The biggest blooms happened between 2002 and 2003 and caused problems for the fishing industry. In 2009, a large fishing boat capsized while trying to catch these jellyfish in Tokyo Bay, but the crew was saved.

Envenomations

Stings from Nomura's jellyfish can cause itching, swelling, and sharp pain. In serious cases, these stings can be very dangerous and might even lead to severe health issues. Scientists are studying the venom to better understand how it affects people and to find ways to treat those who are stung. They have discovered that some special chemicals might help protect the skin and muscles from the worst effects of the venom.

Uses

Since Nomura's jellyfish have been appearing more often, scientists are looking for ways to use them. This could help save money for fisheries that lose money because of the jellyfish.

People in Japan have made ice cream with Nomura's jellyfish, but it must be cleaned and cooked well to be safe to eat. Scientists are also studying the jellyfish for possible medical uses. Some research shows that a substance from the jellyfish might help stop cells from changing in a way that leads to cancer. Another idea is to use the jellyfish to make fertilizer for plants.