Cnidarians are a phylum of animals with a great diversity of aquatic species, distributed in both freshwater and s altwater ecosystems. One type of cnidarians are jellyfish. True jellyfish are exclusively marine and have a defense and hunting system that consists of inoculating their prey with a stinging substance. In the case of people, depending on the species, this substance can result in mild discomfort or death. In this file on our site we will talk about a jellyfish, the medusa nomura, whose scientific name is Nemopilema nomurai, a very particular cnidarian due to its size and level of toxicity.
Characteristics of the nomura jellyfish
The nomura jellyfish is a cnidarian of large dimensions, in fact it is considered one of the largest jellyfish in existence. In this article you can meet the largest jellyfish in the world. Their size can be larger than an adult, that is, they can measure up to about 2 meters long, with a bell 1.20 meters in diameter. They reach weights of 200 kg and even more. 90% of his body is water, he lacks eyes, brain and respiratory tract. It has epitheliomuscular and striated muscle cells. In addition, as in the case of other cnidarians, it has a hydroskeleton formed by a gelatinous substance called mesoglea. The coloration of this jellyfish is variable, being able to be gray or brown and with light pink or white tentacles.
The nomura jellyfish is characterized by having a complex poison, of a protein and toxic type, which can cause various symptoms in people, such as swelling and pain, but also death in high doses. Some studies[1] have shown that there are variations in the venom of this species from one individual to another, which could explain the differences in the levels of affectation to animals and people.
Nomura jellyfish habitat
The nomura jellyfish is found in China, Japan and Korea According to reports[2]of tracks, distributed in both the southern and northern Yellow Seas, as well as the central China Sea. Massive appearances of young jellyfish of this species have been seen in Liaodong Bay in the summer time, while, at the end of the season, they usually move towards the center and north of the Bohai Strait.
The size and weight of this animal makes it prefer areas far from the coast and at different depths, depending on the phase of the life cycle in which it finds itself. Therefore, it can be in surface waters or on the seabed. However, most likely due to climate change, their populations are increasingly abundant and they are present in coastal areas in large numbers, causing fear of people because of their toxins.
Customs of the jellyfish nomura
Previously, the nomura jellyfish did not have very high population growth and, although it had been identified decades ago, it did not usually move to areas very close to the coast. But this situation has changed markedly over time, an aspect that creates problems both for people and for the jellyfish itself, given that its large size means that it commonly gets trapped in fishing netsused by ships.
The nomura jellyfish establishes certain associations with some fish defined as parasitic because, although these fish do not feed on the jellyfish, they camouflage themselves with his body and steal food from him. In other cases, some fish do feed on the body of the cnidarian, causing damage to the point of causing the jellyfish's umbrella to break, causing it to sink to the bottom of the sea, becoming food for other animals.
Nomura jellyfish feeding
The young specimens of this species of jellyfish feed mainly on the zooplankton that they catch with their tentacles. However, as they grow into large animals, they begin to vary their diet, including fish and crustaceans It is also common for them to consume fish eggs and larvae, which influences the decrease in the population of certain species of their natural predators.
Reproduction of the nomura jellyfish
The reproductive process of these animals is similar to that of others of their kind, as you can read in our article on the reproduction of jellyfish. It is quite complex, since it is made up of sexual and asexual phase In general, it begins with the fertilization of the eggs, which, approximately the next day, are transformed into planulae, the larval forms of these animals. After 4-8 days, these larvae settle on a hard substrate to continue their development.
Once fixed on the substrate, the larval forms pass to the stage known as scyphistoma, in which they will undergo a series of changes until they become young jellyfish, known as ephyras, characterized because of its circular shape and made up of eight lobes. It will take up to 50 days for the jellyfish to reach the final appearance that it will maintain throughout its life.
Conservation status of the nomura jellyfish
Populations of jellyfish nomura, at present, have not been reported under any criteria of danger or decline. On the contrary, the evidence indicates an unusual growth of their populations. This increase, apparently, is related to certain environmental problems, such as climate change, which alters the temperature of the water, so that it offers conditions for the species to reproduce more than it would naturally. On the other hand, the overfishing could be affecting the reduction of its natural predators, which also alters its population balance.
