Jellyfish live in the seas, oceans and freshwater lakes. Among these animals, there are dangerous individuals who sting with the help of nematodes. We present interesting facts about jellyfish.
The species composition includes about 3000 names, but new species are still found.
These invertebrates are some of the simplest living organisms. They have no brain, respiratory, circulatory and excretory systems. But they are able to perceive smells and light.
The bodies of jellyfish are transparent, covered with three layers of epidermis and 95-98% consist of water. Externally, they look like jellyfish. For comparison - in a human body about 60 % of water.
Some species have eyes. There are only 12 pairs of them. They are located in such a way that they provide a 360-degree view. Eyes are needed both for spatial orientation and for tracking prey. Jellyfish can hunt for shrimps and fish, stunning them with their tentacles.
They have a special way of delivering poison. Other animals have poison injected during the bite, and the jellyfish have a special organ for this - nematocysts.
Biologists have found bioluminescent, that is, glowing in the dark species.
Life and development
Development begins with an egg from which a larva appears, which is called a planula. It settles at the bottom and grows into a polyp. Then the polyp is formed into an adult.
Some species may reproduce by budding.
Longevity of an individual depends on its size. The lifetime of the smallest species is hours, and giants exist for several years.
Jellyfish can live in both salt and fresh water. Freshwater species are absolutely harmless and leave no burns.
For saltwater species, prolonged precipitation is devastating. During the rainy season, their numbers decline noticeably.
Jellyfish can exist in oxygen-free conditions, in which other invertebrates of the same size will not survive.
Some poisonous individuals have such strong nematocysts that they may be active, even after the death of the jellyfish.
Jellyfish can swim not only along the stream. They swallow some water and then push it back in, and thus move around.
These invertebrates continue to grow in size throughout life.
Most often they live in large colonies, but there are exceptions. Purple striped jellyfish, which lives exclusively near the coast of California, is kept alone or in small groups of up to 10 individuals.
Despite the external fragility, jellyfish can live even at a depth of 10 kilometers, under a huge water column. Deep-sea species are poorly studied due to lack of access to them.
History
It is believed that jellyfish existed on the ground before the dinosaurs. Approximately 600 million years ago, they were born. This is confirmed by the presence of fossils in Utah in 2007.
The name comes from the heroine of the ancient Greek mythology of Medusa Gorgona. The term was coined by Carl Linnaeus in 1752.
The last of the found jellyfish is pink jellyfish. It was found about 10 years ago in the waters of the Caribbean.
In 1991, 2,000 jellyfish were sent into space for scientific purposes. They easily moved weightlessness and even multiplied in space. But the offspring produced during the experiment died when they returned to Earth.
In Asia, some of these invertebrates are consumed as food. There are about 25 names of edible jellyfish. They are eaten in salads or marinated.
Records
- Individual females can reproduce up to 45,000 larvae per day.
- The largest jellyfish is called "Giant Arctic". The largest detected individual has a dome diameter of about 2 m, and the length of the tentacles - more than 35 m.
- The species of nomura reaches a weight of 200 kg, and the diameter of the dome can exceed 2 m. They live mainly in the Yellow Sea and South China Sea. In 2009, a fishing vessel weighing 10 tons was dumped in the Tokyo Bay, trying to pull out nets with a dozen jellyfish.
- The most dangerous of the studied species is the Sea wasp (cubomedusa). Even short contact with tentacles of this species causes unbearable pain. More active contact can lead to serious consequences, including death. Over the past 50 years, wasp poison has killed more than five thousand people. In total, it carries so much poisonous substance that one can kill at least 50 people at a time.
- i.e. the nutriculum tourist psyche lives for a very long time - under unfavorable conditions jellyfish sink to the bottom, turns into a polyp and develops again to an adult. If it wasn't for natural enemies and external influences, these jellyfish would have filled the entire oceanic space.
- The Rocky Archipelago in the Pacific has the largest concentration of jellyfish in the lake. The size of the lake is 450 m long and 170 m wide, and it is home to more than two million individuals.
- The smallest population of the large red jellyfish. To date, only 23 of them have been found.
- Spotted Australian jellyfish can pass through up to 13 tons of water in one day.