Origin
Jellyfish, also known as jellies or sea jellies, are part of Cnidaria. They have different morphologies representing several cnidarian classes: Scyphoza (over 200 species), Staurosis (50 species), Cubosis (20 species) and Hydroza (1000-1500 species).
Jellyfish are found in all oceans from the surface to the depths. Some jellyfish can be found in fresh water, they are only freshwater species of just 25mm, they are colorless and do not sting.
Jellyfish are generally transparent or translucent. Cyanea capillata is the largest known jellyfish and the longest in the world.
Its tentacles are 36.5 m. the most common giant jellyfish is found in the waters of Japan, Korea and China. Its diameter is about 200cm and weight 200kg. Since jellyfish are not actually fish, the word jellyfish is considered an impromptu term, so American public aquarists have popularized the terms jellies or sea jellies (jellyfishes).
The word jellyfish is used to denote various types of cnidarians, which have the basic body structure resembling an umbrella. Scientists use different terms for jellyfish (for example: gelatinous zooplankton).
Feeding Jellyfish
Even though they are not fish, jellyfish are carnivorous animals. They catch prey with the help of tentacles. Through its tentacles it injects a venom that paralyzes or even kills its prey.
The concentration and composition of the venom differ from one species to another. Certain species of jellyfish develop a venom so powerful that it can kill an adult human in just a few minutes.
Some jellyfish have the ability to swim a little faster by actively chasing their prey if the venom is weaker or the animal has escaped.
Jellyfish consume all types of plankton in life, from plants to microscopic animals in the water. They eat fish roe or larvae from other animals, mollusks, crustaceans, or other species of jellyfish.
Appearance sea jellyfish
Jellyfish have no digestive system, respiratory system, central nervous system or circulatory system. They do not need a respiratory system because their skin is very thin and the body is oxygenated by diffusion.
They have limited control in movement, but they move by contractions-pulsations of the bell body. Some species swim most of the time while others are more passive preferring to save energy.
Jellyfish are composed 90% of water, most of their mass is gelatinous, hence the name Jelly. The jellyfish has no brain and nerve system, but there is a network of nerves located in the epidermis. Some can detect the presence of light with the help of sensitive organs.
Behavior sea jellyfish
The presence of" flowers " in the waters is usually seasonal and occurs with the advent of the sun and the increase in temperature. Ocean currents tend to gather jellyfish in groups of hundreds of thousands of individuals.
Jellyfish are able to survive in oxygen-poor water or salty waters that contain more iodine.
Rising global temperatures mean rising water temperatures mean many species of jellyfish live better in warmer waters. Jellyfish are found in groups that can reach 100,000 individuals.
Due to the warming of the waters some jellyfish populations have increased their numbers so much that some species have been classified as invasions. The invaded areas are the Black Sea, the Caspian Sea, the Baltic Sea, the Mediterranean Sea and the Gulf of Mexico.
Jellyfish can cause problems for humans. The most common are stings (sometimes deadly, depending on the species). The other problem is that a lot of people don't know them well but they know that some of them can cause health problems and that affects tourism.
Destroying fishermen's nets is another matter. Only Scyphozoan jellyfish are harvested for consumption, about 12 of the 85 species harvested.
Traditional methods of processing involve procedures that last 20-40 days after the removal of the gonads and mucous membranes.
Umbrella and tentacles are treated with a mixture of salt and several other ingredients. Due to the large amount of water jellyfish loses 7-10% of weight during processing.
After processing the remaining mass contains 94% water and 6% protein. Fresh jellyfish are cream in color, but during prolonged storage the color becomes yellow or brown.
In China jellyfish are processed and left to desarate overnight. The next day they can be eaten boiled or raw. They can be served with oil, soy sauce, vinegar, sugar, as vegetable salad, etc.
In Japan they are cut into slices and served with vinegar as an appetizer.
Breeding sea jellyfish
Jellyfish are usually male or female (occasionally hermaphrodite individuals are also found). In most cases the eggs are released into the water without protection and are fertilized.
In some species sperm swim in the female's mouth to fertilize the eggs inside the body. After fertilization, a larva called a planula is formed.
The Planula is small and covered with cilia. This settles on a rigid surface and develops into a polyp. The polyp is cup-shaped and tentacles begin to appear around an orifice.
Then the jellyfish as we know it develops. The life span of jellyfish lasts from a few hours (in the case of very small hydromeduses) to years, depending on the species.
A species has a longevity of up to 30 years, which is unusual for jellyfish. One species, dohrnii Turritopsis, may be immortal due to the ability to transform between jellyfish and tulip.
They feed continuously. In most species reproduction is controlled by light, so the population spawns at dusk or dawn.
