Animals

Facts about jellyfish

19 jellyfish facts

Gelatinous sea creature

Jellyfish are fascinating creatures and the most ancient animals on Earth. Although boneless, toothless, and brainless, they are efficient predators armed with invasive toxins. There are so widespread, there are no water tanks not filled with at least one species.

1
Jellyfish is in fact a name of a free-swimming phase in the Medusozoa life cycle.
The term “jellyfish” is commonly used to describe a marine animal, distinguished by its umbrella-shaped bells and tentacles, but it is in fact a predatory, sexual stage of medusozoan cnidarians.
2
Jellyfish are commonly found in water tanks all over the world.
They occupy both surface waters and the deep sea.
3
Although their name might be confusing, jellyfish are an invertebrate, not fish.
They do not possess a vertebral column.
4
The jellyfish “bells-and-tentacles” stage is called a medusa.
The name derives from Greek mythology and refers to snake-haired Gorgon Medusa.
5
Jellyfish predate dinosaurs.
Although their fossils are a rarity, since they do not have bones, the oldest shell-like fossils date back to Neoproterozoic Era (1000—550 mya).
6
They are composed of 98% of water.
Jellyfish washed ashore will evaporate in several hours.
7
There are over 2,000 known species of jellyfish.
It is estimated, however, that there might be over 300,000 species. To establish the current number of species, scientists use a method similar to the Drake equation–an equation used to estimate the number of extraterrestrial civilizations in the Milky Way.
8
Jellyfish do not have hearts, lungs, or brains.
They have a rudimentary nervous system, developed to detect vibrations, chemicals, and light, but also to navigate.
9
The largest jellyfish is the Nomura’s jellyfish.
Fully grown, it can reach up to 2 meters in diameter.
10
The smallest known jellyfish come from genera Eleutheria and Staurocladia.
They typically measure up to 0,5 millimeters in diameter.
11
Jellyfish reproduce both sexually and asexually.
While in a polyp stage, jellyfish can multiply themselves.
12
The average lifespan of jellyfish depends on the species.
Some live for several days, some can live up to a year.
13
There is one species of jellyfish considered biologically immortal.
The Turritopsis dohrnii possess an extraordinary skill of reversing their current stage of life. Basically, they can revert to a polyp stage by undergoing the process of transdifferentiation, which can happen infinitely.
14
Jellyfish are not aggressive towards humans, but will most likely sting when touched.
A jellyfish sting is painful and mostly not invasive, although it can be lethal.
15
There are several dangerous jellyfish species.
They mostly occur in northern Australia, and in the Indo-Pacific region. The most venomous is the Australian box jellyfish, whose sting can lead to paralysis, cardiac arrest, or death.
16
Jellyfish are considered a delicacy in various Asian countries.
They are widely consumed in Japan, Taiwan, Vietnam, China, and Korea. Usually, people consume it dehydrated and pickled, with soy sauce and vinegar. Jellyfish salad is a popular side dish in wedding banquets, especially in Japan.
17
Jellyfish are rich in nutrients, antioxidants, and protein.
It is also a great source of collagen.
18
Jellyfish are extremely well adjusted to climate changes and water pollution.
Combining it with their rapid reproduction, their numbers grow at a very high rate.
19
Jellyfish boarded a space shuttle.
In 1991, in the Space Shuttle Columbia, NASA sent thousands of jellyfish into orbit in order to study their behavior in microgravity. They reproduced well but had massive problems functioning back on Earth.

A sad, but the important conclusion from this experiment may suggest people born in space might also experience functionality problems in Earth gravity.

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