✅ Common Jellyfish - Characteristics, Habitat and Habit

Cnidarians are aquatic animals that can also live in fresh water, but most of which are found in marine ecosystems. Their distinctive sign, in addition to the particular shape of their body, is the presence of cnidocytes, cells specialized in the production of toxins that they use to capture their food. Within this group of animals there are different types of jellyfish, including those belonging to the class Scyphozoa, which live only in marine waters and are known as true jellyfish.One of them is the moon jellyfish or the common jellyfish (Aurelia aurita), which we are going to tell you about in this AnimalPlanet fact sheet.

Origin

Africa
America
Asia
Europe
Oceania

Characteristics of Common Jellyfish

Here are the main characteristics of the moon jellyfish (common jellyfish):

Its external coloring is transparent.
Inside, you can see bluish structures: they can take on other colors and they correspond to the gonads of the animal, which have a ringed horseshoe shape.
The coat has a diameter of about 10-35cm.
The tentacles are small: they protrude from the side of the bell and measure between 1 and 5 cm.
The lower part of the bell has four oral arms: these are provided with cnidocytes or stinging cells, where the nematocysts or secretory organelles are found.
They have a variety of eyelashes: which are structured around the bell.
Lack specialized respiratory structures or organs: to carry out this process, they do so by diffusion between the external tissues of the bell.
It absorbs oxygen-rich water: it does so through its gastrovascular cavity and expels oxygen-depleted water by the same means. So this is an additional way to get the compound.
It also does not have a brain, nor a particular digestive, circulatory and excretory system: instead, it has a series of tissues or structures to carry out these functions, for example, ducts radials to transport food and a nervous network involved in various processes. Discover other brainless animals: names and characteristics, in the following article from PlanèteAnimale.
Inside, it is made up of mesoglea: the tissue that characterizes cnidarians and serves as a hydrostatic skeleton.

Habitat of the common jellyfish or the moon jellyfish

The moon jellyfish or the common jellyfish is a cosmopolitan cnidarian, distributed in all the oceans of the world except the Arctic. In this sense, it is present in practically all marine areas of North and South America, Asia, Europe, the coasts of Australia and, although to a lesser extent, in Africa.

This type of true jellyfish can inhabit coastal ocean waters as well as tropical areas. Its temperature range is therefore between 6 and 19° C, although the optimum value for its development is 17° C. A particular characteristic of the moon jellyfish is that, unlike the others, it can live in waters with very low salinity, even below 1%, but grows best around 40% salinity.

In terms of depth levels, this varies considerably and is found at depths over 200 meters, a zone called epipelagic, as well as in the mesopelagic, which goes down to around 1,000 meters.

Habits of the Common Jellyfish

The common jellyfish, depending on the availability of food, temperature and salinity conditions, groups together in large aggregations. Jellyfish are excellent swimmers and this species uses the water propelled by the bell to move horizontally towards the surface.

Although research is lacking, it is believed that common jellyfish are able to communicate chemically through substances they secrete into the water. They also have structures in their mantle that allow them to sense light, depth, and even gravity.

An extremely interesting aspect that has been reported by a study, is that jellyfish of the genus Aurelia, including the common jellyfish, are evidence that these animals can undergo reverse transformation from sexually mature adult stages to the form of polyp. This possibility has been reported in very few species.

Food of Moon Jellyfish (Common Jellyfish)

The moon jellyfish is a carnivorous animal, so it is an active predator. When they sense their potential prey nearby, they use a harpoon-like structure called a nematocyst, with which they inoculate a poisonous substance that paralyzes the captured animal. They then use their arms to carry the prey to under their bell where there is a hole through which they ingest it.

Among the prey that the moon jellyfish feeds on, we find:

Little fish
Copepods
Eggs
Mollusks
Other jellyfish
Plankton

Reproduction of the common jellyfish

These jellyfish exhibit sexual dimorphism, that is, there are differences between females and males. There is no courtship action, and no hierarchical organization related to reproduction is reported.

It has two stages of reproduction:

A sexual phase: the adult male releases a few sperm filaments into the water which, close to the female, and with the water from the currents, are introduced into the female's gastric pouch using eyelashes present in the bell. Once inside, they fertilize the eggs, which are then released into the water. From the fertilized eggs the planula are formed, which are free and swim, thanks to the presence of cilia, in search of a substrate to attach to.
An asexual phase: they then attach and turn into polyps, which reproduce during a second asexual phase. The polyps turn into strobiles, which go through different stages until they become adult juvenile jellyfish.

The reproduction process of the common jellyfish, and in general as for the group of jellyfish, depends on factors in the aquatic environment, such as salinity, temperature and food availability. All the stages last approximately 4 to 6 months.

Conservation status of the common jellyfish

The common jellyfish is not on any endangered animal list. In fact, in some areas, due to its high proliferation, it is considered a problem because it affects certain human activities. However, almost no marine animal escapes the effects of climate change and other anthropogenic effects in general. This jellyfish and other species in general should therefore not be left unattended as they play an important role in ecosystems.