By going on a diving outing, we can enjoy a unique and wonderful experience. Naturally, we have to take into account a series of recommendations so that the immersion is perfect. Even so, we may encounter some inconvenience from time to time, but all we have to do is pay attention and everything will be fine.
What is a jellyfish?
Cnidarian comes from the Greek knidé, which means nettle. Its main characteristic is the possession of stinging cells called cnidocysts or nematocysts.
The word medusa has its origin in one of the three Gorgon sisters, Medusa, a marine divinity from Greek mythology, who had snakes instead of hair and who recalls the shape of these curious animals.
What are they like?
Their body, almost always transparent, is made up of 95% water, a fact that provides them with perfect camouflage. It consists of three main parts: the umbrela, the oral arms (which surround the mouth) and the stinging tentacles. They are radially symmetrical animals. They have an internal cavity, where digestion takes place, called gastrovascular cavity and which has a single opening that performs the functions of mouth and anus. Jellyfish are made up oftwo layers of tissues, the ectoderm or outer layer and the endoderm or inner layer, separated by a layer of connective tissue, the mesoglea.
They have a primitive nervous system, with nerve cells grouped together forming two rings that govern the rhythmic pulsation. At the margin of the bell or umbrella, there are sensory organs: the ocelli (which allow them to detect different intensities of light) and the statocysts (very simple balance organs).
Classification
Cnidarians can present two different morphologies:
- The polyp form, sessile or fixed in the substrate, with a tubular body and with the tentacles and mouth directed upward.
- The jellyfish form, free-living and with its tentacles and mouth facing downwards.
There are more than 9000 known species of cnidarians, which are grouped into 4 classes: polyp and jellyfish phases, true jellyfish, class Cubozoa and class Anthozoa.
Where do jellyfish live?
With the exception of hydras and other freshwater hydrozoans, cnidarians are marine. Inhabitants from the seas tropical to the cold waters of the Arctic.
They have been sailing the seas for more than 650 million years. Jellyfish, also called aguamalas, are pelagic (open sea) animals and are part of the zooplankton, since, although they can propel themselves thanks to rhythmic movements of their umbrella, they basically move dragged by sea currents.
Reproduction
Jellyfish have separate sexes, that is, there are male jellyfish and female jellyfish. To reproduce, males and females release sperm and eggs into the water (sexual reproduction). After fertilization, larvae (planulae) develop, which will give rise to new jellyfish or which will settle and form polyps. From these polyps, of benthic life, through asexual reproduction, free-living jellyfish can develop again.
The largest jellyfish...
The lion's mane jellyfish (Cyanea capillata) has tentacles that can be longer than a blue whale. They are found in both temperate waters and the Arctic.
Voracious predators
Jellyfish are carnivorous and can increase in size quickly and form large numbers of individuals when food is abundant. But if this is scarce, they can shrink again.
They feed mainly on zooplankton, small crustaceans such as krill or copepods, although some small fish or other jellyfish are also part of their diet. It is quite curious to see through the body of the jellyfish its last capture before being digested.
The tentacles, equipped with stinging cells, serve as defense and as a powerful weapon for capturing prey. In contact with the victims, the nematocysts present in the tentacles shoot the harpoon or filament that they contained coiled inside and, through it, a toxic, stinging substance is released, which paralyzes them. The oral arms help in capturing and ingesting food.
Precautions
It is not advisable to swim on beaches when you notice the presence of jellyfish. Even walking along the shore can be dangerous, as traces of tentacles may remain in the sand.Jellyfish can cause stings even hours after they are dead.
What to do if you get a jellyfish sting?
Fresh water should never be applied to wash the affected area, since the change in salinity can cause the stinging cells attached to the skin to break and release the stinging fluid. It is advisable to apply cold to the bite area by putting ice cubes, but always in a plastic bag, not directly on the skin.
The tentacles attached to it can be removed with the help of tweezers, but never with your fingers. In the event of any complication, such as breathing difficulties or heart rhythm disturbances, it is necessary to go to a health center to apply the appropriate measures.
