Sea urchins are the inhabitants of the oceans. These representatives of the ichthyofauna can be dangerous to humans. At the same time, they are of great benefit. Read about the types of these animals, their appearance, reproduction and nutrition in this article.
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The class of these echinoderms is very numerous. Therefore, animals related to it are conditionally divided into two subclasses. The first group is regular hedgehogs, that is, those whose body shape is spherical. The body of irregular echinoderms is more like a distended disc.
There are over 900 animal species, some of which are very common. These include:
- Black sea urchins that have long spines. This animal poses a great danger to humans, as it has long needles. An interesting fact is that the beauty of a black hedgehog can quickly turn into his weapon: at any sign of danger, he directs the needles towards the irritant. That is, a shadow falling on him from any object can be regarded as an attack.
- A round sea urchin, which can also be dangerous to humans. It belongs to one ofthe most common types.
- Japanese sea urchin. The name makes it clear where it lives. This representative of echinoderms can attack a person if he feels the danger emanating from him.
- Slate sea urchin, which has an amazing red color. Its needles have an unusual triangle shape with a blunted top. According to one version, it got its name due to the fact that in ancient times it was used to write on slate boards with the help of its needles.
- This kind of diadem is very dangerous for a person. At the slightest sign of danger, the animal pierces the skin of the victim with fragile needles, and they break. The process of extracting them is very painful. Often this variety is found near the Turkish coasts beloved by tourists.
Description
The animals discussed in this article belong to such a class as echinoderms. Most often, sea urchins have a spherical body, the diameter of which is from 2 to 30 cm, along with needles. On the one hand, it is wrinkled, since the mouth opening is located there. Moreover, it is this part of their body that serves as a means of transportation, because with its help animals move along the seabed. The skeleton of these echinoderms is very well developed, it is soft only near the mouth and anus located on the back. With the help of numerous tubercles covering the surface of the body, needles are attached to it.
The sea urchin described in this article can have almost any color. Some species havethe unique ability to adjust the color of the body to the surrounding space.
Needle
Lime sticks have a cylindrical shape. They are movably attached to the body, which allows them to easily rotate in different directions. They not only protect animals, but also help them move around. Moreover, some of them have a grasping function. In this case, it is customary to call these organs pedicellaria.
Some of the needles contain poisonous glands that secrete a rather strong substance. Since such organs are shorter than the rest, ordinary needles move apart, releasing them outward. Because of the poison, about 80 species of these animals are dangerous for humans. Needles can be up to 30 cm long.
Poison
Sea urchins can fatally poison a person. How does this happen? As soon as the animal feels that it is in danger, it closes its needle-tweezers on the body of the victim and injects poison under the skin. It is a whitish liquid.
Places that have been pierced begin to itch. A person feels a strong burning sensation, his skin acquires a pronounced red tint, swelling may form. All this is accompanied by pain. In severe cases, there is a loss of sensitivity, the victim can be paralyzed. The poison released by the tweezers affects the nervous system. Under its action, breathing is disturbed, and this can be very dangerous for divers.
If you do not get out on land in time and do not help a person, he may die. Indeed, cases have been documented where the affectedpoison man did not have time to rise to the surface and died. In the best case, the pain syndrome will pass in 20 minutes. In less than a week, other signs of poisoning will also disappear. However, the paralysis effect lasts for 6 hours.
To save the life of the victim, it is necessary to limit his mobility, remove the remaining needles from the wounds and go to the hospital as soon as possible.
Habitats
All types of sea urchins live in waters that are characterized by medium or high salinity. For example, the range of black hedgehogs is represented by expanses from Japan and China to East Africa. They can also be found near the Hawaiian Islands. The round hedgehog, as well as other representatives of the echinoderm class, have a similar range. These animals are not found in the low-salinity waters of the Black and Caspian Seas.
The favorite habitat of echinoderms is the seabed. They move along it with the help of ambulacral legs. These organs are long processes, at the end of which there are suckers. They allow animals to move also on vertical surfaces.
Food
It's time to find out what the sea urchin eats. It all depends on which subclass of echinoderms it belongs to. Wrong hedgehogs eat plankton. But the diet of their correct relatives is more diverse. So, these predatory animals are able to hunt crustaceans and mollusks. However, they can eat algae and even carrion. Often they attack other hedgehogs, which are smaller, as well asstarfish attack.
Reproduction
To understand how sea urchins reproduce, you need to know a few facts about them. So, these animals are dioecious, that is, among them there are both female and male individuals. Fertilization is external. This means that the male fertilizes the eggs laid by the female. It takes place in shallow water. However, those species that live in Antarctic waters are viviparous. A special brood chamber is located in the body of the female, in which the eggs develop.
Reproduction of sea urchins is a fairly simple process that most often occurs outside the body of the female. However, those individuals that were born in the waters of the Antarctic leave the mother's body fully formed. After three years, their puberty begins. In total, the life expectancy of these echinoderms is from 12 to 15 years. Cases have been documented when scientists were able to find individuals whose age reached 35 years. Therefore, they are conventionally considered centenarians.
Enemies
Despite the fact that sea urchins have good self-defense, they often become food for other birds, fish and mammals. For the otter, these echinoderms are a special delicacy. The animal catches a prickly ball, and then throws it several times on a hard surface and breaks the shell. Seabirds prey on hedgehogs in a similar way. So, large birds raise prey to a great height and throw off prickly food on stones. The shell breaks and the meat of the animal is left unprotected.
Benefit
The sea urchin, the photo of which is presented in this article, is very much appreciated. Firstly, caviar of such species as fawn, multi-spined and green is very popular. According to Japanese beliefs, this product is able to prolong youth and give a person longevity. Indeed, caviar contains nutrients, essential amino acids and fats. Recently, studies have been carried out, as a result of which scientists have found that the human and sea urchin genomes overlap. That is why long-living animals can save the life span of Homo sapiens. It will be most useful to eat fresh caviar that has not been heat-treated. Not everyone likes it in its pure form, but it gives an interesting taste to salads and other dishes.
Secondly, with the help of these animals you can catch commercial fish. The fact is that echinoderms gather in large groups during the spawning period. They attract fish and crustaceans that don't mind eating sea urchins. And the fishermen at this time catch, for example, flounder.
