There is a huge variety of worms in the world. They live on land, underground, and even in the deep sea. Not always these representatives of the fauna evoke positive emotions in the people observing them, mainly a person dislikes this species. Today we decided to devote an article to one of the representatives of annelids, this is a nereid - a sea worm. We will try to maximally talk about him, describe the appearance and life.
Nereida - Worm: Description of Appearance
Where does this species live? Nereids live at the bottom of the sea. These are not those who are called the daughters of the king of the sea in ancient Greek mythology. These are ordinary worms. The polychaete worm Nereida is annular. His body consists of many rings, as we all know the earthworm.
Nereida is a worm with a snake-like body structure. It has a head, metamerism (trunk), anal lobe and lobiform limbs.
There are eyes on the head of the Nereids - as many as two pairs. Also on the head of the worm there are tentacles, two-segmented fingers.
The limbs of the Nereid are dotted with many bristles (hence the view is multi-bristled), with the help of which it easily moves along the bottom of the sea at a speed that is good for the worm.
Metamerism - repeating, exactly the same parts of the body. In our case, these are rings. Nereida is a worm endowed with specially developed muscles. It can be easily buried in the soil of the bottom to hide from danger, or lay eggs.
Nereida is very small, it rarely reaches four centimeters in length, basically its height is two or three centimeters. But found in fresh waters and individuals up to 90 centimeters! Such a "monster" can be found in the desalinated waters of Japan. It is called the green nereis.
Nereida is a worm that is usually brown in color. It can shimmer with green, blue and red shades. A spectacle, truly, a bewitching look. This worm is beautiful, and absolutely safe for humans. Do not be afraid that he will bite you or decide to live in your body. Nereida lives in harmony with a man, and he is not of interest to her in the quality of food.
The internal structure of the Nereid worm
The muscles in the body of the sea worm Nereid form a skin-muscle sack. This is a structure that does not have an internal cavity. The organs are separated by loose connective tissue, or parenchyma. The body is covered with skin from above, and several layers of muscles are located under it. These muscles are not located in separate bundles, but are tightly fused with the skin. This is the skin-muscle bag.
The intestine of the nereid consists of three compartments: the middle is endodermal, and the extreme (anterior and posterior) are ectodermal.
Nereid food
Nereida is an omnivorous worm, but still prefers algae to a meat diet. Its menu includes mollusks, small invertebrate inhabitants of the seas. These creatures are not dangerous for large and small fish, although they are endowed by nature with powerful jaws with sharp teeth. Also, the Nereid will refuse human food, which falls into the water. So, having met such a creature, do not rush to treat it to sausage or cake, the nereid will not appreciate your menu.
Organic residues at the bottom are also food for this worm. When digging the next hole in the ground, Nereids often swallow silt. The organic substances contained in this marine rock are well absorbed by the body of the worm and contribute to its vital functions.
Nereid as a link in the food chain
This worm itself is constantly in danger. To eat Nereid meat whole lines are lined up. The first are fish and large mollusks. They constantly hunt for a harmless neighbor.
Also, at low tide, the Nereids remain defenseless. Worms left out of the water are excellent food for gulls. These swallows are ready to wait for hours when the water leaves to feast on fish, shellfish and sea worms.
And so it turns out that the predatory nereid itself becomes an object of diet for many representatives of the sea and land. The worm is not endowed with nature's protection, such as large fangs, poison, or an unpleasant odor, so every hungry representative of the fauna can freely eat it.
How do worms breathe?
Nereida, like the earthworm, breathes with the help of the entire surface of the body. If the rain representative of the family crawls to the surface from wet land to breathe, then how does the nereid not die in the water?
Many sea worms, including the heroine of our article, have gills in the form of gills on the blades. In these gills there are many blood vessels. Blood is enriched with oxygen, which was dissolved in sea water, through the same gills it gets rid of carbon dioxide.
Thus, a nereid can spend a long time both in water and on land. Nature took care of its creation, endowing it with two ways of breathing.
How does a marine worm breed?
Many worms are asexual, and multiply by division. Nereids have both a male and a female gender. Fertilization occurs in the external environment.
When the worms reach puberty, and the breeding season begins, they rise from the bottom closer to the surface of the water. They grow new bristles that allow them to swim and rise to the surface.
The bodies of males and females begin to abruptly change shape, color. You might think that at this moment they are turned inside out, and they suffer greatly from pain, but this is far from the case.
After some time, breaks occur in the bodies of Nereids, from which germ cells exit into the water. Mom and Dad after they released cells for reproduction into the water, die.
After fertilization has occurred, eggs begin to grow. Subsequently, tiny larvae - Nereid babies - are born from them. At this moment, they are at great risk: even small but predatory mollusks strive to catch and eat babies.
