Nemertina (worm): description

Nemertina is a worm, a type of ribbon-like. The beings of this category do not have external touch organs. However, they are able to procure food in a rather original way - "firing" in the prey with an abundance of mucus, which is allocated by a long proboscis, which deep into the body of the creature.

What way of life do the animals lead? What does the nemertine (worm) look like? Photo and description of such reptiles will be considered later in the article.

The history of the discovery of Nemerte

For the first time, the existence of nemertein was recognized thanks to the discovery that the scientist G. Barleyz did. In 1758, the researcher identified a worm of the presented type in sea waters, described its morphological structure and even created an image of an animal.

The encyclopedic knowledge of nemerthin in the 19th century expanded significantly. Many zoologists brought to science new, interesting information about these unique animals that live mainly on the seabed. The discovery in the presented area became possible due to the appearance of technical means for working at depth. In this period, the very definition of "nemertiny" was proposed.

Nemerdin was actively studied by the Soviet zoologist NA Livanov. In 1955, he proved that these animals are a transitional branch between flat and ribbon-like worms. Prior to this, such creatures were ranked as annelid worms - annelids.

Appearance

A typical representative of nemertine has a body elongated in anteroposterior direction, somewhat flattened in the dorsal and ventral parts. The body length of individual representatives varies from a few millimeters to tens of meters. However, the measurement of the real magnitude of nemerteen is complicated by the fact that these creatures are able to stretch like leeches.

Nemertina is a worm whose body is divided into the trunk and head part. The border between these areas is the cervical furrow. The head part of the animal contains a mouth opening. The trunk does not have pronounced external organs. On the sides of the body stand out only small gonads. At the back of the worm is a well-visible anal opening.

Skin nemertin can produce a significant amount of mucus. Therefore, most worms of this type look unattractive to predators. Numerous marine species have a vivid color, which is a warning signal of danger to potential enemies in their natural habitat. At the same time, there are enough representatives of the immortality of whitish tones. Some of them have translucent skin, through which the internal organs are visible.

Food

Nemertina is a worm that has an elongated mouth opening of a tubular type. Inside the mouthpiece there is a special proboscis that folds deep into the body cavity and is located above the internal organs when the animal rests. During the hunt, this plastic tube unfolds and is ejected by the worm in the direction of the victim under the influence of hydraulic pressure. The extraction is covered with sticky, thick and corrosive mucus.

How does nemertine feed? The worm can swallow an immobilized victim entirely or split it into parts. Some animals of the presented type envelop the prey in a cocoon of mucus, leaving it prozapas.

Internal structure

Nemertina is a worm that does not have a body cavity per se. All gaps between internal organs are filled with a binding tissue - the parenchyma. The interior is represented by the posterior, middle and anterior gut.

Nemertins possess the most developed circulatory system among all the ribbon-like worms. As for the respiratory organs, such animals do not. Saturation of cells with oxygen occurs by its entry through the skin.

The nervous system is built on the principle of orthogonality. In other words - nerve cells form specific fibers, and those gather in nerve trunks.

Classes

The following classes of nemertines stand out:

1. Anopla - the so-called unarmed worms. A distinctive feature of the creatures of this class is the absence of a proboscis in the oral cavity. The food is captured through a hole that is in the abdominal area. A striking representative of this class is the giant marine nemertine, called Lineus Longissimus, whose body length can reach up to 30 meters with a width of not more than one centimeter.
2. A nemertine worm, the Enopla class, has a proboscis in the anterior part of the body. The latter is thrown out, hitting the victim with several stilettos and enveloping it with thick mucus. Representatives of this class are mostly of modest size.

Lifestyle

Most worms that are classified as nemertines are sea animals that inhabit the bottom. However, many species of freshwater creatures of this type are known. There are also individual land representatives of nemertines.

Nemertina is a worm that leads a predatory life. Some animals of the presented type do not hunt independently, but are scavengers. There are also known nemertins, which parasitize in the mantle cavity of marine mollusks. Currently, there is a detailed description of the order of 1,200 species of these worms.