What are anélidos: classification and examples

Anélidos are eucelome animals that constitute a Filo (Annelida) of more than 10,000 species. They present bilateral symmetry and a vermiform morphology, which is commonly known as Worm formwith more than two cellular layers, tissues and organs. Although most are aquatic organisms, they also occupy terrestrial environments.

ANNELIDS CHARACTERISTICS

Now that you know what annelids are, we present some of its most outstanding characteristics. These characteristics of the anélidos are:

• The body of anélidos is differentiated in an anterior region and posterior region: The previous one is called the prostomium (which corresponds to the head), the trunk and a subsequent one called the pigid (the final part in which the anus is).
• Anélidos are characterized by have suffered an evolutionary process of metamerization: so your body appears divided into metamers or segments arranged along the antero-posterior axis. The anélidos trunk is the only region that has metamers, which are formed from pigidium, so that the younger segments are in front of this and the oldest are in the most previous part.
• The segments of the trunk They are separated by partitions or septa: Each segment has a space inside that corresponds to the celoma, which is covered by a wall called peritoneum. In the segments of the trunk a series of morphological structures are repeated, such as blood vessels, muscles and nephrides.
• The musculature of the body of the anélidos It is divided into circular musculature and musculature Longitudinal: the contractions of the musculature are carried out by segments or groups of segments, along the antero-posterior axis, and is spreading as a peristaltic wave by the body, getting the individual to advance, that is, that this is the mechanism that the anélids use to move, crawling on the ground or swimming in the water.
• Anélidos can present both sexual reproduction as hermaphroditism: They have a closed circulatory system and lack respiratory organs, since they perform the gas exchange with the exterior through the skin, that is, they are sonimal that have skin breathing. Here you can learn everything about hermaphrodite animals: reproduction and examples.

In the most evolved annelids, it is common for the prostomium to merge with one of the segments of the trunk, constituting a secondary compound head. Then, the nervous system of the anterior part of the body also merges and the ganglia of the nervous chain come together forming a ganglionic complex.

Keep reading to know examples of anélidos.

The Anélidos Classification It occurs in three groups: the polychetes (Polychaeta), the oligoquetos (oligochaeta) and the hirudinees (Hirudinea).

Polychaeta (Polychaeta)

It is the most diverse and abundant group of anélidos, with More than 6,000 species. These are Marine annelids mostly, generally benthic and bright colors. They differ between:

• Wandering polystands: They move freely by the substrate.
• Sedentary polysthes: that live in galleries that excavate in the substrate.

Errante polystagetics generally have a flattened body, with well developed heads and some Appendices in the trunk called parapods or podiums (a pair for each segment), that they use in swimming and from which quetas or silks that cover the body surface and that are remarkably visible. Polysthes feed on algae and other nutrients found in the sand.

Most polychetes They are separate sexesalthough there are hermaphrodite specimens. They reproduce sexually and present an external intercourse, so that gametes are released in the water and merger independently, giving rise to new organisms. In reproductive behavior, they usually develop a specialized segment that eliminate during or after the release of gametes.

If you want to know more about the polystagers: what are, examples and habitat, we leave you the following post of ecology.

Oligoquetos (oligochaeta)

The second most abundant anélidos group, with some 3,100 species known. They live in diverse habitats, both terrestrial and sweetacuícoles, with some marine species. They feed on decomposition plant matter. They have an elongated body and a more rounded section, with a less developed head and a lower morphological diversity than the polychetes.

These types of annelids show the following characteristics:

• They lack podiums and have Few Quetas: In addition, they are practically invisible to the naked eye.
• He Prostomium appears little developed: lacking sensory organs and appendices.
• He Metastomy presents a Variable number of segments: With four pairs of side quetas and four other ventrals. In the metastomium there are also a couple of nephridos by segment, dorsal pores that contact celoma with the external environment and female and male pores in segments 14 and 15, respectively.
• He Pigidio presents A ring: Where the anus is located.

Oligoquetos are usually Hermaphrodite animals And, when reaching the adult stadium, they develop a clitel in the metastomy, which is an organ of importance in sexual reproduction. Oligoquetos are also able to reproduce asexually through a fission process.

Most oligoquetos are free life, but there are also specimens within the type of parasitism life. They lack and hear, but they are able to detect light and vibrations and communicate through touch and taste.

Hirudinees (Hirudinea)

They know each other Around 500 species Hirudinees, too known as leeches. They are hermaphrodite organisms that inhabit in sweets, oceans and wet soils. Some are predators who feed on worms, snails, fish and invertebrates and others are parasites. Certain hirudins are hematophagous and others do not.

Some of the characteristics of the hirudins are:

• Your flattened and elongated body is dark color: It also presents windy at each end.
• The prostomium and the First five bodily segments They meet fuses: forming a venous that contains the mouth, while the pigment is merged to the last seven segments of the back, giving rise to another sucker that houses the anus.
• The body of the polystagetic has a fixed number of segments (33): Although the number of rings per segment varies between species.
• They are also characterized by not presenting quetas or podiums.

In the anterior area of ​​the body, genital holes are observed, each individual has a female and a male genital pore, and also, reaching sexual maturity, develop a clitel. Some species have eyes and many have sharp teeth or even jaws. They are deaf And they have a poorly developed vision, so they rely on touch and sense of taste to communicate.

Once explained what they are and their characteristics, some singles are cited Anélidos examples:

• Oligoquetos: common earth worm (Lumbricus terrestris) and TUBIFEX TUBIFEX.
• Polysthes: serpentine tubic worm (Serpula Vermicularis) and Marine sand.
• Hirudinees: HaEMADIPSA PICTA AND MEDICINAL SANGUIJUELA (Hirudo medicinalis).

If you want to read more articles similar to What are anélidos: classification and exampleswe recommend that you enter our biodiversity category.