The Annelids Are worms that have segments in ring shapes around their body, hence the name"annelids".
The term Annelids Comes from the Latin word Anellus , What does it mean Rings. In biology, it is known under this term to set of animal species that form the phylum Annelida .
Earthworm, belonging to the group of Clitellates.
The phylum Annelida Is made up of about 22,000 species, including earthworms, sea worms and leeches.
The annelids are invertebrate and move thanks to the presence of parapods. Some species can shape the individual segments that compose them to generate movement by corrugations called peristalsis.
Some species can be To reproduce asexually . However, the common thing is that Reproduce sexually .
Annelids are of great ecological importance. For example, earthworms open furrows on the ground, allowing oxygen and water to flow more easily.
In the same way, these animals participate in the creation of fertile soils by accelerating the processes of decomposition of matter.
General characteristics of annelids
1-They are multicellular animals, since they are conformed by more than one cell.
2-Annelids are invertebrates.
3-Present bilateral symmetry. This means that if the body is cut transversely, the content of the right cut will be the same as that of the left cut.
4-They have an elongated body separated into segments or rings.
5-They move through parapods. These are small non-articulated structures that facilitate movement in the annelids. It should be noted that many annelids also move through peristalsis. This is a process through which waves are generated by the expansion and contraction of the body of the worm.
6-Breathing is cutaneous, which means it is done through the skin.
7-Some species have a well-developed circulatory system. In these species, two major blood vessels are present: the upper and the lower. The upper moves moves the blood forward, while the lower moves the blood back.
In some annelids, the upper blood vessel presents a series of muscles at its front end, which form a kind of heart. In other species, the heart is at the rear end, where the upper and lower vessels converge.
8-The blood of annelids has hemoglobin.
9-Most species are hermaphrodites. Some species of leeches are young males and when they reach maturity they become females.
10-They can reproduce both sexually and asexually. Some species reproduce only asexually, such as Aulophorus furcatus .
Classification of annelids
Annelids are classified in:
Polychaetes
They present hairs that cover their segments. Most are aquatic, only a few live on land.
Of the aquatic species, most live in the seas, while few species live in bodies of fresh water.
Clitellates
Most do not have hairs in their segments. Some species do have hairs; However, these are found in less quantity than in the Polychaetes .
They are characterized by having an outstanding ring-shaped structure, which surrounds the body of the animal. This structure is the reproductive organ of the Clitellates .
The Clitellates Are classified into two subgroups:
- Oligochaetes . Most live on land and feed on decomposed organic matter.
- Hirudinea . To this group belong the leeches. They have suction cups at both ends of their body. These allow them to travel and feed themselves.
Annelids and ecosystem stability
Annelids, like all living beings , Play an important role in the balance of Ecosystems . The scientist Charles Darwin Was one of the first to study the influence of earthworms on the fertility of soils.
Some species of earthworms live under the soil. These species create furrows in the ground, which allows a better circulation of oxygen and water.
Other species inhabit the surface. Both the species that live under the earth and the species that live on it contribute in the creation of fertile soils, since they accelerate the process of decomposition of the matter when eating and defecating.
Similarly, many annelids are a source of food for birds (such as hens, nightingales, among others) and for some mammals (such as shrews, moles and beavers).
Uses that humans give to annelids
Often different species of annelids are used in bait fishing, as they have proven to be more efficient than artificial flies. In addition, they can be kept alive for several days based on moss.
Many annelids are marketed as bait and as fish feed. Even"farms"of these animals have been created to reduce the ecological impact that their use could generate in the environment.
In the scientific field, marine annelids are studied to study the levels of oxygen, salinity and pollution present in the water.
For their part, leeches have been used in medicine since 30 a. C., approximately. However, its use to extract blood is a practice that has been abandoned in the last century.
At present, leeches are used in microsurgery. Similarly, the saliva of these annelids has been found to have anti-inflammatory and anticoagulant components. These components prevent tumor expansion.
Examples of annelids
Examples of annelids are earthworms ( Lumbricus ), Sea worms ( Will not you ) And leeches ( Hirudo ).
- The worms belong to the family of Lumbrícidos. They feed on particles present in the earth. Their excrement increases the fertility levels of soils.
- Sea worms belong to the Nereids family. They usually reach large size and are colorful.
- Leeches are annelids of the family Hirudíneos. They have mouths composed of three jaws. They feed on blood they get by piercing the skin of other animals.
References
- Annelids. Retrieved on August 23, 2017, from wikipedia.org
- Annelid. Retrieved on August 23, 2017, from britannica.com
- Annelida. Retrieved on August 23, 2017, from tolweb.org
- Annelida. Retrieved on August 23, 2017, from encyclopedia.org
- Annelida. Retrieved on August 23, 2017, from animaldiversity.org
- Animals Annelida. Retrieved on August 23, 2017, from mta.ca
- Annelida. Retrieved on August 23, 2017, from biodiversityexplorer.org.