Annelid worms, invertebrates. Animal Kingdom, Wildlife. Fauna. Zoology. Fauna. Nature of Aragon Spain.

Annelid worms, invertebrates. Animal Kingdom, Wildlife. Fauna. Zoology.

Nature of Aragon > Fauna

Scientific classification: annelids comprising the phylum Annelida.

Bristle worms or polychaetes constitute the class Polychaeta, Oligochaeta class oligochaetes and leeches Hirudinea class.

The annelids, or ringed worms have cylindrical body, soft, elongated with numerous rings. They are animals with segmented body, metameric or rings, by means of internal partitions and with organic systems also positioned so segmented.

The body wall are formed by an external cuticle, circular muscle layer and innermost longitudinal another.

The first segment is usually the head and the rest of the trunk. The head is more formations containing nerve and sensory organs (visual, olfactory, tactile).

May possess setae in silks or skin or legs parapodia shaped bodies are sometimes gill. The digestive system is rectilinear and have excretory organs and circulatory system closed with a glass dorsal and one ventral.

Reproduction is sexual.

In this phylum (or Phylum) are included classes oligochaetes (Oligochaeta or earthworms and freshwater), the HIRUDINEA (Hirudinea or leeches) and polychaetes (Polychaeta or marine worms).

Since these animals are appearing obvious modifications of evolution, in which a region become differentiated anterior and posterior cephalic or caudal, bilaterally symmetrical, appropriate conditions for movement in one direction.


The body wall consists of a very thin cuticle with various cell types, a basement membrane collagen material and below three fiber layers smooth musculature (a circilar, one longitudinal and one oblique). Each body segment wall has prolongations (called parapodia) and many setae.

The body is elongated and rounded section, with the mouth at one end and the anus at the other and has bilateral symmetry.

It consists of several similar units, or segments, separated by grooves externally and internally by septa (septa). The segments usually have lobes (Parapodia) with bristles (setae or setae) that serve as a means of locomotion.

The bodily fluid filled cavity (coelom) provides some structural lift, so that the body is flexible.

The circulatory system is closed, with a dorsal and a ventral vessel, linked by corners. Blood hemoglobin or emeritina usually.

The digestive system is usually a straight tube with a pharynx (or horn) generally rigid and provided with jaws and intestine where nutrients are absorbed.

The head may have eyes, palps or tentacles. Polychaetes grow by addition of segments to the body at the rear end.

They usually have separate sexes and reproduce by releasing sperm and eggs into the water. By contrast, the usual pattern of bristle worms or polychaetes is hermaphroditism, in which fertilization occurs internally. These capsules to house animals produce eggs.


Oligochaetes ("few septa"), have the body divided into segments that manifest externally in the form of rings, is sleek, tailored to the excavation.
The head is reduced or lacking palps eye and is located in the mouth end.
Not possess parapodia or "feet". They have skin breathing.

There are nearly 3,000 species, terrestrial and freshwater.

The most representative species of this class are:



Tubifex (freshwater worm)


These animals with a constant number of body segments, divided externally into rings whose number does not match the internal segmentation.

The body is flattened, with a suction cup at the front and one at the rear. The mouth is located in front or inside of the first cup.

The body wall is similar to that of the previous groups carrying clitellum and possess several sensory organs (tactile, sensitive and simple eyes stains).

Un ejemplo típico de Hirudíneo es la sanguijuela común (Hirudo medicinalis), que vive entre la vegetación o en el agua y que se alimenta de la sangre de los vertebrados.

Ecology and Evolution

Some polychaetes are active predators. Others have adopted a sedentary lifestyle and extract food particles or water fund deposits.

The earthworm feeding ground by passing through your body to extract nutrients from it, and thus enriches and aerates the soil with their tunnels. So, play an essential role in soil ecology.

Most leeches suck the blood of other animals, and are still used for medical purposes for bloodletting, a blood extract is used as an anticoagulant.
Ciertas especies son depredadoras.

Annelid fossils are rare, hard to soft body is preserved. The known fossils date back over 500 million years.

Perhaps flatworms descendent (flatworms) and led to believe that the arthropods.

Often some aberrant marine annelids are allocated to separate classes, some can even be in different phyla.

Other information about fauna in Aragón:

A small list of species in Aragon would be the following:

Vertebrates Invertebrates








   images about the fauna in Aragon.
   photographs on invertebrates.
   beneficial animals for agriculture.

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Also you can dedicarte to the intangible ones: from the legend compilation that also does to universal Aragon.

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Annelid worms, invertebrates. Animal Kingdom, Wildlife. Fauna. Zoology. physiology, metazoans, coelomates, worms, ecology, zoogeography, water, moisture, wetlands, stone, earth, food, gastronomy

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