Worms Vermiforms. Invertebrates Animal Kingdom. Fauna Fauna. Natural Patrimony Aragonese. Aragon. Spain. 
Aragon > Nature of Aragon > Fauna

Worms Vermiforms. Invertebrates Animal Kingdom. Fauna

The Platelmintos

They are worms with flattened bodies and almost always parasites.
They don't have locomotive appendages and some have cilia.
They mostly lack digestive, circulatory, respiratory, or sensory organs.
They usually have suction cups and are hermaphroditic.
The parasitic forms need two guests, one for the larval state and one for the adult state.
They are classified in: Turbelarios, Trematodos and Cestodos.


They are small, some microscopic, with the body covered with vibrating cilia for locomotion.
They are aquatic and terrestrial.
They have digestive system without anus and ventral mouth with extensible pharynx. Some species have simple eyes.

Some examples:
Bipalium, a giant freshwater turbelar (30 cm)

Platelmintos regeneration capacity

Each piece in which a planaria is divided will originate a complete individual and if the head is cut off, each of the halves regenerates the remaining half.

The trematodes

They are flat worms, all parasites, up to a few centimeters in length.
Its body, sometimes cylindrical, is provided with suction cups or fixing hooks, which is attached to the parasitized host.
His metamorphosis is complicated and he needs to parasitize in two or three guests to complete his cycle.
The best known trematodes are Schistosoma and Fasciola hepatic or "liver ache", which sometimes cause very serious diseases.

The Schistosoma manson i or Bilharzia is the parasite that causes biltrarziasis or schistosomiasis, disease that causes intestinal and cardiac disorders in man, anemia, liver lesions and can cause death.
It is widespread in tropical regions, where it is estimated that more than ten million people suffer from it.
In adult state it invades the circulatory, digestive, respiratory, etc.


  1. The Egg is deposited in the feces.
  2. It becomes larva larva.
  3. Penetrates in a Water Snail (First guest).
  4. It transforms into Cercaria (second larval phase), which penetrates through the human skin into the bloodstream.
  5. Finally parasites Man (ultimate Guest).

The liver ache or Hepatic fasciola is a parasitic platelminto that causes a disease called hepatic dystomatosis, which causes a chronic and inflammatory process of the liver with digestive and nutritional disorders.
It wreaks havoc on sheep and other pets and even attacks man if he consumes vegetables contaminated with his eggs.


  1. Eggs are expelled in the droppings.
  2. The miracidium larva develops in the water.
  3. The larva miracidio swims freely and parasites in an aquatic snail.
  4. In the snail, miracidium becomes a sporocist full of germs.
  5. The germs inside the sporocist are transformed into cercariae that are expelled by the snail and, swimming, become enchanted in the vegetables.
  6. Encysted cercariae are eaten with vegetables by the lamb and become staves that cause cysts in the liver.

The cestodes or Tenias

They are flatworm or flat worms, parasites, that live as adults inside their guests' bodies.
They have no digestive system and feed by absorption through their skin.
They are formed by a head or scolex, with suction cups and sometimes armed with hooks with which they are fixed to the walls of the organism. Its body is a succession of rings or proglottids that can measure between 5 and 10 meters in length.

Each of the rings has a complete hermaphrodite reproductive system, which, once mature, comes loose with eggs.
There are numerous species of cestodes, but the best known are Tenia solium or solitary, Tenia saginata and Tenia equinococus.

Cycle of the tenia solium or solitary

The pig ingested, among the food, eggs of had had expelled in the feces of infected people. Inside, eggs originate larvae that cross the walls of the intestine and are encyst in the form of cysticercos in their flesh, which when ingested by man without being sufficiently cooked can be parasitized.

The Tenia equinococus

More dangerous than the previous ones is the Tenia equinococus transmitted by the dog.
Eggs expelled in the dog's feces can be involuntarily ingested by man and can cause the terrible hydatid cyst.
It grows in the liver, brain, lungs, etc., in an excessive way, full of vesicles, which can cause death if it breaks.

It is an endemic disease of the Ebro Valley.

The asquelmintos

They form a very diverse group of worms that have a common characteristic among themselves: they all have a single cavity where their body organs are located, without segments or rings, although some outwardly seem to be ringed.

Asquelmints are divided into the following classes: Rotifers, Gasterotrics, Quinorrincos, Priapuloids, Nematomorphs and Nematodes.
They are very little known, except the nematodes.


They are microscopic asquelmintos worms that live in ponds and streams of water. They are very abundant.
They have a crown of cilia that serves as a rotating organ and a kind of nail to fix.
They have no respiratory or circulatory system.
They have separate sexes.
Many are invertebrate parasites.


They are microscopic aquatic worms of which there are about 200 species, provided with vibrating cilia, which serve as an organ of locomotion, in their ventral face.
They are similar to rotifers and live in the muddy bottoms of the ponds next to the infusoria.

Cinorrincos or Quinorrincos

They are marine worms that measure a maximum of 1 mm and live on the seaweed or in the mud.
His body is covered with plates with spines, and they appear segmented. The head and pharynx is retractable, and catches the food by sucking it. There are about 100 species.
Its development is done through successive changes.


They are marine worms of about 8 or 10 cm in length, with a soft and cylindrical body.
They have the anterior part of the body in the form of a proboscide or retractable tube with rows of hooks and the mouth at its end.
The lower limb is branched with a respiratory plume. Dig with the trunk in the sand to feed on organic materials.

Nematomorphs or fat ones

They are cylindrical and filiform worms that, in their larval state, are parasites of arthropods, and of free life in their adult state. They live in fresh and marine waters. They present sexes separated and often tangled male and female, similar to a bundle of threads. They are usually vulgarly called "horse hairs."

Acantocephalos or equinorrincos

They are parasitic worms of the digestive system in vertebrates. Their larvae parasitize in crustaceans or insects.
They have no digestive tract, feeding through the skin.
They have a retractable tube armed with hooks at their head end.
They are viviparous and the sexes are separated, being the females of greater size, some of which can measure 60 cm in length.
Man can be parasitized rarely.

The Nematodes

They are elongated cylindrical worms, very narrow at the ends.
The sexes are separated and there is a variation or dimorphism between them, being almost always older the female.
They have few sensory organs, but some species of aquatic life have a pair of simple eyes.
There is no other type in the Animal Kingdom that has as many individuals as nematodes. They live in every imaginable condition.

They can withstand drying, large temperature variations and a wide variety of chemical agents. They are parasites of animal and human plants and most are dangerous.

The best known are: the filaria, the intestinal worm, the ascaris, the hookworm, the trichina, etc.

Most produce extremely dangerous anemias and diseases, among which trichinosis stands out.

The trichina

It is a very small nematode (one millimeter in length) that can cause trichinosis, a serious disease almost always fatal to man, which can be contracted by eating infected and undercooked pork.

The pig acquires it by ingesting meat from infected rats, and its larvae are engulfed between muscle fibers. Trichina penetrates all corners of the body through the blood and lymphatic vessels causing death.
The infected pig is the transmitter of the parasite to man.


They are very small organisms (1 mm) that live mainly in mosses, lichens, sand and wet soils, and also in freshwater. Their body is elongated with segments and they have four pairs of locomotor appendages provided with strange nails.
His mouth is sucking and they are covered by a thin cuticle, which change in growth, with varied drawings.


They are marine worms except some terrestrial, and freshwater, flattened, without segments, long and with retractable proboscis.
They live under the stones on the rocks in the sand and sometimes also inside other animals.
They are similar to flat worms and have great regeneration power.
The Lineus can reach up to 30 m in length.

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.

Also Aragon enjoys a diverse and varied Nature where passing by plants, animals, Geology, or landscapes we can arrive at a fantastic bestiary that lives in its monuments.

The information will not be complete without a stroll by its three provinces, with shutdown in some of its spectacular landscapes like Ordesa, the Moncayo, Monegros or by opposition the Ebro.

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

Fauna | Flora | Geology | Fungi | Water
Landscape | Monegros | Moncayo | Ebro | Ordesa
Bestiary | Books | Buffon | Activities | Culturales | Zh2o | Photografies
Document | Nature in Aragon

The pasapues project is an extension of the Aragón project is like that, and tries to collect and relate all possible types of documentary information about Aragon: texts, books, articles, maps, illustrations, photographs, narrations, etc., and proceed to its publication and diffusion.

Worms Vermiforms. Invertebrates Animal Kingdom. Fauna zoology, reproduction, genome, physiology, metazoans, celomados, worms, ecology, zoogeography, water, humidity, earth

Copyright 1996-2021 © All Rights Reserved Francisco Javier Mendivil Navarro, Aragon (Spain)

Explanations or to correct errors please press here

Legal Warning.. This activity of the Asociacion Cultural Aragon Interactivo y Multimedia
As opposed to the threat of the hope of the water trasvase: CONGRATULATIONS.

This website does not directly use cookies for user tracking,
  but third-party products such as advertising, maps or blog if they can do it.
If you continue you accept the use of cookies on this website.