Platyhelminths is the name of a group of worms from soft and generally flat body, which are mostly parasites of other animals, although there are some of free life.
You flatworms are animals whose body structure is very simple, there are more than 20 thousand described species, the tapeworms, schistosomes and planarians.
Tapeworms, for example, cause illness when raw or undercooked beef and pork are eaten, once they are infected by the worm's eggs.
Photo of a tapeworm in the human intestine
Also read about the annelids and the Nematodes.
Anatomy, Physiology and Habitat
- They are terrestrial or aquatic animals (fresh or salt water);
- has the body with bilateral symmetry: that is, the two sides of the body are similar;
- They are accolades: there is no body cavity, the space between the organs is filled with connective tissue;
- Nervous system: have a pair of brain ganglia connected to two longitudinal nerve cords, from which nerves depart for the whole body, carrying the stimuli captured by the sensory cells;
- Incomplete digestive system: the food enters through the mouth and digestive enzymes, produced in the specialized cells of the walls of the gastrovascular cavity, act on it. The remains are eliminated through the mouth;
- Excretory System: there is protonefrids (branched tubules with cells specialized in absorbing excretions accumulated between tissues) with flame cells (multiflagellate) or solenocytes (only scourge). There are excretory pores on the dorsal surface of the body;
- Circulatory System absent: the gastrovascular cavity is very branched and carries nutrients straight to the body's cells;
- absent respiratory system: gas exchanges are carried out directly between the environment and the body's cells;
- Reproductive system: reproduction can be asexual (as in some planarians that occur fragmentation) or sexual, some species of planarians and tapeworms are monoic (hermaphrodites) and schistosomes are dioic. Planarians have internal fertilization and direct development, while the others go through larval stages in development.
Occurrence of Diseases
external structure of the Taenia solium
In countries in Africa and Asia and in poorer regions of South America, worm infestation is common, as sanitation is deficient there is no same control as in countries in Europe, North America and Australia, where there are few cases of taeniasis, as there is inspection of meat for the consumption.
In Brazil it is more common to Taenia solium, which infects pork, so it should always be well cooked. Another common disease in Africa and Asia that also occurs in Brazil is schistosomiasis.
