The white planaria is a primitive creature that can inhabit not only fresh water bodies, but also in salt water. The presented form of a flat worm does not harm animals or humans. However, this creature also does not belong to the category of beneficial organisms. What is a planaria? The structural features of such a flat worm will be considered below.
What is a planaria?
In fresh water bodies, at the very bottom, under pebbles and snags, you can find a miniature creature in the form of a flat white worm with a translucent body structure. Scientists classify such organisms as harmless parasites.
Visually at a planarium, both body surfaces are symmetrical and reflect each other. Despite the negative reputation of parasitic flatworms, such an animal does not pose any danger to other living organisms. Experts attribute planaria to predators that feed on simple organic compounds, small crustaceans, and fish fry.
The external structure of the planarium
Planaria has a bipolar body. The right side of the creature is mirrored in relation to the left. The conditional dividing line runs along the entire body. Such an external structure of the white planaria allows it to live in conditions not only of water bodies, but also of land.
The body length of a flat worm is no more than two centimeters. Thickness can reach 5 mm. In the front of the body, the planaria has a special extension, where the tactile tentacles are located. The back of the worm is narrowed and somewhat pointed at the end. On the entire surface of the body are the so-called cilia, the movement of which contributes to the movement of the creature in space.
The internal structure of the planarium
Planaria has the following internal structure:
- A muscle bag is a specific fiber that runs across the entire body. When they contract, the flatworm lengthens. The back and abdominal cavity of the animal are connected by longitudinal muscle fibers.
- Sense organs - tactile cells, paired tentacles, balance organ, primitive eyes that can respond to light.
- Nervous system - nodes in the form of clusters of receptors, nerve branches.
- Excretory system - branched tubules that permeate the entire body of a creature.
- Digestive system - special epithelial cells that enable a flatworm to capture prey. Retractable pharynx is responsible for the absorption of food. Food is digested in a single-layer intestine. The waste is discharged outward, passing back through the mouth opening.
How does the planarium move?
So we examined the structure of the planarium. Now let's find out how this primitive animal moves.
Planaria creeps under water, moving on solid objects. A flatworm moves extremely smoothly, evenly and slowly. Looking at the planarium in the aquarium, you might think that the animal is swimming in the water column without much effort. In fact, on the body of the worm there are many invisible cilia invisible to the human eye.
Among other things, planarians secrete specific mucus, with the help of which paths are laid on objects for multiple movement. Small planarians are able to swim, performing paddle-like movements with cilia.
Lifestyle
Planaria are active in the dark. A flat worm is hiding under stones, snags, underwater foliage.
The creature is dangerous for the mollusks. Planaria enter their respiratory system, which leads to the gradual death of the mollusk.
In the process of life, planarians produce mucus, which swells in water, forming a kind of web. Thanks to this, the creature envelops its potential prey.
Development
A primitive creature, in spite of its attitude to the category of parasitic flatworms, is completely independent of other organisms. For the development of the planaria, no intermediate or final owners are required. On the contrary, close relatives of this creature, such as tapeworms and flukes, parasitize in the body of animals and humans, without which there is no possibility for development and reproduction without it.
Breeding
Planaria belongs to the category of hermaphrodites. A creature is characterized by several methods of reproduction at the same time:
- Division - during the onset of sexual activity, the body of a flatworm exfoliates. The adult individual is gradually divided into several parts. After some time has passed, the mechanisms necessary for normal functioning are formed in both halves. As a result of such simple manipulations, one parasite is transformed into several full-fledged individuals.
- Sexual method - mature planaria lays eggs on a fertile substrate. To fertilize the masonry, flatworms are touched by bodies for several moments. Thus, as a result of the union of female and male germ cells, a zygote is formed. A cocoon is formed from it, where eggs are preserved until their full maturity. Typically, the appearance of numerous young individuals of the planaria takes from two to three weeks.
Interesting Facts
The simple structure of the planaria contributes to its highest survivability. The body of a flatworm has regenerative abilities. Even after the separation of the head from the body, a new one gradually grows in its place. If you divide an adult into separate pieces, over time, the original organism can be restored from them. This feature contributes to the survival of the planaria in the most adverse conditions.
The specific structure of the planaria gives it the ability to withstand aggressive environmental factors. For example, with a lack of oxygen for breathing, an increase in temperature, the creature becomes inactive. In the future, planarians are able to independently break up into separate pieces. The latter are regenerated upon the occurrence of favorable conditions.
Planaria are extremely sensitive to potential prey. With a lack of food in the habitats, flatworms sense nutrients at a considerable distance. Sensing food, planarium colonies crawl out of their own shelters and in hundreds move to the places where the prey is located.
Aquarium planaria content
Despite the gentle structure of the planaria, the softness of the outer cover, such a creature can be kept in the aquarium. Moreover, the flat worm is not able to harm the other inhabitants of the artificial reservoir. As already noted above, planaria emits an abundance of rather unpleasant mucus in the process of life. Therefore, even large fish such creatures do not like. Smaller predators, who decided to attack the planar, envelop themselves with sticky substance and lose their motion, remaining paralyzed for some time.
Planaria in the aquarium does not need special feed. The creature feeds on the vital products of other animals, decomposing residues, particles of dead plants.
Finally
So we examined the internal as well as the external structure of flatworms. Planaria is a harmless parasite due to its lifestyle. Throughout life, such a flatworm does not require a host. Unlike its parasitic counterparts, the creature presented is able to independently obtain food in natural habitats.