Circulation in Porifers: Characteristics and Functioning

The Circulation in poriferous Or sponges is a peculiar process, since these living beings do not have a circulatory system like the common animal.

The Poriferous Are invertebrate animal organisms, commonly known as sponges. Most are marine, although you can get some groups of these in freshwater lakes. Approximately 9,000 species of poriferous have been identified.

Species of poriferous, calcarea.

These sponges are the simplest of all macroscopic animals: they are composed of cells so simple that they can not form specialized tissues. This is why they lack digestive, nervous, respiratory or circulatory systems.

Circulation in poríferos

Despite being so simple organisms, poriferous get all the nutrients and oxygen they need to survive through the flow of water.

Similarly, this"circulatory system"of water keeps the sponges clean, because it allows them to remove waste.

Based on these premises, it can be said that the circulatory system of the sponges consists in the absorption of water through the pores of its external walls.

This water circulates through the atrium of the sponge (inner cavity) thanks to the constant movement of the flagella of its cells.

Once the poriferous have absorbed the necessary elements of the water, it is expelled through a hole in the upper part, called the oculus.

The body of the sponges

The body of a sponge is composed of a cavity called atrium or spongiocele, covered by two thin walls pierced by pores (hence the scientific name"poríferos").

These walls are separated by a sheet called mesoglea, composed mainly of collagen, a gelatinous material.

They are organisms so simple that they possess only two types of cells: the Coanocytes and the Amebocytes . The coanocitos present flagella (filaments located in the outer layers of a cell) and are fixed to the inner walls of the sponge. The amebocitos circulate freely by the mesoglea.

Some species are more complex and have skeletons composed of Spicules (Deposits of mineral salts that resemble needles), which may be lime or silica.

Poriferous classes

The absence or presence of spicules and the material of which they are composed (in the case of spicules) allow to classify the poríferos into three groups: Hexactinelides , Calcareous Y Demosponjas .

The hexactinelid sponges, also known as siliceous sponges, have silica spicules (hence their name) and have a glassy appearance. Calcareous sponges have lime spicules and are considered the simplest species of the poriferous family.

Finally, the sponges, or sponges corneas, are characterized by the absence of spicules; Most sponges are part of this class.

Benefits of poriferous

Some sponges release toxic or poisonous substances as a defense method. Most of these substances are used by humans for the creation of medicines.

Similarly, the body of some poríferos is used as bath sponges, as is the case of the Spongia officinalis .

Reproduction in poríferos

Sponges are usually hermaphrodites. There are viviparous species and oviparous species. Both species can reproduce sexually, expelling spermatozoa in water.

The viviparous species capture sperm through their pores and carry them to mesoglea, where fertilization occurs.

On the other hand, the oviparous species expel spermatozoa and eggs to the water and the fertilization takes place outside the body of the parents.

Likewise, poriferous can reproduce asexually. Due to the simplicity of their organization, sponges can be regenerated from fragments of their bodies, giving rise to a new individual.


The poríferos are fed through a particular system, exclusive of this family. Instead of mouths, the sponges have small pores in their outer walls, which absorb the water. Subsequently, the water is filtered to obtain the nutrients it can provide.

Sponges feed on microscopic particles, mainly bacteria, protozoa and algae, as well as tiny remains of organic matter.

These remains are assimilated by poriferous cells (coanocitos and amoebocitos) through a process known as phagocytosis.

Through this process of water absorption and particle digestion, sponges play an important role in the cleaning of marine waters. In fact, a pore of 1 cm in diameter and 10 cm high can filter 20 liters of water a day.

Breathing in porphyry

As previously stated, the pores of the sponges absorb large amounts of water and it circulates through the body of the organism.

In this way, nitrogen residues (mainly ammonia) are cleaned up, and gas exchange also occurs, allowing the sponges to obtain the necessary oxygen.

Although this system can not be compared to the respiratory, digestive and circulatory systems of animals with heart, it could be said that the water circulation in the poríferos fulfills the functions of all these.

In any case it allows the sponges to absorb oxygen from the water, as well as nutrients that can be found in it.

In this sense, it could be said that poríferos have a wide circulatory system since their"blood", the water, is not confined to their bodies, but is found in the whole ocean.


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