CIRCULATION IN PORIFEROUS: CHARACTERISTICS AND OPERATION - BIOLOGY - 2025

The circulation Porifera or sponges is a peculiar process, since these living things have a circulatory system as the common animal.

The Porifera are animals invertebrate organisms, commonly referred to as sponges. They are mostly marine, although some groups of these can be found in fresh waters such as lakes. Approximately 9000 species of poriferous have been identified.

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

Circulation in poriferous

Despite being such simple organisms, porifers obtain all the nutrients and oxygen they need to survive through the flow of water.

In the same way, this "circulatory system" of water keeps the sponges clean, because it allows them to remove residues.

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

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

Once the porifers have absorbed the necessary elements from the water, it is expelled through a hole in the upper part, called an osculum.

The body of sponges

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

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

They are organisms so simple that they have only two types of cells: choanocytes and amoebocytes. Choanocytes have flagella (filaments located in the outer layers of a cell) and are attached to the inner walls of the sponge. Amoebocytes circulate freely in the mesoglea.

Some species are more complex and have skeletons composed of spicules (mineral salt deposits that resemble needles), which can be made of lime or silica.

Poriferous classes

The absence or presence of spicules and the material of which they are composed (if there are spicules) allow poriferous to be classified into three groups: hexactinellids, calcareous and demo-sponges.

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

Lastly, demo-sponges, or horny sponges, are characterized by the absence of spicules; most sponges are in this class.

Benefits of porifers

Some sponges release toxic or poisonous substances as a defense method. Most of these substances are used by humans to create drugs.

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

Reproduction in porifers

Sponges are generally hermaphroditic. There are viviparous species and oviparous species. Both species can reproduce sexually, expelling sperm into the water.

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

For their part, oviparous species expel sperm and eggs into the water and fertilization takes place outside the body of the parents.

Similarly, porifers can reproduce asexually. Due to the simplicity of their organization, sponges can regenerate from fragments of their bodies, giving rise to a new individual.

Feeding

Porifers feed through a particular system, exclusive to this family. Instead of mouths, sponges have tiny pores on their outer walls, which absorb water. Later, the water is filtered to obtain the nutrients that it can provide.

Sponges feed on microscopic particles, primarily bacteria, protozoa, and algae, as well as minute debris of organic matter.

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

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

Poriferous respiration

As mentioned above, the pores of the sponges absorb large amounts of water and this circulates throughout the body of the organism.

In this way, nitrogenous residues (mainly ammonia) are cleaned and, in the same way, gas exchange occurs that allows the sponges to obtain the necessary oxygen.

Although this system cannot be compared with the respiratory, digestive and circulatory systems of animals with hearts, it could be said that the circulation of water in porifers 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 porifers have an extensive circulatory system since their “blood”, the water, is not confined to their bodies, but is found throughout the ocean.

References

1. Porifera. Retrieved on February 23, 2017, from circusystem.weebly.com.
2. Sponges. Retrieved on February 23, 2017, from mcwdn.org.
3. Porifera. Retrieved on February 23, 2017, from mesa.edu.au.
4. Lepore, T. Porifera Circulatory System. Retrieved on February 23, 2017, from study.com.
5. Phylum Porifera - Characteristics, Types, Functions and Reproduction. Retrieved on February 23, 2017, from biologyboom.com.
6. Porifera. Retrieved on February 23, 2017, from circulat0ryencyclopedia.weebly.com.
7. Seashores' Friends. Retrieved on February 23, 2017, from mesa.edu.au.